Adaptive array antenna

• US 6,400,318 B1
• Filed: 04/28/2000
• Issued: 06/04/2002
• Est. Priority Date: 04/30/1999
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kasami, Hideo, Obayashi, Shuichi, Shoki, Hiroki
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/559,573
• Time in Patent Office: 767 Days
• Field of Search: 342/378, 342/380, 342/383, 342/372
• US Class Current: 342/383
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays

Abstract

In an adaptive array antenna, the phase-shifted amount of one of a plurality of phase shifters is changed to a value obtained by increasing a currently set phase-shifted amount by a predetermined angle, and then, to a value obtained by decreasing the currently set phase-shifted amount by a predetermined angle. The variation in strength of a received signal combined at this time is detected by a signal strength detector, and a partial differential coefficient of a performance function with respect to the phase-shifted amount is derived using only the detected variation in strength of the received signal. Thus, the phase control based on the partial differential coefficient of the performance function with respect to the phase-shifted amount is carried out with a simple circuit construction without the need of signals of each antenna element.

Claims

1. An adaptive array antenna comprising:

a plurality of antenna elements;

a plurality of weighting sections which weight received signals, which are received by said antenna elements, by weights which are set, respectively;

a combining section which combines the received signals weighted by said plurality of weighting sections;

a signal strength detecting section which detects the strength of the received signal combined by said combining section; and

a weight control section which calculates a weight on the basis of the strength of the received signal detected by said signal strength detecting section, and which sets the calculated weight in each of said plurality of weighting sections,

wherein said weight control section comprises;

a changing part which changes the weight which is set in one of said plurality of weighting sections; and

a setting part which calculates a weight on the basis of the variation in strength of the received signal detected by said signal strength detecting section when said weight is changed by said changing part, and for setting the calculated weight in said one of said plurality of weighting sections.

2. An adaptive array antenna as set forth in claim 1, wherein said adaptive array antenna comprises:

a plurality of antenna elements;

a plurality of phase shifting sections which control a phase of the received signals, which are received by said antenna elements, in accordance with phase-shifted amounts which are set, respectively;

a combining section which combines the received signals which are phase-controlled by said plurality of phase shifting sections;

a signal strength detecting section which detects the strength of the received signal combined by said combining section; and

a phase-shifted amount control section which calculates a phase-shifted amount on the basis of the strength of the received signal detected by said signal strength detecting section, and which sets the calculated phase-shifted amount in each of said plurality of phase-shifting sections, and

said phase-shifted amount control section comprises;

a phase-shifted amount operating section which operates phase-shifted amounts in said plurality of phase shifting sections on the basis of various signal strengths, which are outputted from said signal strength detecting section, and a plurality of phase-shifted amounts, by a plurality of cycles to output the operated phase-shifted amounts;

initial value storing sections which store the initial value for each of said plurality of phase shifting sections;

a first phase-shifted amount storing section which stores first phase-shifted amounts, which are operated by said phase-shifted amount operating section on the basis of said initial value stored in each of said plurality of initial value storing sections, to be set in each of said plurality of phase shifting sections;

a second phase-shifted amount storing section which stores second phase-shifted amounts, which are operated by said operating section so as to increase said first phase-shifted amounts by a predetermined angle, respectively, in said plurality of phase shifting sections;

a third phase-shifted amount storing section which stores third phase-shifted amounts, which are operated by said operating section so as to decrease said first phase-shifted amounts by a predetermined angle, respectively, in said plurality of phase shifting sections;

a plurality of phase-shifted amount setting sections which set the phase-shifted amounts of said plurality of phase shifting sections, which are operated by said phase-shifted amount operating section on the basis of the phase-shifted amounts stored in any one of said first through third phase-shifted amount storing sections;

a first signal strength storing section which stores a first signal strength detected by said signal strength detecting section while said second phase-shifted amounts are set in said plurality of phase shifting sections; and

a second signal strength storing section which stores a second signal strength detected by said signal strength detecting section while said third phase-shifted amounts are set in said plurality of phase shifting sections, and

wherein said phase-shifted amount operating section operates a new phase-shifted amount, which is obtained by increasing said first phase-shifted amount by a value in proportion to a difference between said first signal strength and said second signal strength, when said difference is inputted, to input the new phase-shifted amount to said first phase-shifted amount to repeat the operation by a plurality of cycles until said difference is zero, and said phase-shifting amount operating section has an update stopping section which stops the operation of said phase-shifted amount control section on the basis of a predetermined condition.

