JP3135732B2 - Slot-coupled microstrip antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slot-coupled microstrip antenna used for, for example, an array antenna for satellite mobile communication.

[0002]

2. Description of the Related Art A conventional dual-frequency linearly polarized microstrip antenna is described in "Two-frequency dual-strip microstrip antenna using slot coupling method" by Hisao Iwasaki et al. , AP88-19, pp. 67-72, 1988 is known. In this paper, a dual-frequency microstrip antenna (hereinafter referred to as a first conventional example) shown in FIG. 9 is disclosed. In this antenna, two rectangular slots 4b and 5b located immediately below a circular radiation conductor 1 are disclosed. Are provided at positions at an angle of 90 ° with respect to the center of the circular radiation conductor 1.

By forming the rectangular slots 5b and 6b of the first conventional microstrip antenna in the same shape, the resonance frequencies when the antenna side is viewed from the two feeding terminals T1 and T2 are matched. In addition, by setting the excitation phase difference of each microwave signal input to both the power supply terminals T1 and T2 to 90 °, it is possible to excite radiated radio waves so as to be circularly polarized.

On the other hand, a microstrip antenna shown in FIG. 12 (hereinafter referred to as a second conventional example) is also known as a circularly polarized microstrip antenna or a dual-frequency linearly polarized microstrip antenna.

In these conventional microstrip antennas, two feeding microstrip conductors 6b and 7 are provided.
b or 6c, 7c and two coupling rectangular slots 4b, 5b, or 4 provided for coupling the circular radiation conductor 1.
In the first conventional microstrip antenna of FIG. 9, both c and 5c are formed such that their longitudinal directions are respectively in the radial direction of the radiation conductor 1 from the center of the circular radiation conductor 1, while FIG. In the second conventional microstrip antenna, both longitudinal directions are formed so as to be parallel to the tangential direction of the circumference of the circular radiation conductor 1 and along the circumference.

In these conventional microstrip antennas, since there are two feed terminals T1 and T2, the mutual coupling amount between these feed terminals T1 and T2,
That is, isolation becomes a problem. If the mutual coupling amount is large, the following problem occurs.

First, when two microwave signals having a phase difference of 90 ° from each other are excited to emit circularly polarized radio waves, these power supply terminals T1, T
Since the input impedance changes at each of the power supply terminals T1 and T2 due to mutual coupling between the two, the axial ratio characteristic of the circularly polarized wave of the radiated radio wave is deteriorated. Next, second, when the resonance frequency measured at each of the power supply terminals T1 and T2 is made to match the transmission frequency and the reception frequency, respectively, so that the microstrip antenna operates as a dual-frequency antenna. It is also conceivable that large power on the transmitting side leaks into the receiving circuit side due to mutual coupling, causing the receiving circuit to malfunction or, in the worst case, damaging the receiving circuit. For this reason, it is desirable to minimize the coupling. The largest cause of the mutual coupling is caused by the fact that the coupling rectangular slot is formed offset from the center of the radiation conductor 1 and excited, as described below.
It is an M ₂₁ mode.

FIG. 11 is a plan view showing the direction of a high-frequency current in the TM ₂₁ mode when a microwave signal is inputted and excited via the feed terminal T1 or T2 in the first conventional microstrip antenna. . As is clear from FIG. 11, in the configuration in which the longitudinal directions of the coupling rectangular slots 4b and 5b are respectively formed in the radial direction of the radiation conductor 1 from the center of the circular radiation conductor 1, both slots 4b and 5b are formed.
For both b and 5b, the high-frequency current flowing directly above the slot 4b and the slot 5b is orthogonal to the longitudinal direction of each of the slots 4b and 5b, and the coupling between the coupling rectangular slots 4b and 5b and the mode current is performed. You can see it happen. Therefore,
In the first conventional configuration shown in FIG. 9, as it can be seen from the frequency characteristics of mutual coupling coefficient S ₁₂ of FIG. 10, TM ₂₁
It can be seen that mutual coupling between the two feeding terminals T1 and T2 occurs via the mode. Here, the mutual coupling coefficient S ₁₂ are mutually coupling coefficient from the feeding terminal T1 to the power supply terminal T2,
The same applies hereinafter.

