U.S. patent application number 12/273187 was filed with the patent office on 2009-06-04 for slot antenna for mm-wave signals.
This patent application is currently assigned to Sony Corporation. Invention is credited to Mohamed RATNI.
Application Number | 20090140943 12/273187 |
Document ID | / |
Family ID | 39327003 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090140943 |
Kind Code |
A1 |
RATNI; Mohamed |
June 4, 2009 |
SLOT ANTENNA FOR MM-WAVE SIGNALS
Abstract
The present invention relates to an antenna (1) for radiating/or
receiving mm-wave signals, comprising a substrate (2), a planar
conducting layer (3) formed on said substrate (2), and a radiation
element (4) being formed as a slot in said planar conducting layer
(3), said slot comprising a middle part (4a) and two outer parts
(4b) being connected by said middle part (4a) and extending away
from said middle part (4a), said antenna further comprising a
feeding structure (5) adapting to feed signals to said middle part
(4a) of said slot. The antenna provides a low-cost structure with a
high gain.
Inventors: |
RATNI; Mohamed; (Esslingen,
DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Sony Corporation
Tokyo
JP
|
Family ID: |
39327003 |
Appl. No.: |
12/273187 |
Filed: |
November 18, 2008 |
Current U.S.
Class: |
343/767 |
Current CPC
Class: |
H01Q 13/106 20130101;
H01Q 1/007 20130101; H01Q 21/28 20130101; H01Q 13/16 20130101; H01Q
3/30 20130101; H01Q 21/064 20130101; H01Q 3/24 20130101; H01Q
21/205 20130101; H01Q 25/00 20130101 |
Class at
Publication: |
343/767 |
International
Class: |
H01Q 13/10 20060101
H01Q013/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2007 |
EP |
07 122 149.3 |
Claims
1. Antenna (1) for radiating and/or receiving mm-wave signals,
comprising a substrate (2), a planar conducting layer (3) formed on
said substrate (2), and a radiation element (4) being formed as a
slot in said planar conducting layer (3), said slot comprising a
middle part (4a) and two outer parts (4b) being connected by said
middle part (4a) and extending away from said middle part (4a),
said antenna (1) further comprising a feeding structure (5) adapted
to feed signals to said middle part (4a) of said slot.
2. Antenna (1) according to claim 1, wherein said two outer parts
(4b) are parallel to each other.
3. Antenna (1) according to claim 1, wherein said middle part (4a)
and said two outer parts (4b) have a U-shape.
4. Antenna (1) according to claim 1, wherein the width (w1) of each
of the two outer parts (4b) increases in a direction away from said
middle part (4a).
5. Antenna (1) according to claim 1, wherein the width of each of
the two outer parts (4b) is constant.
6. Antenna (1) according to claim 1, wherein both outer parts (4b)
have the same length (l2) and width (w1).
7. Antenna (1) according to claim 1, wherein the width (w1) of each
of the two outer parts is more than two times the width (w2) of
said middle part (4a).
8. Antenna (1) according to claims 1, wherein the distance (13)
between the two outer parts (4a) is larger than the width (w1) of
each of the two outer parts (4b).
9. Antenna (1) according to claim 1, wherein each of the two outer
parts (4b) is longer than wide.
10. Antenna (1) according to claim 1, wherein said feeding
structure (5) is a microstrip feeding line arranged on a side of
said substrate (2) opposite to the planar conducting layer (3).
11. Antenna (1) according to claim 1, wherein said planar
conducting layer (3) and said feeding structure (5) are printed
elements.
12. Antenna (1) according to claim 1, wherein said slot is adapted
to radiate signals with linear polarization.
13. Antenna (1) according to claim 1, having a reflector plane (6)
arranged in a predefined distance from a side of said substrate (2)
opposite to the planar conducting layer (3).
14. Antenna (1) according to claims 1, wherein the length and width
dimensions of the planar conducting layer (9) are in the range of
half of the wavelength.
