JP2000244229A - Microstrip antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the gain of the zenith direction that is higher than the gain of the low elevation angle direction by means of only a single antenna element by placing the metallic reflecting plates at the ground electrode side with a space set between them. SOLUTION: An electrode 12 that is accordant with the wavelength of the radio wave received on the surface of a dielectric substrate 11 having a dielectric constant of about 20 is formed as an antenna element and connected to a hot side when it's mounted. A ground electrode 13 is formed on the back side of the substrate 11 in a conductor pattern of a metallic plate or a printed circuit board where the substrate 11 is mounted and then connected to a ground side. The electrode 13 is set opposite to a metallic plate 15 via a spacer 14 made of a material such as plastics that can transmit the radio waves, and the plate 15 serves as a reflecting plate. A conductor film that is formed on the bottom surface of the spacer 14 can replace the plate 15. The antenna element and the spacer 14 are covered with a cover 16 made of a material that can transmit the radio waves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip antenna suitable for receiving radio waves from a single geosynchronous satellite, and more particularly, to a microstrip antenna having a higher zenith reception sensitivity than a low elevation angle direction. It relates to a strip antenna.

[0002]

2. Description of the Related Art A microstrip antenna used in a GPS receiver or the like has the directivity shown in FIG. 6, and has a high gain in the zenith direction and a low gain when the elevation angle is low. However, the decrease in the gain in the low elevation angle direction is relatively small, and is not very suitable as a narrow directivity antenna used for receiving digital audio broadcasting by a geostationary satellite.

The size of the element of the microstrip antenna changes depending on the relative dielectric constant of the substrate. When a substrate having a high dielectric constant is used, the size can be reduced. As shown by a solid line 68 in FIG. 6 is lower than when a substrate having a low dielectric constant such as Teflon shown by a dashed line 69 in FIG. 6 is used, but the decrease in gain in the low elevation angle direction is small, and it is smaller than when a substrate having a low dielectric constant is used. The gain is higher. However, as long as a single microstrip antenna is used, the gain in the zenith direction is maximized, and the gain is slightly reduced in the low elevation angle direction.

[0004] Unlike a GPS receiver or the like, fixed reception at home, portable radio reception in a stationary state at a destination such as a picnic, etc., it is more advantageous to aim at a satellite that can receive one specific strong radio wave. is there. The antenna used here is advantageously a small circularly polarized antenna having appropriate directivity. If a directional antenna having a high zenith gain and a low elevation angle gain can be realized, the effective receiving sensitivity can be improved.

[0005]

SUMMARY OF THE INVENTION The present invention provides a circularly polarized antenna suitable for portable radio and the like, in which the gain in the zenith direction can be made higher than the gain in the low elevation angle direction by using only one antenna element. Is what you do.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by reducing the size of a ground electrode of a microstrip antenna and by arranging a metal reflector at an interval on the ground electrode side. Is what you do.

That is, a microstrip antenna having electrodes on both surfaces of a dielectric substrate is characterized in that a metal layer is provided on the ground electrode side at a distance from the ground electrode. Alternatively, in a microstrip antenna having electrodes on both surfaces of a dielectric substrate, a feature is that the ground electrode side is attached to a metal plate at a distance from the ground electrode.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A microstrip antenna according to the present invention receives a directly arriving wave of a circularly polarized wave in a forward rotation direction, and is reflected by a metal layer arranged at a distance from a ground electrode to be in a reverse rotation direction. The reflected wave of the circularly polarized wave is received. In other words, an image antenna is present together with the real antenna, and a directional characteristic obtained by combining their gains is obtained.It is possible to adjust the directivity according to the size of the ground electrode and the distance between the ground electrode and the metal layer. Become.

[0009]

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

FIG. 1 is a front sectional view showing an embodiment of the present invention. As an antenna element, an electrode 12 corresponding to the wavelength of a radio wave to be received is formed on the surface of a dielectric substrate 11 having a dielectric constant of about 20, and this electrode is connected to the hot side during mounting. On the back surface of the dielectric substrate 11, a ground electrode 13 connected to the ground side is formed. The ground electrode 13 can be formed of a metal plate on which a dielectric substrate is mounted or a conductor pattern of a wiring substrate.

The ground electrode 13 is connected to a metal plate 15 through a spacer 14 made of a material such as plastic which allows radio waves to pass.
And is facing. A conductor film may be formed on the bottom surface of the spacer instead of the metal plate. The antenna element and the spacer are covered with a cover 16 made of a material that allows radio waves to pass. It is also possible to provide a space between the spacer 14 and the ground electrode 13 and incorporate a circuit therein.

