U.S. patent application number 14/096771 was filed with the patent office on 2014-06-05 for antenna and printed-circuit board using waveguide structure.
This patent application is currently assigned to NEC CORPORATION. The applicant listed for this patent is Noriaki Ando, Hiroshi Toyao. Invention is credited to Noriaki Ando, Hiroshi Toyao.
Application Number | 20140152520 14/096771 |
Document ID | / |
Family ID | 42315483 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140152520 |
Kind Code |
A1 |
Toyao; Hiroshi ; et
al. |
June 5, 2014 |
ANTENNA AND PRINTED-CIRCUIT BOARD USING WAVEGUIDE STRUCTURE
Abstract
An antenna includes a first conductive plane, a second
conductive plane disposed in parallel with the first conductive
plane, a power-supply unit applying a high frequency signal between
the first conductive plane and the second conductive plane, and at
least one shunt which is aligned in the second conductive plane and
includes a transmission line including an open end aligned in a
plane above or below the second conductive plane and a conductive
via electrically connecting another end of the transmission line to
the first conductive plane. A distance between a bottom surface of
the transmission line and the second conductive plane is less than
a distance between the bottom surface of the transmission line and
the first conductive plane. The transmission line is formed on a
plane positioned to face the second conductive plane outside a
region circumscribed between the first conductive plane and the
second conductive plane.
Inventors: |
Toyao; Hiroshi; (Tokyo,
JP) ; Ando; Noriaki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toyao; Hiroshi
Ando; Noriaki |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
NEC CORPORATION
Tokyo
JP
|
Family ID: |
42315483 |
Appl. No.: |
14/096771 |
Filed: |
December 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12457802 |
Jun 22, 2009 |
|
|
|
14096771 |
|
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|
|
Current U.S.
Class: |
343/776 ;
333/238; 343/772 |
Current CPC
Class: |
H03H 7/46 20130101; H01Q
13/08 20130101; H01Q 15/006 20130101; H01L 2924/15192 20130101;
H01Q 15/008 20130101; H01P 1/2005 20130101; H01L 2224/16225
20130101; H01P 3/003 20130101 |
Class at
Publication: |
343/776 ;
343/772; 333/238 |
International
Class: |
H01P 3/00 20060101
H01P003/00; H01Q 13/08 20060101 H01Q013/08 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2009 |
JP |
2009-041356 |
Claims
1. An antenna, comprising: a first conductive plane; a second
conductive plane disposed in parallel with the first conductive
plane; a power-supply unit applying a high frequency signal between
the first conductive plane and the second conductive plane; and at
least one shunt which is aligned in the second conductive plane and
which comprises a transmission line comprising an open end aligned
in a plane above or below the second conductive plane and a
conductive via electrically connecting another end of the
transmission line to the first conductive plane, wherein a distance
between a bottom surface of the transmission line and the second
conductive plane is less than a distance between the bottom surface
of the transmission line and the first conductive plane, wherein
the transmission line is formed on a plane which is positioned to
face the second conductive plane outside a region circumscribed
between the first conductive plane and the second conductive plane,
and wherein a clearance is formed at a position corresponding to
the conductive via in the second conductive plane so as to prevent
the second conductive plane from being electrically connected to
the conductive via.
2. An antenna, comprising: a first conductive plane; a second
conductive plane disposed in parallel with the first conductive
plane; a power-supply unit applying a high frequency signal between
the first conductive plane and the second conductive plane; and at
least one shunt which is aligned in the second conductive plane and
which comprises a transmission line including an open end aligned
in a plane above or below the first conductive plane and a
conductive via electrically connecting the transmission line to the
second conductive plane.
3. The antenna according to claim 2, wherein the power-supply unit
includes a power-supply via which connects the second conductive
plane to an input port disposed on a backside of the first
conductive plane, and wherein a power-supply clearance is formed to
prevent the power-supply via from being electrically connected to
the first conductive plane.
4. The antenna according to claim 2, wherein the power-supply unit
includes a microstrip line which is laid in a same plane as the
second conductive plane and is connected to an external periphery
of the second conductive plane.
5. The antenna according to claim 2, wherein the power-supply unit
includes a coplanar line laid in the first conductive plane and a
power-supply via connecting the coplanar line to the second
conductive plane.
6. An array antenna, including: a plurality of antennas which are
aligned in a same plane, wherein each antenna comprises: a first
conductive plane; a second conductive plane disposed in parallel
with the first conductive plane; a power-supply unit applying a
high frequency signal between the first conductive plane and the
second conductive plane; and at least one shunt which is aligned in
the second conductive plane and which comprises a transmission line
including an open end aligned in a plane above or below the first
conductive plane and a conductive via electrically connecting the
transmission line to the second conductive plane.
7. A printed-circuit board, comprising: a first conductive plane; a
second conductive plane which is smaller than the first conductive
plane and which is disposed in parallel with the first conductive
plane; a power-supply unit applying a high frequency signal between
the first conductive plane and the second conductive plane; and at
least one shunt which is aligned in the second conductive plane and
which comprises a transmission line including an open end aligned
in a plane below or above the first conductive plane and a
conductive via electrically connecting the transmission line to the
second conductive plane.
8. The printed-circuit board according to claim 7, wherein the
second conductive plane vertically overlaps the first conductive
plane in a plan view.
9. An electronic device, including: an antenna which comprises: a
first conductive plane; a second conductive plane disposed in
parallel with the first conductive plane; a power-supply unit
applying a high frequency signal between the first conductive plane
and the second conductive plane; and at least one shunt which is
aligned in the second conductive plane and which comprises a
transmission line including an open end aligned in a plane above or
below the first conductive plane and a conductive via electrically
connecting the transmission line to the second conductive
plane.
10. An electronic device, including: a printed-circuit board which
comprises a first conductive plane; a second conductive plane which
is smaller than the first conductive plane and which is disposed in
parallel with the first conductive plane; a power-supply unit
applying a high frequency signal between the first conductive plane
and the second conductive plane; and at least one shunt which is
aligned in the second conductive plane and which comprises a
transmission line including an open end aligned in a plane below or
above the first conductive plane and a conductive via electrically
connecting the transmission line to the second conductive plane.
Description
[0001] The present application is a Divisional application of U.S.
patent application Ser. No. 12/457,802, filed on Jun. 22, 2009,
which is based on and claims priority from Japanese patent
application No. 2009-041356, filed on Feb. 24, 2009, the entire
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to waveguide structures for
use in propagation of electromagnetic waves such as microwaves and
millimeter waves, and in particular to electromagnetic-band-gap
(EBG) structures for suppressing propagation of electromagnetic
waves in specific frequency bands. Specifically, the present
invention relates to antennas and printed-circuit boards using
waveguide structures as well as electronic devices including
printed-circuit boards.
[0004] The present application claims priority on Japanese Patent
Application No. 2009-41356, the content of which is incorporated
herein by reference.
[0005] 2. Description of the Related Art
[0006] Various technologies regarding waveguide structures,
printed-circuit boards, and antennas for preventing propagation of
electromagnetic waves in specific frequency bands have been
developed and disclosed in various documents. [0007] Patent
Document 1: U.S. Patent Application Publication, US 2005/019051 A1
[0008] Patent Document 2: U.S. Patent Application Publication, US
2005/0205292 A1 [0009] Patent Document 3: U.S. Patent Application
Publication, US 2007/0176827 A1
[0010] Recently, methods for artificially controlling frequency
dispersions of electromagnetic waves by use of repetitively aligned
conductive patches have been provided. Among those structures,
structures having band gaps in frequency dispersions are referred
to as EBG structures, which are expectedly applied to filters for
suppressing propagation of unwanted noise in printed-circuit boards
or substrates of device packages.
[0011] Patent Document 1 teaches an EBG structure for reducing
noise propagating between parallel plates. The EBG structure
includes conductive patches which are aligned in a third layer
between parallel plates and which serve as capacitances for one
conductive plane of the parallel plates, and shunts (or
admittances) for connecting the conductive patches to another
conductive plane of the parallel plates, wherein the shunts are
repetitively aligned in a one-dimensional manner or a
two-dimensional manner along the parallel plates. Due to band gaps
occurring in frequency bands in which the shunts serve as
inductances in the EBG structure, it is possible to set band gaps
by controlling serial-LC resonance frequencies of shunts.
[0012] Securing adequate capacitances and inductances in the above
EBG structure leads to increasing the areas of conductive patches
or increasing the lengths of conductive vias, which in turn makes
it difficult to reduce the sizes of structures.
[0013] Patent Document 2 teaches a structure in which chip
capacitors are mounted on the surface and are connected in parallel
between conductive planes and conductive patches. This structure
increases capacitances without increasing the areas of conductive
patches.
[0014] However, Patent Document 2 discloses that using chip
capacitors increases the number of parts so as to increase the
manufacturing cost.
[0015] In the above circumstances, the inventor has recognized that
it is necessary to fabricate an EBG structure (or a waveguide
structure) and a printed-circuit board with a reduced size, without
using chip components, and with low manufacturing cost.
[0016] Conventionally, flat panel antennas for microwaves and
millimeter waves have been developed, and in particular, small-size
and low-frequency antenna structures using the meta-material
technology have been developed. This technology is advantageous in
reducing sizes of wireless communication devices for use in
reception/transmission of electromagnetic waves such as microwaves
and millimeter waves.
[0017] The relationship between the wave number (or wavelength) and
the frequency in electromagnetic waves propagating through
dielectric media are referred to as dispersion characteristics of
media. Recently, meta-material technologies in which conductive
patterns or conductive structures are repetitively aligned so as to
artificially control the dispersion characteristics in propagation
of electromagnetic waves through structures have been developed and
studied in various application fields of engineering.
[0018] It is possible to reduce the size of antennas by use of the
meta-material technology. Patent Document 3 teaches a small-size
antenna structure based on composite right-handed or left-handed
(CRLH) principles showing the right-handed property or the
left-handed property due to the operating frequency.
[0019] The antenna of Patent Document 3 employs a CRLH line
structure repetitively aligning a plurality of unit structures
including conductive planes, conductive patches disposed in
parallel with conductive planes, and conductive vias connected
between conductive planes and conductive patches, thus utilizing a
length-related resonance of the CRLH line structure in the
left-handed frequency range. Conventional media (e.g. right-handed
media) suffers from the large size of an antenna structure because
the wavelength of electromagnetic waves becomes longer as the
frequency becomes lower. In contrast, left-handed media is capable
of reducing the size of an antenna structure because the wavelength
of electromagnetic waves becomes shorter as the frequency becomes
lower.
