U.S. patent number 3,631,500 [Application Number 05/018,876] was granted by the patent office on 1971-12-28 for energy density antenna apparatus for mobile radio receiver.
This patent grant is currently assigned to Hokkaido University. Invention is credited to Kiyohiko Itoh.
United States Patent |
3,631,500 |
Itoh |
December 28, 1971 |
ENERGY DENSITY ANTENNA APPARATUS FOR MOBILE RADIO RECEIVER
Abstract
An energy density antenna has a magnetic current antenna in the
form of a slot in a conducting plate and an electric current
antenna in the form of a unipole normal to the plate with the
signals from each antenna independently coupled to separate square
law detectors and combined to provide an output signal which is
relatively immune to fading due to motion of the antenna through a
standing wave pattern.
Inventors: |
Itoh; Kiyohiko (Sapporo,
JA) |
Assignee: |
Hokkaido University (Sapporo,
Hokkaido, JA)
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Family
ID: |
12016433 |
Appl.
No.: |
05/018,876 |
Filed: |
March 12, 1970 |
Foreign Application Priority Data
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Mar 18, 1969 [JA] |
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44/20057 |
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Current U.S.
Class: |
343/725; 343/767;
455/273; 343/703; 455/137; 455/278.1 |
Current CPC
Class: |
H01Q
21/29 (20130101) |
Current International
Class: |
H01Q
21/00 (20060101); H01Q 21/29 (20060101); H01q
013/10 (); H01q 021/00 (); H04b 007/08 () |
Field of
Search: |
;343/725,767,703
;325/365-367,373-375,377,305 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"The A.R.R.L. Antenna Book," The American Radio Relay League, West
Hartford, Conn. 1956, TK6565A6A6; page 279.
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Primary Examiner: Saalbach; Herman Karl
Assistant Examiner: Nussbaum; Marvin
Claims
What is claimed is:
1. An energy density antenna apparatus for mobile radio comprising
an electric current antenna and a magnetic current antenna, said
magnetic current antenna comprising a conductive surface having
slot means therein resonant at the frequency of said energy and
said electric current antenna being a linear conductor
substantially normal to said surface; and separate coupling means
for said magnetic and electric current antennas substantially
matching the impedances of said antennas wherein electromagnetic
energy may be obtained in proportion to energy density of the space
in which standing wave is induced by multireflection of radio
waves.
2. The antenna apparatus as set forth in claim 1 wherein the
magnetic current antenna is a slot antenna approximately one-half
wavelength long and one-fourth wavelength wide.
3. The antenna apparatus as set forth in claim 1 wherein said slot
antenna is provided with a slot formed on a conductive plate and a
box-shaped air cavity connected to and facing said slot.
4. The antenna apparatus as set forth in claim 1 wherein said slot
antenna is provided with a slot formed on a conductive plate and an
air cavity comprising of a cylindrical conductor having a slot
formed correspondingly to said slot.
5. The antenna apparatus as set forth in claim 1 wherein said slot
antenna is provided with a unipole antenna within a slot
therefor.
6. The antenna apparatus as set forth in claim 1 wherein said slot
antenna is provided with a cavity having a bigger cross section
than the area of said slot formed on a conductive plate.
7. The energy density antenna apparatus for mobile radio as set
forth in claim 1 comprising of square law rectifiers to which are
fed signals received by said electric current antenna and magnetic
current antenna respectively, and a summing amplifier to which are
fed outputs of said square law rectifiers.
8. The antenna according to claim 1 in which said magnetic current
antenna comprises a pair of orthogonally intersecting slots in a
conducting plate and said electric current antenna comprises a
unipole antenna normal to the plane of said slots and positioned at
the intersection thereof.
9. Apparatus according to claim 8 and including a cruciform
box-shaped air cavity connected to said plate and facing said
intersecting slots.
10. Apparatus according to claim 8 and including a rectangular
box-shaped cavity having a bigger cross section than the extended
dimensions of said intersecting slots connected to said plate and
facing said intersecting slots.
Description
BACKGROUND OF THE INVENTION
The present invention is related to an energy density antenna
apparatus for mobile radio receiver, and more particularly to
energy density antenna apparatus of electric current and magnetic
current coupling type.
When vehicles such as automobiles equipped with radio receivers run
among the mountains or between high buildings in big cities, there
are such problems as fading by standing waves caused by the
interference of incident waves reflected by buildings and the like,
besides the fading due to insensitive areas of the radio waves due
to obstacles in the wave paths.
Having examined the fading caused by these standing waves, we found
that the maximum fading frequency fd is expressed by the formula:
fd=2V/.lambda. (Hz.) when the vehicles run at a speed of V(M) per
second in the coherent standing waves caused by the radio wave
having the wave length of .lambda. (M). When the employed frequency
is 1,000 (MHz), and the speed of the vehicle V=60(km./hr.), then
fd.congruent.110 (Hz), which in turn will have a bad consequence to
the communications by mobile radio.
Previously, these type of antenna generally used received either
one of electric field or magnetic field of the radio wave only.
This meant the prior type apparatus could not meet the
aforementioned problem. Other apparatus such as energy density
antenna apparatus in which dipole antenna and loop antenna are
combined have been suggested to obviate this problem. Such a
combination creates a difficulty in impedance matching because the
rediation resistance of loop antenna at one-tenth wavelength is
about 2.5.OMEGA., and the coaxial system ordinarily used has
50.OMEGA. impedance.
