JPH08172313A - Circularly polarized microstrip antenna - Google Patents

Abstract

PURPOSE: To eliminate reactance and susceptance components generated at a feeding point and to allow frequency with a high axial ratio to agree with frequency with matched input impedance by shifting the position of a degenerate separation segment for solving the degeneration of a mode perpendicular to a radiating conductor from the feeding point by a specific angle. CONSTITUTION: In the circularly polarized wave microstrip antenna 4 excited in a TMnm mode (n=1, 2,...), the position of the degenerative separation segment 7 for solving the degeneration of the mode perpendicular to the radiating conductor 3 is shifted from the feeding point by (90/2n)+k(360/2n)} deg.. Thereby reactance and susceptance components generated at the feeding point can be eliminated and a circularly polarized wave can be excited. When the phase of the circularly polarized wave is adjudged to eliminate the reactance and susceptance components generated at the feeding point, frequency for exciting the circularly polarized wave can be made to agree with the frequency for matching input impedance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip antenna that produces circularly polarized waves.

[0002]

2. Description of the Related Art FIG. 10 shows, as a conventional example, a journal Vol. J64-B No. 7 (612-
618) is a block diagram showing a conventional fundamental mode (TM ₁₁ ) excited circularly polarized microstrip antenna,
(A) is a top view, (b) is an AA sectional view. In the figure, 1 is a ground conductor, 2 is a dielectric substrate, and 3 is a radiating conductor, and a microstrip antenna 4 is constructed from these. Further, 5 is a coaxial pin for feeding the microstrip antenna, and 6 is a coaxial connector, through which the microstrip antenna is excited. Reference numeral 7 denotes a degenerate separation segment provided to solve the degeneracy of the orthogonal modes of the radiation conductor.

Next, the operation will be described. 11 and 12
[Fig. 3] is a diagram for explaining the operating principle of a conventional circularly polarized microstrip antenna. 11A is a mode function when a degenerate separation segment is added, and FIG. 11B is a diagram showing an equivalent circuit thereof. In general, in order to excite circularly polarized waves, it is necessary to excite two orthogonal feed points with a phase difference of 90 degrees. Therefore, a T-branch circuit or a hybrid circuit is required, and the power feeding circuit becomes complicated. Therefore, even with one-point feeding, a simple circular polarization can be excited by providing a degenerate separation segment for solving the degeneration of the mode orthogonal to the radiation conductor. The principle of this operation will be described below. If a degenerate separation segment is provided in the direction of an angle of 45 degrees with respect to the feeding point, the degeneracy of the two orthogonal modes is released, and it can be considered as two modes Φa and Φb having different resonance frequencies. The microstrip antenna can be represented by a parallel resonance circuit having an inductance L, a capacitance C, and a conductance G near its resonance frequency. Since there are two modes, La and C respectively
It is represented by a parallel resonant circuit of a, Ga and Lb, Cb, Gb. Also, the inductance of the feeding point is represented by Lp. FIG. 12 shows the amplitude and phase resonance characteristics of the two parallel resonance circuits. Let the resonance frequency of Φa be fa and the resonance frequency of Φb be fb. From the figure, it can be seen that circularly polarized waves are excited at a frequency f'where the amplitudes of the two modes are equal and the phase difference is 90 degrees. The phase at this circular polarization excitation frequency is 0 degree.

FIG. 13 shows a conventional example such as IEEE T.
rans. Antenna & Propagat. , Vo
l. AP-32, No. 9,991-994,1984
The conventional higher-order mode TMnm mode (n = 2,
3 ,. ． ． ． ) A schematic configuration diagram of an excited circularly polarized microstrip antenna or a diagram for explaining the operating principle. In the figure, 17 is a TM ₂₁ mode excitation microstrip antenna, 18 is a branch line hybrid circuit, 1
Reference numeral 9 is a chip resistor that absorbs the reflected wave. Higher mode T
In order to excite a circularly polarized conical beam in the Mnm mode, two beams separated by 90 / 2n (n = 2, 3, ...) Degrees are used.
It is necessary to excite the point with a phase difference of 90 degrees. FIG.
(A) is an example using a hybrid power supply circuit. FIG.
3 (b) shows a current distribution when power is supplied from two power supply points. Although all the components are canceled out in the front direction, vertical and horizontal components of the radiated electric field are generated corresponding to the two feeding points in the wide angle, respectively, and a phase difference of 90 degrees is given to the two feeding points. A circular polarization having a conical beam as shown in 13 (c) is excited.

