JP2001127523A - Microstrip array antenna with radome - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microstrip array antenna with radome that can efficiently emit power of an array center with high power density and where a change in an element impedance is eliminated at array circumferential parts with much contribution to beam shaping such as a low side lobe so as to obtain a desired radiation characteristic. SOLUTION: The interval between the antenna and the radome is selected about a half of a center frequency of the antenna in the middle of the array, about 1/4 of the center frequency at the array circumferential parts. The radome has curvatures consisting of curves smoothly joining the intermediate parts between the middle and the circumferential parts of the radome.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip array with a radome for generating a fixed beam having a small, thin, lightweight and simple structure and having a radome for protecting the antenna surface for use outdoors or the like. It is about an antenna.

[0002]

2. Description of the Related Art Normally, a microstrip array antenna obtains desired radiation characteristics by feeding each radiating element with a desired excitation amplitude and phase (hereinafter referred to as "excitation distribution").
As one technique for achieving a desired excitation distribution for each radiating element, a phase shifter and a high-power amplifier (transmitting / receiving module) are directly connected to each radiating element to control the amplitude and phase of each radiating element. Active phased array system,
As another method, there is a passive phased array system in which a phase shifter is connected to each radiating element to control the phase of each radiating element. These two array systems are mainly used for beam scanning. Since the whole configuration including the phase shifter and the transmission / reception module becomes complicated, it is not usually used for an antenna that generates a fixed beam.
It will be omitted from the following description.

As an example of the configuration of a feeder circuit of a microstrip array antenna that generates a fixed beam, a coplanar feeder in which a microstrip line is provided on the same plane as a radiating element, and a power combining / distribution circuit is formed by the microstrip line. There is a method. Further, as another example, a second dielectric substrate is provided on the back surface of a first dielectric substrate composed of a radiating element and a ground conductor, and a microstrip line or a triplate line is provided on the second dielectric substrate. And the like, to constitute a power combining / distribution circuit, and to directly connect the radiating element and the feeding circuit with a feeding pin, or to provide a slot or the like to electromagnetically couple the radiating element and the feeding circuit. There is a multi-layer power supply system that excites

FIG. 9 shows an example of a microstrip array antenna. In the figure, 1 is a ground conductor, 2 is a dielectric substrate, 3 is a radiating element, and these constitute a microstrip antenna 4. Reference numeral 5 denotes a strip conductor, and the ground conductor 1 and the dielectric substrate 2 constitute a microstrip line 6. Reference numeral 7 denotes a T-branch line as an example of a power combining / distributing circuit. Reference numeral 8 denotes a power supply point, and it is assumed that power is supplied from the rear surface by pins using a coaxial connector. Alternatively, power may be supplied from a waveguide via a waveguide / microstrip line converter.

Next, the operation will be described. Here, the case of a transmission antenna is considered. The radio wave input to the antenna is mode-converted from the coaxial connector to the microstrip line 6 at the feeding point 8, and each of the T-branch lines 7 constituted by the microstrip line 6 is formed on a coplanar plane with a desired excitation distribution. Are supplied to the microstrip antenna 4. By directly connecting the end of the microstrip line 6 to the end of the microstrip antenna 4, the microstrip antenna 4 is excited by the electric field at the end. The excited microstrip antenna 4 causes a resonance phenomenon by setting the antenna length to about a half wavelength, and is radiated.

[0006] When the microstrip array antenna is used outdoors, a radome made of a dielectric is usually attached for the purpose of protecting the surface of the antenna. FIG. 10 shows an example of a microstrip array antenna with a radome. In the figure, reference numeral 9 denotes a microstrip array antenna having the same configuration as that of FIG. 9, for example, and reference numeral 10 denotes a radome. Radomes are required to have high radio wave transmittance, mechanical strength, and weather resistance. Normally, the distance between the microstrip array antenna 9 and the radome 10 is about 1/2 of the center frequency of the antenna in order to improve the efficiency of the antenna.
Often referred to as wavelength.

Next, the operation of the radome will be described. The microstrip array antenna 9 operates in the same manner as in FIG. 9 and emits radio waves. A part of the radiated radio wave is refracted and transmitted through the radome and radiated in a desired direction, a part is reflected by the radome and returns toward the antenna surface, and a part disappears as a dielectric loss inside the radome. At this time, by setting the interval between the antenna and the radome to be about 波長 wavelength, the waves reflected by the radome become in-phase on the antenna surface and re-emitted, so that the efficiency of the antenna can be increased.

