JP2004072489A - Side lobe suppression method for adaptive antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide new techniques which remove unwanted waves and take out only a desired signal by effectively suppressing a side lobe caused by a disturbing wave even when errors occur in a coming direction of a desired signal component due to a change in electric wave environments. <P>SOLUTION: Four auxiliary arrays 21 to 24 are arranged at uniform intervals around a main array 11 to constitute an adaptive antenna. On a basis of the DCMP method, the amplitude and the phase of a main output signal including desired signal components from the main array 11 and the auxiliary arrays 21 to 24 are controlled to minimize the output power of the main output signal. Then, amplitudes and phases of output signals from auxiliary arrays 21 to 24 are controlled so that the output power of the output signal may be a side lobe level of the main array 11 or lower. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sidelobe suppression method for an adaptive antenna, which can be suitably used as an antenna control technique in a radio wave environment where unnecessary wave suppression is required in a radar, a mobile communication base station, or the like.
[0002]
[Prior art]
Techniques for extracting only a desired signal in an environment where various signals are mixed are required in many fields. As a countermeasure, there is a method of receiving signals using a high gain array. However, when a strong interference wave arrives at the side lobe, it is necessary to suppress the interference even with a high gain array.
[0003]
As a side lobe suppression method, there is a side lobe canceller proposed by Howells et al., But there is a risk that the output of the high gain array is canceled by a strong interference wave. A method has been proposed to address this problem by adding a limiter to a filter or amplifier in a feedback circuit, but the limiter value depends on the input signal strength. Therefore, it has not been possible to effectively suppress only the side lobe.
[0004]
On the other hand, a method called a direction-constrained output power minimization (DCMP) method has been proposed. In this method, for example, by controlling the amplitude and phase of an output signal, the output power of the output signal is minimized while the signal output of the desired signal is kept constant, and a desired signal component is extracted. It is. According to the DCMP method, unnecessary waves can be suppressed by adaptively changing the directivity. However, the output value around the desired direction changes in the radio wave environment, and the output value changes in the arrival direction of the desired signal component. There is a problem that even if there is a slight error, it changes greatly. Therefore, even when there is some error in the arrival direction of the desired signal, the characteristics have been deteriorated.
[0005]
Further, as a technique to which the DCMP method is applied, a method using a desired wave block filter has been proposed. However, also in this method, there is a problem that the block filter has to be configured according to a desired signal property, and it is not possible to cope with various kinds of interference waves.
[0006]
[Problems to be solved by the invention]
The present invention effectively suppresses side lobes caused by interfering waves without affecting the directional characteristics of the main lobe even when an error occurs in the arrival direction of a desired signal component due to a change in the radio wave environment. It is another object of the present invention to provide a novel technique for removing unnecessary waves and extracting only a desired signal.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention disposes at least one auxiliary array around a main array and adjusts an amplitude and a phase of an output signal from the auxiliary array to adjust the amplitude and phase of the output signal from the main array and the auxiliary array. In a state where the strength of the desired signal included in the combined output signal is constrained to be constant, the output power of the combined output signal is minimized, and the output power of the output signal from the auxiliary array is The present invention relates to a side lobe suppression method for an adaptive antenna, wherein the side lobe level of the main array is suppressed by setting the side lobe level to be equal to or less than the side lobe level of the main array.
[0008]
In the adaptive antenna side lobe suppression method of the present invention, the amplitude and phase of the output signal from the auxiliary array are adjusted based on the DCMP method described above, and the main signal is adjusted under the condition that the signal strength of the desired signal is constant. A constraint condition is provided such that the output power of the combined output signal from the array and the auxiliary array is minimized. Further, an additional constraint is provided to adjust the amplitude and phase of the output signal from the auxiliary array so that the output power of the output signal is less than or equal to the side lobe level of the main array. Therefore, even when the radio wave environment changes, side lobes can be effectively suppressed without affecting the output value of a desired signal, and unnecessary signals can be efficiently removed.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments of the invention.