As a conventional example, FIG. 14 shows a technical report A.A of the Institute of Electronics, Information and Communication Engineers. It is a schematic block diagram which shows the conventional sequential array shown by P83-57,49-54,1983, and a figure explaining the operating principle. It is difficult to excite a perfect circularly polarized wave, and it is generally an elliptically polarized wave. Especially in the case of single-point power feeding, the frequency band in which circularly polarized waves are excited is narrow. Therefore,
In order to obtain a circularly polarized wave with a good axial ratio, the two microstrip antennas are both excited by circularly polarized wave in the same plane, the second microstrip antenna is rotated by 90 degrees with respect to the first microstrip antenna, and the phase is changed. Also change 90 degrees. By this sequential array, the major axes of the two elliptical polarized waves are combined with an inclination of 90 degrees, so that circular polarized waves with a good axial ratio are excited.

[0006]

By providing the degenerate separation segment as described above, circular polarization can be excited even with one-point feeding, but there are the following problems. The microstrip antenna can be fed by using a feeding pin, feeding directly by a microstrip line, or electromagnetically coupling by a slot, but the input impedance differs depending on the feeding method. Since there is reactance and susceptance at the feeding point depending on the feeding method, the frequency at which matching can be achieved is determined including these. On the other hand, the frequency at which circularly polarized waves are excited does not basically depend on the feeding method, but is determined by the relationship between the microstrip antenna and the degenerate separation segment. Therefore, there is a problem that the frequency at which the circularly polarized wave is excited and the frequency at which the input impedance is matched are different. For example, when the power is fed through the coaxial pin, the input impedance includes the inductance Lp of the pin, so that by solving the degeneracy of the two orthogonal modes, matching can be achieved at a frequency different from the frequency at which circular polarization is excited. That is, there is a problem that the axial ratio is poor at a frequency where the input impedance is matched.

Further, when a degenerate separation segment for canceling the degeneration of modes orthogonal to the radiation conductor is provided, if the shape of the degenerate separation segment is made to be a convex portion, the antenna size becomes large, and the element spacing is limited when arrayed. There was a problem that was done. Further, even when the concave portion is provided, it is necessary to repeat the trial and error by changing the dimensions of the radiation conductor and the concave portion so as to improve the axial ratio at the design frequency, which causes a problem that the design is difficult.

Furthermore, the higher mode TMnm mode (n =
2, 3 ,. ． ． , M = 1) Excitation When circularly polarized waves are excited in a microstrip antenna, 9 points are used at two feeding points.
A T-branch feeding or a hybrid feeding circuit is required to provide a phase difference of 0 degree, which causes a problem that the size of the entire antenna is increased.

Further, in the case of a sequential array in which a plurality of microstrip antennas are rotated on the same plane in order to improve the axial ratio, at least two or more microstrip antennas are required, which makes it difficult to reduce the size. was there.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention uses Examples 1 to 4 of the present invention as TMn.
In a circularly polarized microstrip antenna excited in m modes (n = 1, 2, 3, ...), the position of the degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiation conductor is set to the feeding point ( 90 / 2n) + k (360/2
n) degrees (k = 0,1,2,3, ...).

In the first embodiment of the present invention, the TMnm mode (n = 1, 2,
3 ,. ． ． In a circularly polarized microstrip antenna excited by), the position of the degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiation conductor is set to (9
0 / 2n) + k (360 / 2n) degrees (k = 0, 1, 2,
3 ,. ． ． ． ).

In a fifth embodiment of the present invention, in a circularly polarized microstrip antenna provided with a degenerate separation segment for canceling the degeneracy of a mode orthogonal to the radiation conductor, in a circumferential direction along the boundary of the radiation conductor of the degeneration separation segment. The degenerate separation segment is formed by connecting two points A and B and three points C where two lines extending from the respective points toward the center intersect.

In the sixth embodiment of the present invention, the higher mode TMn
In a circularly polarized microstrip antenna excited in m modes (n = 2, 3, ...), a degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiation conductor is approximately oblique to the feeding point (90). / 2n) + k (360/2
n) degrees (k = 0, 1, 2, 3, ..., 2n) for 2n
It is provided individually.

