JPH0541608A - Microstrip antenna - Google Patents

Abstract

(57) [Abstract] [Purpose] Compared with the conventional example, it is not necessary to use a semi-rigid cable or the like, so it is easy to fabricate, the placement of the feed line is simple, and the influence of mutual influence on the frequency of transmission and reception is suppressed. Provide a strip antenna. In a microstrip antenna including a circular or rectangular microstrip patch 2 and a ground conductor plate 1, a feed line 4 between the patch 2 and the ground conductor plate 1 has an arbitrary length from the outside to the inside of the patch. , 5 to 2
The main feed line is inserted and the two feed lines 4 and 5 do not overlap each other and are arranged at an angle of approximately 90 degrees.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip antenna comprising a microstrip patch capable of simultaneous transmission and reception and a ground conductor plate.

[0002]

2. Description of the Related Art In a mobile satellite communication system for communicating between a mobile unit such as an automobile and a fixed station or between the mobile unit and a mobile unit via a satellite, an antenna provided on the mobile unit is small and lightweight. It is required that radio waves with circular polarization can be transmitted and received at different frequencies. This separates the receive channel from the transmit channel, which has a much higher output. That is, in order to prevent a transmission signal from leaking into a reception signal, a diplexer is generally used when an antenna element for both transmission and reception is used, and a filter is used when an antenna element for transmission and reception separation is used.

In the active array antenna, one transmitting / receiving separating element is required for each antenna element. Transmission / reception separating elements such as diplexers and filters are generally bulkier and heavier than antenna elements. As the number of elements increases, the weight becomes heavier and the volume increases, so that the spatial occupied area of the antenna becomes larger. As it is, it is not suitable for mobile objects. Therefore, it is necessary to reduce isolation between transmitting and receiving between antenna elements and reduce the demands on filters and diplexers.

As a first conventional example showing a solution to this problem, there is a microstrip antenna proposed by Shiokawa et al. (Institute of Electronics, Information and Communication Engineers, Antenna and Propagation Study Group A, P86-60) shown in FIG. This antenna is a circularly polarized antenna, and is a transmission / reception separated antenna in which transmission and reception are performed by separate elements. This antenna utilizes the frequency selectivity between the upper patch for transmission and the lower patch for reception. The proposed antenna isolation between transmission and reception is -28 dB. Since the required isolation is 60 to 70 dB, it is necessary to provide a band filter at this stage in order to obtain the isolation to satisfy the required value.

Since this antenna has a structure in which the transmitting antenna 30 and the receiving antenna 31 are vertically stacked, the planar area is small. Since the method of stacking the transmitting and receiving antennas is used, the structure of the antennas is complicated, and the coaxial lines of the semi-rigid cables 32, 33, 34, 35 are used, so soldering work or the like is required. Further, in order to separate the transmitting antenna 30 and the receiving antenna 31, it is necessary to make the receiving antenna 31 into an annular shape.
And the receiving antenna 31 must be short-circuited with a large number of ground pins.

Therefore, the structure of this antenna is complicated, the number of manufacturing steps increases, and the manufacturing cost increases. To generate circularly polarized waves, the semi-rigid cables 32 and 3
3. A 90-degree hybrid for generating a 90-degree phase difference is required between the semi-rigid cables 34 and 35.

A second conventional example showing another solution is a circularly polarized wave simultaneous transmission / reception composite antenna disclosed in Japanese Patent Laid-Open No. 2-116202. As shown in FIG. 24, this antenna uses a microstrip line 43 formed on the same plane as the rectangular patch antenna 40 to directly connect the antenna end face 4
1 is fed to generate a frequency f1 which is a horizontally polarized wave, and the microstrip line 44 directly connects the antenna end face 4
2 is fed to generate a frequency f2 which is a vertically polarized wave.
In addition, FIG. 24 shows a configuration in which four antennas are used and the antenna is spatially rotated clockwise by 90 degrees and power is supplied with a phase difference of 90 degrees.