[0008] Alternatively, as shown in p301 of the Antenna Engineering Handbook, edited by the Institute of Electronics, Information and Communication Engineers, the wavefront of the radiated radio wave and the radome plane are attached at an angle,
The reflected wave does not return to the antenna aperture.

[0009]

The conventional microstrip array antenna with a radome is configured as described above, and when the radome shape is a flat plate, it is easy to increase the efficiency of the radiated power. That is, the radio wave radiated from the radiating element 3 is reflected by the radome 10 and has the same phase in the radiating element 3, and a part is reflected on the radiating element surface and re-radiated.
However, a part of the reflected wave from the radome 10 is received by the radiating element 3, and the received power and the reflected wave generated between the microstrip line 6 and the radiating element 3 are strengthened in phase with each other, so that the radiated The reflection characteristic of the element 3 deteriorates, that is,
Since the reflected wave from the radome 10 exists in the same phase in the vicinity of the radiating element, the active impedance of the radiating element deviates from the matching, and there is a problem that the reflection characteristics of the entire antenna deteriorate. Further, there is a problem that the radiation characteristic (for example, side lobe characteristic) of the antenna deteriorates because the impedance matching of the feed circuit is broken due to the deterioration of the reflection characteristic of the radiating element 3 and the excitation distribution deviates from a desired value. . In particular, when a T-branch line that is easy to design, compact in configuration, and easy to manufacture as a power supply circuit is used as a power distribution / combination circuit, the deterioration of the excitation distribution due to the reflected wave of the power supply circuit increases. When the influence of the radome is large, a power combining / distribution circuit with little change in performance due to the reflection characteristics of the Wilkinson circuit or the like, or a feeder circuit with a more complex configuration such as a multilayer antenna must be used. There was a problem that had to be done.

Further, there are many demands for the radome surface to have a curvature for reasons such as prevention of adhesion of rainwater, ice and snow, easy removal of the mold when the radome is integrally formed, and appearance of the antenna. In this case, since the radome is usually placed near the antenna, the electromagnetic field in the vicinity of the radome is not a plane wave, but is a Fresnel region where the quasi-electrostatic field and the induced electromagnetic field are dominant. -It was difficult to analyze the effects of scattering and reflection, and the radome had to be experimentally determined.

Further, with the advance of digital modulation technology, the bit rate tends to increase in order to increase the transmission capacity. In the future, when the reflected wave from the radome is re-emitted from the antenna aperture, the delay time of the reflected wave will be increased. As a result, the delay wave may be superimposed on the signal wave and emitted, so that the communication quality may be degraded.

The present invention has been made to solve such a problem, and efficiently radiates electric power at the center of an array having a high power density, and has a large contribution to beam shaping such as low side lobes. SUMMARY OF THE INVENTION An object of the present invention is to provide a microstrip array antenna with a radome that eliminates a change in element impedance and obtains a desired radiation characteristic.

[0013]

A microstrip array antenna with a radome according to the first invention uses a microstrip antenna fed by a microstrip line, and sets an interval between the antenna and the radome near the center of the antenna. A radome having a curvature such that the interval gradually changes so that the wavelength is about 約 of the center frequency and about ４ wavelength near the periphery of the antenna.

A microstrip array antenna with a radome according to a second aspect of the present invention uses a microstrip antenna fed by pins, and the distance between the antenna and the radome is set to be about 1/1 / the center frequency of the antenna near the center of the antenna. A radome having a curvature such that the interval gradually changes so as to have two wavelengths and a wavelength of about 1/4 near the periphery of the antenna is used.

A microstrip array antenna with a radome according to a third aspect of the present invention is a flat-plate radome in which the distance between the antenna and the radome is about 1/4 wavelength.

Further, in the microstrip array antenna with a radome according to the fourth invention, a barrier made of a metal body is provided around the antenna so as to protrude from the antenna surface.

A microstrip array antenna with a radome according to a fifth aspect of the present invention is provided with a radio wave absorber protruding from the antenna surface around the antenna.

A microstrip array antenna with a radome according to a sixth aspect of the present invention uses a radome having an integral radiation opening and a side wall, and a metal wall provided inside the radome side wall.

A microstrip array antenna with a radome according to a seventh aspect of the present invention uses a radome in which a radiation opening and a side wall are integrally formed, and a radio wave absorber is attached to the inside of the radome side wall.