[0020] Patent Document 3 teaches that for the purpose of lowering
the frequency range securing the operation of left-handed media, a
conductive element is arranged between the conductive plane and the
conductive patch so as to increase the capacitance formed between
adjacent conductive patches. For the same purpose, a slit is formed
in proximity to the connection between the conductive plane and the
conductive via so as to form a coplanar line, thus increasing the
inductance formed between the conductive plane and the conductive
patch.
[0021] The inventor has recognized that the left-handed media of
Patent Document 3 using the repetitive structure cannot operate as
antennas in low frequency range under cutoff frequencies thereof.
In short, the antenna structure of Patent Document 3 suffers from
the limitation in lowering frequencies. For this reason, it is
difficult to design small-size antennas operating in low
frequencies based on the conventional technology.
SUMMARY
[0022] The present invention seeks to solve the above problem, or
to improve upon the problem at least in part.
[0023] The present invention is directed to an antenna or a
printed-circuit board, which includes a plurality of unit
structures repetitively aligned in a one-dimensional manner or in a
two-dimensional manner. The present invention is also directed to
an electronic device incorporating the antenna and/or the
printed-circuit board.
[0024] The unit structure is constituted of a first conductive
plane and a second conductive plane which are disposed in parallel
with each other, a power-supply unit applying a high frequency
signal between the first conductive plane and the second conductive
plane, and at least one shunt which is aligned in the second
conductive plane and which is constituted of a transmission line
having an open end aligned in a plane above or below the second
conductive plane and a conductive via electrically connecting the
transmission line to the first conductive plane.
[0025] Alternately, the unit structure is constituted of a first
conductive plane and a second conductive plane which are disposed
in parallel with each other, a power-supply unit applying a high
frequency signal between the first conductive plane and the second
conductive plane, and at least one shunt which is aligned in the
second conductive plane and which is constituted of a transmission
line having an open end aligned in a plane above or below the first
conductive plane and a conductive via electrically connecting the
transmission line to the second conductive plane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The above features and advantages of the present invention
will be more apparent from the following description of certain
preferred embodiments taken in conjunction with the accompanying
drawings, in which:
[0027] FIG. 1 is a cross-sectional view of an EBG structure used
for explaining a waveguide structure according to a first
embodiment of the present invention;
[0028] FIG. 2 is a plan view of the EBG structure corresponding to
the waveguide structure of the first embodiment;
[0029] FIG. 3 is a circuit diagram showing an equivalent circuit of
the EBG structure;
[0030] FIG. 4 is a graph plotting the imaginary part of admittance
in the EBG structure;
[0031] FIG. 5 is a graph showing calculation results regarding
insertion loss in propagation of electromagnetic waves through the
EBG structure;
[0032] FIG. 6 is a cross-sectional view showing an EBG structure
including an additional dielectric layer deposited above
transmission lines;
[0033] FIG. 7A is a plan view showing spiral-shaped transmission
lines;
[0034] FIG. 7B is a plan view showing meandering transmission
lines.
[0035] FIG. 8 is a plan view showing an EBG structure in which
transmission lines are aligned to detour around a component X;
[0036] FIG. 9 is a cross-sectional view of an EBG structure used
for explaining a waveguide structure according to a second
embodiment of the present invention;
[0037] FIG. 10 is a cross-sectional view showing a variation of the
EBG structure shown in FIG. 9;
[0038] FIG. 11 is a cross-sectional view of an EBG structure used
for explaining a waveguide structure according to a third
embodiment of the present invention;
[0039] FIG. 12 is a cross-sectional view showing a variation of the
EBG structure shown in FIG. 11;
[0040] FIG. 13 is a cross-sectional view of an EBG structure used
for explaining a waveguide structure according to a fourth
embodiment of the present invention;
[0041] FIG. 14 is a circuit diagram showing an equivalent circuit
of the EBG structure shown in FIG. 13.
[0042] FIG. 15 is a cross-sectional view showing a first variation
of the fourth embodiment which is created based on the EBG
structure of the second embodiment;
[0043] FIG. 16 is a cross-sectional view showing a second variation
of the fourth embodiment which is created based on the EBG
structure of the third embodiment;
[0044] FIG. 17 is a cross-sectional view of an EBG structure used
for explaining a waveguide structure according to a fifth
embodiment of the present invention;
[0045] FIG. 18 is a plan view of the EBG structure shown in FIG.
17;
[0046] FIG. 19 is a cross-sectional view showing a variation of the
fifth embodiment which is crated based on the EBG structure shown
in FIG. 15;
[0047] FIG. 20 is a plan view showing another variation of the
fifth embodiment including spiral-shaped transmission lines;
[0048] FIG. 21 is a plan view showing a printed-circuit board
incorporating the EBG structure according to a sixth embodiment of
the present invention;
[0049] FIG. 22 is a cross-sectional view of the printed-circuit
board shown in FIG. 21;
[0050] FIG. 23 is a plan view showing a variation of the sixth
embodiment;
[0051] FIG. 24 is a plan view showing a printed-circuit board
according to a seventh embodiment of the present invention;
[0052] FIG. 25 is a plan view showing a first variation of the
seventh embodiment in which two types of EBG structures are
alternately aligned in the noise propagation direction;
[0053] FIG. 26 is a plan view showing a second variation of the
seventh embodiment in which two types of EBG structures are aligned
in a checkered pattern;
[0054] FIG. 27 is a fragmentary plan view showing a variation of
the first embodiment;
[0055] FIG. 28 is a cross-sectional view showing a further
variation of the second embodiment;
[0056] FIG. 29 is a perspective view showing an antenna according
to an eighth embodiment of the present invention;
[0057] FIG. 30 is a plan view of the antenna viewed in a Z-axis
direction;
[0058] FIG. 31 a plan view of the antenna through a conductive
patch viewed in the Z-axis direction;
[0059] FIG. 32 is a plan view of a conductive plane included in the
antenna;
[0060] FIG. 33 is a cross-sectional view taken along line A-A in
FIGS. 30 and 31;
[0061] FIG. 34 is a cross-sectional view taken along line B-B in
FIGS. 30 and 31;
[0062] FIG. 35 is a circuit diagram showing an equivalent circuit
of a meta-material structure applied to the antenna of FIG. 29;
[0063] FIG. 36 is a graph showing dispersion characteristics of the
meta-material structure;
[0064] FIG. 37 is a graph showing the result of three-dimensional
electromagnetic analysis regarding the S parameter with respect to
the antenna of FIG. 29;
[0065] FIG. 38 is a circular graph showing the result of
electromagnetic analysis regarding the emission directivity at the
first resonance frequency of a first band with respect to the
antenna of FIG. 29;
[0066] FIG. 39 is a circular graph showing the result of
electromagnetic analysis regarding the emission directivity at the
first resonance frequency of a second band with respect to the
antenna of FIG. 29;
[0067] FIG. 40 is a plan view showing a 4.times.2 alignment of
shunts in the conductive patch;
[0068] FIG. 41 is a plan view showing a 4.times.1 alignment of
shunts in the conductive patch;
[0069] FIG. 42 is a plan view showing a single shut formed in the
conductive patch;
[0070] FIG. 43 is a plan view showing that linear-shaped
transmission lines are aligned in the conductive patch;
[0071] FIG. 44 is a fragmentary plan view showing a ramification of
transmission lines;
[0072] FIG. 45 is a plan view showing a rectangular-shaped
conductive patch;
[0073] FIG. 46 is a cross-sectional view showing that the
conductive via shown in FIG. 33 is replaced with a through via;
[0074] FIG. 47 is a plan view showing an antenna according to a
ninth embodiment of the present invention viewed in the Z-axis
direction;
[0075] FIG. 48 is a plan view of the antenna excluding transmission
lines viewed in the Z-axis direction;
[0076] FIG. 49 is a plan view of a conductive plane included in the
antenna of FIG. 47;
[0077] FIG. 50 is a cross-sectional view taken along line A-A in
FIGS. 47 to 49;
[0078] FIG. 51 is a cross-sectional view taken along line B-B in
FIGS. 47 to 49.
[0079] FIG. 52 is a cross-sectional view showing an antenna
according to a tenth embodiment of the present invention in the X-Z
plane;
[0080] FIG. 53 is a cross-sectional view showing an antenna
according to an eleventh embodiment of the present invention in the
X-Z plane;
[0081] FIG. 54 is a cross-sectional view showing an antenna
according to a twelfth embodiment of the present invention in the
X-Z plane;
[0082] FIG. 55 is a perspective view showing an antenna according
to a thirteenth embodiment of the present invention;
[0083] FIG. 56 is a perspective view showing an antenna according
to a variation of the thirteen embodiment;
[0084] FIG. 57 is a plan view showing an antenna according to a
fourteenth embodiment of the present invention; and
[0085] FIG. 58 is a plan view showing an antenna according to a
fifteenth embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0086] The present invention will be now described herein with
reference to illustrative embodiments. Those skilled in the art
will recognize that many alternative embodiments can be
accomplished using the teachings of the present invention and that
the invention is not limited to the embodiments illustrated for
explanatory purposes.
[0087] In the following description regarding waveguide structures
and printed-circuit boards according to the present invention with
reference to the accompanying drawings, a vertical direction in
FIG. 1 will be referred to as a thickness direction of a board.
1. First Embodiment
[0088] FIG. 1 is a cross-sectional view of an EBG structure
according to a first embodiment. FIG. 2 is a plan view of the EBG
structure; and FIG. 1 is a cross-sectional view taken along line
A-A in FIG. 1.
[0089] The EBG structure (or the waveguide structure) of the first
embodiment is a parallel-plate conductive structure; as shown in
FIG. 1, and includes first and second conductive planes 1 and 2,
which are aligned in parallel with a distance therebetween in the
thickness direction, as well as a unit structure 3. The unit
structure 3 includes a transmission line 4, which is laid in a
layer different from the layers of the first and second planes 1
and 2, and a conductive via 5 for electrically connecting the
transmission line 4 and the first conductive plane 1.
