JPH0119641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna that can control side lobes of the antenna in order to reduce interference from a certain direction. More specifically, the present invention relates to an antenna that uses a reflecting mirror to share two orthogonal polarized waves, and that can reduce side lobes in a particular direction.

Taking the case of a receiving antenna as an example of a conventional antenna of this kind, as shown in Figure 1, in addition to the main antenna, there is a sub antenna oriented in the direction of the interference wave source in the main radiation direction, and the main antenna and the sub antenna are connected to each other. By combining the received interference waves so that they cancel each other out, the side lobe of the main antenna in the direction of the interference wave source is apparently lowered.

That is, in FIG. 1, the interference wave received by the sub-antenna 2 directed in the direction of the interference wave source in the main radiation direction passes through the variable attenuator 3 and the variable phase shifter 4, and is transferred to the main antenna 1 by the combining circuit 5. The side lobe in the direction of the interference wave source is combined with the received interference wave. At this time,
If the variable attenuator 3 and the variable phase shifter 4 are adjusted so that the output 6 of the combining circuit 5 has zero interference wave output, only the desired wave will appear at the output 6 without any interference wave output.

However, in the configuration shown in Figure 1,
When the main antenna 1 is an antenna that can share two orthogonal polarizations, a sub antenna 2, a variable attenuator 3, a variable phase shifter 4, and a combining circuit 5 are provided for each polarization, or the sub antenna 2 is also the same as the main antenna 1. As an antenna that can share two orthogonal polarized waves, after separating each polarized wave with a polarization splitter, it is necessary to provide a variable attenuator 3, a variable phase shifter 4, and a combining circuit for each polarized wave, making the configuration complicated. However, it also had the disadvantage of being economically expensive. Furthermore, it is almost impossible to match the electrical lengths between the main antenna 1 and the combining circuit 5 and between the auxiliary antenna 2 and the combining circuit 5 over a wide band, and performance can only be obtained in a narrow band. Furthermore, when the direction of the interference wave source changes, it is necessary to change the direction of the sub antenna 2 and readjust the variable attenuator 3 and variable phase shifter 4 for each polarized wave. .

In order to solve these drawbacks, the present invention employs a reflective phased array antenna configuration for the secondary antenna, and installs the secondary antenna so that its aperture approximately coincides with a part of the inner surface of the reflector of the main antenna. A polarization-selective element is attached to the aperture of the phased array antenna, which allows only radio waves of the target polarization to pass through and reflects radio waves of other polarizations, thereby reducing radiation from the primary radiator of the main antenna. By using a part of the target polarized radio waves, the direction of the interference wave source can be changed by eliminating the need for a synthesis circuit, and by controlling the phase shifter and attenuator in the phased array antenna. Even if the antenna changes, it can be handled without moving the antenna, and the drawings will be explained in detail below.

FIG. 2 shows an embodiment of the present invention, in which the main antenna is a horn reflector antenna and the number of frequency bands for controlling side lobes is one. In the figure, 10 is a primary horn that can share two orthogonal polarizations, 11 is a parabolic reflector, 12 is a sub-array antenna with a reflective phased array antenna configuration, and 12a is a radio wave of one polarization that passes through, and a radio wave of the other polarization. It is a polarization-selective element that reflects most of the radio waves in the mirror, and it is fitted into a cutout of a mirror surface so that it is almost flush with the mirror surface. 12b is a phase shifter, 12c is an attenuator, 12d is a shorting surface for reflection, and 12b, 12c,
12d are attached in a hierarchical manner. Figure 3 is the second
FIG.

In the figure, most of the two orthogonally polarized radio waves radiated from the primary horn 10 are reflected by the parabolic reflector 11 and have the same phase at the aperture surface, forming a main beam in the front direction.

On the other hand, the radio waves incident on the polarization selective element 12a, except for the polarized radio waves passing through, are reflected by this surface to form the main beam, but the polarized radio waves that have passed through the polarization selector 12b The light passes through the attenuator 12c, is reflected by the short-circuit surface 12d, passes through the attenuator 12c and phase shifter 12b again, and is radiated to the outside through the polarization selective element 12a. By electronically controlling the phase shifter 12b and the attenuator 12c from the outside to give the radio waves the necessary phase shift and attenuation, it is possible to obtain the desired radiation directivity for the sub-array antenna 12. Further, when only the direction of radiation directivity of the sub array antenna 12 is changed, the attenuator 12c may be a fixed attenuator set in advance, or may not be used.