By using this structure, a composite antenna for simultaneous circular polarization transmission / reception is realized. Circular polarization is realized by creating orthogonal polarizations with different frequencies for each antenna element and using a pair of elements. Therefore, the transmitting antenna and the receiving antenna can be separated. This antenna is
Simple to configure. Furthermore, the antenna element and the feed line can be formed on the same substrate.

However, in this structure, the end face of the antenna must be directly fed with the microstrip line. The input impedance of the antenna viewed from the end face of the antenna is 200 to 300Ω. Since the characteristic impedance of the feed line is 50Ω, a transformer having a line length of λg / 4 must be provided in order to achieve impedance matching. Furthermore, a transformer having a line length of λg / 4 for transmission and a transformer for reception is required, and since it forms an array, it must be provided for each antenna element. In order to perform wide-angle beam scanning of 60 degrees or more, the element spacing of the array antenna needs to be about a half wavelength. Therefore, it is required to dispose the power supply lines including the impedance transformers having the line lengths of λg / 4 for the transmission power lines and the reception power lines in the limited space.

For this reason, the feed lines may be close to each other,
Since the antenna element and the feed line are close to each other, mutual coupling occurs between the two, and the antenna element has an equal amplitude of 90.
The condition that power must be supplied with a phase difference of 10 degrees is lost, and good circular polarization cannot be generated. Furthermore, mutual coupling occurs between the power supply line for transmission and the power supply line for reception, so that the isolation between the transmission band and the reception band deteriorates.

Reference by the same inventor AP-S90pp80
3-806, SELFDIPLEXING CIRCULARLY POLARIZED ANT
As reported in ENNA, the isolation between transmit and receive is only 20 to 23 dB. Further, when the substrate thickness is increased, coupling between the transmission port and the reception port due to the higher-order mode TM20 occurs, the isolation deteriorates, and the degree of separation between transmission and reception decreases.

Further, in the mobile satellite communication system, the antenna provided in the mobile unit is small and
There is a demand for a high-performance and high-performance antenna that is lightweight and capable of wide-angle, high-speed beam scanning to enable communication while tracking satellites, and that is capable of transmitting and receiving radio waves by circular polarization. FIG. 25 is a plan view of a circularly polarized microstrip antenna element 20 which is a third conventional example used in this type of mobile satellite communication system, and FIG.
It is a longitudinal cross-sectional view about AA in FIG. Figure 2
5 and FIG. 26, a circular microstrip patch 5 made of a conductor plate is formed on the upper surface of a rectangular dielectric substrate 51.
2 is formed, and the ground conductor plate 53 is formed on the back surface of the dielectric substrate 51. Microstrip patch 52
A conductor pin 54 electrically connected to the patch 52 is provided penetrating the dielectric substrate 51 at a position on the right side of the center Q of the figure, and the other end of the conductor pin 54 is connected to the ground conductor plate 5.
3 is contactlessly penetrated and is connected to the central electrode 55a of the connector 55 provided on the back surface of the ground conductor plate 53. The outer electrode 55b of the connector 55 is electrically connected to the ground conductor plate 53. Reference numeral 59 is a conductor pin provided at a position rotated 90 degrees about Q from the position of the conductor pin 54. The conductor pin 59 is also provided with a connector 56 similar to the connector 55.

Here, 90 is attached to either the connector 55 of the conductor pin 54 or the connector 56 of the conductor pin 59.
Insert a phase shifter that delays the phase,
When signals having a phase difference of 90 degrees with each other are fed to the patch 52 via 56, circularly polarized wave is radiated from the circularly polarized microstrip antenna 50.

FIG. 27 is a plan view of a circularly polarized microstrip antenna 60 which is a fourth conventional example used in the above-mentioned mobile satellite communication system, and FIG. 28 shows a line AA of FIG. FIG.