[0090] Specifically, the EBG structure includes a first dielectric
layer 6, and a second dielectric layer 7 which is disposed on an
upper surface of the first dielectric layer 6 in the thickness
direction, wherein the first conductive plane 1 is disposed on a
lower surface of the first dielectric layer 6 in the thickness
direction, and the second conductive plane 2 is disposed between
the first dielectric layer 6 and the second dielectric layer 7. The
conductive via 5 is elongated in the thickness direction from the
upper surface of the second conductive plane 2 to the lower surface
of the first conductive plane 1. The transmission line 4 is
disposed on the upper surface of the second dielectric layer 7 in
the thickness direction. That is, the transmission line 4 is
disposed to face the second conductive plane 2 outside a region
circumscribed between the first conductive plane 1 and the second
conductive plane 2.
[0091] The transmission line 4 uses the second conductive plane 2
as a return path, wherein one end thereof (i.e. a right-side end in
FIG. 1) serves as an open end so that the transmission line 4
serves as an open stub. The other end of the transmission line 4
(i.e. a left-side end in FIG. 1) is electrically connected to a pad
8 which is formed in the same plane as the transmission line 4 and
which is electrically connected to the first conductive plane 1 via
the conductive via 5 elongated in the thickness direction. The
second conductive plane 2 is equipped with a clearance 9 which
overlaps with the conductive via 5 in position, so that the
conductive via 5 is electrically isolated from and is not brought
into contact with the second conductive plane 2 by means of the
clearance 9.
[0092] In the above EGB structure, the transmission line 4, the
conductive via 5, and the pad 8 are devoted to a shunt, which is
combined with the clearance 9 so as to form the unit structure 3.
One or more unit structures 3 are repetitively aligned at a lattice
point defined by an independent vector A=(A1,A2) and B=(B1,B2) on
the X-Y plane. The first embodiment exemplarily refers to a
tetragonal lattice defined by A=(a,0) and B=(0,a) shown in FIG. 2
as a basic-mode lattice point. In the first embodiment, the
transmission line 4 is inclined to the tetragonal lattice of
A=(a,0) and B=(0,a) by a certain angle, wherein it is possible to
secure a long length d with respect to the transmission line 4
without interfering with the clearance 9 in its periphery. Strictly
speaking, the transmission line 4 is not included in the
cross-section taken along line A-A in FIG. 2; for the sake of
convenience, the transmission lines 4 are illustrated using dotted
lines in FIG. 1. For the sake of convenience, FIG. 2 shows the
second conductive plane 2 via the perspective scope of the second
dielectric layer 7.
[0093] Next, a basic operating principle of the above EBG structure
will be described.
[0094] FIG. 3 shows an equivalent circuit along the X-axis or
Y-axis in FIG. 2. FIG. 4 is a graph for plotting the imaginary part
of a parallel shunt. FIG. 5 is a graph showing calculation results
regarding an insertion loss in propagation of electromagnetic waves
through the EBG structure of the first embodiment.
[0095] Each repetitive unit 10 of the equivalent circuit shown in
FIG. 3 is constituted of a serial impedance 11 and a parallel shunt
12. The serial impedance includes an inductance 13 formed between
the first and second conductive planes 1 and 2. The parallel shunt
12 includes a capacitance 14 formed between the first and second
conductive planes 1 and 2, an inductance 15 of the conductive via
5, and the transmission lines 4. The overall equivalent circuit of
the EBG structure is formed by repetitively connecting one or more
repetitive units 10.
[0096] In the EBG structure, band gaps occur in frequency bands in
which the parallel shunts 12 serve as inductances. An admittance Y
representative of the parallel shunt 12 is given by equation
(1).
Y = 1 Z in + .omega. L via + .omega. C plane ( 1 ) ##EQU00001##
[0097] Y: Admittance
[0098] Z.sub.in: Input impedance of the transmission line 4 in view
of the pad 8
[0099] .omega.: Angular frequency
[0100] L.sub.via: Inductance
[0101] C.sub.plane: Capacitance
[0102] The input impedance Z.sub.in of the transmission line 4 in
view of the pad 8 is given by equation (2).
Z in = Z 0 .times. Z T + Z 0 tan ( .beta. d ) Z 0 + Z T tan (
.beta. d ) .beta. = .omega. eff 0 .mu. 0 ( 2 ) ##EQU00002##
[0103] Z.sub.in: Input impedance of the transmission line 4 in view
of the pad 8
[0104] Z.sub.0: Characteristic impedance
[0105] Z.sub.T: Terminating resistance
[0106] d: Length of the transmission line
[0107] .omega.: Angular frequency
[0108] .di-elect cons..sub.eff: Effective dielectric constant
[0109] .di-elect cons..sub.0: Dielectric constant of a vacuum
[0110] .mu..sub.0: Magnetic permeability of a vacuum
[0111] FIG. 4 shows frequency-dependent impedance curves 16 based
on the imaginary part of the admittance Y calculated by equations
(1) and (2) using parameters such as the capacitance 14 of 0.73 pF,
the inductance 15 of 0.22 nH, the characteristic impedance of
20.25.OMEGA. of the transmission line 4, the length d=7.5 mm of the
transmission line 4, and the effective dielectric constant
.di-elect cons..sub.eff=3.47 of the transmission line 4. The
transmission line 4 is of an open-end type so that the terminating
resistance Z.sub.T thereof is presumed to be infinite. Due to an
impedance-converting effect of the transmission line 4, the
capacitive property (where Im(Y)>0) and the inductive property
(where Im(Y)<0) alternately emerge in the impedance Im(Y) based
on the admittance Y. In FIG. 4, the impedance Im(Y) becomes
negative in frequency bands 17, thus showing the inductive
property. For this reason, it is anticipated that band gaps may
likely occur in the frequency bands 17.
[0112] In the EBG structure, a physical structure corresponding to
the repetitive unit 10 of the equivalent circuit is repetitively
aligned at the lattice point defined by a certain lattice distance
"a" on the X-Y plane. Due to a repetitive boundary condition
imposed on the repetitive unit 10 of the equivalent circuit shown
in FIG. 3, it is necessary to calculate band gaps in consideration
of the structural repetitiveness. FIG. 5 shows calculation results
regarding an insertion loss (S21) in propagation of electromagnetic
waves through the EBG structure by a distance of 7.times.a. A
dotted curve 18 shown in FIG. 5 shows the calculation result which
is produced by imposing the repetitive boundary condition on the
repetitive unit 10 of the equivalent circuit while using the same
parameters of circuit components used for producing calculation
results of FIG. 4. A solid curve 19 shown in FIG. 5 shows the
result of numerical calculation by way of three-dimensional
electromagnetic analysis. A model subjected to electromagnetic
analysis is designed with prescribed structural dimensions, such as
the thickness t=400 .mu.m of the first dielectric layer 6, the
thickness h=60 .mu.m of the second dielectric layer 7, the width
b=300 .mu.m of the conductive via 5, and the length d=7.5 mm of the
transmission line 4. FIG. 5 shows that calculated band gaps of the
equivalent circuit significantly match the result of
electromagnetic analysis.
[0113] Calculated frequency bands of band gaps shown in FIG. 5
significantly match the frequency bands 17 shown in FIG. 4. This
indicates that frequency bands of band gaps occurring in the EBG
structure can be approximately illustrated by frequency
characteristics of admittances. Since the admittance Y of the
parallel shunt 12 is determined by equations (1) and (2), it is
possible to bring band gaps into desired frequency bands by
appropriately setting parameters of these equations. In particular,
the length d of the transmission line 4 has a relatively high
degree of freedom in designing; hence, it is possible to easily
control band gaps by varying the length d. Frequencies of band gaps
can be lowered by increasing the length d of the transmission line
4 but without necessarily changing its area; hence, it is possible
to reduce the mounting area of the EBG structure. Since the EBG
structure does not need chip components, it is possible to reduce
the manufacturing cost in comparison with the conventional
arts.
[0114] First embodiment of FIG. 1 shows that no structure exists
above the transmission lines 4, whereas it is possible to modify it
such that a certain structure is mounted on the transmission lines
4. As shown in FIG. 6, for example, it is possible to arrange an
additional dielectric layer (i.e. a third dielectric layer 20)
above the transmission lines 4, thus increasing the effective
dielectric constant of the transmission line 4. Equation (2)
indicates that the impedance converting effect appears markedly on
the transmission line 4 as the effective dielectric constant of the
transmission line 4 becomes higher; hence, it is possible to lower
the frequencies of band gaps without increasing the length d of the
transmission line 4. For lowering frequencies of band gaps, it is
preferable to use a dielectric material having a high dielectric
constant for the third dielectric layer 20. For not lowering
frequencies of band gaps, it is possible to use any type of
dielectric materials for additional dielectric layers deposited
above the transmission lines 4.
[0115] As long as one end of the transmission line 4 serves as an
open end while the other end is connected to the pad 8, it is
possible to employ any type of arrangements and shapes to the
transmission lines 4, which do not affect the inherent property of
the present invention.
[0116] In the first embodiment, as shown in FIG. 2, the
transmission lines 4 are inclined to the X-axis and Y-axis with
certain angles therebetween so as not to interfere with the
clearances 9 in their periphery, whereas they can be aligned in
parallel with the X-axis and Y-axis without interference with the
clearances 9. Although the first embodiment is designed such that
the transmission lines 4 are linearly elongated as shown in FIG. 2,
it is possible to employ the spiral shapes shown in FIG. 7A or the
meandering shapes shown in FIG. 7B, for example. These examples
adequately secure the length d of the transmission line 4 within a
small mounting area.
[0117] It is possible to design an EBG structure shown in FIG. 27
in which two transmission lines 4A and 4B of different lengths
having respective open ends are connected to the pad 8. In the EBG
structure of FIG. 27 in which the transmission lines 4A and 4B
differ from each other in terms of impedance conversion periods, it
is possible to independently set a plurality of band gaps, thus
securing a high degree of freedom in setting frequency bands.
Herein, it is not necessary that the transmission line 4B be
directly connected to the pad 8; hence, it is possible to create
another structure including ramification in which the transmission
line 4B is ramified from the intermediate point of the transmission
line 4A, for example.
[0118] The transmission lines 4 are not necessarily aligned with
the same arrangement and the same shapes shown in FIG. 2 in
connection with all the unit structures 3. For example, it is
possible to align the transmission lines 4 while avoiding a
component X mounted on the surface as shown in FIG. 8, thus
securing high-density packaging.