FIG. 1 is a diagram showing an example of an array arrangement in the side lobe suppression method of the present invention. As shown in FIG. 1, in this example, four auxiliary arrays 21-24 are arranged at equal intervals around the main array 11 to constitute an adaptive antenna. The main array 11 can be comprised of a high gain array, such as an atmospheric radar, for example, and the auxiliary arrays 21-24 can be comprised of receive-only arrays.
[0010]
In the present invention, based on the DCMP method, the amplitude and phase of the output signal from the auxiliary array 21-24 are adjusted so that the signal intensity of the desired signal is kept constant, and the signals from the main array 11 and the auxiliary array 21-24 are kept constant. The combined output power of the combined output signal is minimized. At the same time, the amplitude and phase of the output signals from the auxiliary arrays 21-24 are controlled so that the output power of the output signals is less than the side lobe level of the main array 11. As a result, even when the radio wave environment for the adaptive antenna shown in FIG. 1 changes, the side lobe is effectively suppressed without affecting the output value of the desired signal, and the unnecessary signal is efficiently removed. Will be able to
[0011]
For example, an atmospheric radar having an antenna pattern as shown in FIG. 2 is used as the main array 11, a reception-only array is used as the auxiliary array 21-24, and the distance between the main array 11 and the auxiliary array 21-24 is desired. It is set to 8λ, which is eight times the wavelength λ of the signal. Then, the direction of the desired signal is set to 0 degree with respect to the main array 11, the direction of the interference signal is set to 80 degrees, and the power of the desired signal and the power of the interference wave are set to 20 dB and 80 dB, respectively. Under these conditions, side lobe suppression was performed according to the above-described method of the present invention. As a result, an antenna pattern as shown in FIG.
[0012]
Note that the side lobe level of the main array 11 was set to 0 dB, and the output power of the output signal from the auxiliary array 21-24 was set to 0 dB. Further, the noise level was set to 0 dB.
[0013]
On the other hand, FIG. 4 shows the result of executing only the DCMP method under the above-described conditions and not executing the constraint condition on the output power of the output signals of the auxiliary arrays 21-24.
[0014]
As is clear from FIGS. 3 and 4, in the case of following the method of the present invention, it is understood that a desired signal pattern can be obtained by suppressing the side lobe even when the above-mentioned interfering wave exists. On the other hand, when only the DCMP method is used, it can be seen that a desired signal pattern cannot be obtained as a side effect of suppressing an interference wave.
[0015]
As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and any modification may be made without departing from the scope of the present invention. And changes are possible.
[0016]
【The invention's effect】
As described above, according to the present invention, even when an error occurs in the arrival direction of a desired signal component due to a change in a radio wave environment, a side lobe caused by an interfering wave can be generated without affecting a main lobe. It is possible to effectively suppress the signal, remove unnecessary waves, and extract only a desired signal.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an array arrangement in a side lobe suppression method of the present invention.
FIG. 2 is a graph showing an antenna pattern of an atmospheric radar used as an example of a main array.
FIG. 3 is a graph showing an antenna pattern obtained according to the method of the present invention.
FIG. 4 is a graph showing an antenna pattern obtained according to a conventional method.
[Explanation of symbols]
11 Main array 21-24 Auxiliary array

Claims (5)

Arranging at least one auxiliary array around the main array, adjusting an amplitude and a phase of an output signal from the auxiliary array, and adjusting a magnitude of a desired signal included in a combined output signal from the main array and the auxiliary array. In a state in which the output power of the combined output signal is minimized while the output power of the output signal from the auxiliary array is set to be equal to or less than the side lobe level of the main array while the output power of the combined output signal is minimized. And suppressing a side lobe level of the main array. The method of claim 1, further comprising at least two auxiliary arrays. 3. The method according to claim 1, wherein the main array is a high gain array. 4. The side lobe suppression method for an adaptive antenna according to claim 1, wherein the auxiliary array is a reception-only array. The side lobe suppression method according to any one of claims 1 to 4, wherein the main array is an atmospheric radar, and is configured to suppress unnecessary reflected waves from the main array.

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