15. Antenna array (10) comprising a plurality of antennas (1)
according to claim 1 having a common substrate (7), said antenna
array (10) being steerable.
16. Antenna array (10) according to claim 15, comprising beam
steering elements (9) adapted to change the radiation direction of
the each of the antennas (1).
17. Antenna array (10) according to claim 15, wherein the beam
steering elements (9) comprise phase shifters adapted to shift the
signal phase for each antenna (1).
Description
[0001] The present invention relates to a slot antenna for
radiating and/or receiving mm-wave signals. Specifically, the
present invention relates to a slot antenna which is adapted to
transmit and/or receive electromagnetic signals in a wireless
communication system operating in a high-frequency range, such as
the GHz frequency range or the mm wavelength range and is suited
for high data rate communication.
[0002] The object of the invention is hereby to propose such a slot
antenna for radiating and/or receiving mm-wave signals which has a
simple structure and can therefore be produced at low-cost while
still being adapted to be used in a high frequency bandwidth and
for high data rate applications.
[0003] The above object is achieved by an antenna for radiating
and/or receiving mm-wave signals as defined in the enclosed
independent claim 1. The antenna according to the present invention
comprises a substrate, a planar contacting layer formed on said
substrate and a radiation element being formed as a slot in said
planar contacting layer, said slot comprising a middle part and two
outer parts being connected by said middle part and extending away
from said middle part, said antenna further comprising a feeding
structure adapted to feed signals to the middle part of said
slot.
[0004] The antenna of the present invention therefore has a simple
structure and can be manufactured at low-cost while still providing
a very good performance for high data rate applications in high
frequency bandwidth.
[0005] It is to be understood that the antenna of the present
invention could be used as a pure receiving antenna or a pure
radiating/transmitting antenna, or could be used in applications in
which electromagnetic signals are radiated from as well as received
by the antenna.
[0006] The antenna of the present invention is particularly
suitable for high frequency bandwidth applications, i.e.
applications in the GHz frequency range, such as a frequency range
between 20 and 120 GHz. These frequency ranges typically enable
high data rate applications since they provide a large frequency
bandwidth availability. It would, however, also be possible to use
the antenna of the present invention in different frequency ranges
and bandwidths depending on the wanted application.
[0007] Hereby, by varying the measures of the antenna of the
present invention, such as the width and the length and the
proportions of the different elements of the present antenna, a
specific adaptation to the respectively required frequency range
and bandwidth can be achieved. Also, the simple structure and
low-cost solution of the antenna of the present invention makes the
antenna specifically useful for consumer electronic applications.
However, the antenna of the present invention can also be used in
other applications if wanted and/or necessary.
[0008] Advantageous sub features of the present invention are
defined in the dependent claims.
[0009] Advantageously, two outer parts of the slot are parallel to
each other. Further advantageously, the middle part and the two
outer parts form a U together. In other words, the slot has a
U-shape. Such a shape is advantageous as it leads to the radiation
of electromagnetic signals with linear polarization. Signals with
linear polarization are advantageous for indoor applications,
specifically for indoor with line of sight and also for non line of
sight signals. Such an antenna shape, however, may also be
advantageous in selected outdoor applications. The U-shape of the
slot leads to a quite large frequency bandwidth around the
operation frequency of about 10 percent. For example, in case that
the operation frequency is around 60 GHz the achieved frequency
bandwidth is around 6 GHz with such a shape. Further
advantageously, the width of each of the two outer parts of the
slot increases in the direction away from the middle part. By such
a tapering of the two outer parts, the antenna impedance can be
reduced and matched to the impedance of the feeding structure,
which is typically 50 Ohm.
[0010] Alternatively, the width of each of the two outer parts of
the slot can remain constant, i.e. untapered.