Further, a microstrip array antenna with a radome according to the eighth invention is one in which the microstrip antenna is circularly polarized wave excitation.

Further, in the microstrip array antenna with a radome according to the ninth aspect, the thickness of the radiation opening of the radome is set to about half a wavelength / √ (relative permittivity of the radome).
It is what it was.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a schematic configuration diagram showing Embodiment 1 of the present invention.
Reference numeral 10 is exactly the same as that of the conventional example. The microstrip antenna 9 has a configuration as shown in FIG. 9, for example. About λ / 2 (λ:
Free space wavelength), and about λ /
No. 4 is characterized in that the intermediate portion is a curved radome having a curvature smoothly connected.

Next, the operation will be described. In general, in an array antenna, the side lobe level when the excitation amplitude of each radiating element is uniform is about 13 dB, and the amplitude distribution over the aperture is tapered to obtain low side lobe characteristics. In many cases, the density is high and the power density in the peripheral portion is low (for example, -10 dB or less in the central portion). Also, depending on the use of the antenna, it is often practiced to add an amplitude / phase taper to obtain a specific shaped beam, but in this case also, the power density in the central part is usually increased. Therefore, by setting the distance between the antenna 9 and the radome 10 to be approximately λ / 2 near the center of the array, the radio wave radiated from the antenna 9 and reflected by the radome 10 is again in-phase on the antenna surface and re-radiated. In this way, most of the power can be radiated efficiently.

On the other hand, the excitation distribution around the array plays an important role in obtaining a low side lobe characteristic or an advanced shaped beam. As in the first embodiment of the present invention, the distance between the antenna 9 and the radome 10 is set to about λ / 4 in the periphery of the array, so that the radiation from the antenna 9 is achieved.
Since the radio waves reflected by the radome 10 are reversed in phase on the antenna surface and cancel each other, the electromagnetic field near the radiating element becomes an electromagnetic field similar to the state without the radome 10, and the influence on the reflection characteristics of the radiating element is reduced. It is possible to reduce the size of the antenna, obtain a reflection characteristic substantially the same as that of the antenna alone without the radome, and reduce the adverse effect on the excitation distribution. Therefore, an effect of easily obtaining desired radiation characteristics such as low side lobe characteristics is obtained.

As described above, according to the first embodiment of the present invention, the design of the microstrip array antenna 9 and the radome 10 can be performed independently, and the curvature is small so that the performance of the antenna alone is not impaired. Radome can be easily obtained. For example, in the C band (about 6 GHz), which is often used for communication, the difference in the distance between the antenna and the radome between the center of the array and the periphery of the array is about 1
It becomes 2.5 mm (≒ λ / 4), so that an aesthetically excellent radome having a gentle curvature can be obtained. Here, as the material of the radome 10, a dielectric material with low reflection and low dielectric constant and low loss may be used. For example, if polypropylene or polycarbonate is used, an integrally molded radome excellent in mass productivity can be easily obtained. . In addition, radome 1
A thickness of 0 is advantageous for lower loss when it is thin, but especially in the millimeter wave band, the thickness of the radome is not negligible compared to the wavelength, so the reflected wave of a plane wave to a layer having a different dielectric constant According to the concept of the above, the thickness of the radome 10 is set to be an integral multiple of approximately half a wavelength / √ (relative dielectric constant of the radome).
The radome reflection can be reduced by canceling the reflected waves of the upper surface and the lower surface of the laser beam. In addition, since the microstrip line and the feed circuit are formed in the same plane, there is an effect that a low-cost thin antenna that can be easily manufactured by one etching can be obtained. Further, the present invention does not depend on the shape of the microstrip antenna, and may be a square, a circle, a triangle, or another shape. The present invention is also effective when a Wilkinson circuit, a hybrid circuit, or the like is used as the power combining / distributing circuit constituting the power supply circuit in addition to the T branch circuit.

Embodiment 2 FIG. FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention, in which reference numeral 11 denotes a feed pin connected to a radiating element, and reference numeral 12 denotes a feed circuit formed on the back surface of the microstrip array antenna 9. This power supply circuit 12
Is composed of a microstrip line, a triplate line, a rectangular coaxial line, and the like, and is connected to a radiating element by a feed pin 11. By providing the feed circuit on the back of the radiating element, it is possible to eliminate the influence of the reflected wave on the radome on the feed circuit and to reduce the deterioration of the excitation distribution, thereby further improving the antenna radiation characteristics.