Therefore, in polarization for controlling side lobes, if you want to lower the side lobes in a certain characteristic direction in the radiation directivity from the disparate reflecting mirror surface 11 other than the sub array antenna 12 to avoid interference, the sub array This can be achieved by directing the directional main beam of the antenna in the direction of the side lobe, matching the amplitudes, and making the phases opposite. The size of the sub array antenna 12 is determined by the direction and level of the side lobes of the main antenna to be lowered to avoid interference waves. In a normal horn reflector antenna, the sidelobe level is about -20 dB or less, so the sub array antenna
The size of 2 can be made considerably small and poses no problem in terms of configuration and structure.

FIG. 4 shows another embodiment of the present invention, in which the main antenna is a horn reflector antenna,
A case is shown in which there are two polarizations to control side lobes. In the figure, 13 is the sub array antenna 12
This is a sub-array antenna for controlling side lobes of polarized waves different from that of the sub-array antenna 12, and its configuration and function are the same as those of the sub-array antenna 12. FIG. 5 is a front view of FIG. 4.

Therefore, in this case, in the radiation directivity of the main antenna in two orthogonal polarized waves, side lobes in the same direction or in different directions can be lowered in order to avoid interference waves.

As explained above, according to the present invention, what conventionally required a sub-antenna to be installed in addition to the main antenna and a circuit for adjusting and synthesizing the amplitude and phase of the interference waves between the two antennas has been replaced with an orthogonal antenna. 2
Even in the case of a dual-polarization antenna, by providing a sub-array antenna in a part of the parabolic reflecting mirror surface, using a polarization-selective element in its opening, and making this sub-array antenna a reflective phased array antenna. This eliminates the need for a circuit that adjusts and synthesizes the amplitude and phase, and allows the side lobe in the direction of the interference wave source to be lowered with the polarization corresponding to the polarization selective element, and when changing the direction in which the side lobe is desired to be lowered. This method has the advantage that it is only necessary to electronically control the phase shifter and attenuator in the sub-array antenna from the outside, and there is no need to change the installation direction of the antenna. Furthermore, even if the polarizations that control the side lobes are two orthogonal polarizations, the sub array antenna is provided through the polarization selective element, so the sub array antenna can be set up for each polarization without affecting other polarizations. Furthermore, there is an advantage that side lobes in different directions for each polarized wave can be lowered.

In addition, the polarization selective elements of each sub-array antenna almost coincide with the parabolic reflecting mirror surface, which serves as the aperture of the sub-array antenna, so there is no need for a feed line, and furthermore, the phase shifter and attenuator By making the length shorter, the frequency characteristics of the radiation waves from the sub-array antenna can be made close to the frequency characteristics of the main antenna, which has the advantage of providing broadband characteristics.

Although the above explanation has been given for the embodiment of a horn reflector antenna, it can also be applied to other types of antennas using reflectors, such as parabolic antennas, Cassegrain antennas, offset antennas, etc. , the same effect can be obtained.

As described above, the antenna device according to the present invention that can reduce interference waves has two orthogonal polarizations, can easily change the direction in which the side lobe is desired to be lowered, and can obtain broadband characteristics, making it practical. The value above is great.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a conventional antenna device, FIG. 2 is a sectional view showing an embodiment of the antenna device according to the present invention, FIG. 3 is a front view of the antenna device shown in FIG. 2, and FIG. FIG. 5 is a sectional view showing another embodiment of the invention, and FIG. 5 is a front view of FIG. 4. 1...Main antenna, 2...Sub antenna, 3...
Variable attenuator, 4... Variable phase shifter, 10... Primary horn, 11... Parabolic reflector, 12, 13...
Sub-array antenna, 12a, 13a...polarization selective element, 12b, 13b...phase shifter, 12c, 1
3c...attenuator, 12d, 13d...short circuit surface. Note that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Scope of Claims] 1. A primary horn that transmits or receives radio waves, a reflecting mirror that faces the primary horn and reflects radio waves, and a part of the reflecting mirror that is provided substantially flush with the mirror surface. An antenna device comprising a polarization selective element and a plurality of reflective array elements each comprising a phase shifter, an attenuator, and a shorting surface attached to the selective element in a hierarchical manner. 2. The device according to claim 1, characterized in that a plurality of reflective array elements each consisting of a polarization selective element, a phase shifter, an attenuator, and a shorting surface are provided for each orthogonal polarization. antenna device.