[0119] FIG. 2 shows the tetragonal lattice as the lattice point for
repetitively aligning the unit structure 3; but this is not a
restriction. For example, it is possible to employ triangular
lattices or a one-dimensional repetitive alignment, thus
demonstrating satisfactory effects.
[0120] For the sake of convenience in manufacturing, the pads 8 are
aligned in connection with the transmission lines 4 and the
conductive vias 5, whereas it is possible to modify the EBG
structure not including the pads 8 without affecting the inherent
properties of the present invention.
2. Second Embodiment
[0121] Next, a waveguide structure according to a second embodiment
of the present invention will be described with reference to FIG.
9.
[0122] FIG. 9 is a cross-sectional view showing an EBG structure
according to the second embodiment.
[0123] The EBG structure of the second embodiment is a variation of
the EBG structure of the first embodiment, wherein parts identical
to those of the first embodiment are designated by the same
reference numerals, thus avoiding duplicate descriptions
thereof.
[0124] The EGB structure of the second embodiment shown in FIG. 9
is characterized in that a transmission line 4 is embedded inside
the region sandwiched between the first conductive plane 1 and the
second conductive plane 2. Specifically, the first conductive plane
1 is attached to the lower surface of the first dielectric layer 6
in its thickness direction while the second conductive plane 2 is
attached to the upper surface of the second dielectric layer 7 in
its thickness direction in the EBG structure of the second
embodiment. The transmission line 104 which uses the second
conductive plane 2 as a return path is laid in the intermediate
layer circumscribed between the first dielectric layer 6 and the
second dielectric layer 7.
[0125] Similar to the transmission line 4 for use in the first
embodiment, one end of the transmission line 104 is an open end,
thus serving as an open stub. The other end of the transmission
line 104 is connected to the pad 8 which is positioned in the same
plane as the transmission line 104, wherein the pad 8 is
electrically connected to the first conductive plane 1 via a
conductive via 105. Similar to the first embodiment, the pad 8, the
transmission line 104, and the conductive via 105 serve as an
shunt, which is combined with the clearance arranged for the second
conductive plane 2 so as to form the unit structure 3. The
arrangement of the unit structure 3 as well as the arrangement and
shape of the transmission line 104 employed in the second
embodiment are similar to those employed in the first
embodiment.
[0126] Since the transmission line 104 is shielded by the first and
second conductive planes 1 and 2 in the EBG structure of the second
embodiment, it is possible to reduce the number of unwanted
electromagnetic waves being emitted from the transmission line 104
to the exterior surface.
[0127] FIG. 9 shows the second embodiment in which the conductive
via 105 is a through-via; but this is not a restriction as long as
the pad 8 is electrically connected to the first conductive plane
1. As shown in FIG. 10, for example, it is possible to arrange a
conductive via 105_X of a non-through-via type without affecting
the property of the present invention. Since the EBG structure
shown in FIG. 10 does not need the clearance 9 for the second
conductive plane 2, it is possible to eliminate electromagnetic
waves from being emitted from the clearance 9 to the exterior
surface.
[0128] Next, an EBG structure according to a further variation of
the second embodiment will be described with reference to FIG.
28.
[0129] The EBG structure of FIG. 28 is designed based on the EBG
structure of FIG. 9, wherein a third dielectric layer 220 is
disposed above the second conductive plane 2, and a second
transmission line 204B having an open end is disposed above the
third dielectric layer 220. The upper end of the conductive via 105
is left-side end of the second transmission line 204B laid on the
third dielectric layer 220 via the pad 8, while the right-side end
of the second transmission line 204B is an open end. The clearance
9 is formed at the position of the conductive via 105 in the second
conductive plane 2, which is not electrically connected to the
conductive via 105. IN the EBG structure of FIG. 28, the
transmission line 104 and the second transmission line 204B operate
as open stubs independently. When the transmission line 104 and the
second transmission line 204B are designed to have different
lengths, it is possible to secure different impedance conversion
periods therefor, in other words, it is possible to set a plurality
of band gaps independently, thus securing a high degree of freedom
in setting frequency bands. Similar to the foregoing embodiments,
it is possible to arrange various patterns with respect to the
arrangement and shape regarding the transmission line 104 and the
second transmission line 204B; that is, it is possible to employ
spiral shapes or meandering shapes, for example.
3. Third Embodiment
[0130] Next, a waveguide structure according to a third embodiment
of the present invention will be described with reference to FIG.
11.
[0131] FIG. 11 is a cross-sectional view showing an EBG structure
according to the third embodiment.
[0132] The EBG structure of the third embodiment is a variation of
the EBG structure of the second embodiment, wherein parts identical
to those of the second embodiment are designated by the same
reference numerals, thus avoiding duplicate descriptions
thereof.
[0133] The EBG structure of the third embodiment shown in FIG. 11
is formed using a unit structure 203 including a first transmission
line 204A laid between the first conductive plane 1 and the second
conductive plane 2, a second transmission line 204B positioned to
face the second conductive plane 2 outside a region circumscribed
between the first conductive plane 1 and the second conductive
plane 2, a first conductive via 205A for electrically connecting
one end of the first transmission line 204A (i.e. a left-side end
in FIG. 11) to the first conductive plane 1, and a second
conductive via 205B for electrically connecting the other end of
the first transmission line 204A (i.e. a right-side end in FIG. 11)
to the second transmission line 204B.
[0134] Similar to the second embodiment, the third embodiment is
designed such that the first conductive plane 1 is attached to the
lower surface of the first dielectric layer 6 in its thickness
direction while the second conductive plane 2 is attached to the
upper surface of the second dielectric layer 7 in its thickness
direction. A third dielectric layer (i.e. a surface dielectric
layer 220) for covering the second conductive plane 2 is deposited
on the upper surface of the second dielectric layer 7. The first
transmission line 204A is aligned at the position of the
transmission line 104 used in the second embodiment (i.e. the
position between the first dielectric layer 6 and the second
dielectric layer 7), while the second transmission line 204B whose
one end is an open end is aligned on the upper surface of the
surface dielectric layer 220 in its thickness direction. The first
transmission line 204A uses the second conductive plane 2 as a
return path, wherein pads 8A and 8B which are aligned in the same
plane as the first transmission line 204A are electrically
connected to the opposite ends of the first transmission line 204A.
The second transmission line 204B uses the second conductive plane
2 as a return path, wherein one end of the second transmission line
204B is an open end, thus serving as an open stub. The other end of
the second transmission line 204B is electrically connected to the
pad 8 which is aligned in the same plane as the second transmission
line 204B.
[0135] The pad 8A attached to the first transmission line 204A is
electrically connected to the first conductive plane 1 via a first
conductive via 205A which is elongated in the thickness direction.
The pad 8B attached to the first transmission line 204A is
electrically connected to the pad 8 attached to the second
transmission line 204B via a second conductive via 205B which is
elongated in the thickness direction. The clearance 9 is arranged
for the second conductive plane 2 in connection with the second
conductive via 205B, so that the second conductive plane 2 is
electrically isolated from and is prevented from contacting the
second conductive via 205B by means of the clearance 9.
[0136] Since the first transmission line 204A laid in the
intermediate layer and the second transmission line 204B laid in
the surface layer collectively serve as an open stub in the EBG
structure of the third embodiment, it is possible to secure an
adequate transmission-line length d within a small area in
packaging.
[0137] Similar to the first and second embodiments, various
patterns can be created in terms of the arrangement and shapes of
the first and second transmission lines 204A and 204B. It is
possible to employ spiral shapes or meandering shapes, for example.
Thus, it is possible to produce the EBG structure which can be
mounted on a small area in packaging.
[0138] FIG. 11 shows the third embodiment in which both the first
and second conductive vias 205A and 205B are of a non-through-via
type, whereas it is possible to use through vias. As shown in FIG.
12, for example, it is possible to replace the second conductive
via 205B with another second conductive via 205B_X serving as a
through via. In the EBG structure shown in FIG. 12, the clearance 9
is formed at a prescribed position corresponding to the second
conductive via 205B_X in relation to the first conductive plane 1,
thus preventing the first conductive plane 1 from being
electrically connected to the second conductive plane 2. In
addition, it is possible to use a through via as the first
conductive via 205A.
4. Fourth Embodiment
[0139] Next, a waveguide structure according to a fourth embodiment
of the present invention will be described with reference to FIG.
13.
[0140] FIG. 13 is a cross-sectional view showing an EBG structure
according to the fourth embodiment.
[0141] The EBG structure of the fourth embodiment is a variation of
the EBG structure of the first embodiment, wherein parts identical
to those used in the first embodiment are designated by the same
reference numerals, thus avoiding duplicate descriptions
thereof.
[0142] In contrast to the EBG structure of the first, second, and
third embodiments in which the transmission lines 4, 104, 204A, and
204B are aligned in only the second conductive plane 2 within the
first and second conductive planes 1 and 2 and are each configured
to use the second conductive plane 2 as a return path, the fourth
embodiment is characterized in that transmission lines 304A and
304B are arranged for the first and second conductive planes 1 and
2 respectively. That is, the EBG structure of the fourth embodiment
is mirror-plane symmetrical to the EBG structure of the first
embodiment in the vertical direction. As shown in FIG. 13, it is
formed using a unit structure 303 including the first transmission
line 304A which is laid in the layer different from the layers of
the first and second conductive planes 1 and 2 and which uses the
first conductive plane 1 as a return path, the second transmission
line 304B which is laid in the layer different from the layers of
the first and second conductive planes 1 and 2 and which uses the
second conductive plane 2 as a return path, and a conductive via
305 for electrically connecting the prescribed ends of the
transmission lines 304A and 304B together.
[0143] Specifically, the fourth embodiment is designed in such a
manner similar to the first embodiment that the first conductive
plane 1 is aligned on the lower surface of the first dielectric
layer 6 in its thickness direction while the second conductive
plane 2 is inserted between the first dielectric layer 6 and the
second dielectric layer 7. A third dielectric layer (i.e. a
backside dielectric layer 320) for covering the first conductive
plane 1 is deposited on the lower surface of the first dielectric
layer 6 in its thickness direction. In addition, the first
transmission line 304A is aligned on the lower surface of the
backside dielectric layer 320 in its thickness direction, while the
second transmission line 304B is aligned on the surface of the
second dielectric layer 7 in its thickness direction. That is, the
first and second transmission lines 304A and 304B are positioned
outside the region sandwiched between the first and second
conductive planes 1 and 2.