In the seventh embodiment of the present invention, the first radiating conductor and the second radiating conductor are vertically stacked and both are circularly polarized wave excitation.
The power supply position of the radiation conductor of 180 / to the first radiation conductor
It is rotated by n (n = 1, 2, 3, ...) Degrees and the phase is 18
0 / n (n = 1, 2, 3, ...) Degrees are changed.

[0015]

In Embodiments 1 to 4 of the present invention, the circular polarization microstrip antenna excited in the TMnm mode (n = 1, 2, 3, ...) Is used to solve the degeneration of the mode orthogonal to the radiation conductor. The position of the degenerate separation segment is (90 / 2n) + k (360 / 2n) degrees (k
= 0, 1, 2, 3 ,. ． ． ． ), The reactance and susceptance components generated at the feeding point can be canceled to excite circularly polarized waves.

In the first embodiment of the present invention, the TMnm mode (n = 1, 2,
3 ,. ． ． In a circularly polarized microstrip antenna excited by), the position of the degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiation conductor is set to (9
0 / 2n) + k (360 / 2n) degrees (k = 0, 1, 2,
3 ,. ． ． ． ), It is possible to cancel the inductance component of the feed pin and excite the circularly polarized wave.

In the fifth embodiment of the present invention, in a circularly polarized microstrip antenna having a degenerate separation segment for solving the degeneracy of a mode orthogonal to the radiation conductor, in the circumferential direction along the boundary of the radiation conductor of the degenerate separation segment. Of 2
A degenerate separation segment is formed by connecting three points A, B and a point C where two lines extending from each point toward the center intersect, and the acute angle formed by the line segments C-A and C-B is α. ,
By changing this α, it is possible to adjust the frequency at which the axial ratio, which is the design frequency, becomes the minimum.

In the sixth embodiment of the present invention, the higher mode TMn
In a circularly polarized microstrip antenna excited in m modes (n = 2, 3, ...), a degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiation conductor is approximately oblique to the feeding point (90). / 2n) + k (360/2
n) degrees (k = 0, 1, 2, 3, ..., 2n) for 2n
Circularly polarized waves can be excited with a simple structure by providing them individually.

In the seventh embodiment of the present invention, the first radiating conductor and the second radiating conductor are vertically stacked and both are excited by circular polarization.
The power supply position of the radiation conductor of 180 / to the first radiation conductor
Rotate by n (n = 1, 2, 3, ...) Degrees and phase is 1
Circularly polarized waves with a good axial ratio can be excited even with one element by changing 80 / n (n = 1, 2, 3, ...).

[0020]

【Example】

Example 1. First Embodiment FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention. FIG. 1A is a top view, and FIG. 1B is its AA.
It is sectional drawing. In the figure, 1 is a ground conductor plate, 2 is a dielectric substrate, and 3 is a radiation conductor, and these constitute a microstrip antenna 4. 6 is a coaxial connector, and 5
Is the feeding pin of the inner conductor. Reference numeral 7 denotes a degenerate separation segment provided to solve the degeneracy of orthogonal modes of the radiation conductor 3.

Next, the operating principle will be described. There are various feeding methods for the microstrip antenna. Since there is a reactance and a susceptance at the feeding point according to the feeding method, matching can be achieved by including the reactance and the susceptance. On the other hand, the frequency at which circularly polarized waves are excited does not basically depend on the feeding method, but is determined by the relationship between the microstrip antenna and the degenerate separation segment. Therefore, by adjusting the phase at the time of circularly polarized wave excitation so as to cancel the reactance and susceptance generated at the feeding point, the frequency at which circularly polarized wave is excited and the frequency at which the input impedance can be matched can be matched. FIG. 2 is a diagram showing resonance characteristics of two mode functions when a degenerate separation segment is attached. If a degenerate separation segment is provided at an angle of 45 degrees to the feeding point, the degeneracy of two orthogonal modes is solved, and two modes with different resonance frequencies Φ
It can be divided into a and φb. The mode function and its equivalent circuit when the degenerate separation segment is added are the same as in FIG. La, Ca, Ga and L respectively
It can be represented by a parallel resonant circuit of b, Cb, and Gb.
The inductance of the feeding point is represented by Lp. When the position of the degenerate separation segment is shifted 45 degrees obliquely with respect to the feeding point, the sizes of the two modes Φa and Φb change. Figure 2
2A shows the amplitude and phase of the resonance characteristic when β> 45 degrees and FIG. 2B shows the resonance characteristic amplitude and phase. When β> 45 degrees, the amplitude of Φa becomes larger than Φb, and Φa
Circularly polarized waves are excited at a frequency f ′ at which the amplitudes of Φb and Φb are equal and the phase difference is 90 degrees. At this time, the phase obtained by combining Φa and Φb at the frequency f ′ is capacitive (Capacit).
Ivey) is shown. Conversely, if β <45 degrees,
The amplitude of Φb is larger than Φa, the amplitudes of Φa and Φb are equal, and the circularly polarized wave is excited at the frequency f ′ at which the phase difference is 90 degrees.
The phase in which b is combined is inductive (Inductive)
Is shown. That is, by changing the positional relationship between the feeding point and the degenerate separation segment, the phase at the circular polarization generation frequency can be changed, and the reactance and susceptance components generated at the feeding point can be canceled.