Embodiment 3 FIG. 3 is a schematic configuration diagram showing a third embodiment of the present invention, which is characterized by using a flat plate radome in which the distance between the microstrip array antenna 9 and the radome 10 is maintained at about λ / 4. With this configuration, radio waves radiated from the antenna and reflected by the radome are reversed in phase on the antenna surface and cancel each other, so that the electromagnetic field near the radiating element is an electromagnetic field similar to the state without the radome 10. An influence on the reflection characteristics of the radiating element can be reduced, the reflection characteristics are almost the same as those of the antenna alone without the radome, and the adverse effects on the excitation distribution can be reduced. Therefore, the feed circuit design including the impedance characteristics of the microstrip array antenna 9 can be easily and independently performed without considering the influence of the radome 10. In addition, the reflected wave from the radome has an opposite phase on the radiating element surface to prevent re-emission, so that the effect of suppressing the emission of delayed waves can be obtained.

Embodiment 4 FIG. 4 is a schematic configuration diagram showing a fourth embodiment of the present invention, in which reference numeral 13 denotes a metal casing, which is characterized by surrounding the periphery of the microstrip array antenna 9. Providing a metal wall around the microstrip array antenna 9 has the effect of suppressing unnecessary radiation in a wide angle direction of the antenna and reducing radio wave interference. In particular, when the power density at the periphery of the array is designed to be extremely low (for example, -20 dB or less at the center of the array) in order to obtain a low side lobe or a highly shaped beam, the element pattern from the radiating element at the periphery of the array is used. Since the radiated power of the array is small, even if the periphery of the array is surrounded by a metal wall, the effect on the array radiation pattern is small, and the effect of suppressing unnecessary radiation can be obtained with a simple configuration. Further, since only the opening of the radome 10 needs to be manufactured, the radome 10 has a substantially planar configuration, so that mass productivity can be improved and the cost can be reduced. Although the figure shows an example in which the metal wall 13 is simply configured as an example of the metal wall, the wall may be formed of a plate material or the like separately from the wall.

Embodiment 5 FIG. 5 is a schematic configuration diagram showing a fifth embodiment of the present invention, which is characterized in that a radio wave absorber 14 is mounted inside a metal casing 13. The radio wave absorber 14 absorbs unnecessary radiation in the wide-angle direction, thereby absorbing multiple reflected waves due to reflection and scattering between the microstrip array antenna 9 and the radome 10, thereby further reducing radio wave interference. Has the effect of doing In particular, when the amplitude taper of the array is designed to be small (for example, -5 dB or less at the center of the array) in order to obtain a high gain, the radiated power of the element pattern from the radiating element at the periphery of the array cannot be ignored. By surrounding the array with a radio wave absorber, multiple reflection waves are absorbed, and the effect of suppressing unnecessary radiation can be obtained while reducing the influence on the array radiation pattern. In the figure, as an example of the radio wave absorber 14, a cone obtained by mixing carbon or the like with a foam material is shown.
A planar radio wave absorber using ferrite or the like may be used.

Embodiment 6 FIG. FIG. 6 is a schematic diagram showing a sixth embodiment of the present invention. A radome 10 having an opening and a side wall integrally formed is used. A metal tape 15 is formed on the inner wall of the radome 10 so as to surround the microstrip array antenna 9. Is pasted. With this configuration, it is possible to reduce the weight of the antenna device while reducing unnecessary radiation in the wide-angle direction, and to improve the appearance. Although the figure shows an example in which a metal tape 15 is attached to provide a metal wall, a metal wall may be generated by depositing a metal body on the inner wall of the radome.

Embodiment 7 FIG. 7 is a schematic configuration diagram showing a seventh embodiment of the present invention, in which a radome 10 in which an opening and a side wall are integrally formed is used, and a radio wave absorber is provided on the inner wall of the radome 10 so as to surround the microstrip array antenna 9. 14 is attached. With this configuration, unnecessary radiation in the wide-angle direction is further reduced,
The weight of the antenna device can be reduced, and the appearance can be improved. Further, with respect to the aging of the radio wave absorber, the radome 10 may be removed and the internal radio wave absorber may be replaced, so that the maintainability can be improved.