[0144] Open ends are formed at one end of the first transmission
line 304A (i.e. a right-side end in FIG. 13) and one end of the
second transmission line 304B, so that the first and second
transmission lines 304A and 304B serve as open stubs. The pads 8
which are formed in the same planes as the first and second
transmission lines 304A and 304B are electrically connected to the
other end of the first transmission line 304A (i.e. a left-side end
in FIG. 13) and the other end of the second transmission line 304B.
The pad 8 attached to the first transmission line 304A is
electrically connected to the pad 8 attached to the second
transmission line 304B via a conductive via 305 which is elongated
in the thickness direction. The clearances 9 are formed at the
positions corresponding to the opposite ends of the conductive via
305 in the first and second conductive planes 1 and 2, which are
thus electrically isolated from each other and are not brought into
contact with each other via the clearances 9.
[0145] FIG. 14 is a circuit diagram showing an equivalent circuit
of the EBG structure of the fourth embodiment.
[0146] A repetitive unit 310 of the equivalent circuit shown in
FIG. 14 is constituted of a serial impedance 311 and a parallel
shunt 312. Similar to the first embodiment, the serial impedance
311 is composed of an inductance 13 formed between the first and
second conductive planes 1 and 2. The parallel shunt 312 is
constituted of a capacitance 314 formed between the first and
second conductive planes 1 and 2, and an inductance 315 of the
conductive via 305, as well as the first and second transmission
lines 304A and 304B. The parallel shunt 312 used in the fourth
embodiment is designed such that the open stub of the second
transmission line 304B is additionally connected in series with the
parallel shunt 12 used in the first embodiment. Similar to the
first embodiment, the fourth embodiment is characterized in that
band gaps occur in frequency bands in which the parallel shunt 312
becomes negative.
[0147] The EBG structure of the fourth embodiment is mirror-plane
symmetrical to the EBG structure of the first embodiment in the
vertical direction. Instead, it can be reconfigured in a manner
mirror-plane symmetrical to the EBG structure of the second or
third embodiment in the vertical direction.
[0148] Specifically, it is possible to create an, EBG structure
shown in FIG. 15 based on the EBG structure of the second
embodiment, wherein a third dielectric layer 120 is inserted
between the first conductive plane 1 and the first dielectric layer
6; a first transmission line 104A which uses the first conductive
plane 1 as a return path is aligned between the first dielectric
layer 6 and the third dielectric layer 120; and a second
transmission line 104B which uses the second conductive plane 2 as
a return path is aligned between the first dielectric layer 6 and
the second dielectric layer 7. Open ends are formed at one end of
the first transmission line 104A and one end of the second
transmission line 104B, while the pads 8 are electrically connected
to the other ends of the transmission lines 104A and 104B. The pads
8 attached to the first and second transmission lines 104A and 104B
are electrically connected together via a conductive via 105_X of a
non-through-via type.
[0149] It is possible to create an EBG structure shown in FIG. 16
based on the EBG structure of the third embodiment, wherein a third
dielectric layer 320A is inserted between the first conductive
plane 1 and the first dielectric layer 6, and a backside dielectric
layer 320B for covering the first conductive plane 1 is deposited
on the lower surface of the third dielectric layer 320A in its
thickness direction. In addition, a third transmission line 204C
which uses the first conductive plane 1 as a return path is laid
between the first conductive plane 1 and the first transmission
line 204A, in other words, between the first dielectric layer 6 and
the third dielectric layer 320A. Furthermore, a fourth transmission
line 204D which uses the first conductive plane 1 as a return path
is positioned to face the first conductive plane 1 outside a region
circumscribed between the first conductive plane 1 and the second
conductive plane 2, in other words, it is aligned on the lower
surface of the backside dielectric layer 320B in its thickness
direction. The pads 8A and 8B which are formed in the same plane as
the third transmission line 204C are electrically connected to the
opposite ends of the third transmission line 204C. One end of the
fourth transmission line 204D is an open end, and the pad 8 which
is formed in the same plane as the fourth transmission line 204D is
electrically connected to the other end of the fourth transmission
line 204D.
[0150] The pad 8A attached to the first transmission line 204A is
electrically connected to the pad 8A attached to the third
transmission line 204C via the first conductive via 205A which is
elongated in the thickness direction. The pad 8B attached to the
third transmission line 204C is electrically connected to the pad 8
attached to the fourth transmission line 204D via a third
conductive via 205C which is elongated in the thickness direction.
The clearance 9 is formed at a prescribed position corresponding to
the third conductive via 205C in the first conductive plane 1;
hence, the first conductive plane 1 is electrically isolated from
and is prevented from contacting the third conductive via 205C by
means of the clearance 9.
[0151] All the EBG structures shown in FIGS. 13, 15, and 16 are
designed in a mirror-plane symmetrical manner in the vertical
direction; but this is not a restriction. It is possible to create
an asymmetrical structure in which the first transmission line 304A
has a linear shape while the second transmission line 304B has a
spiral shape, for example. It is possible to make the second
dielectric layer 7 differ from the backside dielectric layer 320 in
thickness. In this case, it is noticed that the effective
dielectric constant of the first transmission line 304A should
differ from the effective dielectric constant of the second
transmission line 304B.
5. Fifth Embodiment
[0152] Next, a waveguide structure according to a fifth embodiment
of the present invention will be described with reference to FIGS.
17 and 18.
[0153] FIG. 17 is a cross-sectional view of an EBG structure
according to the fifth embodiment. FIG. 18 is a plan view of the
EBG structure, so that FIG. 17 is a cross-sectional view taken
along line B-B in FIG. 17.
[0154] The EBG structure of the fifth embodiment is a variation of
the EBG structure of the fourth embodiment, wherein parts identical
to those of the fourth embodiment are designated by the same
reference numerals, thus avoiding duplicate descriptions
thereof.
[0155] In contrast to the EBG structure of the fourth embodiment
shown in FIG. 13 in which the first transmission line 304A which
uses the first conductive plane 1 as a return path is electrically
connected to the second transmission line 304B which uses the
second conductive plane 2 as a return path via the conductive via
305, the EBG structure of the fifth embodiment shown in FIG. 17 is
designed such that the second transmission line 304B which uses the
second conductive plane 2 as a return path is electrically
connected to the first conductive plane 1 via a first conductive
via 405A, while the first transmission line 304A which uses the
first conductive plane 1 as a return path is electrically connected
to the second conductive plane 2 as a second conductive via 405B.
That is, the fifth embodiment is formed using a unit structure 403
including the first conductive via 405A for electrically connecting
the first conductive plane 1 to the second transmission line 304B,
and the second conductive via 405B for electrically connecting the
second conductive plane 2 to the first transmission line 304A.
[0156] Specifically, the fifth embodiment is designed in such a
manner similar to the fourth embodiment that the backside
dielectric layer 320 is deposited on the lower surface of the first
dielectric layer 6 in its thickness direction; the first conductive
plane 1 is inserted between the first dielectric layer 6 and the
backside dielectric layer 320; and the second conductive plane 2 is
inserted between the first dielectric layer 6 and the second
dielectric layer 7.
[0157] In addition, the first transmission line 304A is aligned on
the lower surface of the backside dielectric layer 320 in its
thickness direction, while the second transmission line 304B is
aligned on the upper surface of the second dielectric layer 7 in
its thickness direction.
[0158] The pads 8 are electrically connected to the left-side ends
of the first and second transmission lines 304A and 304B. In a plan
view, the pad 8 attached to the first transmission line 304A is
shifted in position from the pad 8 attached to the second
transmission line 304B. In addition, the pad 8 attached to the
second transmission line 304B is electrically connected to the
first conductive plane 1 via the first conductive via 405A, while
the pad 8 attached to the first transmission line 304A is
electrically connected to the second conductive plane 2. That is, a
first shunt is formed by the first transmission line 304A, the pad
8, and the second conductive via 405B, while a second shunt is
formed by the second transmission line 304B, the pad 8, and the
first conductive via 405A. In a plan view of FIG. 18, the second
shunt is formed at the position corresponding the first shunt
subjected to parallel translation by A/2+B/2=(a/2,a/2) and further
subjected to vertical inversion on the X-Y plane.
[0159] The EBG structure of the fifth embodiment makes it possible
to locate the shunts with a high density in a plan view of FIG. 18;
hence, it is possible to reduce the area of the EBG structure in
packaging.
[0160] The EBG structure of the fifth embodiment is a variation of
the EBG structure shown in FIG. 13, wherein it can be modified in a
manner similar to the EBG structure shown in FIG. 15.
[0161] Specifically, the EBG structure shown in FIG. 19 is created
based on the EBG structure shown in FIG. 15, wherein the second
transmission line 104B which uses the second conductive plane 2 as
a return path is electrically connected to the first conductive
plane 1 via a first conductive via 105A, and the first transmission
line 104A which uses the first conductive plane 1 as a return path
is electrically connected to the second conductive plane 2 via a
second conductive via 105B.
[0162] In addition, it is possible to create an asymmetrical
structure in which one of first and second transmission lines is
aligned inside the region between the first and second conductive
plane 1 and 2, and the other is aligned outside the region, wherein
the second transmission line is electrically connected to the first
conductive plane 1 via a first conductive via, and the first
transmission line is electrically connected to the second
conductive plane 2 via a second conductive via.
[0163] FIG. 18 shows the fifth embodiment including the first and
second transmission lines 304A and 304B both having linear shapes,
which can be varied in various manners similar to the foregoing
embodiments. For example, it is possible to employ spiral shapes as
shown in FIG. 20.
[0164] Both the first and second transmission lines 304A and 304B
are not necessarily formed in the same shape; hence, it is possible
to create combinations in which one transmission line has a linear
shape while another transmission line has a spiral shape, for
example.
[0165] The fifth embodiment is not necessarily applied to the
tetragonal lattice and is thus applicable to other types of
lattices as well.
6. Sixth Embodiment
[0166] Next, a sixth embodiment of the present invention will be
described with respect to a printed-circuit board with reference to
FIGS. 21 and 22.