FIG. 14 is a plan view showing the direction of the TM ₂₁ mode high-frequency current when a microwave signal is input and excited via the feed terminal T1 or T2 in the second conventional microstrip antenna. The TM ₂₁ mode is orthogonal to the TM ₂₁ mode of the first conventional example. As is clear from FIG. 14, the coupling rectangular slots 4c, 5
In the configuration in which the longitudinal direction of each c is parallel to the tangent of the circumference of the circular radiation conductor 1 and is formed along the circumference, both slots 4c and 5 are formed as in the first conventional example.
c, the high-frequency current flowing directly above the slots 4c and 5c is orthogonal to the longitudinal direction of each of the slots 4c and 5c, and causes coupling between the coupling rectangular slots 4c and 5c and the mode current. I understand. Therefore, FIG.
The second in the conventional example of configuration shown, as can be seen from the frequency characteristics of mutual coupling coefficient S ₁₂ of FIG. 13, that through the TM ₂₁ mode is mutual coupling between the two power supply terminals T1, T2 occurs Understand.

[0010]

As described above, in the conventional microstrip antenna, the mutual coupling between the two feeding terminals is relatively large, and as a result, radiation occurs when circularly polarized wave excitation is performed. There is a problem that the axial ratio characteristics of circularly polarized waves are deteriorated, and the reception characteristics are deteriorated due to leakage from the transmission side to the reception side when two frequencies are shared.

[0011] An object of the present invention is to solve the above problems and solve the above problem.
An object of the present invention is to provide a microstrip antenna which has no mutual coupling between two feed terminals and has better axial ratio characteristics of circularly polarized waves or better dual frequency characteristics than the conventional example.

[0012]

To achieve the above object, a slot-coupled microstrip antenna according to the present invention comprises: a first dielectric substrate on which a radiation conductor having a circular or ring shape is formed; A first dielectric substrate sandwiched between a second dielectric substrate on which first and second power supply lines are formed
A slot-coupled microstrip antenna that excites the radiation conductor with each of the microwave signals input to the first and second feeder lines via the second and third coupling slots, respectively. The centers of the two coupling slots are formed symmetrically with respect to the center of the radiation conductor, and the longitudinal direction of the first coupling slot is parallel to a tangent to the outer periphery of the radiation conductor. And the longitudinal direction of the second coupling slot is formed so as to be the radial direction of the radiation conductor from the center of the radiation conductor, and the longitudinal direction of the first coupling slot and the second The longitudinal direction of the coupling slot is perpendicular to each other.

[0013]

In the slot-coupled microstrip antenna constructed as described above, the centers of the first and second coupling slots are formed at positions symmetrical to each other about the center of the radiation conductor. In addition, the longitudinal direction of the first coupling slot is parallel to a tangent to the outer periphery of the radiation conductor, and the longitudinal direction of the second coupling slot is parallel to the radiation conductor from the center of the radiation conductor. It is formed so as to be in the radial direction, and the longitudinal direction of the first coupling slot and the longitudinal direction of the second coupling slot are orthogonal to each other.

Here, the direction of the TM ₂₁ mode high-frequency current when a microwave signal is input through the first feed line and the radiating conductor is excited through the first coupling slot is as follows. For example, as shown in FIG.
In the example, it is assumed that the first coupling slot corresponds to the rectangular slot 4 and the second coupling slot corresponds to the rectangular slot 5 for convenience of explanation. ) Although orthogonal to the longitudinal direction of the first coupling slot,
Are parallel to the longitudinal direction of the rectangular slot. Also,
The direction of the TM ₂₁ mode high-frequency current when a microwave signal is input through the second power supply line and the radiation conductor is excited through the second coupling slot is shown in FIG. 5, for example. As described above, while being orthogonal to the longitudinal direction of the second coupling slot, it is parallel to the longitudinal direction of the first rectangular slot. That is, the directions of the TM ₂₁ mode high-frequency currents are parallel to each other between the case where excitation is performed via the first power supply line and the case where excitation is performed via the second power supply line, as in the conventional example. Because
The mutual coupling coefficient between the antennas connected to the two feeding lines can be made extremely small as compared with the conventional example.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1A is a plan view of a circularly polarized microstrip antenna according to a first embodiment of the present invention, and FIG. 1B is a plan view of FIG. A- of A)
It is a longitudinal cross-sectional view about the A 'line.