[0011] Further advantageously, both outer parts of the slot have
the same length and width. In other words, the two outer parts
could be mirror-symmetric in relation to a symmetry axis extending
between the two outer parts and perpendicular to the middle part of
the slot. Further advantageously, the width of each of the two
outer parts of the slot is more than two times of the width of the
middle part. Further advantageously, the distance between the two
outer parts, i.e. the length of the middle part, is larger than the
width of each of the two outer parts. Further advantageously, each
of the two outer parts is longer than wide.
[0012] Further advantageously, the feeding structure is a
microstrip feeding line arranged on a side of said substrate
opposite to the planar conducting layer. Hereby, the decoupling of
the feeding structure from the radiation element has the advantage
of suppressing side lobes in the antenna characteristics as
compared to structures in which the feeding structure is placed in
the same layer as the radiation element. Thus, in the antenna of
the present invention, only the shape of the radiation slots
determines the antenna radiation pattern, since the side lobe
radiation is greatly reduced and therefore the axial ratio of the
radiation pattern is greatly decreased, so that the antenna of the
present invention is particularly advantageous to be used in an
array antenna in which a high gain can be realized and in which the
radiation beam can be steered.
[0013] Further advantageously, the planar conducting layer and/or
the feeding structure are printed elements. By printing the planar
conducting layer, for example a copper layer, onto a single layer
substrate, the slot can be simply etched with simple etching
technology, so that a low-cost structure is achieved. If
additionally a simple 50 Ohm microstrip feeding line is printed
onto the opposite side of the substrate, i.e. onto the other side
opposite to the planar conducting layer, a simple and low-cost
feeding structure is achieved.
[0014] Further advantageously, the antenna of the present invention
has a reflector plane arranged in a predefined distance from the
side of the substrate opposite to the planar conducting layer. Such
a reflector plane arranged below the antenna is advantageous to
avoid backside radiation and is helpful to direct the radiation
pattern to the side of the substrate on which the planar conducting
layer with the slot is located, therefore increasing the antenna
gain in one direction. Between the reflector plane and the
substrate, a low dielectic material or air can be provided.
[0015] Advantageously, the length and width dimensions of the
planar conducting layer are in the range of half of the wavelength
of the operation frequency. These dimensions make the antenna of
the present invention quite suitable for applications in the
mm-wave frequency range.
[0016] The present invention is further directed to an antenna
array comprising a plurality of antennas according to the present
invention. Hereby, the plurality of antennas advantageously have a
common substrate and the radiation direction can be changed. For
example, the antenna array may comprise beam steering elements
adapted to change the radiation direction of each of the antennas.
Advantageously, the beam steering elements hereby comprises phase
shifters adapted to shift the signal face for each antenna.
[0017] Particularly, the arrangement of the feeding structure on
the substrate side opposite to the side on which the planar
conductive layer is located and therefore decoupling the feeding
network from the radiation structure suppresses the side lobes in
the radiation patterns so that an antenna array with a very high
gain can be achieved. Further, a very reliable beam steering with a
high accuracy can be provided due to the fact that--if at all--only
very small side lobes are present.
[0018] The present invention will be further explained on the basis
of the following description of advantageous embodiments relating
to the enclosed drawings, in which
[0019] FIG. 1 shows a perspective view of an embodiment of an
antenna according to the present invention,
[0020] FIG. 2 shows a perspective view of the planar conductive
layer and the feeding structure of the embodiment of FIG. 1,
[0021] FIG. 3 shows a top-view of the embodiment of FIGS. 1 and
2,
[0022] FIG. 4 shows an antenna gain versus frequency diagram of the
antenna of the previous figures,
[0023] FIG. 5 shows a polar plot of the antenna of the previous
figures in the E-plane,
[0024] FIG. 6 shows a polar plot of the antenna of the previous
figures in the H-plane,
[0025] FIG. 7 shows a voltage standing wave ratio versus frequency
of the antenna of the previous figures,
[0026] FIG. 8 shows a perspective view of an embodiment of a beam
steering antenna array according to the present invention,
[0027] FIG. 9 shows a functional bloc diagram of the beam steering
antenna array of FIG. 8,
[0028] FIG. 10 shows a diagram of an antenna gain versus frequency
of the embodiment of FIGS. 8 and 9, and
[0029] FIG. 11 shows a polar plot of the antenna array of FIGS. 8
and 9 with a steered beam.