Embodiment 8 FIG. FIG. 8 is a schematic configuration diagram showing an eighth embodiment of the present invention. As an example of circularly polarized wave excitation of the microstrip antenna 4, (a) shows a one-point feeding system, and (b) shows a two-point feeding system. It is shown. In the single-point feeding method (a), a circular polarization is excited by providing a notch 16 or the like to solve the degeneracy of orthogonal modes. Although the wiring of the microstrip line 6 of the power supply circuit can be made compact, the frequency bandwidth in which circular polarization occurs is narrow in principle. The two-point feeding method (b) is a method of exciting two orthogonal points with a phase difference of 90 °. It is possible to achieve a wider band than the one-point feeding system. Although FIG. 8B shows a form in which power is supplied to the microstrip antenna 4 using the T branch circuits 7a and 7c, a Wilkinson circuit, a hybrid circuit, or the like that can achieve a wider band may be used. By combining the radome according to the present invention with a circularly polarized excitation microstrip array antenna, the reflected wave from the radome becomes reverse-polarized, so the effect of the reflected wave from the radome on the desired polarization component near the radiation element Can be reduced, the deterioration of the reflection characteristics of the radiation element can be reduced, and the deterioration of the frequency characteristics of circularly polarized waves can be reduced.

[0033]

According to the first aspect of the present invention, a microstrip antenna fed by a microstrip line is used, and the interval between the antenna and the radome is set to about 1/2 wavelength of the antenna center frequency near the center of the antenna. The use of a radome with a curvature of about 1/4 wavelength near the periphery of the antenna radiates power efficiently from the center of the array and less disturbs the excitation distribution around the array. Therefore, there is an effect that an antenna in which the side lobe characteristics of the antenna are less deteriorated can be obtained. Also, the configuration of the microstrip antenna is simplified, miniaturization, weight reduction, and improvement in mass production can be achieved. In addition, a curved radome that can reduce the deterioration of the excitation distribution while increasing the efficiency of the antenna can be easily obtained. effective.

According to the second aspect of the present invention, the surface on which the radiating elements are arranged and the surface forming the feeder circuit are separated by using the microstrip antenna as the pin feeder, so that the reflected wave from the radome is fed to the feeder circuit. Eliminate the effect,
There is an effect that desired radiation characteristics can be easily obtained.

According to the third aspect of the present invention, by using a flat plate radome having an interval between the antenna and the radome of about 1/4 wavelength, the reflection characteristic of the radiating element can be kept almost the same as that without the radome. This has the effect of reducing the excitation distribution deterioration due to the change in antenna impedance, and the effect of suppressing the re-emission of delayed waves, which is a cause of communication quality deterioration.

According to the fourth aspect of the present invention, since the metal wall is provided around the antenna, there is an effect that unnecessary radiation in a wide angle direction can be suppressed and a radiation pattern disturbance due to the surrounding environment can be reduced.

According to the fifth aspect of the present invention, by providing a radio wave absorber around the antenna, it is possible to absorb multiple reflected waves between the antenna and the radome, further reducing unnecessary radiation in a wide angle direction,
While further reducing the disturbance of the radiation pattern due to the surrounding environment,
This has the effect of minimizing deterioration of radiation characteristics in a desired direction.

According to the sixth aspect of the present invention, since the metal wall is provided inside the radome in which the opening and the side wall are integrally formed, there is an effect of improving the aesthetic appearance while reducing unnecessary radiation.

According to the seventh aspect, the radio wave absorber is provided inside the radome having the opening and the side wall integrated with each other, so that unnecessary radiation is reduced, the appearance is improved, and the maintenance property is further improved. Has the effect of improving.

According to the eighth aspect of the present invention, since the radiating element is circularly excited, the reflected wave from the radome is reversed, so that the effect of the reflected wave can be reduced, and the antenna radiation characteristics and impedance can be reduced. This has the effect of improving the characteristics. Also,
The effect of reducing deterioration of the frequency characteristics of circularly polarized waves due to the influence of the radome can be obtained.

According to the ninth aspect, the thickness of the radiation opening of the radome is set to approximately half a wavelength / √ (relative permittivity of the radome).
By canceling the reflected waves from the upper surface and the lower surface of the radome, the reflection from the radome surface is minimized, which is effective in improving the radiation efficiency of the antenna.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing Embodiment 1 of a microstrip array antenna with a radome according to the present invention.

FIG. 2 is a schematic configuration diagram showing Embodiment 2 of a microstrip array antenna with a radome according to the present invention.

FIG. 3 is a schematic configuration diagram showing Embodiment 3 of a microstrip array antenna with a radome according to the present invention.

FIG. 4 is a schematic configuration diagram showing Embodiment 4 of a microstrip array antenna with a radome according to the present invention.