FIG. 3 shows the measured values of the input impedance when the power is fed by the coaxial pin and β is changed. β = 45 degrees and 5
The case of 5 degrees is shown. In the case of β = 45 degrees, inductive property is shown at the frequency (circular small arc is drawn on the locus of impedance) at which circularly polarized wave is generated by the inductance of the coaxial pin, and matching is not achieved at this frequency. I understand. It can be seen that when β = 55 degrees, a capacitive component is generated and the inductance of the coaxial pin is canceled out, and there is almost matching at the frequency at which circular polarization is generated. Here, an example of a circular microstrip antenna is shown, but it is also effective for other shapes of a microstrip antenna such as a rectangle, an ellipse, and a triangle. Also, although an example of one element is shown,
It is also effective for array antennas.

Embodiment 2 FIG. Second Embodiment FIG. 4 is a schematic configuration diagram of a circularly polarized microstrip antenna showing a second embodiment of the present invention. FIG. 4A is a top view and FIG. 4B is a sectional view taken along line AA. In the figure, 7 is a degenerate separation segment for solving the degeneracy of orthogonal modes of the radiation conductor 3, and 11 is a microstrip line. When the microstrip line is directly fed, the same principle as when feeding the coaxial pin shown in FIG. 1 is used to change the angle β between the microstrip line and the degenerate separation segment to cancel out the capacitance generated at the feeding point and achieve matching. be able to.

Example 3. FIG. 5 is a schematic configuration diagram of a circular polarization microstrip antenna showing a third embodiment of the present invention. 5A is a top view and FIG. 5B is a cross-sectional view taken along line AA. In the figure, 11 is a microstrip line. In this case, the microstrip line and the microstrip antenna are placed close to each other and coupled by an electromagnetic field. Capacitance occurs at this coupling. By changing the angle β between the microstrip line and the degenerate separation segment according to the same principle as the case where power is fed by the coaxial pin in FIG. 1, the capacitance generated at the feeding point can be canceled and matching can be achieved.

Example 4. Fourth Embodiment FIG. 6 is a schematic configuration diagram of a circularly polarized microstrip antenna showing a fourth embodiment of the present invention. FIG. 6A is a top view and FIG. 6B is a sectional view taken along line AA. In the figure, 11 is a microstrip line,
12 is a coupling slot. In this case, the microstrip antenna is electromagnetically coupled from the microstrip line through the coupling slot. Capacitance occurs at this coupling. According to the same principle as in the case where power is fed by the coaxial pin in FIG. 1, by changing the angle β between the microstrip line and the degenerate separation segment, the capacitance for generating the feed point can be canceled and matching can be achieved.

Example 5. 7 is a schematic configuration diagram of a circularly polarized microstrip antenna showing a fifth embodiment of the present invention. FIG. 7A is a top view and FIG. 7B is a sectional view taken along line AA. The case where power is supplied through the coaxial pin is shown. In the figure, the opening angle of the degenerate separation segment is α. This α
By changing the, the frequency at which circularly polarized waves are generated changes. FIG. 7C shows the measured value of the axial ratio minimum frequency when α is changed. By changing α from 10 degrees to 180 degrees, the minimum axial ratio frequency changes from 1.53 GHz to 1.58 GHz even if the radius of the radiation conductor is constant. Therefore, by changing this α, even if the radius is fixed, the axial ratio minimum frequency can be easily adjusted, and the design becomes easy.