[0030] FIG. 1 shows a perspective view of an embodiment of an
antenna 1 for radiating and/or receiving mm-wave signals of the
present invention. The antenna has a high gain directional
radiation pattern within predetermined frequency bandwidth of
operation and is connectable for example to analogue front-end
circuitry of a wireless RF transceiver. The antenna is designed to
advantageously operate in the GHz frequency range, more
specifically in the 20 to 120 GHz frequency range, even more
specifically in the 50 to 70 GHz frequency range, and most
specifically in the 59 to 65 GHz frequency range. However, the
antenna operation is not limited to these frequency ranges, but can
be adopted to operate in different frequency ranges by a
corresponding downsizing or upsizing of the antenna measures and
ratios.
[0031] The antenna 1 comprises a substrate 2 which can be formed
from any suitable material, such as a dielectric material or the
like, and may be formed as a single layer. A planar conducting
layer 3 is formed on the substrate 2, for example, by forming a
copper layer on the upper side of the substrate 2, for example by a
printing technique. In the planar conducting layer 3, a radiation
element 4 is formed, which has the shape of a slot. The slot is for
example formed by etching technology.
[0032] On the side of the substrate 2 opposite to the conducting
layer 3, a feeding structure 5 is provided, by which
electromagnetic signals are supplied to the radiation element 4 in
order to be transmitted or by which electromagnetic signals
received by the radiation element 4 are supplied to processing
circuitry connected to the feeding structure. Further, in a
predetermined distance from the side of the substrate 2 on which
the feeding structure 5 is provided, a reflector plane 6, formed by
a conducting, for example metal, plane is located. The reflector
plane operates as an electromagnetic wave screen to reflect
electromagnetic waves transmitted and/or received by the radiation
element 4 to cancel or suppress radiation on the backside of the
substrate 2 and to increase the antenna gain in the main direction
of the antenna, which is the direction perpendicular to the plane
of the conducting layer 3 pointing away from the substrate 2. There
might be applications, however, in which the antenna of the present
invention can be implemented without such a reflector plane 6.
[0033] The feeding structure 5 can be any kind of suitable feeding
structure, but is advantageously embodied as a microstrip feeding
line which is applied to the backside of the substrate 2 by
printing technology. Hereby, the microstrip feeding line
advantageously has a 50 Ohm impedance.
[0034] The operation principle of the antenna 1 of the present
invention is as follows. An exciting electromagnetic wave is guided
to the radiation element 4 through the feeding structure 5. In the
radiation element 4, i.e. the slot, the magnetic field component of
the exciting electromagnetic wave excites an electric field within
the slot. Hereby, in order to achieve a large frequency bandwidth
at the operation frequency, for example a frequency bandwidth of 10
percent of the operation frequency, the radiation element 4
according to the present invention comprises a middle part 4a and
two outer parts 4b which are connected by said middle part 4a and
extend away from said middle part 4a, so that a slot antenna is
formed. The specific shape of the radiation element is shown in
more detail in the perspective view of the planar conductive layer
3 and the feeding structure 5 of FIG. 2 and the top view of the
antenna 1 in FIG. 3.
[0035] In the shown embodiment of the antenna 1, the slot of the
radiation element 4 generally has a U-shape, in which the two arms
of the U are formed by the mentioned outer parts 4b and the base
connecting the two outer parts 4b is formed by a middle part 4a.