Similar to the above-mentioned conventional example, the microstrip patch 62 and the ground conductor plate 63 are formed on each surface of the dielectric substrate 61, and the conductor pin 64 and the center are arranged at the same positions as the conductor pins 64. Electrode 65a and outer electrode 65
A connector 65 of b is provided. Then, a "U" -shaped notch 6 is formed on the peripheral edge of the microstrip patch on a line that makes an angle of 45 degrees with the line connecting the center Q of the microstrip patch 62 and the position of the conductor pin 64.
2a and 62b are provided. When a signal is supplied from the connector 65 to the circularly polarized microstrip antenna 60 formed in this way, circularly polarized radio waves are radiated.

29 is a plan view of a circularly polarized microstrip antenna 70, which is a fifth conventional example used in the mobile satellite communication system, similar to the above-mentioned conventional example, and FIG. It is a longitudinal cross-sectional view about the 29 AA line. A microstrip patch 72 and a ground conductor plate 73 are formed on each surface of the dielectric substrate 71.
A connector 75 including a central electrode 75a and an outer electrode 75b is provided at the same position as described above. A slot 76 is provided at the center of the microstrip patch centering on Q on a line forming an angle of 45 degrees with the line connecting the center Q of the microstrip patch 72 and the position of the connector 75. In this case, the length of the slot 76 must be very small in order to generate circularly polarized waves. When a signal is supplied from the connector 75 to the circularly polarized wave microstrip antenna 70 thus formed, circularly polarized radio waves are radiated at a resonance frequency substantially the same as that of a patch antenna having no slot.

A plurality of the antennas 50, 60, 70 of the third, fourth, or fifth conventional examples are arranged in an array, and a variable phase shifter is connected to the connector of each antenna.
The other end of these variable phase shifters is connected to a transmitter or receiver via a power divider / combiner. In the system configured as described above, beam scanning is performed by controlling the phase amount in each phase shifter.

[0018]

The antenna of the first conventional example requires two transmitting antennas and two receiving antennas. In addition, in order to obtain isolation between the two, the receiving antenna must be annular and a large number of ground pins must be provided between the antenna and the ground conductor plate. Furthermore,
Requires coaxial connectors for power transmission lines for transmission and reception,
A 90 degree hybrid is also needed to generate circular polarization. Therefore, this antenna has a problem in that the structure is complicated and the work such as soldering is required, so that the number of manufacturing steps increases and the manufacturing cost increases.

The antenna of the second conventional example has a simple structure, but in order to match the antenna element and the feed line, an impedance conversion transformer of λg / 4 is used for each feed port for transmission and reception. Therefore, the arrangement of the feeding lines is complicated, the line intervals are dense, mutual coupling between the lines occurs, the amplitude and phase of the feeding current deviate from desired values, and accurate feeding cannot be achieved. Therefore, there is a problem that the characteristics of the antenna are deteriorated.

In the antenna 50 of the third conventional example,
Two conductor pins 54 and 59 and connectors 55 and 56 are required, and antennas 60 and 7 of the fourth and fifth conventional examples are required.
In the case of 0, the conductor pins 64 and 74 are required, and the structure is complicated, so that the number of manufacturing steps increases and the manufacturing cost becomes high.

In both the third, fourth and fifth conventional examples, the first and second examples
As in the conventional example, connecting to a variable phase shifter or a power distributor / combiner via a coaxial line such as a semi-rigid cable results in a large power feed loss and a large antenna system shape including these functional circuits. There was a problem.

The object of the present invention is to solve the above-mentioned problems, and because it is not necessary to use a semi-rigid cable or the like as compared with the conventional example, it is easy to manufacture, the arrangement of the power feeding line is simple, and the transmission and reception frequencies can be adjusted. An object is to provide a microstrip antenna that suppresses mutual influences.

Another object of the present invention is to provide a close-coupled circular polarization microstrip antenna in which the antenna element has good circular polarization characteristics.

[0024]

To achieve the above object, the present invention provides a microstrip antenna comprising a circular or rectangular microstrip patch and a ground conductor plate, wherein the patch is provided between the patch and the ground conductor plate. Insert two feed lines of arbitrary length from the outer side to the inner side, the two feed lines do not overlap each other, and
It is characterized by being arranged at an angle of 0 degree.