Example 6. FIG. 8 is a schematic configuration diagram of a circularly polarized microstrip antenna according to a sixth embodiment of the present invention, showing the case of TM ₂₁ mode excitation. Figure 8 (a)
Is a top view. In the figure, β is the angle between the feed pin and the degenerate separation segment. Next, the operation principle will be described. As in the case of the basic mode (TM ₁₁ ), the degeneracy of orthogonal modes can be solved by providing the degenerate separation segment. This is shown in FIG. 8 (b). In the case of TM ₂₁ mode, β = 22.5 degrees results in a distribution as shown in FIG. Similar to the case of FIG. 13, all the components are canceled in the front direction, but in the wide angle, each component is 2
A vertical component and a horizontal component of the radiated electric field are generated corresponding to one mode, and a 90-degree phase difference is provided between the modes, so that circularly polarized waves can be generated. Although the example of the TM ₂₁ mode is shown here, the present invention is also effective in the case of TM ₃₁ , TM ₄₁ and TM ₅₁ .

Example 7. FIG. 9A is a schematic configuration diagram of a circularly polarized microstrip antenna showing a seventh embodiment of the present invention. In the figure, 13 is a second ground conductor plate, 14 is a third dielectric substrate, 15 is a second radiation conductor, and 16 is an opening. Next, the operation principle will be described. The first radiation conductor and the second radiation conductor are each excited by circular polarization.
It is difficult to obtain perfect circular polarization, and it is generally elliptically polarized. Complete circular polarization excitation becomes possible by using elliptical polarization as a sequential array. Therefore, by arranging the first radiating conductor and the second radiating conductor in the vertical direction and forming a sequential array in the vertical direction, the axial ratio of circularly polarized waves is improved over a wide band. Although the example of the rectangular microstrip antenna is shown here, it may be circular. Also, although an example of the rectangular opening is shown, a circular opening may be used. Furthermore, although an example of one element is shown, the present invention is also effective for an array antenna.

[0029]

According to the first to fourth embodiments of the present invention, in the circularly polarized microstrip antenna excited in the TMnm mode (n = 1, 2, 3, ...), the degeneration of the mode orthogonal to the radiation conductor is suppressed. The position of the degenerate separation segment for solving is (90 / 2n) + k (360 / 2n) with respect to the feeding point.
(K = 0,1,2,3, ...), the reactance and susceptance components generated at the feeding point are canceled by constructing the frequency offset and the frequency at which the axial ratio is good and the input impedance is matched. There is an effect that can match.

In the first embodiment of the present invention, the TMnm mode (n = 1, 2,
3 ,. ． ． ． ), The position of the degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiation conductor is (90 / 2n) + k (360 / 2n) degrees (k = 0, 1,
2, 3 ,. ． ． ． ), It is possible to cancel the inductance of the coaxial pin, and to match the frequency with a good axial ratio and the matched frequency of the input impedance.

In a fifth embodiment of the present invention, in a circularly polarized microstrip antenna provided with a degenerate separation segment for solving the degeneracy of a mode orthogonal to the radiation conductor, in the circumferential direction along the boundary of the radiation conductor of the degenerate separation segment. Of 2
A degenerate separation segment is formed by connecting three points A, B and a point C where two lines extending from each point toward the center intersect, and the acute angle formed by the line segments C-A and C-B is α. ,
By changing this α, it is possible to adjust the frequency at which the axial ratio becomes the minimum, which has the effect of facilitating the design.

In the sixth embodiment of the present invention, the higher mode TMn
In a circularly polarized microstrip antenna excited in m modes (n = 2, 3, ...), a degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiation conductor is approximately oblique to the feeding point (90). / 2n) + k (360/2
n) degrees (k = 0, 1, 2, 3, ..., 2n) for 2n
By providing the individual pieces, circular polarized waves can be excited with a simple structure, and the size can be reduced.

In the seventh embodiment of the present invention, the first radiating conductor and the second radiating conductor are vertically stacked and both are excited by circular polarization.
The power supply position of the radiation conductor of 180 / to the first radiation conductor
Rotate by n (n = 1, 2, 3, ...) Degrees and phase is 1
By changing 80 / n (n = 1, 2, 3, ...) Degree, there is an effect that even one element can excite a circular polarized wave having a good axial ratio over a wide band.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a circular polarization microstrip antenna showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the operating principle of the first embodiment.

FIG. 3 is a diagram showing measured values of Example 1 of the present invention shown in FIG.

