JPH0119643B2 - - 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, and more specifically, in an antenna that uses a reflecting mirror.
The present invention relates to an antenna that can reduce side lobes in a certain direction.

Taking the case of a conventional receiving antenna as this type of antenna, as shown in Figure 1, in addition to the main antenna, there is a sub antenna whose main radiation direction is directed toward the interference wave source, and the main antenna and the sub antenna receive signals. By combining the interference waves so that they cancel each other out, the side lobe in the direction of the interference wave source of the main antenna is apparently lowered.

That is, in FIG. 1, the interference wave received by the sub-antenna 2 whose main radiation direction is directed toward the interference wave source 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. It is combined with the interference wave received by the side lobe in the direction of the interference wave source. At this time, if the variable attenuator 3 and variable phase shifter 4 are adjusted so that the interference wave output becomes zero at the output 6 of the combining circuit 5, no interference wave will be output and only the desired wave will appear at the output 6. .

However, in the configuration shown in Figure 1,
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 only narrow band performance can be obtained. Further, when the direction of the interference wave source changes, there is a drawback that it is necessary to change the direction of the sub antenna 2 and readjust the variable attenuator 3 and the variable phase shifter 4.

In order to solve these drawbacks, the present invention employs a reflective phased array antenna structure as the sub-antenna, and installs the sub-antenna so that its aperture almost coincides with a part of the inner surface of the reflector of the main antenna. By using a part of the radiation waves from the antenna's primary radiator, the direction of the interference wave source can be changed by eliminating the need for a combining circuit, and by controlling the phase shifter and attenuator in the phased array antenna. The antenna is designed so that 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 10 is a primary radiator, 11 is a parabolic reflector, 12 is a sub-array antenna having a reflective phased array configuration, and 1
Reference numeral 2a denotes a radiating element, which is fitted into a notched portion of a mirror surface so that it is substantially flush with the mirror surface. 12b is a phase shifter, 12c
is an attenuator, 12d is a short circuit surface for reflection,
They are mounted in a layered manner above the radiating element on the back surface of the reflecting mirror. FIG. 3 is a front view of FIG. 2.

In the figure, most of the radio waves emitted from the primary radiator 10 are reflected by the parabolic reflector 11,
The beams have the same phase at the aperture plane and form a main beam in the front direction. On the other hand, the radio wave incident on the radiating element 12a passes through the phase shifter 12b and the attenuator 12c, and then passes through the short circuit surface 12d.
is reflected at the attenuator 12c and the phase shifter 12b again.
, and is radiated from the radiating 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 the 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 the directivity of the radiated radio waves from the reflecting mirror surface 11 other than the sub array antenna 12, if you want to lower the side lobe in a certain direction due to interference, change the main beam of the directivity of the sub array antenna in the direction of the side lobe. This can be achieved by 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. In a normal parabolic antenna, the sidelobe level is approximately -
Since it is 25 dB or less, the size of the sub array antenna 12 can be made considerably smaller than the parabolic reflector 11, and there are no problems in terms of configuration or structure.

As explained above, according to the present invention, what conventionally required a circuit to install another sub-antenna of the main antenna and adjust and synthesize the amplitude and phase of the interference waves between the two antennas is replaced by a parabolic antenna. By installing a sub-array antenna in a part of the reflector and making this antenna a reflective phased array antenna, there is no need for a circuit that adjusts and synthesizes the amplitude and phase, and the direction in which you want to lower the side lobe can be changed. In this case, it is only necessary to electronically control the phase shifter and attenuator in the sub-array antenna from the outside, and there is an advantage that it is not necessary to change the installation direction of the antenna. Furthermore, the aperture of each radiating element of the sub-array antenna is arranged almost in line with the parabolic reflecting mirror surface, eliminating the need for a feed line.Furthermore, by shortening the length of the phase shifter and attenuator, the sub-array The frequency characteristic of the phase of the radiation wave from the antenna can be made close to the frequency characteristic of the main antenna, which has the advantage of providing broadband characteristics.

Note that although the above explanation has been given for one embodiment of a parabolic antenna, the same can be applied to other types of antennas that use reflectors, such as horn reflector 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 can easily change the direction in which the side lobe is desired to be lowered, and can also obtain broadband characteristics, so it has great practical value.

[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, and FIG. 3 is a front view of the antenna device shown in FIG. 2. 1...Main antenna, 2...Sub antenna, 3...
Variable attenuator, 4... Variable phase shifter, 10... Primary radiator, 11... Reflector, 12... Sub array antenna, 12a... Radiation element, 12b... Phase shifter, 1
2c...Attenuator, 12d...Short circuit surface. It should be noted that the same or corresponding parts in the drawings are designated by the same reference numerals.

Claims (1)

[Claims] 1. A primary radiator that emits or receives radio waves, a reflecting mirror that is placed opposite to this primary radiator and reflects radio waves, and a radiating element that is provided in a part of this reflecting mirror surface so that it is almost flush with the mirror surface. , and a phase shifter, an attenuator, and a plurality of array elements configured as short-circuit planes, which are attached to the radiating element in a hierarchical manner.