The microstrip antenna according to a second aspect of the invention is characterized in that a slot is provided on the patch and at least one of the feed lines is inserted from the same direction as the slot.

According to a third aspect of the present invention, in a microstrip antenna including a rectangular microstrip patch and a ground conductor plate, a space between the rectangular patch and the ground conductor plate is substantially parallel to the centerline of the rectangular patch. The feed line is inserted from the outside of the ground conductor plate at an arbitrary position between the edges of a rectangular patch.

[0027]

According to the present invention, a microstrip antenna capable of transmitting and receiving at different frequencies at the same time can be realized,
In addition, the isolation level between the power feeding lines of the transmitting and receiving antennas can be about -32 dB or more. Therefore, the value of the isolation level required for the filter or diplexer can be reduced. Moreover, since the antenna element and the feed line are matched, λg which is conventionally required
No impedance transformer with a length of / 4 is required. For this reason, the placement of the power supply line becomes easy,
Since the coupling between the lines or between the line and the antenna is significantly reduced, the current can be controlled with high accuracy, and thus good antenna characteristics can be obtained. Further, since the coaxial connector is not used, the manufacture is easy and the cost can be reduced.

[0028]

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

FIG. 1 is a plan view of a two-frequency circular microstrip antenna according to the first embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA. 1 and 2,
Reference numeral 1 is a square-shaped dielectric substrate having a predetermined thickness, 2 is a circular patch made of a conductor plate, 3 is a ground conductor, and 4 and 5 are feeder lines having an arbitrary length from the outside to the inside of the patch. ..

The feed lines 4 and 5 are arranged so as not to overlap each other and to form an angle of 90 degrees. In Figure 3,
The feed line length Sl (distance between the center of the circular patch 2 and the feed line end) when the feed line 4 shown in FIG. 1 is removed and the patch antenna is excited by feeding only the feed line 5
Shows the relationship between resonance frequency and reflection loss. Feed line length Sl
Is measured with the center of the circular patch 2 as the origin, and is positive when the feed line end exceeds the center of the circular patch 2 and negative when the feed line end does not exceed the center. From Fig. 3, the resonance frequency changes depending on the length of the feeder line, and the length of the feeder line is -25 mm and 5
It can be seen that a match can be made with the feed line (impedance 50 Ω) when mm.

When a probe feed such as a conventional semi-rigid cable is used, the resonance frequency of the circular patch antenna is uniquely determined by the radius r. However, if this feeding method is used, even if the radius r of the circular patch is constant, the feeding line length S
Changing 1 changes the resonance frequency. That is, the resonance frequency can be controlled by the length of the feeding line. From this result, in the antenna shown in FIG.
FIG. 4 shows the reflection loss and the mutual coupling of the feed lines 4 and 5 when viewed from the feed lines 4 and 5 when the length of the feed line 5 is 5 mm and the length of the feed line 5 is 5 mm.

The resonance frequency seen from the power feeding line 4 is 1.52.
9 GHz, resonance frequency from power supply line 5 is 1.58 GH
z. Further, the isolation level between the feed lines 4 and 5 is about -35 dB. That is, it is understood that the dual-frequency microstrip antenna is realized by using this method.

FIG. 5 shows a circular patch antenna with a slot according to the second embodiment in which one slot 6 is newly provided in the circular patch shown in FIG. FIG. 6 is a sectional view taken along line AA of FIG. The slot 6 is on the same line as the feed line 5, and is orthogonal to the feed line 4.

FIG. 7 shows changes in the resonance frequency when the feed line 5 shown in FIG. 5 is removed, the length of the feed line 4 is set to -25 mm, and the slot length Ls is changed. From this figure, as the slot 6 is lengthened, the resonance frequency monotonously decreases. Using this result, in the antenna shown in FIG.
FIG. 8 shows the reflection loss seen from the feed line 4 and the feed line 5 and the mutual coupling between the feed lines 4 and 5 when the slot length Ls is 20 mm and the lengths of the feed lines 4 and 5 are -25 mm. .. From these results, the isolation between the feed lines is about -32 dB. The resonance frequency viewed from the power supply line 4 is 1.531 GHz, and the resonance frequency viewed from the power supply line 5 is 1.633 GHz. From this result, it can be seen that a two-frequency microstrip antenna is obtained by using this antenna method.