FIG. 2 is a front cross-sectional view showing another embodiment of the present invention. The provision of a hot-side electrode 22 and a ground electrode 23 on a dielectric substrate 21 is the same as described above. In this example,
Only the spacer 24 is arranged on the ground electrode 23 side and assembled, and mounting is performed directly on a metal plate 25 such as a roof of an automobile, and the metal plate 25 is used as a reflection plate. This makes it easy to reduce the size because it is not necessary to integrate the metal layer serving as the reflector with the antenna element.

Hereinafter, the receiving operation of the microstrip antenna according to the present invention will be described. In the communication between the satellite and the ground, linear polarization is not suitable because the relative position and angle of the transmitting antenna and receiving antenna change, and circular polarization, which does not affect the sensitivity even if the mutual position rotates, is generally used. .
When circularly polarized light is reflected by a metal surface, right-handed polarized light has the property of being left-handed polarized light, and left-handed polarized light has the property of being right-handed polarized wave.

The directivity of the microstrip antenna for circularly polarized waves in the forward turning direction and the directivity for circularly polarized waves in the reverse turning direction were measured. As shown in FIG. 3, when the size of the ground electrode is set to 1/3 wavelength or less, two curves 38 whose two directivity characteristics are almost mirror-symmetric with respect to the ground plane,
39, and the gain in the reverse turning direction shown by the broken line 39 is 1 or 2
It is only dB smaller. Although not shown, when the size of the ground electrode is about 波長 wavelength, the gain of the circularly polarized wave in the reverse rotation direction on the rear surface is smaller than the gain of the circularly polarized wave in the forward rotation direction from the front by 15 dB or more. That is, in this case, there is almost no influence of the reflected wave.

As described above, when the size of the ground electrode is set to 1/3 wavelength or less, a real antenna for receiving a desired wave in the forward turning direction directly arriving from the front direction is reflected by a metal surface for the purpose of a reflection effect. Further, it is possible to make an image antenna that receives a reflected wave in the opposite turning direction from the back surface direction, and it is possible to obtain a directional characteristic that combines the characteristics of both antennas.

FIG. 4 shows a microstrip antenna,
This shows that an image antenna made of a metal plate 45 having a radio wave reflection effect and a real antenna receiving a directly arriving wave act as a two-element array antenna which is coaxially arranged at a predetermined distance. When the size of the ground electrode becomes 波長 wavelength, the gain of the image antenna becomes small and does not function as an array antenna.

The metal layer acting as a reflector is 1 /
It is desirable to make it as large as possible over two wavelengths. By adjusting the distance between the ground electrode and the metal layer,
The gain in the zenith direction can be increased, and the gain in the low elevation angle direction can be reduced. The distance is 1/4 wavelength to 1/8
As shown in FIG. 5, when the wavelength was set, an antenna having a very large zenith gain could be formed.

The microstrip antenna according to the present invention is not limited to the above example, and the antenna element may be formed integrally with a printed circuit board. The metal layer also has a certain area made of a material that reflects radio waves. It is not particularly limited as long as it has the structure, and a structure for maintaining the interval can be arbitrarily selected. And circularly polarized waves also turn right,
Any of left turn may be used. The present invention can be applied to all circularly polarized antennas.

[0019]

According to the present invention, it is possible to obtain a microstrip antenna in which the directivity in the zenith direction can be extremely enhanced only by using a single antenna element, and the degree thereof can be adjusted by selecting an interval. You can also.
This provides an inexpensive antenna that is effective for receiving radio waves from a single geostationary satellite.

Further, since only a metal layer is added, which can be replaced by an external metal plate or the like, the outer case for housing the antenna element can be downsized.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention.

FIG. 2 is a front sectional view showing another embodiment of the present invention.

FIG. 3 is an explanatory diagram of characteristics of a microstrip antenna according to the present invention.

FIG. 4 is an explanatory diagram of characteristics of a microstrip antenna according to the present invention.

FIG. 5 is an explanatory diagram of characteristics of a microstrip antenna according to the present invention.

FIG. 6 is an explanatory diagram of characteristics of a microstrip antenna.

[Explanation of symbols]

 11, 21: Dielectric substrate 13, 23: Ground electrode 15, 25: Metal plate

Claims (4)

[Claims] 1. A microstrip antenna having electrodes on both sides of a dielectric substrate, wherein a metal layer is provided on the ground electrode side at a distance from the ground electrode. 2. A microstrip antenna having electrodes on both surfaces of a dielectric substrate, wherein the ground electrode is attached to a metal plate with a space between the ground electrode and the ground electrode. 3. The microstrip antenna according to claim 1, wherein a size of a ground electrode formed on a surface of the dielectric substrate is equal to or less than one third of a wavelength of a radio wave to be received. 4. The distance between a ground electrode formed on a surface of a dielectric substrate and a metal layer or a metal plate is １ ／ to ８ of a wavelength of a radio wave to be received.
A microstrip antenna as described.