[0167] FIG. 21 is a plan view of the printed-circuit board
according to the sixth embodiment, and FIG. 22 is a cross-sectional
view taken along line C-C in FIG. 21.
[0168] The sixth embodiment is directed to a printed-circuit board
50 incorporating the aforementioned EBG structure. Specifically,
the printed-circuit board 50 shown in FIGS. 21 and 22 includes a
ground plane 51, a power-supply plane 52, a device 53 serving as a
noise source, a device 54 sensitive to noise, and an EBG region 55
laid between the devices 53 and 54. As shown in FIG. 22, both the
device 53 serving as the noise source and the device 54 sensitive
to noise are connected to the ground plane 51 and the power-supply
plane 52. The ground plane 51 and the power-supply plane 52 form a
parallel-plate waveguide. In conventional printed-circuit boards,
noises generated by noise-source devices propagate through
parallel-plate waveguides so as to affect noise-sensitive devices,
thus causing operational errors. The printed-circuit board 50 of
the sixth embodiment shown in FIG. 21 is characterized in that the
EBG region 55 corresponding to the aforementioned EBG structure is
disposed to cut off a noise propagation path, thus suppressing
propagation of noise between the devices 53 and 54. Thus, it is
possible to reduce operational error occurring in the
noise-sensitive device 54.
[0169] The printed-circuit board 50 of FIG. 22 employs the EBG
structure of the first embodiment, which can be replaced with the
EBG structures of the other embodiments.
[0170] FIG. 21 shows that the EBG region 55 is arranged in a band
shape; however, it is possible to employ any type of arrangements
which can cut out the noise propagation path. It is possible to
arrange the EBG structure surrounding the noise-sensitive device 54
as shown in FIG. 23.
[0171] The sixth embodiment is directed to the EBG structure
installed in the printed-circuit board 50; but this is not a
restriction. It is possible to install the aforementioned EBG
structure in package substrates of devices or the like.
7. Seventh Embodiment
[0172] Next, a printed-circuit board according to a seventh
embodiment of the present invention will be described with
reference to FIG. 24.
[0173] FIG. 24 is a plan view of the printed-circuit board 50
according to the seventh embodiment, wherein parts identical to
those of the sixth embodiment are designated by the same reference
numerals, thus avoiding duplicate descriptions thereof.
[0174] The printed-circuit board 50 of the seventh embodiment
includes a plurality of waveguide structures using open-end
transmission lines having different lengths, wherein these
waveguide structures are shifted in terms of band gaps.
[0175] Similar to the sixth embodiment, the printed-circuit board
50 of the seventh embodiment includes the ground plane 51, the
power-supply plane 52, the device 53 serving as a noise source, and
the noise-sensitive device 54. The seventh embodiment is
characterized in that a first EBG structure 56 and a second EBG
structure 57 are formed in the EBG region for cutting off the noise
propagation path, thus suppressing propagation of noise between the
devices 53 and 54. Herein, the first EBG structure 56 and the
second EBG structure 57 are aligned in parallel in the noise
propagation direction. The first EBG structure 56 and the second
EBG structure 57 use respective open-stub transmission lines of
different lengths so that they differ from each other in terms of
frequency bands of band gaps. The lengths of transmission lines are
set in such a way that band gaps cause by the first EBG structure
56 are deviated from band gaps caused by the second EBG structure
57; thus, it is possible to achieve "broad" band gaps, which cannot
be obtained by a single EBG structure, by way of the EBG region
55.
[0176] FIG. 25 shows a first variation of the seventh embodiment in
which first EBG structures 156 and second EBG structures 157 are
alternately aligned in a stripe manner in the noise propagation
direction.
[0177] FIG. 26 shows a second variation of the seventh embodiment
in which the first EBG structures 156 and the second EBG structures
157 in a checkered pattern (or in checkers).
[0178] Both variations of the seventh embodiment achieve broad band
gaps with the EBG region 55.
[0179] In this connection, it is possible to employ other types of
arrangements in which the first and second EBG structures are
intermixed together. Band gaps can be further enlarged by
intermixing various types of EBG structures with deviated band
gaps.
8. Eighth Embodiment
[0180] Next, an antenna according to an eighth embodiment of the
present invention will be described.
[0181] FIG. 29 is a perspective view showing the antenna according
to the eighth embodiment of the present invention. FIG. 30 is a
plan view of the antenna viewed in an Z-axis direction. FIG. 31 a
plan view of the antenna through a conductive patch viewed in the
Z-axis direction. FIG. 32 is a plan view of a conductive plane
included in the antenna. FIG. 33 is a cross-sectional view taken
along line A-A in FIGS. 30 and 31. FIG. 34 is a cross-sectional
view taken along line B-B in FIGS. 30 and 31.
[0182] As shown in FIG. 33, the antenna of the eight embodiment is
constituted of a conductive plane (or a first conductive plane)
1001, a first dielectric layer 1002 disposed on the conductive
plane 1001, a second dielectric layer 1003 disposed on the first
dielectric layer 1002, and a conductive patch (or a second
conductive plane) 1004 disposed on the second dielectric layer
1003. The conductive patch 1004 is positioned in parallel with the
conductive plane 1001. As shown in FIG. 30, the conductive patch
1004 is smaller than the conductive plane 1001 such that the
conductive patch 1004 is positioned to completely overlap with the
conductive plane 1001 in plan view.
[0183] A transmission line 1006 which uses the conductive patch
1004 as a return path is aligned on a prescribed plane positioned
to face the conductive patch 1004 in the layer sandwiched between
the first dielectric layer 1002 and the second dielectric layer
1003. As shown in FIGS. 31 and 33, one end of the transmission line
1006 is electrically connected to the conductive plane 1001 via a
conductive via 1005, while the other end of the transmission line
1006 is an open end, thus achieving the function of an open
stub.
[0184] In the eight embodiment, the conductive via 1005 and the
transmission line 1006 serve as a shunt. The antenna according to
the present invention employs a structure including a plurality of
shunts aligned in the conductive patch 1004. The eight embodiment
refers to a basic structure in which a tetragonal lattice is
aligned with a lattice spacing "a", wherein 4.times.4 shunts are
aligned in the antenna of the eight embodiment shown in FIG.
29.
[0185] The antenna of the eighth embodiment serves as a patch
antenna when electric excitation occurs between the conductive
plane 1001 and the conductive patch 1004. As shown in FIGS. 32 and
34, a power-supply via 1007 is arranged as a power-supply unit
securing signal transmission between the conductive plane 1001 and
the conductive patch 1004. The power-supply via 1007 supplies
high-frequency signals. One end of the power-supply via 1007 is
connected to the conductive patch 1004, while the other end thereof
is electrically insulated from the conductive plane 1001 by means
of a power-supply clearance 1008 arranged for the conductive plane
1001. The other end of the power-supply via 1007 and the
power-supply clearance 1008 form an input port for signals, wherein
a signal input unit such as a coaxial cable is connected to the
backside of the conductive plane 1001 so as to supply signals of a
wireless communication circuit (not shown) to the antenna, for
example. As the signal input unit other than the coaxial cable, it
is possible to name a microstrip line or a strip line formed on the
backside of the conductive plane.
[0186] Since the external periphery of the conductive patch 1004
has a high impedance, it is difficult to establish impedance
matching with the power-supply system. Since the eighth embodiment
can be freely designed in terms of the position of the power-supply
via 1007 without interference with the shunt(s), it is possible to
set the power-supply via 1007 to the position establishing
impedance matching with the power-supply system for the conductive
patch 1004. For the sake of convenience, FIGS. 20, 30, and 31 are
illustrated in a perspective manner through the first dielectric
layer 1002 and the second dielectric layer 1003.
[0187] Next, a basic principle for reducing the size of the antenna
will be described.
[0188] Similar to conventional patch antennas, the antenna of the
present invention serve as a resonator causing a half-wavelength
resonation in the X-axis direction of the conductive patch. In
general, the relationship between the wavelength and the frequency
in a resonator depends upon the dispersion characteristics of media
inside a resonator. The dispersion characteristics regarding a
dielectric constant .di-elect cons. and a relative permeability
.mu. in a dielectric substance is given by equation (3), where "c"
denotes speed of light in a vacuum state. Equation (3) shows that
an angular frequency .omega. (2.pi.f) is proportional to a wave
number k (=2.pi./.lamda.).
.omega. = c .mu. k ( 3 ) ##EQU00003##
[0189] The antenna of the present invention is designed to
repetitively align shunts in the conductive patch so as to serve as
a right-handed meta-material structure, thus effectively
controlling the dispersion characteristics of the conductive
patch.
[0190] FIG. 35 shows an equivalent circuit regarding propagation of
electromagnetic waves in the space circumscribed by the conductive
plane 1001 and the conductive patch 1004 of the antenna of FIG. 29
in the X-axis direction. A dotted-line region in FIG. 35 designates
an equivalent circuit of a square-shaped unit structure with
one-side length "a". In FIG. 35, C.sub.PPW and L.sub.PPW designate
a capacitance and an inductance in a parallel-plate unit structure
composed of the conductive plane 1001 and the conductive patch
1004. L.sub.via designates an inductance of the conductive via
1005. An open stub corresponds to the transmission line 1006.
[0191] According to the meta-material structure used in the antenna
of the present invention, an admittance Y including C.sub.PPW,
L.sub.via, and the open stub as defined in equation (4) serves as a
right-handed media in a frequency range indicating the capacitive
property (where Im(Y)>0), while it serves as a electromagnetic
band gap in a frequency range indicating the inductive property
(where Im(Y)<0). Herein, Z.sub.in denotes an input impedance of
the open stub defined by equation (5). In equation (5), Z.sub.0
denotes a characteristic impedance of the transmission line 1006
(i.e. the open stub in FIG. 35); d denotes the length of the
transmission line 1006; and .di-elect cons..sub.eff denotes an
effective dielectric constant.
Y = 1 Z in + .omega. L via + .omega. C PPW ( 4 ) Z in = - Z 0 tan (
.omega. eff c d ) ( 5 ) ##EQU00004##
[0192] The dispersion characteristics of a repetitive structure is
produced by applying a repetitive boundary condition to the
equivalent circuit of the unit structure shown in FIG. 35. FIG. 36
shows an example of the dispersion characteristics which is
produced using prescribed dimensions of the antenna of FIG. 29 such
as a=3 mm, t=800 .mu.m, h=60 .mu.m, w=100 .mu.m, b=300 .mu.m, and
d=5.4 mm, as well as the dielectric constant of .di-elect
cons.=4.188 and the relative permeability of .mu.=1 in the first
dielectric layer 1002 and the second dielectric layer 1003. In FIG.