Next, using the antennas shown in FIGS. 1 and 5, an array antenna having a feed line length in which four elements are spatially rotated clockwise by 90 degrees each and the feed phase is delayed by 90 degrees is provided. It is shown in FIG. This power feeding method is the same as the second conventional example. By using this method, 2
It is clear that a frequency circularly polarized antenna can be obtained. Here, the polarization direction of each element antenna corresponding to each resonance frequency is arbitrary. Furthermore, array antennas that minimize the feed line insertion loss are shown in FIGS. 9 (b) and 9 (c). Figure 9 (b)
Is a diagram showing a patch of the array antenna, and FIG. 9 (c) is a diagram showing a feed line (transmission Tx, reception Rx) of the array antenna, which is effective for increasing the gain of the transmission antenna (reversely, reception is performed. Higher gain of the antenna). Here, the circular polarization is shown by four elements, but the same effect can be obtained by using a sequential array array of two or more elements.

When this method is used, since the antenna element and the feed line are matched with each other by 50Ω, it is necessary in the conventional method, and the impedance transformer having the length of λg / 4 is unnecessary in the present invention. Therefore, a sufficient space can be provided between the power feeding lines and between the power feeding line and the patch antenna. Therefore, the isolation between transmission and reception can obtain the same characteristics as those shown in FIGS.

In the above embodiments, the microstrip patch has a circular shape, but the present invention is not limited to this.
Other shapes such as a rectangle and an ellipse may be used. Further, the slot is not limited to the rectangular shape, and may have an elliptic shape, a rhombic shape, or the like having the same effect.

10 and 11 are a plan view of a microstrip antenna according to the third embodiment of the present invention and a sectional view taken along the line AA. The cross slot 7 may be provided on the patch antenna as in this embodiment. Also,
The feed lines 4 and 5 are inserted from the same direction as the orthogonal slots of the cross slot 7. Furthermore, the feed line length may be different and the slot length may be different. Further, it is not necessary for the slot and either or both of the feed lines to be on the same line. Further, in one slot and cross slot, each feed line does not have to be on the same plane.

12 and 13 are a plan view of a proximity coupling circular microstrip antenna according to a fourth embodiment of the present invention and a sectional view taken along the line AA. In FIGS. 12 and 13, reference numerals 11 and 12 denote dielectric substrates each having a rectangular shape and a predetermined thickness.
13 is a rectangular patch made of a conductor plate, 14 is a ground conductor,
Reference numeral 15 is a microstrip feed line having an arbitrary length from the outside to the inside of the rectangular patch.

The resonance frequency of the rectangular patch antenna uniquely corresponds to the external dimensions of the rectangular patch antenna. Therefore, consider the antenna shown in FIG. The dimensions of the antenna are La and Lb, and La> Lb. When the power is fed from the feeding point A on the center line of La, the resonance frequency is fa,
The resonance frequency when power is supplied from the direction of the power supply point B on the center line of Lb is fb, and both frequencies have a relationship of fa> fb.

Therefore, as shown in FIG.
Is shifted from the feeding point A at the center of La to the feeding point A'to the left (the shift means to shift the center line of the line by more than the line width when the line is assumed to be at the center). That is, it does not mean a shift due to a manufacturing error.), As shown in FIG. 14, a first linear polarization microstrip antenna having a resonance frequency fa and a linear polarization microstrip having a resonance frequency fb lower than the resonance frequency fa. A strip antenna is formed. First, second
The frequency characteristics of the amplitude value and the phase value of the excitation current of the linearly polarized microstrip antenna are as shown in FIG.
At the frequency fo at which the excitation currents la and lb of the two linearly polarized microstrip antennas have the same amplitude value and the phase difference is 90 degrees, the linearly polarized waves radiated from the first and second antennas are spatially combined. And functions as a circularly polarized antenna.

