JP2540979B2 - Parabolic antenna system - Google Patents

Description

The present invention relates to an antenna system used for wireless communication,
In particular, the present invention relates to a parabolic antenna system that prevents effects such as fading that leads to deterioration of communication quality.

(Prior Art) In wireless communication performed by receiving electromagnetic waves with one antenna, if fading, rain attenuation, or the like occurs, communication quality deteriorates due to a decrease in cross polarization discrimination. For example,
As shown in this figure, the direct cause of the cross polarization discrimination is a 180 ° phase shift between the direct wave 21 and the direct wave 21, as shown in the figure. The disturbing wave 22 enters the main beam 23 of the parabolic antenna 1 and interferes with each other to lower the level of the main polarization component. This direct wave 21 and jammer
The interference between 22 and 22 in the main beam 23 of the parabolic antenna 1 is caused by the main beam of the parabolic antenna 1 as shown in FIG.
This is because the phase characteristics within 23 are constant.

Conventionally, as a means for preventing the deterioration of the communication quality of wireless communication due to the above-mentioned fading or rain attenuation, which deteriorates the cross polarization discrimination, space diversity using a plurality of antennas and receiving devices, angular diversity, etc. There was diversity reception.

(Problems to be Solved by the Invention) However, in diversity reception that prevents deterioration of communication quality of wireless communication caused by deterioration of cross polarization discrimination due to conventional fading, rain attenuation, and the like, a plurality of antennas and receiving devices are used. Since it is required, it is economically expensive and physically requires a vast installation site.

As described above, the conventional diversity reception has a problem to be solved.

(Means for Solving the Problem) A parabolic antenna system of the present invention includes a reflector having a paraboloid of revolution, and a plurality of receivers provided at the focal point of the reflector to receive radio signals. A detector that detects cross polarization discrimination from radio signals received by the plurality of receivers, and an electromagnetic field intensity distribution in the opening of the reflecting mirror according to a decrease in cross polarization discrimination detected by the detector. Or an aperture distribution controller for making the electromagnetic field intensity distribution and the electromagnetic field phase distribution of the opening of the reflecting mirror non-rotationally symmetric or non-axisymmetric with respect to an arbitrary straight line passing through the center of the reflecting mirror. And

(Example) Next, an Example is given and this invention is demonstrated in detail.

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, 1 is a reflecting mirror, 2 and 3 are receivers, 4 and 5 are variable resistance attenuators, 6 and 7 are polarization splitters, 8 and 9 are couplers, 10 is a cross polarization discrimination monitor, and 11 Is a drive control unit. The configuration and operation of this embodiment will be described below.

Two receivers 2 at the focal point of the reflector 1 in the shape of a paraboloid of revolution
It is equipped with 3 and has the structure of a parabolic antenna. The radio wave signal entering the reflecting mirror 1 is focused on the reflecting mirror 1 and enters the two receivers 2 and 3. The radio signals that have entered the receivers 2 and 3 pass through the variable resistance attenuators 4,5 and enter the demultiplexers 6 and 7, and are separated into the desired polarization component and the cross polarization component, and one polarization Summed up into wave components. The polarization components (desired polarization component and cross polarization component) combined into one are branched by the couplers 8 and 9, respectively, and enter the cross polarization identification monitor 10 to measure the cross polarization identification. It Here, in the main beam of the parabolic antenna, the direct wave and the phase of the direct wave are approximately 180
When the cross polarization discrimination degree decreases due to the interference with the deviated interference wave, the information is transmitted from the cross polarization discrimination degree monitor 10 to the drive control section 11, and the drive control section 11 changes the variable resistance attenuation. Drive signals are output to the devices 4 and 5, respectively, and the electromagnetic field intensity distribution in the opening of the reflecting mirror 1 is changed so as to be non-rotationally symmetric or non-axisymmetric with respect to an arbitrary straight line passing through the center of the reflecting mirror 1. . In the antenna, the characteristics for transmission and the characteristics for reception are the same. Considering that the parabolic antenna of this embodiment is for transmission, and electromagnetic waves are radiated from the receivers 2 and 3, these two radiations are considered. When the variable resistance attenuators 4 and 5 are driven so that the electromagnetic field strengths of the generated electromagnetic waves are different, the electromagnetic field strength distribution in the opening of the reflecting mirror 1, that is, the parabolic antenna changes. The change of the distribution is the same as the change of the electromagnetic field intensity distribution of the opening when it is used for reception. If the electromagnetic field intensity distribution at the opening of the reflecting mirror 1 is non-rotationally symmetric or non-axisymmetric with respect to an arbitrary straight line passing through the center of the reflecting mirror 1, there will be a phase difference in the main beam of the parabolic antenna of this embodiment. Occurs, the phase shift of the interfering wave from the direct wave deviates significantly from 180 degrees, the interference of the direct wave and the interfering wave in the main beam of the parabolic antenna becomes small, and the level drop of the direct wave caused by this interference is reduced. The cross polarization discrimination degree is recovered. In other words, the deterioration of cross polarization discrimination due to fading is improved.