36, the horizontal axis represents the wave number, and the
vertical axis represents the frequency. FIG. 36 clearly shows that
the dispersion characteristics regarding the antenna of the present
invention pass through the origin and does not have a cutoff in the
low frequency range. It also shows that bands and band gaps
alternately emerge in the order of a first band, a first band gap,
a second band, and a second band gap in the low frequency range.
This is because the capacitive property (where Im(Y)>0) and the
inductive property (where Im(Y)<0) periodically changes over
with respect to the admittance Y due to the impedance conversion
effect of the open stub.
[0193] In general, the condition for causing a half-wavelength
resonation in a resonator having a length L is given by equation
(6) where "n" denotes an integral number.
k = n .pi. L ( 6 ) ##EQU00005##
[0194] In an N.times.N alignment of shunts (where N denotes an
integral number) in the antenna of the present invention, the
length L of the conductive patch 1004 in the X-axis direction is
given by L=N.times.a, which is substituted for equation (6) so as
to produce a resonance condition of the antenna of the present
invention defined in equation (7).
k = n .pi. Na ( where n = 0 , 1 , , N - 1 ) ( 7 ) ##EQU00006##
[0195] Vertical lines in the graph of FIG. 36 indicate wave numbers
satisfying the resonance condition with respect to the antenna of
FIG. 29 where N=4, and a=3 mm. Intersecting points between the
vertical lines and the dispersion characteristics in FIG. 36
indicate half-wavelength resonance frequencies. FIG. 36 shows that
resonance points corresponding to n=0, 1, 2, and 3 emerge in the
first and second bands. Resonance antennas such as patch antennas
are normally designed to use a first resonance. The antenna of the
present invention may serve as a multi-band antenna, since it is
varied in terms of the first resonance in connection with different
bands.
[0196] A straight line passing through the origin in FIG. 36
indicates a "dielectric" dispersion characteristics regarding only
a dielectric media having a dielectric constant of .di-elect
cons.=4.188. The resonance frequency of a conventional patch
antenna corresponding to the antenna of FIG. 29 excluding shunts is
given by intersecting points of the dielectric dispersion
characteristics crossing the vertical lines in FIG. 36. FIG. 36
shows that the first resonance of the first band occurs around 3
GHz in the antenna of the present invention compared to the
conventional patch antenna in which the first resonance occurs
around 6 GHz. This indicates that the wavelength of electromagnetic
waves is reduced to approximately a half of the wavelength during
propagation in a dielectric substance by way of the meta-material
structure of the antenna of the present invention. This proves that
the size of the antenna of FIG. 29 is reduced to a half the size of
the conventional patch antenna.
[0197] Since such a wavelength reduction effect of the
meta-material structure occurs at all the resonance points below
the straight line representing the dielectric dispersion
characteristics in FIG. 36, it is possible to achieve a small-size
antenna by use of the second and third resonances of the first
band, or the third resonance of the second band, for example.
[0198] Since the wavelength becomes longer at the resonance points
above the straight line of the dielectric dispersion
characteristics rather than the propagation in the dielectric
substance, it is possible to enhance an emission efficiency by
enlarging the size of the antenna. FIG. 37 shows the result of
three-dimensional electromagnetic analysis with respect to the
antenna of FIG. 29. In FIG. 37, the horizontal axis represents the
frequency, and the vertical axis represents the S parameter (S11)
in view of the input port of the power-supply unit. FIG. 37 shows
that dips occur at prescribed frequencies substantially suiting to
the dispersion characteristics of FIG. 36, thus proving that the
antenna operates at desired frequencies according to
calculations.
[0199] FIG. 38 shows the result of electromagnetic analysis
regarding the emission directivity at 3.42 GHz which is the first
resonance frequency of the first band, and FIG. 39 shows the result
of electromagnetic analysis regarding the emission directivity at
8.86 GHz which is the first resonance frequency of the second band.
In FIGS. 38 and 39, radius directions represent the gain of the
antenna (dBi); dotted curves represent the emission directivity in
the X-Z plane; and solid curves represent the emission directivity
in the Y-Z plane. FIGS. 38 and 39 show that, similar to the
conventional patch antenna, the antenna of the present invention
demonstrate good emission characteristics in the Z-axis
direction.
[0200] As the admittance Y of the meta-material structure applied
to the antenna of the present invention is given by equations (4)
and (5), it is possible to bring resonance frequencies into desired
operating ranges by appropriately setting parameters in these
equations. Due to a high degree of freedom of the transmission-line
length d, it is possible to easily control the operating range of
the antenna by changing the transmission-line length d.
[0201] The meta-material structure of the antenna of the present
invention possesses right-handed dispersion curves in which all the
bands are included in the positive direction. In particular, the
first band possesses an ascending curve passing through the origin
so that no cutoff exists in the low frequency range lower than the
first band gap. In contrast to the left-handed meta-material
structure of Patent Document 3 in which cutoffs should occur in the
low frequency range, it is possible to easily lower the frequency
range with respect to the antenna of the present invention.
[0202] FIG. 29 shows the 4.times.4 alignment of shunts, whereas the
antenna of the present invention does not necessarily require an
symmetrical alignment of shunts in the X-axis and Y-axis directions
since it exploits the half-wavelength resonance in the X-axis
direction. It is possible to employ a 4.times.2 alignment shown in
FIG. 40 or a 4.times.1 alignment shown in FIG. 41, for example.
These alignments offer "isotropic" dispersion of media in which
unwanted resonance does not occur in the Y-axis direction, thus
achieving a highly stabilized operation compared to the symmetrical
alignment.
[0203] It is possible to create a structure of FIG. 42 in which
only one shunt is disposed in the conductive patch 1004. The
conductive loss of the transmission line 1006 and the dielectric
loss of the surrounding dielectric substance are not negligible
elements in the antenna of the present invention. The
aforementioned alignments shown in FIGS. 40, 41, and 42 are
designed to reduce the number of shunts, thus reducing the
conductive loss and dielectric loss. Thus, it is possible to
improve an emission efficiency of the antenna.
[0204] Any shapes are applied to the transmission line 1006 without
affecting the essential characteristics of the present invention as
long as one end of the transmission line 1006 is connected to the
conductive via 1005 while the other end thereof is an open end.
FIG. 29 shows the spiral-shaped transmission line 1006, whereas it
is possible to employ a linear shape for the transmission line 1006
as shown in FIG. 43. It is possible to employ other shapes such as
a meandering shape with respect to the transmission line 1006.
[0205] The transmission lines 1006 are not necessarily formed in
the same arrangement and shape in all the unit structures. For
example, it is possible to arrange a spiral-shaped transmission
line in one unit while arranging a linear transmission line in
another unit.
[0206] It is possible to create a ramification in which the
transmission line 1006 is branched away into transmission lines
1006A and 1006B having open ends. In the case of a single
transmission line whose length is determined so as to set the first
band or the first band gap to a desired frequency band, the
frequency bands of the second band and its following bands should
be automatically determined based on equations (4) and (5). In the
case of FIG. 44, the transmission lines 1006A and 1006B have
different impedance conversion periods so as to set the first and
second bands independently, thus achieving a high degree of freedom
in setting frequency bands.
[0207] In this connection, the branching point between the
transmission lines 1006A and 1006B is not necessarily disposed in
proximity to the conductive via 1005; hence, it is possible to
create the structure in which the transmission line 1006B is
branched away from an intermediate portion of the transmission line
1006B.
[0208] Although the eighth embodiment shows the square-shaped
conductive patch 1004, any shapes are applied to the conductive
patch 1004 without affecting the essential characteristics of the
present invention. It is possible to create the structure of FIG.
45 in which the conductive patch 1004 is formed in a rectangular
shape, for example.
[0209] FIG. 33 shows that the conductive via 1005 is a
non-through-type via; but this is not a restriction as long as the
transmission line 1006 is electrically connected to the conductive
plane 1001. For example, it is possible to employ the structure of
FIG. 46 using a through via as the conductive via 1005 without
affecting the essential characteristics of the present invention.
For the purpose of electric insulation secured between the
conductive patch 1004 and the through-via-type conductive via 1005,
it is necessary to form a clearance 1010 at the position of the
conductive via 1005 in the conductive patch 1004. Employing the
through via makes it possible to collectively process the
conductive vias 1005 by use of drills after the lamination of a
substrate, thus reducing the manufacturing cost.
9. Ninth Embodiment
[0210] Next, a ninth embodiment of the present invention will be
described with reference to FIGS. 47 to 51, wherein parts identical
to those of the eighth embodiment are designated by the same
reference numerals. FIG. 47 is a plan view showing an antenna
according to the ninth embodiment viewed in the Z-axis direction.
FIG. 48 is a plan view of the antenna excluding the transmission
lines 1006 viewed in the Z-axis direction. FIG. 49 is a plan view
of the conductive plane 1001. FIG. 50 is a cross-sectional view
taken along line A-A in FIGS. 47 to 49. FIG. 51 is a
cross-sectional view taken along line B-B in FIGS. 47 to 49.
[0211] The antenna of the ninth embodiment is created by partially
changing the layered structure of the antenna of the eight
embodiment.
[0212] As shown in FIG. 50, the antenna of the ninth embodiment is
constituted of the conductive plane 1001, the first dielectric
layer 1002 deposited on the conductive plane 1001, and the second
dielectric layer 1003 deposited on the first dielectric layer 1002,
wherein the conductive patch 1004 composed of a metal is disposed
in a layer sandwiched between the first dielectric layer 1002 and
the second dielectric layer 1003. In addition, the transmission
line 1006 which uses the conductive patch 1004 as a return path is
aligned on the second dielectric layer 1003 in a plane so as to
face the conductive patch 1004. As shown in FIGS. 47 and 50, one
end of the transmission line 1006 is electrically connected to the
conductive plane 1001 via the conductive via 1005, while the other
end thereof is an open end, thus achieving the function of an open
stub. As shown in FIGS. 48 and 50, the clearance 1009 is formed at
the position of the conductive via 1005 in the conductive patch
1004, which is electrically insulated from the conductive via 1005.