The two outer parts 4b generally extend parallel to each other and
perpendicular to the middle part 4a. The shown U-shape of the slot
leads to the frequency bandwidth of approximately 10 percent of the
operation frequency, for example a frequency bandwidth of 6 GHz and
an operation frequency around 60 GHz. In the shown embodiment, the
transition between the middle part 4a and the two outer parts or
arms 4b is rounded. However, in different applications, the
transition between the middle part 4a and the two outer parts 4b
could be rectangular with corners.
[0036] As indicated in FIG. 2, the shape of the planar conductive
layer and thus the substrate 2 is generally rectangular with
equally long sides rl1 and rl2 presenting a quadratic shape.
However, different shapes could be applied in which rl1 is smaller
or larger than rl2.
[0037] FIG. 3 which is a top-view of the antenna 2 also shows the
feeding structure 5 on the backside of the substrate 2 unlashed
lines in order to show the arrangement of the feeding structure 5
in relation to the radiation element 4. Specifically, the feeding
structure 5, in the shown embodiment a printed microstrip line,
feeds or leads signals away from the middle part 4a of the
radiation element 4. Hereby, the feeding structure is located on
the backside of the substrate 2 opposite to the planar conductive
layer 3 and the slot 4, so that the feeding structure and the
radiation element are decoupled in order to suppress side lobes of
the radiation characteristic. The feeding structure 5 hereby feeds
signals to the middle part 4a of the radiation element 4 from a
direction which is opposite to the direction in which the two outer
parts 4b of the radiation element 4 extend. In the two dimensional
projection visualized in FIG. 3, it can be seen that the feeding
structure 5 overlaps with the middle part 4a of the radiation
element 4 in order to ensure a good coupling across the substrate
2.
[0038] The planar conductive layer 3 and thus the substrate 2 have
two symmetry axis A and B which split the conductive layer 3 in
half in the length as well as in the width direction. Hereby, the
feeding structure 5 extends along and symmetrically to the
symmetry-axis A and the slot of the radiation element 4 is arranged
mirror symmetrically to axis A. In other words, the two outer parts
4b of the radiation element 4 extends generally parallel to the
axis A and are mirror symmetric with respect to it. The base line
of the middle part 4a of the radiation element 4 is arranged on the
symmetry axis B. In other words, the distance between the base line
of the middle part 4a is half of the length of the conducting layer
3 in this direction.
[0039] Generally, it is advantageous, if the two outer parts 4b are
tapered, i.e. if the width of the two outer parts 4b increases away
from the middle part 4a. Hereby, the imaginary part of the complex
impedance of the radiation element can be decreased so that the
over all impedance of the antenna 1 is decreased and can be matched
to the impedance of the feeding structure of for example 50
Ohm.
[0040] Further, in case that the two outer parts 4b are tapered,
the width w1 of the two outer parts at their ends is larger than
the width w2 of the middle part 4a. Advantageously, the width w1 of
the ends of the two out parts 4b is more than two times larger than
the width w2 of the middle part 4a. Further, the length 13 of the
middle part 4a is larger than the width w1 of the ends of the two
outer parts 4b. In other words, the distance between the two outer
parts 4b is larger than the respective width w1. Further, the over
all width w3 of the radiation element 4 is larger than its length
12, whereby each of the two outer parts 4b has a length 12 which is
longer than its width w1. The shown shape and dimensions of the
planar conducting layer 3 and the radiation element 4 are
particularly suitable for radiating and receiving signals in the 50
to 70 GHz frequency range. FIG. 4 visualizes an antenna gain versus
frequency plot of the embodiment of the antenna 1 of the present
invention shown in FIGS. 1, 2 and 3. It can be seen, that an
antenna gain above 8 dBi can be achieved between 55 and 65 GHz with
a single antenna 1 as explained. FIG. 4 shows a polar plot of the
antenna 1 in the E-plane and FIG. 5 shows a polar plot of the
antenna 1 in the H-plane. It can be seen that the antenna 1 of the
embodiment shown in FIGS. 1, 2 and 3 shows a 3 dB HPBW (Half power
beam width at 3 dB lower than the maximum gain) of more than 80
degrees in the E-plane and 62 degrees in the H-plane. FIG. 6 shows
a VSWR (Voltage standing wave ratio) representing the matching of
the antenna 1 which is less than 2 in a frequency bandwidth between
59 and 65 GHz, so that a bandwidth of approximately 10 percent of
the operation frequency (approximately 62 GHz) is therefore
achieved.