FIG. 2 is a block diagram of another embodiment of the present invention. In the figure, 1 is a reflecting mirror, 2 and 3 are receivers, 4 and 5 are variable resistance attenuators, 6 and 7 are polarization splitters, 8 and 9 are couplers, 10 is a cross polarization discrimination monitor, and 11 Is a drive control unit, and 12 and 13 are variable phase shifters. In the present embodiment, variable phase shifters 12 and 13 are added to the embodiment shown in FIG. 1, and when a decrease in cross polarization discrimination degree is detected by the cross polarization discrimination degree monitor 10, the information is drive-controlled. With respect to the section 11, the drive control section 11 drives the movable resistance attenuators 4 and 5 so that the electromagnetic field intensity distribution at the opening of the parabolic antenna of this embodiment is non-rotationally symmetric or any straight line passing through the center of the reflecting mirror 1. Is changed so as to be non-axisymmetric with respect to, so that a phase difference occurs in the main beam of the radiation pattern of the antenna. Further, the drive control unit 11 drives the variable phase shifters 12 and 13 so that the electromagnetic wave phase distribution in the opening of the reflecting mirror 1, that is, the parabolic antenna is non-rotationally symmetric or non-rotating with respect to an arbitrary straight line passing through the center of the reflecting mirror 1. Change it to be line symmetric,
The direction of the main beam can be freely scanned. These controls can improve the deterioration of cross polarization discrimination due to the interference between the interfering wave and the direct wave, and further, the effect of angular diversity can be obtained by changing the direction of the main beam of the parabolic antenna.

It will be described below that a phase difference occurs in the main beam of the parabolic antenna. Consider a simple one-dimensional source. It is shown that in a one-dimensional line source, the radiation pattern is asymmetric in phase within the main beam when the field intensity distribution is asymmetric. As shown in FIG. 3, assuming an asymmetric current distribution having an electromagnetic field intensity of a in the negative direction of the x-axis and b in the positive direction, the directivity f in this case is f.
(Θ) is Is represented. In this case, the electromagnetic field intensity distribution of the radiation pattern is The pattern intensity is symmetric because | f (θ) | = | f (−θ) | On the other hand, the phase is Then, it becomes asymmetric with respect to the observation angle, and it can be seen that a phase difference occurs in the beam.

(Effect of the Invention) As described in detail above, according to the present invention, the electromagnetic field intensity distribution in the opening of the parabolic antenna is rotationally asymmetrical or asymmetrical with respect to an arbitrary straight line passing through the center of the parabolic antenna. It is possible to prevent the deterioration of cross polarization discrimination due to the interfering waves whose phases are shifted by approximately 180 degrees. Also, the electromagnetic wave phase distribution of the opening of the parabolic antenna is set to non-rotationally symmetric or to any straight line passing through the center of the parabolic antenna. Since the direction of the main beam can be arbitrarily changed by changing so as to be non-axisymmetric, diversity reception that requires a plurality of antennas and receiving devices can be realized with one parabola antenna system. Therefore, the present invention can provide wireless communication with high communication quality with one parabola antenna, and can realize diversity reception such as site diversity and angular diversity with one parabola system. You can provide something that does not require a large space.

 The present invention has the above effects.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of another embodiment of the present invention, FIG. 3 is a diagram showing the current distribution of a one-dimensional linear wave source, and FIG. Waves and phases are almost
The figure which shows the operation of fading by the interference wave which shifted 180 degrees, Figure 5 the figure which shows the beam quality of the parabona antenna,
FIG. 6 is a diagram showing the phase characteristics of the parabolic antenna. 1 …… parabolic antenna, 2,3 …… receiver, 4,5 …… variable resistance attenuator, 6,7 …… polarizer, 8,9 …… coupler, 10 ……
Cross polarization discrimination monitor, 11 …… Drive controller, 12,13 ……
Variable phase shifter, 15 …… Current distribution, 21 …… Direct wave, 22 …… Interfering wave, 23 …… Main beam, 24 …… Beam phase characteristics.

Claims (1)

(57) [Claims] 1. A reflecting mirror having the shape of a paraboloid of revolution, a plurality of receivers provided at the focal point of the reflecting mirror for receiving radio signals, and crossed from radio signals received by the plurality of receivers. A detector that detects the degree of polarization discrimination, and an electromagnetic field intensity distribution in the opening of the reflecting mirror or an electromagnetic field intensity distribution in the opening of the reflecting mirror depending on the decrease in the cross polarization discrimination detected by the detector. And an aperture distribution controller that makes the electromagnetic field phase distribution non-rotationally symmetric or non-axisymmetric with respect to an arbitrary straight line passing through the center of the reflecting mirror.