JPS6211805B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna system that removes unnecessary radio waves during reception using a radar antenna, a communication antenna, or the like.

Generally, when a receiving antenna receives unnecessary radio waves other than the desired signal, the S/N ratio deteriorates, and when the field strength of the unnecessary radio waves increases, the receiver becomes saturated and radar echoes are generated in the direction where there is no target. Such inconveniences may occur. To avoid this, conventional methods have sharpened antenna directivity or used antennas with suppressed side ropes to avoid receiving unnecessary radio waves. Or, by taking advantage of the fact that the frequencies of the desired signal and unnecessary radio waves are not necessarily the same,
An adaptive array is used that combines antenna directivity using a correlation circuit to remove unnecessary radio waves that have no correlation with the desired signal.

Among these conventional methods, the former has drawbacks such as a large antenna due to the formation of a sharp beam, and a decrease in antenna efficiency due to sidelobe suppression. Although the latter method requires a small antenna, it essentially does not work if the desired signal and unnecessary signal are the same, and has the drawback that unnecessary signal removal is impossible.

The present invention has been made in view of the above drawbacks, and
This is an attempt to remove unnecessary radio waves having the same frequency as the desired signal without using a large antenna.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of an embodiment of the present invention.
In the figure, 1 is an antenna that receives a desired signal from a specific direction θd. Although this figure shows an array, an aperture antenna with a null in directivity may also be used. Reference numeral 2 denotes an array antenna consisting of element antennas with a directivity of 3 having a null in the θd direction. 4 is a circuit that controls the directivity of the antenna 1, and is a circuit that can direct the null of the directivity in any direction. Such a circuit can be realized, for example, by the configuration example shown in FIG.

5 is a circuit that detects the arrival direction of radio waves received by the antenna 2, and the function of this circuit can be realized by detecting the phase difference between the element antennas constituting the antenna 2 and the time difference of the received waves. 6
is a circuit that generates a control signal for circuit 3 corresponding to the arrival direction of radio waves received by antenna 2; for example, circuit 3 is composed of a voltage-controlled variable phase shifter, and the output of circuit 4 is a phase difference. In some cases, it is a phase and voltage switching circuit, and such circuits are well known in the art.

Next, the operation of this embodiment will be explained with reference to the drawings.
In FIG. 3, the desired signal 7 is from the direction of θd,
It is assumed that the unnecessary radio waves 8 arrive from the direction θu. Since the direction θd of the desired signal is known in advance, the null of the directivity of the element antennas constituting the antenna 2 is directed in the direction of θd. Therefore, the desired signal is not received by the antenna 2. On the other hand, since it is extremely rare for the arrival direction of unnecessary radio waves to completely match the arrival direction of the desired signal, only unnecessary radio waves are received by the antenna 2. Therefore, the arrival direction of the radio waves detected by the circuit 5 is the arrival direction of the unnecessary radio waves.

Since the circuit 6 is a control signal generation circuit for directing the null of the directivity of the antenna 1 toward the arrival direction of the unnecessary radio waves detected by the circuit 5, for example, the variable phase shifters 41 to 43 in the circuit 4 in FIG. The phase shift amount of circuit 6
It is possible to direct the null direction of the directivity of the antenna 1 to the arrival direction of unnecessary radio waves by controlling the output of the antenna 1. As a result, the directivity of the antenna 1 as shown in FIG. 4 is obtained, and the antenna 1 becomes an antenna that does not receive unnecessary radio waves 12.

As described above, according to the antenna system of the present invention, it is possible to obtain an antenna that receives only the desired signal arriving from a known direction and does not receive unnecessary radio waves from a different direction even if they have the same frequency. /N good reception. It is also possible to prevent reception interference due to unnecessary radio waves with a high electric field strength, and there are effects such as saturation of the receiver and generation of false echoes from sources other than the main beam in radar. Further, according to the present invention, there is no need to sharpen the beam or suppress side ropes in order to remove unnecessary radio waves, and there is also the advantage that the antenna can be made smaller and used more efficiently.

In the above description, the antenna 1 is described as an array antenna, but the antenna 1 is not limited to an array antenna, and may be a single antenna having a null. At that time, the circuit 4 functions as a rotary table, and the circuit 6 outputs a rotation angle control signal for the rotary table. Also, antenna 1 and antenna 2 are described as being in different positions, but antenna 5
As shown in the figure, it is also possible to share the antenna at the same location. It is clear that in FIG. 5, 9 is a circuit for extracting the sum and difference of two signals, 11 and 12 are the outputs of antenna 1, and 21 and 22 are the outputs of antenna 2. When the present invention is applied to a radar, a transmitting antenna is provided separately, or the output of the circuit 6 is cut off during transmission, and the circuit 4 is directed in a desired beam direction, thereby resulting in a radar that eliminates interference waves.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a specific example of the circuit 4 in FIG. 1, FIG. 3 is a diagram showing the direction of arrival of unnecessary radio waves, and FIG. FIG. 5 is a diagram showing another embodiment of the present invention. 1... Receiving antenna, 2... Array antenna for receiving unnecessary radio waves, 3... Element antenna pattern of antenna 2, 4... Directivity control circuit of antenna 1,
5... Unnecessary radio wave arrival direction detection circuit, 6... Control signal generation circuit corresponding to the unwanted radio wave arrival direction, 9...
Magic T, 21, 22... difference signal output of magic T, 41, 42, 43... variable phase shifter, 44...
...output synthesizer.

Claims (1)

[Claims] 1 An antenna that receives radio waves arriving from a predetermined direction, a directivity control circuit that controls the directivity of this antenna, and an array that has a directional null in the direction of arrival of the radio waves and is composed of a plurality of element antennas. It has an antenna, a detection circuit that detects the direction of arrival of radio waves received by this array antenna, and a circuit that generates a control signal corresponding to the direction of arrival detected by this circuit. An antenna system characterized by controlling the directivity so that the null direction of the directivity of this antenna matches the arrival direction of radio waves received by the array antenna.