FIG. 5 is a schematic configuration diagram showing Embodiment 5 of a microstrip array antenna with a radome according to the present invention.

FIG. 6 is a schematic configuration diagram showing Embodiment 6 of a microstrip array antenna with a radome according to the present invention.

FIG. 7 is a schematic configuration diagram showing Embodiment 7 of a microstrip array antenna with a radome according to the present invention.

FIG. 8 is a schematic configuration diagram showing Embodiment 8 of a microstrip array antenna with a radome according to the present invention.

FIG. 9 is a schematic configuration diagram showing a conventional microstrip array antenna.

FIG. 10 is a schematic configuration diagram showing a conventional microstrip array antenna with a radome.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 ground conductor, 2 dielectric substrate, 3 radiating element, 4 microstrip antenna, 5 strip conductor, 6 microstrip line, 7 T branch line, 8 feed point, 9
Microstrip array antenna, 10 radome, 11 power supply pin, 12 power supply circuit, 13 metal housing, 14 radio wave absorber, 15 metal tape, 16 notch for circular polarization excitation.

Claims (9)

[Claims] A ground conductor, a dielectric substrate provided on the ground conductor, a microstrip line provided on the dielectric substrate, provided on the same plane as the microstrip line, and connected to the microstrip line. In a microstrip array antenna in which a plurality of microstrip antennas having a radiating element fed by being performed are arranged on a plane to form an array antenna,
A radome made of a dielectric material is provided in the radiation direction of the microstrip array antenna. In the vicinity of the center of the microstrip array antenna, the interval between the microstrip array antenna and the radome is about 波長 wavelength of the center frequency of the antenna. In the vicinity of the periphery of the microstrip antenna, the distance between the antenna and the radome is about 1/4 wavelength of the center frequency, and the distance between the antenna and the radome is about 1/4 wavelength to about 1/4 wavelength.
A microstrip array antenna with a radome, characterized in that the radome opening has a curvature so that the above-mentioned interval changes smoothly up to the wavelength. 2. An array antenna comprising a plurality of microstrip antennas having a ground conductor, a dielectric substrate provided on the ground conductor, and a radiating element provided on the dielectric substrate, forming an array antenna. A feed pin is connected to the strip antenna, the feed pin is guided to the ground conductor side through the dielectric substrate, and each feed pin is connected to a feed circuit in a microstrip array antenna. A radome made of a dielectric material is provided in the radiation direction. In the vicinity of the center of the microstrip array antenna, the distance between the microstrip array antenna and the radome is about 波長 wavelength of the center frequency of the antenna, and Near the periphery of the antenna, the distance between the antenna and the radome is the center It is about １ ／ wavelength of the frequency, and the interval is about 波長 wavelength to about １ ／ wavelength in the middle part.
A microstrip array antenna with a radome, characterized in that the radome opening has a curvature so that the above-mentioned interval changes smoothly up to the wavelength. 3. The microstrip array antenna according to claim 1, further comprising a radome made of a dielectric material in a radiation direction, wherein a distance between the microstrip array antenna and the radome is about １ ／ of a center frequency of the antenna.
A microstrip array antenna with a radome, wherein the microstrip array antenna is constituted by a flat radome having a wavelength. 4. The microstrip array with a radome according to claim 1, wherein a barrier made of a metal body is provided around the array antenna so as to protrude from a surface of the antenna in a radio wave radiation direction. antenna. 5. The microstrip array antenna with a radome according to claim 1, wherein a radio wave absorber is provided around the array antenna so as to protrude from a surface of the antenna in a radio wave radiation direction. 6. The radome is formed integrally with a side wall surrounding the periphery of the array antenna, and a metal body is deposited on the inside of the side wall of the radome, or a metal tape is adhered to the radome side wall. The microstrip array antenna with a radome according to any one of claims 1 to 3, wherein a metal wall is provided. 7. The radome according to claim 1, wherein the radome is integrally formed with a side wall surrounding the periphery of the array antenna, and a radio wave absorber is attached to the inside of the side wall of the radome. 2. A microstrip array antenna with a radome according to item 1. 8. The microstrip array antenna with a radome according to claim 1, wherein the radiating element of the microstrip array antenna with a radome is a circularly polarized wave excitation. 9. The microstrip array antenna with a radome according to claim 1, wherein the thickness of the radial opening of the radome is approximately half a wavelength / √ (relative permittivity of the radome). A microstrip array antenna with a radome according to the present invention.