FIG. 4 is a schematic configuration diagram of a circular polarization microstrip antenna showing a second embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a circular polarization microstrip antenna showing a third embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a circular polarization microstrip antenna showing a fourth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a circular polarization microstrip antenna showing a fifth embodiment of the present invention and a diagram showing measured values of axial ratio minimum frequencies when α is changed.

FIG. 8 is a schematic configuration diagram of a circular polarization microstrip antenna showing a sixth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a circularly polarized microstrip antenna according to a seventh embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a circularly polarized microstrip antenna showing a conventional example.

11 is a diagram for explaining the operation principle of FIG.

FIG. 12 is a diagram explaining the operation principle of FIG. 10;

13A and 13B are a schematic configuration diagram showing a conventional TM ₂₁ mode excitation circularly polarized microstrip antenna and a diagram for explaining the operation principle.

FIG. 14 is a schematic configuration diagram of a circularly polarized microstrip antenna showing a conventional sequential array.

[Explanation of symbols]

1 ground conductor plate, 2 dielectric substrate, 3 radiation conductor, 4 microstrip antenna, 5 coaxial pins, 6 coaxial connector, 7 degenerate separation segment, 8 first dielectric substrate, 9 second dielectric substrate, 10 strip Conductor, 1
1 microstrip line, 12 coupling slots, 1
3 Second Ground Conductor Plate, 14 Third Dielectric Substrate, 15
Second radiation conductor, 16 openings, 17 TM ₂₁ mode excitation microstrip antenna, 18 branch line type hybrid circuit, 19 chip resistor.

Claims (5)

[Claims] 1. A ground conductor, a dielectric substrate formed above the ground conductor, a radiation conductor formed above the dielectric substrate, a feed line for feeding the radiation conductor, and for solving degeneracy of a mode orthogonal to the radiation conductor. In the circularly polarized microstrip antenna including the degenerate separation segment, the position of the degenerate separation segment is (90 / 2n) with respect to the feed line.
+ K (360 / 2n) degrees (n = 1, 2, 3, ..., k
= 0, 1, 2, 3 ,. ． ． ) A circularly polarized microstrip antenna characterized by being staggered. 2. A ground conductor, a dielectric substrate formed on the ground conductor, a radiation conductor formed on the dielectric substrate, a feed line for feeding the radiation conductor, and for decompressing modes orthogonal to the radiation conductor. In the circularly polarized microstrip antenna including the degenerate separation segment, the position of the degenerate separation segment is set to (9
0 / 2n) + k (360 / 2n) degrees (n = 1, 2,
3 ,. ． ． , K = 0, 1, 2, 3 ,. ． ． ) A circularly polarized microstrip antenna characterized by being staggered. 3. A circular polarization comprising a ground conductor, a dielectric substrate, and a radiation conductor, a feed line feeding the radiation conductor, and a degenerate separation segment for canceling degeneracy of modes orthogonal to the radiation conductor. In the microwave microstrip antenna, a shape is formed by connecting two points A and B in the circumferential direction along the boundary of the radiating conductor of the degenerate separation segment and a point C where two lines extending from each point toward the center intersect. A circularly polarized microstrip antenna characterized in that a degenerate separation segment is constituted, an acute angle formed by the line segments CA and CB is α, and the frequency at which the axial ratio is minimized is adjusted by changing this α. . 4. A higher-order mode TMnm mode (n = 2, 3, ..., M = 1), which comprises a ground conductor, a dielectric substrate, and a radiation conductor, and is provided with a feed line for feeding the radiation conductor.
In the circularly polarized microstrip antenna excited by, the degenerate separation segment for solving the degeneracy of the mode orthogonal to the radiating conductor is approximately oblique to the feeding point (90/2).
n) + k (360 / 2n) degrees (k = 0, 1,
2 ,. ． ． ． 2n pieces are provided in (1). 5. A ground conductor, a dielectric substrate, a first radiation conductor,
The second radiation conductor is arranged above the first radiation conductor, and the first radiation conductor and the second radiation conductor are both circularly polarized wave excitation, and the feeding position of the second radiation conductor is 180 / n (n = 1, 2,
3 ,. ． ． ． ) Degrees, and the phase is 180 / n (n =
1, 2, 3 ,. ． ． ． ) A circularly polarized microstrip antenna characterized by varying the degree.