In the circularly polarized microstrip antenna of the first embodiment, a dielectric substrate 2 is sandwiched between a circular radiating conductor 1 and a grounding conductor plate 3, and rectangular slots 4 and 5 for coupling are provided.
Is provided on the ground conductor plate 3, and the coupling rectangular slots 4, 5 are different from the first and second conventional examples in that the circular radiating conductor 1 is provided.
Are formed at symmetrical positions with respect to the center of the circular radiation conductor 1, and the longitudinal direction of the slot 4 is parallel to the tangent to the circumference of the circular radiation conductor 1 and along the circumference, and the slot 5 Are formed so that the longitudinal direction of the radiating conductor 1 is the radial direction of the radiating conductor 1 from the center of the circular radiating conductor 1, and the longitudinal direction of the slot 4 and the longitudinal direction of the slot 5 are formed to be orthogonal to each other. I do.

As shown in FIG. 1, a circular radiation conductor 1 is formed at a central position on the surface of a dielectric substrate 2, and
Between the back surface of the dielectric substrate 2 and the front surface of the dielectric substrate 8, a rectangular slot for coupling is formed such that the longitudinal direction of the slot 4 is parallel to the tangent of the circumference of the circular radiating conductor 1 and along the circumference. 4 are formed, and the ground conductor plate 3 on which the coupling rectangular slot 5 is formed is sandwiched so that the longitudinal direction of the slot 5 is in the radial direction of the radiation conductor 1 from the center of the circular radiation conductor 1. Here, the rectangular slots 4, 5 are provided at point-symmetrical positions, which are 180 ° with respect to the center of the circular radiating conductor 1, and the longitudinal direction of the rectangular slot 5 is the longitudinal direction of the rectangular slot 4. Are formed so as to be orthogonal to. As a result, the center of the rectangular slot 4, the center of the circular radiation conductor 1, and the center of the rectangular slot 5 are on one straight line parallel to the longitudinal direction of the rectangular slot 5.

Further, on the back surface of the dielectric substrate 8, the feeding microstrip conductor 6 passes just below the central portion in the longitudinal direction of the slot 4 and the longitudinal direction of the conductor 6 is orthogonal to the longitudinal direction. At the same time, the power supply microstrip conductor 7 is formed so as to pass right below the central portion in the longitudinal direction of the slot 5 and to make the longitudinal direction of the conductor 7 orthogonal to the longitudinal direction. Here, the microstrip conductor 6 and the ground conductor plate 3 constitute a first power supply microstrip line, while the microstrip conductor 7 and the ground conductor plate 3 constitute a second power supply microstrip line, Feeding terminals T are provided at each edge of the dielectric substrate 8 of each of the microstrip conductors 6 and 7.
1, T2 are provided.

In the microstrip antenna of the first embodiment configured as described above, the first and second feeding microstrip lines are connected to the circular radiating conductor 1 via the coupling rectangular slots 4 and 5, respectively. And electromagnetically coupled. Also, a linearly polarized electromagnetic wave excited when a microwave signal is input to the first microstrip line via the first power supply terminal T1, and a second microstrip via the second power supply terminal T2. The coupling rectangular slots 4 and 5 are formed such that linearly polarized electromagnetic waves excited when a microwave signal is input to the line are orthogonal to each other.