SUMMARY OF THE INVENTION
One object of the present invention is to provide an improved
energy density antenna apparatus for mobile radio receiver while
eliminating fading by standing wave.
Another object of the present invention is to provide an energy
density antenna apparatus for mobile radio receivers wherein it is
easy to match the antenna apparatus with the feeder system in
impedance to be connected thereto.
Still another object of the present invention is to provide an
antenna apparatus in which the coupling between electric current
antenna and magnetic current antenna is minimized.
Further, another object of the present invention is to provide an
antenna apparatus suitable for loading in a space where there is a
limit in thickness.
According to one embodiment of the present invention the,
aforementioned fading caused by said standing wave can be
eliminated by combining an electric current antenna and a magnetic
current antenna which receive respectively and independently of
each other electric field energy and magnetic field energy of the
space where such electromagnetic field is and conducting a suitable
gain adjustment thereon. This embodiment provides an antenna system
in which the magnetic current antenna is used to match the slot
antenna with the feeder line easily by the offset feeder
method.
According to another embodiment of this invention, the coupling
between the electric current antenna and magnetic current antenna
is minimized because the former is placed within the latter.
According to still another embodiment of this invention, a cavity
having a larger cross section than the area of the slot forming the
aforementioned magnetic antenna is utilized. This will enable the
effective loading of the apparatus because of its thinness of the
body.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and features of the present invention will now be
described references being made to the attached drawings in
which:
FIG. 1 shows a simplified perspective view of one embodiment of the
present invention;
FIGS. 2 and 3 show perspective views of the cavity of a magnetic
current antenna to be utilized by the embodiment shown in FIG. 1
and;
FIGS. 4 and 5 show simplified perspective views of antenna
according to another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the accompanying drawings, FIG. 1 shows an energy density
antenna apparatus of electric current and magnetic current coupling
type in which an incoming wave receives along the direction of the
Y-axis a plane wave having only Ez-Hx component and which is a
linear polarized wave determined by three-dimensional Cartesian
coordinates. In the drawings, antenna apparatus 10 is provided with
conductive plate 11 on which are formed magnetic current antenna
which is a slot antenna 12, and unipole antenna 13 adjacent to said
slot antenna. Thus, the Ez component Ez-Hx component forming said
plane wave is received by said unipole antenna 13 and fed to a
square law rectifier 15 by way of coaxial cable 14. Hx component is
taken out as the voltage induced by electric current Jy as it
crosses slot 16 of said slot antenna 12 on the conductive plate 11.
This is then fed to a square law rectifier 18 by way of coaxial
cable 17. Reference numeral 19 indicates a summing amplifier which
is fed with rectified signals obtained by said respective square
law rectifiers 15, 18. The summing amplifier 19 adjust gains of
these rectified signals suitably, and supplies a signal
proportionate to 1/2(.epsilon..sub.o IE .sup.2 +.mu..sub.o HI
.sup.2) as an output, wherein IE and HI designate electric field
and magnetic field of incoming wave, respectively, E.sub.o
designates dielectric constant in vacuum and .mu..sub.o designates
permeability in vacuum.
FIGS. 2 and 3 of the attached drawings show perspective view of a
cavity of magnetic current antenna utilized in one embodiment of
present invention as shown in FIG. 1. FIG. 2 shows a slot shaped
cavity 21 having an opening in a plane-shaped conductive plate 11
at one end thereof which is approximately one-half wavelength
(.lambda./2) in length and one-fourth wavelength (.lambda./4) is
width. FIG. 3 shows a cylindrical conductor 31 of an approximately
one-sixteenth wavelength diameter having a slot 32 which is about
one-half wavelength in its length alone the axis thereof.
FIG. 4 shows another embodiment of the present invention wherein
the essential part of antenna apparatus to receive an incoming wave
is composed of Ez-Hx-Hy components. Said antenna apparatus 10 is
provided with a unipole antenna 43 at a cross point of slot
antennas 41 and 42 located perpendicular to each other on the
conductive plate 11. Each of the slots 44. 45 for slot antennas 41
and 42 are formed by locating them perpendicular to cavities 46, 47
having the same length and width, or having the same shape as those
cavities shown in FIG. 2 or 3. When the unipole antenna 43 is
placed at the cross point of slot antennas 41 and 42, the coupling
of the two are maintained at minimum. However, this construction
with a considerable depth in the air cavities 46 and 47 presents a
problem in loading the apparatus onto vehicles.
FIG. 5 shows an embodiment of the present invention which tries to
solve the foregoing problem by providing a box-type cavity 48 which
would be open to each of slots 44, 45 and also be wide enough to
embrace them in whole at the back of the plate 11. This will, thus,
shorten the depth of the cavity 48. In this embodiment, it is also
possible to provide the unipole antenna 13 in the slot 16 of the
slot antenna 12 when receiving a plane wave. This also enables
minimizing of the coupling of the two antennas.
In the embodiment above described, signals are to be fed from the
unipole antenna and slot antenna by way of coaxial cable. The use
of Lecher wires and the like in place of cable may be utilized.
The slot antenna utilized in the said embodiments will have the
same characteristics as that of one-half wavelength dipole antenna
having the diameter of a=D/2 , wherein D is the width of the slot.
Accordingly, when unipole antenna and dipole antenna are designed
in such a way as to have the width of each in the manner as
described heretofore, unipole antenna and slot antenna having the
same frequency bandwidth, same shrinkage rate and same impedance
can be obtained.
* * * * *