The antenna dimensions are La = 58 mm and Lb = 5.
6 mm, substrate thickness h = 1.6 mm, offset amount Lo 14.4 mm, microstrip line length Ls 13.
6 mm. The frequency characteristic of the reflection loss of the antenna of the present invention is shown in FIG. The dielectric constant of the dielectric substrate is 2.55. The characteristic impedance of the power supply line 15 is 50Ω.
Is. FIG. 18 shows the radiation directivity of this antenna. The radiation power in the maximum radiation direction θ = 0 degrees is normalized as 0 dB. As can be seen from this figure, the circularly polarized antenna obtained an axial ratio (difference between the maximum value and the minimum value of the radiated power) of about 0.2 dB in the front direction.

FIG. 19 shows the axial ratio when the feed line length Ls and the offset amount Lo are changed. It can be seen from FIG. 19 that good circular polarization characteristics are obtained near the center line and the center of the edge. Moreover, the positional accuracy of the power supply line 15 may be rough.

20 to 22 show modifications of the close-coupling circular microstrip antenna according to the present invention. The feed line 15 does not need to be parallel to the center line, and may have a certain inclination. Also, the ratio of the lengths of the rectangular patches (Lb
/ La) may be arbitrary and may be Lb> La.

When this method is used, the feeder line 15 and the radiating element are electromagnetically and non-contactly coupled to each other without using a direct connection such as a pin, so that the soldering shown in the conventional example is unnecessary. .. Further, since the antenna element and the feed line 15 are matched with each other, an impedance transformer having a length of λg / 4, which is conventionally required, is unnecessary. Further, as compared with the conventional example, the 90-degree hybrid for generating the circularly polarized wave is unnecessary, and the power supply circuit can be simplified.

[0046]

As described above, according to the present invention of claim 1, a microstrip antenna capable of transmitting and receiving at different frequencies at the same time can be realized, and the isolation level between the feeding lines of the transmitting and receiving antennas can be realized. About −
32 dB or more can be obtained. Therefore, the value of the isolation level required for the filter or the diplexer can be reduced, so that the cost and size of the antenna system can be reduced.

Further, since the antenna element and the feed line are matched with each other, the impedance transformer having a length of λg / 4, which is conventionally required, is unnecessary. For this reason, the arrangement of the feed line is simplified, and the coupling between the lines or between the line and the antenna is significantly reduced, so that the current can be controlled with high accuracy, so that good antenna characteristics can be obtained. Further, since the coaxial connector is not used, the manufacture is easy and the cost can be reduced.

According to the present invention of claim 3, the feed line and the radiating element are connected in a non-contact manner in an electromagnetic field without using a direct connection such as a pin or the like, so that the solder gap shown in the conventional example is used. It becomes unnecessary. Therefore, the manufacturing cost can be reduced and the reliability can be improved. Further, since the antenna element and the feeding line are matched, the impedance transformer having the length of λg / 4, which is conventionally required, is unnecessary.
For this reason, the arrangement of the feed line is simplified, and the coupling between the lines or between the line and the antenna is significantly reduced, so that the current can be controlled with high accuracy, so that good antenna characteristics can be obtained. Further, as compared with the conventional example, a 90-degree hybrid for generating circularly polarized waves is not required, and the power feeding circuit can be simplified.

[Brief description of drawings]

FIG. 1 is a plan view of a dual frequency microstrip antenna according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of the dual frequency microstrip antenna shown in FIG.

FIG. 3 is a diagram showing a resonance frequency characteristic of the microstrip antenna at one frequency in FIG.

4 is a diagram showing experimental values of resonance characteristics and mutual coupling of the microstrip antenna at two frequencies in FIG.

FIG. 5 is a plan view of a dual frequency microstrip antenna according to a second embodiment of the present invention.