The impedance matching between each feeding microstrip line and the antenna is based on the arrangement and length of the coupling rectangular slots 4 and 5 and the length of the coupling rectangular slots 4 and 5 and each feeding microstrip from the coupling rectangular slots 4 and 5. It is obtained by adjusting the length of each matching stub formed by the lines up to the respective open ends which are the feed terminals T1 and T2 of the strip line. In the microstrip antenna,
The impedance when viewed from the power supply terminal T1 on the antenna side and the impedance when viewed from the power supply terminal T2 on the antenna side are set to match.

Now, the respective microwave signals having the same frequency and having a phase difference of 90 ° are fed to the antenna via feed terminals T1 and T2, respectively, so that the respective rectangular signals are used for the respective rectangular signals. The circular radiating conductor 1 is excited via the circular radiating conductor 1 through the circular radiating conductor 1 in a direction perpendicular to the circular radiating conductor 1 and from the ground conductor plate 3 to the circular radiating conductor 1. Polarized electromagnetic waves are emitted toward free space. Here, the phase of the microwave signal fed through the feed terminal T1 is advanced by 90 ° compared to the phase of the microwave signal fed through the feed terminal T2, so that the electromagnetic wave of left-hand circular polarization Can be emitted, while a right-handed circularly polarized electromagnetic wave can be emitted by delaying by 90 °.

The inventor prototyped the microstrip antenna of the first embodiment and measured the respective frequency characteristics of the reflection coefficients S ₁₁ and S ₂₂ and the mutual coupling coefficient S ₁₂ at the respective feed terminals T1 and T2. The parameters of the prototype microstrip antenna are as follows.

(A) Relative permittivity of dielectric substrate 2: 2.60, thickness:
3.2 mm (b) Relative permittivity of the dielectric substrate 8: 2.60, thickness:
0.8 mm (c) Radius of circular radiation conductor 1: 32.0 mm (d) Rectangular slot for coupling 4: 25.0 mm length x 1.5
mm width (e) Coupling rectangular slot 5: 21.0 mm length x 1.5
mm width (f) Distance between center of rectangular slot 4 and center of radiation conductor:
17.0 mm (g) Distance between center of rectangular slot 5 and center of radiation conductor:
20.0 mm (h) Impedance of the first and second microstrip lines: 50Ω

FIG. 2 is a graph showing the frequency characteristics of the reflection coefficients S ₁₁ and S ₂₂ of the microstrip antenna of FIG. As is clear from FIG. 2, the resonance frequency of the antenna measured at both power supply terminals T1 and T2 is about 1.60 GHz.
It can be seen that they match each other.

[0026] FIG. 3 is a graph showing a frequency characteristic of the mutual coupling coefficient S ₁₂ of the microstrip antenna of FIG.
In the case of the conventional example (see FIGS. 10 and 13), the mutual coupling coefficient S
₁₂ is about -20 dB, whereas in the case of the first embodiment, as is clear from FIG.
Mutual coupling coefficient S ₁₂ indicating the leakage to the other power supply terminal T2 from it can be seen that are suppressed below -30 dB. The reason why the mutual coupling coefficient is reduced in the first embodiment will be described below.

[0027] FIG. 4 is a plan view showing the direction of the TM ₂₁ mode of the high-frequency current when excited by entering the microwave signal through the feed terminal T1 in microstrip antenna of FIG. As is clear from FIG. 4, the direction of the high-frequency current is orthogonal to the longitudinal direction of the rectangular slot 4 used for excitation,
Are parallel to the longitudinal direction. FIG. 5 is a plan view showing the direction of the TM ₂₁ mode high-frequency current when a microwave signal is input through the feed terminal T2 and excited in the microstrip antenna of FIG. 1, as is apparent from FIG. The direction of the high-frequency current is orthogonal to the longitudinal direction of the rectangular slot 5 used for excitation, but is parallel to the longitudinal direction of the rectangular slot 4.