In the ninth embodiment, the conductive via 1005, the transmission
line 1006, and the clearance 1009 serve as a shunt. The ninth
embodiment is similar to the eighth embodiment in terms of the
arrangement of the shunt and the shape of the transmission line
1006. The ninth embodiment is equipped with the power-supply via
1007 as a power-supply unit. As shown in FIGS. 49 and 51, one end
of the power-supply via 1007 is connected to the conductive patch
1004, while the other end thereof is electrically insulated from
the conductive plane 1001 by means of the power-supply clearance
1008 formed in the conductive plane 1001. The power-supply via 1007
and the power-supply clearance 1008 serve as an input port of
signals.
[0213] The operating principle of the ninth embodiment is identical
to that of the eighth embodiment. The dielectric loss of a
dielectric substance surrounding the transmission line 1006 is not
a negligible element in the antenna of the present invention,
wherein the ninth embodiment is designed to further reduce the
dielectric loss in comparison with the eight embodiment because the
transmission line 1006 is surrounded by air. Thus, it is possible
to improve the emission efficiency of the antenna.
10. Tenth Embodiment
[0214] Next, a tenth embodiment of the present invention will be
described. FIG. 52 is a cross-sectional view showing an antenna
according to the tenth embodiment of the present invention viewed
in a X-Z plane including the conductive via 1005.
[0215] As shown in FIG. 52, the tenth embodiment is designed to
partially modify the eight embodiment in such a way that one end of
the transmission line 1006 is connected to the conductive patch
1004 by means of the conductive via 1005. In the tenth embodiment,
the transmission line 1006 is aligned in a plane to face the
conductive plane 1001 so as to serve as an open stub which uses the
conductive plane 1001 as a return path. The equivalent circuit of
the tenth embodiment is identical to the equivalent circuit shown
in FIG. 35; hence, the operating principle of the tenth embodiment
is identical to that of the eighth embodiment. In addition, the
tenth embodiment is identical to the eighth embodiment in terms of
the layered structure, the arrangement of the shunt, the shape of
the transmission line 1006, and the structure of the power-supply
unit. FIG. 52 shows that the conductive via 1005 is a
non-through-type via, whereas similar to the eighth embodiment, it
is possible to use a through via.
11. Eleventh Embodiment
[0216] Next, an eleventh embodiment of the present invention will
be described. FIG. 53 is a cross-sectional view showing an antenna
according to the eleventh embodiment in the X-Z plane including the
conductive via 1005.
[0217] As shown in FIG. 53, the antenna of the eleventh embodiment
is constituted of the conductive plane 1001, the first dielectric
layer 1002 deposited under the conductive plane 1001, and the
second dielectric layer 1003 deposited on the conductive plane
1001. The transmission line 1006 which uses the conductive plane
1001 as a return path is aligned under the first dielectric layer
1002 in a plane to face the conductive plane 1001. In addition, the
conductive patch 1004 composed of a metal is disposed on the second
dielectric layer 1003. One end of the transmission line 1006 is
electrically connected to the conductive patch 1004 by means of the
conductive via 1005, while the other end thereof is an open end,
thus serving as an open stub. A clearance 1011 is formed at the
position of the conductive via 1005 in the conductive plane 1001,
which is electrically insulated from the conductive via 1005. In
the eleventh embodiment, the conductive via 1005, the transmission
line 1006, and the clearance 1011 serve as a shunt. The eleventh
embodiment is identical to the eight embodiment in terms of the
arrangement of the shunt, the shape of the transmission line 1006,
and the structure of the power-supply unit.
[0218] The operating principle of the eleventh embodiment is
identical to that of the eighth embodiment. The dielectric loss of
a dielectric substance surrounding the transmission line 1006 is
not a negligible element in the antenna of the present embodiment,
wherein the eleventh embodiment is designed to further reduce the
dielectric loss in comparison with the eighth embodiment because
the transmission line 1006 is surrounded by air. Thus, it is
possible to improve the emission efficiency of the antenna.
12. Twelfth Embodiment
[0219] Next, a twelfth embodiment of the present invention will be
described. FIG. 54 is a cross-sectional view showing an antenna
according to the twelfth embodiment of the present invention in the
X-Z plane including the conductive via 1005.
[0220] As shown in FIG. 54, the antenna of the twelfth embodiment
is constituted of the conductive plane 1001 as well as the first
dielectric layer 1002, the second dielectric layer 1003, and a
third dielectric layer 1015 which are sequentially deposited on the
conductive plane 1001. The conductive patch 1004 composed of a
metal is disposed in the layer sandwiched between the second
dielectric layer 1003 and the third dielectric layer 1015. In
addition, a first transmission line 1006A which uses the conductive
patch 1004 as a return path is deposited in the layer sandwiched
between the first dielectric layer 1002 and the second dielectric
layer 1003 in the plane to face the conducive patch 1004.
Furthermore, a second transmission line 1006B which uses the
conductive patch 1004 as a return path and whose length differs
from the length of the first transmission line 1006A is disposed on
the third dielectric layer 1015. First ends of the transmission
lines 1006A and 1006B are electrically connected to the conductive
plane 1001 by means of the conductive via 1005, while second ends
thereof are open ends, thus serving as open stubs. As shown in FIG.
54, the clearance 1009 is formed at the position of the conductive
via 1005 in the conductive patch 1004, which is electrically
insulated from the conductive via 1005. In the twelfth embodiment,
the conductive via 1005, the transmission lines 1006A and 1006B,
and the clearance 1009 serve as a shunt.
[0221] The twelfth embodiment is identical to the eighth embodiment
in terms of the arrangement of the shunt, the shape of the
transmission line, and the structure of the power-supply unit. The
operating principle of the twelfth embodiment is identical to that
of the eighth embodiment.
[0222] In the case of a single transmission line whose length is
determined so as to set the first band or the first band gap to a
desired frequency range, the second band and its following bands
should be automatically determined based on equations (4) and (5).
In contrast, it is possible to set the first and second bands
independently in the twelfth embodiment due to different impedance
conversion periods applied to the transmission lines 1006A and
1006B, thus securing a high degree of freedom in setting frequency
bands.
13. Thirteenth Embodiment
[0223] Next, a thirteenth embodiment of the present invention will
be described. FIGS. 55 and 56 are perspective views showing an
antenna according to the thirteenth embodiment of the present
invention. The antenna of the eighth embodiment is designed such
that the power-supply via 1007 serves as the power-supply unit for
the conductive patch 1004, and an input port of signals is formed
by use of the power-supply via 1007 and the power-supply clearance
1008 disposed in the conductive plane 1001. As the power-supply
method applied to this structure, it is possible to name the method
for directly connecting a coaxial cable to the backside of the
conductive plane 1001 and the method in which a microstrip line or
a strip line serving as a power-supply line is formed on the
backside of the conductive plane 1001 and is connected to the
backside of the conductive plane 1001. The method using the coaxial
cable suffers from an enlargement of size and is not suited to the
purpose of the present invention for reducing the size of an
antenna. The method using the power-supply line formed on the
backside of the conductive plane 1001 should increase the number of
layers, which in turn leads to the complexity of the overall
structure.
[0224] As shown in FIG. 55, the thirteenth embodiment is designed
to partially modify the eighth embodiment in such a way that the
power-supply unit is formed using a microstrip line 1020 formed in
the same plane as the conductive patch 1004. The microstrip line
1020 is connected to the external periphery of the conductive patch
1004 so as to receive signals from a wireless communication circuit
(not shown) by means of the antenna. It is difficult to establish
impedance matching between the power-supply unit and the external
periphery of the conductive patch having high impedance. As shown
in FIG. 56, a rectangular cutout 1021, which may be similarly used
in the conventional patch antenna, is formed in the conductive
patch 1004 so as to locate the microstrip line 1020 in the external
periphery of the conductive patch 1004 subjected to impedance
matching with the power-supply unit. That is, the thirteenth
embodiment is designed to reduce the size of the antenna and to
secure a power-supply operation with a simple structure.
14. Fourteenth Embodiment
[0225] Next, a fourteenth embodiment of the present invention will
be described. FIG. 57 is a plan view of the conductive plane 1001
included in an antenna according to the fourteenth embodiment of
the present invention. The fourteenth embodiment is designed to
partially modify the eighth embodiment in such a way that the
power-supply unit is formed using a coplanar line 1022 formed in
connection with the conductive plane 1001 and the power-supply via
1007. The coplanar line 1022 is connected to the power-supply via
1007 so as to receive signals from a wireless communication circuit
(not shown) by means of the antenna. The fourteenth embodiment is
designed to reduce the size of the antenna and to secure a
power-supply operation with a simple structure.
15. Fifteenth Embodiment
[0226] Next, a fifteenth embodiment of the present invention will
be described. FIG. 58 is a plan view of an antenna according to the
fifteenth embodiment of the present invention. As shown in FIG. 58,
the fifteenth embodiment is directed to an array antenna in which a
plurality of array elements 1030 is aligned on a printed-circuit
board 1031. This array antenna achieves a beam-shaped directivity
so as to increase a gain in a beaming direction. FIG. 58 shows that
four array elements 1030 each corresponding to the antenna of the
thirteenth embodiment are aligned in parallel and are supplied with
electric power by way of the microstrip line 1020. It is possible
to use antennas of the other embodiments as the array elements
1030. Increasing the number of array elements 1030 sharpens beams
and increases a gain in a beaming direction.
[0227] The antennas of the present invention are designed to
repetitively align shunts including open stubs and conductive vias
so as to effectively control dispersion characteristics of media,
wherein dispersion characteristics of media are set to shorten
wavelengths to be shorter than wavelengths of conventional
dielectric substances, thus markedly reducing the sizes of
antennas. The repetitive structures of the present invention serve
as right-handed media so as to eliminate cutoff frequencies, thus
easily lowering frequency bands.
[0228] In this connection, it is possible to arbitrarily combine
the foregoing embodiments or to increase or decrease the number of
parts in the foregoing embodiments. In addition, it is possible to
provide electronic devices equipped with the aforementioned
printed-circuit boards and/or the aforementioned antennas.
[0229] Lastly, it is apparent that the present invention is not
limited to the above embodiments, but may be modified and changed
without departing from the scope and spirit of the invention.
* * * * *