6 is a sectional view taken along line AA of the dual frequency microstrip antenna shown in FIG.

FIG. 7 is a diagram showing a resonance frequency characteristic of the microstrip antenna at one frequency in FIG.

FIG. 8 is a diagram showing experimental values of resonance characteristics and mutual coupling of the microstrip antenna at two frequencies in FIG.

FIG. 9 is a plan view of a four-element circular polarization array antenna to which the present invention has been applied.

FIG. 10 is a plan view of a dual frequency microstrip antenna according to a third embodiment of the present invention.

11 is a sectional view taken along line AA of the dual frequency microstrip antenna shown in FIG.

FIG. 12 is a plan view of a close-coupled circularly polarized microstrip antenna according to a fourth embodiment of the present invention.

13 is a cross-sectional view taken along the line AA of the close-coupled circularly polarized microstrip antenna shown in FIG.

FIG. 14 is a diagram illustrating the principle of a close-coupled circularly polarized microstrip antenna according to the fourth embodiment.

FIG. 15 is a diagram illustrating the principle of a close-coupled circularly polarized microstrip antenna according to the fourth embodiment.

FIG. 16 is a diagram showing frequency characteristics of the amplitude value and the phase value of the excitation current of the close-coupled circularly polarized microstrip antenna according to the fourth example.

FIG. 17 is a diagram showing reflection loss characteristics of a close-coupled circularly polarized microstrip antenna according to the fourth example.

FIG. 18 is a diagram showing radiation directivity of a close-coupled circularly polarized microstrip antenna according to a fourth example.

FIG. 19 is a diagram showing a relationship among a feed line offset amount Lo, a feed line length Ls, and a circular polarization characteristic of a proximity coupling circular polarization microstrip antenna according to a fourth example.

20 is a diagram showing a first modification of the close-coupled circularly polarized microstrip antenna shown in FIG.

21 is a diagram showing a second modification of the close-coupled circularly polarized microstrip antenna shown in FIG.

22 is a diagram showing a third modification of the close-coupled circularly polarized microstrip antenna shown in FIG.

FIG. 23 is a plan view of a circularly polarized microstrip antenna as a first conventional example.

FIG. 24 is a plan view of a circularly polarized microstrip antenna which is a second conventional example.

FIG. 25 is a plan view of a circularly polarized microstrip antenna as a third conventional example.

FIG. 26 is a sectional view taken along line AA of the close-coupled circularly polarized microstrip antenna shown in FIG. 25.

FIG. 27 is a plan view of a circularly polarized microstrip antenna as a fourth conventional example.

28 is a sectional view taken along line AA of the close-coupled circularly polarized microstrip antenna shown in FIG.

FIG. 29 is a plan view of a circularly polarized microstrip antenna as a fifth conventional example.

30 is a cross-sectional view taken along the line AA of the close-coupled circularly polarized microstrip antenna shown in FIG.

[Explanation of symbols] 1, 11 ... Dielectric substrate 2 ... Circular patch 3 ... Ground conductor plate 4, 5 ... Feed line 6 ... Slot 7 ... Cross slot 13 ... Rectangular patch

Claims (3)

[Claims] 1. A microstrip antenna comprising a circular or rectangular microstrip patch and a ground conductor plate, wherein a feed line having an arbitrary length from the outside to the inside of the patch is provided between the patch and the ground conductor plate. A microstrip antenna in which two power feed lines are inserted so that they do not overlap each other and are arranged at an angle of approximately 90 degrees. 2. The microstrip antenna according to claim 1, wherein a slot is provided on the patch, and at least one of the feed lines is inserted from the same direction as the slot. 3. A microstrip antenna comprising a rectangular microstrip patch and a ground conductor plate, wherein the edge of the rectangular patch that is substantially parallel to the centerline of the rectangular patch is between the rectangular patch and the ground conductor plate. A microstrip antenna characterized in that a feed line is inserted from outside the ground conductor plate at an arbitrary position between them.