Therefore, unlike the conventional example, the directions of the high-frequency currents in the TM ₂₁ mode are not parallel to each other between the case where excitation is performed via the power supply terminal T1 and the case where excitation is performed via the power supply terminal T2. The mutual coupling coefficient between the antennas connected to the feed terminals T1 and T2 can be made extremely small as compared with the conventional example. As a result, it is possible to prevent the axial ratio of circularly polarized waves of the circularly polarized microstrip antenna of the first embodiment from deteriorating.

<Second Embodiment> FIG. 6A is a plan view of a dual-frequency linearly polarized microstrip antenna according to a second embodiment of the present invention, and FIG. FIG. 6A is a vertical sectional view taken along line BB ′ of FIG.

In the dual-frequency linearly polarized microstrip antenna of the second embodiment, the slot 4a and the slot 5a are different from those of the first embodiment in that the slot 5a has a circular direction in which the longitudinal direction of the slot 5a is circular. The slot 4a is formed so as to be parallel to the circumferential tangent line and along the circumference, and so that the longitudinal direction of the slot 4a is in the radial direction of the radiating conductor 1 from the center of the circular radiating conductor 1. The lengthwise direction of the slot 5a is formed to be orthogonal to the lengthwise direction of the slot 5a, and the length of the slot 4a in the lengthwise direction is significantly shorter than that of the slot 5a.
2 is characterized by having different resonance frequencies when the antenna is viewed. Hereinafter, differences from the first embodiment will be described.

As shown in FIG. 6, the rectangular slots 4a, 5a
a are 180 degrees from each other about the center of the circular radiation conductor 1.
Are provided at the positions of the point symmetry, that is, each position of °, and are formed so that the longitudinal direction of the rectangular slot 4a is orthogonal to the longitudinal direction of the rectangular slot 5a. Where
The center of the rectangular slot 5a, the center of the circular radiating conductor 1,
The center of the rectangular slot 4a is on one straight line parallel to the longitudinal direction of the rectangular slot 4a. Then, on the back surface of the dielectric substrate 8, the power supply microstrip conductor 6 a passes directly below the longitudinal center of the slot 4 a and the conductor 6
a is formed so that the longitudinal direction thereof is perpendicular to the longitudinal direction, and the power supply microstrip conductor 7a passes directly below the central portion in the longitudinal direction of the slot 5a, and the longitudinal direction of the conductor 7a corresponds to the longitudinal direction. They are formed so as to be orthogonal. Here, the microstrip conductor 6a and the ground conductor plate 3 constitute a first power supply microstrip line, while the microstrip conductor 7a and the ground conductor plate 3 constitute a second power supply microstrip line, Feed terminals T1 and T2 are provided at the respective edge portions of the dielectric substrate 8 of the microstrip conductors 6a and 7a.

In the microstrip antenna of the second embodiment configured as described above, the first and second feeding microstrip lines are respectively connected to the circular radiation conductor 1 via the coupling rectangular slots 4a and 5a. And electromagnetically coupled. Also, a linearly polarized electromagnetic wave excited when a microwave signal is input to the first microstrip line via the first power supply terminal T1, and a second microstrip via the second power supply terminal T2. The coupling rectangular slots 4a and 5a are formed such that linearly polarized electromagnetic waves excited when a microwave signal is input to the line are orthogonal to each other.

Now, two microwave signals having frequencies respectively corresponding to the respective resonance frequencies are fed to the antenna via the feed terminals T1 and T2, respectively, so that the microstrip antenna transmits the circular radiation conductor 1 to the circular radiation conductor 1. In the vertical direction and in the direction from the ground conductor plate 3 to the circular radiating conductor 1, two linearly polarized electromagnetic waves having two mutually different frequencies are radiated toward free space.

The inventor prototyped the microstrip antenna according to the second embodiment in the same manner as the first embodiment, and determined the reflection coefficients S ₁₁ and S ₂₂ and the mutual coupling coefficient S ₁₂ at the respective feed terminals T 1 and T 2. Were measured for each frequency characteristic.