[0041] FIG. 8 shows a perspective view of an embodiment of an
antenna array 10 in which the antenna 1 of the present invention
can be implemented. The antenna array 10 of FIG. 8 shows the
implementation of four antennas 1 in a quadratic structure on a
common substrate 7. In other words, the common substrate 7, which
is for example a single layer substrate similar to substrate 2, has
four planar conductive layers printed on its top-side, each of the
planar conductive layers comprising a radiation element 4. The
feeding structure of the antenna array 10 corresponds to the
feeding structure 5 shown and explained in relation to the antenna
1 of FIGS. 1, 2 and 3. Similarly, the antenna array 10 also may
comprise a reflector plane 8, being for example a metallic layer
being located in a predetermined distance from the substrate 7.
However, the reflector plane 8 can also be omitted depending on the
application. All elements, functionalities and characteristics
explained in relation to the antenna 1 of FIGS. 1, 2 and 3 also
apply to the antenna array 10 comprising several antennas 1 as
shown in FIG. 8. Instead of four antennas 1, a higher or lower
number of antennas 1 can be provided in the antenna array 10 of the
present invention. Hereby, the antenna array 10 may have a
quadratic structure with identical length rl3 and width rl4 of e.g.
4.5 mm. However, the antenna array 10 can also have different
length and width.
[0042] FIG. 9 shows a functional bloc diagram of the antenna array
10 with four antennas 1. Each of the antennas 1 has an allocated
phase-shift element 9, for example a phase-shifter bank, by means
of which the phase of the respective antenna can be changed in
order to change the over all radiation pattern of the antenna array
10. Hereby, changing the phase input of each antenna 1 and then
steering the individual radiation patterns of each antenna 1, the
over all radiation pattern of the antenna array 10 can be steered
within a specific angular range around the main lobe direction,
which is the direction perpendicular to the plane of the planar
conductive layers of antennas 1 away from the substrate 7. FIG. 9
shows a suggestion for a specific implementation and circuitry in
order to realize the beam steering possibility. Each phase shifter
9 is connected to its respective antenna via the RF switch 11.
Further, each phase shifter 9 is connected to a respective power
divider 13 by means of another RF switch 12. The two power dividers
13 are connected to a main power divider 14. The power dividers 14
and 13 are used to divide (in case of using the antenna 10 as
transmit antenna array) or to sum (in case of using the antenna
array 10 as receive antenna array) an equal signal strength to the
four antennas 1 (in case of transmitting) or to an analogue RF
front-end (in case of receiving). Additionally, a feeding structure
(not shown) such as microstrip lines is used as feeding lines for
each antenna 1, identical to the feeding structure 5 explained in
relation to antenna 1 of FIGS. 1, 2 and 3.
[0043] The phase shifters 9 are used to shift the signal phase at
each antenna 1 in order to obtain the desired beam steering pattern
direction. Any kind of broad bandwidth microstrip phase shifter can
be used and implemented with the antenna array 10 in order to steer
the beam pattern. FIG. 10 shows an antenna array gain versus
frequency plot for the antenna array of FIG. 8. It can be seen that
the antenna array 10 provides a gain of more than 12 dBi in the
frequency range between 55 and 65 GHz. FIG. 11 shows a polar plot
of the antenna for a steering angle of 30 degrees.
[0044] The shape instructor of antenna 1 of the present invention
is therefore particularly useful and advantageous for
implementation in antenna arrays, such as antenna array 10, with
beam steering due to the simple and low-cost structure and the high
gain in GHz frequency range.
* * * * *