FIG. 7 is a graph showing frequency characteristics of the reflection coefficients S ₁₁ and S ₂₂ of the microstrip antenna of FIG. As is clear from FIG. 7, each of the resonance frequencies of the antenna measured at both the feeding terminals T1 and T2 is about 1.
50 GHz and about 1.60 GHz, which are different from each other.

[0036] FIG. 8 is a graph showing a frequency characteristic of the mutual coupling coefficient S ₁₂ of the microstrip antenna of FIG.
In the case of the conventional example (see FIGS. 10 and 13), the mutual coupling coefficient S
₁₂ is about −20 dB, whereas in the case of the second embodiment, as is clear from FIG.
Mutual coupling coefficient S ₁₂ indicating the leakage to the other power supply terminal T2 from it can be seen that are suppressed below -35 dB. The reason why the mutual coupling coefficient is reduced in the second embodiment is the same as in the first embodiment.

Therefore, unlike the conventional example, the directions of the TM ₂₁ mode high-frequency currents are not parallel to each other between the case where excitation is performed via the power supply terminal T1 and the case where excitation is performed via the power supply terminal T2. The mutual coupling coefficient between the power supply terminals T1 and T2 can be extremely reduced as compared with the conventional example. As a result, it is possible to significantly suppress the sneak path from the transmission side to the reception side in the microstrip antenna of the dual-frequency linearly polarized wave of the second embodiment.
Therefore, for example, it is possible to reduce the load capability of unnecessary band suppression in the band-pass characteristic of the band-pass filter in the duplexer connected to the power supply line of the antenna, so that the band-pass filter can be reduced in size and weight. Thus, the entire antenna device including the duplexer can be reduced in size and weight.

<Other Embodiments> In the above embodiments, the material of the dielectric substrate 2 may be air, a foam material, a honeycomb material, or a laminate of these materials.

In the above embodiment, the microstrip line is used as the power supply line. However, the present invention is not limited to this, and may be a triplate line, a coplanar line, or a slot line.

In the above embodiment, a circular radiation conductor is used as the radiation conductor 1. However, the present invention is not limited to this, and a ring-shaped radiation conductor such as an annular shape may be used.
In this case, one of the outer peripheral edge and the inner peripheral edge of the ring-shaped radiation conductor is connected to a ground conductor via a conductor formed on an inner peripheral surface in a through hole formed in the dielectric substrate 2. It may be connected to the plate 3 and grounded.

In the above embodiment, a rectangular slot is used as a power supply slot. However, the present invention is not limited to this, and a diamond-shaped, elliptical, or "dog-bone type" in which both ends of a rectangular slot are vertically extended. "May be rectangular slots.

[0042]

As described above in detail, according to the present invention, the first radiating conductor having the circular or ring shape is formed.
The first and second coupling slots interposed between the first dielectric substrate and the second dielectric substrate on which the first and second power supply lines are formed, respectively. And a slot-coupled microstrip antenna that excites the radiation conductor with each microwave signal input to the second power supply line, wherein the centers of the first and second coupling slots are aligned with the center of the radiation conductor. The first coupling slot is formed at a position that is symmetrical with respect to the center, the longitudinal direction of the first coupling slot is parallel to a tangent to the outer periphery of the radiation conductor, and the longitudinal direction of the second coupling slot is The radial direction of the radiation conductor is formed from the center of the radiation conductor, and the longitudinal direction of the first coupling slot and the longitudinal direction of the second coupling slot are formed to be orthogonal to each other. And . Therefore, as in the conventional example, the directions of the TM ₂₁ mode high-frequency currents are parallel to each other between the case where the excitation is performed via the first power supply line and the case where the excitation is performed via the second power supply line. Therefore, the mutual coupling coefficient between the antennas connected to the two feeding lines can be made extremely small as compared with the conventional example.

Thus, when the microstrip antenna is used as a circularly polarized microstrip antenna, it is possible to prevent the axial ratio of circularly polarized waves from deteriorating.
On the other hand, when the microstrip antenna is used as a dual-frequency linearly polarized microstrip antenna,
Since the sneak from the transmission side to the reception side can be greatly suppressed, for example, the load capability of unnecessary wave suppression in the band-pass characteristic of the band-pass filter in the duplexer connected to the feeding line of the antenna is reduced. Therefore, there is an advantage that the size and weight of the band-pass filter can be reduced, whereby the entire antenna device including the duplexer can be reduced in size and weight.

[Brief description of the drawings]

FIG. 1A is a plan view of a microstrip antenna according to a first embodiment of the present invention, and FIG.
FIG. 4 is a vertical sectional view taken along line AA ′ of FIG.

FIG. 2 is a graph showing frequency characteristics of reflection coefficients S ₁₁ and S ₂₂ of the microstrip antenna of FIG.

3 is a graph showing a frequency characteristic of the mutual coupling coefficient S ₁₂ of the microstrip antenna of FIG.

FIG. 4 is a plan view showing the direction of a TM ₂₁ mode high-frequency current when a microwave signal is input and excited via a feed terminal T1 in the microstrip antenna of FIG. 1;

5 is a plan view showing the direction of a TM ₂₁ mode high-frequency current when a microwave signal is input through a feed terminal T2 and excited in the microstrip antenna of FIG. 1;

FIG. 6A is a plan view of a microstrip antenna according to a second embodiment of the present invention, and FIG.
FIG. 4 is a vertical sectional view taken along line BB ′ of FIG.

7 is a graph illustrating frequency characteristics of reflection coefficients S ₁₁ and S ₂₂ of the microstrip antenna of FIG.

8 is a graph showing a frequency characteristic of the mutual coupling coefficient S ₁₂ of the microstrip antenna of FIG.

9A is a plan view of a first conventional microstrip antenna, and FIG. 9B is a vertical cross-sectional view taken along line CC ′ of FIG. 9A.

10 is a graph showing a frequency characteristic of the mutual coupling coefficient S ₁₂ of the microstrip antenna of FIG.

11 is a plan view showing the direction of the TM ₂₁ mode of the high-frequency current when excited by feeding a microwave signal through the power supply terminals T1 or T2 in the microstrip antenna of FIG.

FIG. 12A is a plan view of a second conventional microstrip antenna, and FIG. 12B is a DD ′ of FIG.
It is a longitudinal cross-sectional view about a line.

13 is a graph showing a frequency characteristic of the mutual coupling coefficient S ₁₂ of the microstrip antenna of FIG. 12.

14 is a plan view showing the direction of the TM ₂₁ mode of the high-frequency current when excited by feeding a microwave signal through the power supply terminals T1 or T2 in the microstrip antenna of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Circular radiation conductor, 2, 8 ... Dielectric substrate, 3 ... Ground conductor plate, 4, 5, 4a, 5a ... Rectangular slot, 6, 7, 6a, 7a ... Power supply microstrip conductor, T1, T2 ... Power supply Terminal.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Fujise 5th Sanraya, Daiya, Seika-cho, Soraku-cho, Kyoto Prefecture ATR Optical Co., Ltd. ⁷ , DB name) H01Q 13/00-13/28 H01Q 1/27-1/52 H01Q 5/00 H01Q 21/24

Claims (1)

(57) [Claims] A first dielectric substrate on which a radiation conductor having a circular or ring shape is formed, and a second dielectric substrate on which first and second power supply lines are formed. A slot-coupled microstrip antenna that excites the radiation conductor with each of the microwave signals input to the first and second power supply lines via the provided first and second coupling slots, respectively. The centers of the first and second coupling slots are formed at positions symmetrical to each other about the center of the radiation conductor, and the longitudinal direction of the first coupling slot is set at the outer periphery of the radiation conductor. The second coupling slot is formed so as to be parallel to a tangent line and the longitudinal direction of the second coupling slot is the radial direction of the radiation conductor from the center of the radiation conductor, and the longitudinal direction of the first coupling slot is formed. And above Slot coupled microstrip antenna, characterized in that the longitudinal direction of the second coupling slot is formed so as to be perpendicular to each other.