3. An adaptive array antenna as set forth in claim 2, wherein said initial value storing section stores initial values Φ

1(0) through Φ

n(0) of said phase-shifted amount, respectively, and inputs the initial values Φ

1(0) through Φ

n(0) to Φ

1(k) through Φ

n(k) of said first phase-shifted amount storing section, respectively, when said phase-shifted amount control section is first operated;

said first phase-shifted amount storing section stores phase-shifted amounts Φ

1(k) through Φ

n(k) (n is the number of antenna elements, and k is the number of phase-shifted amount updating operations), respectively, which are set in the phase shifting section;

said second phase-shifted amount storing section stores phase-shifted amounts Φ

1′

(k) through Φ

n′

(k), respectively, which are calculated by increasing said Φ

1(k) through Φ

n(k) by a predetermined angle, respectively;

said third phase-shifted amount storing section stores phase-shifted amounts Φ

1″

(k) through Φ

n″

(k), respectively, which are calculated by decreasing said Φ

1(k) through Φ

n(k) by a predetermined angle, respectively;

said phase-shifted amount setting section sets a phase-shifted amount, which is stored in any one of said first phase-shifted amount storing section, said second phase-shifted amount storing section and said third phase-shifted amount storing section, in each of said plurality of phase shifting sections;

said first signal strength storing section stores a strength Pi′

serving as said first signal strength detected by said signal strength detecting section while Φ

1(k), Φ

2(k), . . . , Φ

i−

1(k), Φ

i′

(k), Φ

i+1(k), . . . , Φ

n(k) (1≦

i≦

n) are set in said phase shifting section, respectively;

said second signal strength storing section stores a strength Pi″

serving as said second signal strength detected by said signal strength detecting section while Φ

1(k), φ

2(k), . . . , Φ

i−

1(k), Φ

i″

(k), Φ

i+1(k), . . . , Φ

n(k) are set in said phase shifting section, respectively;

said phase-shifted amount operating sections calculate a new phase-shifted amount Φ

i(k+1), which is obtained by increasing said Φ

i(k) by a value in proportion to a difference between said signal strengths Pi′ and

Pi″

, to input the calculated phase-shifted amount to Φ

1(k) of said first phase-shifted amount storing section; and

said update stopping section stops the operation of said phase-shifted amount control sections after repeating the operation of said phase-shifted amount control sections predetermined times.

4. An adaptive array antenna as set forth in claim 1, wherein said adaptive array antenna comprises:

a plurality of antenna elements;

a phase shifting section which shifts phase-controls received signals, which are received by said antenna elements, in accordance with phase-shifted amounts which are set, respectively;

a combining section which combines said received signals phase-controlled by said phase shifting section;

a reference signal generating section which generates a reference signal;

an error detecting section which outputs a difference between the received signal, which is combined by said combining section, and said reference signal which is generated by said reference signal generating section;

an error signal strength detecting section which detects the signal strength of an error signal detected by said error detecting section; and

a phase-shifted amount control section which calculates a phase-shifted amount on the basis of the signal strength of said error signal detected by said error signal strength detecting section, and which sets the calculated phase -shifted amount in each of said plurality of phase shifting sections, said phase-shifted amount control section comprises;

a phase-shifted amount operating section which operates phase-shifted amounts in said plurality of phase shifting sections on the basis of various signal strengths, which are outputted from said error signal strength detecting section, and a plurality of phase-shifted amounts, by a plurality of cycles to output the operated phase-shifted amounts;

an initial value storing section which stores the initial value for each of said plurality of phase shifting sections;

a first phase-shifted amount storing section which stores first phase-shifted amounts, which are operated by said phase-shifted amount operating section on the basis of said initial value stored in each of said plurality of initial value storing sections, to be set in each of said plurality of phase shifting sections;

a second phase-shifted amount storing section which stores second phase-shifted amounts, which are operated by said operating section so as to increase said first phase-shifted amounts by a predetermined angle, respectively, in said plurality of phase shifting sections;

a third phase-shifted amount storing section which stores third phase-shifted amounts, which are operated by said operating section so as to decrease said first phase-shifted amounts by a predetermined angle, respectively, in said plurality of phase shifting sections;

a plurality of phase-shifted amount setting sections which store the phase-shifted amounts of said plurality of phase shifting sections, which are operated by said phase-shifted amount operating section on the basis of the phase-shifted amounts stored in any one of said first through third phase-shifted amount storing sections;

a first error signal strength storing section which stores a first error signal strength detected by said error signal strength detecting section while said second phase-shifted amounts are set in said plurality of phase shifting sections; and

a second error signal strength storing section which stores a second error signal strength detected by said error signal strength detecting section while said third phase-shifted amounts are set in said plurality of phase shifting sections, and

wherein said phase-shifted amount operating section operates a new phase-shifted amount, which is obtained by increasing said first phase-shifted amount by a value in proportion to a difference between said first error signal strength and said second error signal strength, when said difference is inputted, to input the new phase-shifted amount to said first phase-shifted amount to repeat the operation by a plurality of cycles until said difference is zero, and said phase-shifting amount operating section has an update stopping section which stops the operation of said phase-shifted amount control section on the basis of a predetermined condition.

5. An adaptive array antenna as set forth in claim 4, wherein said first phase-shifted amount storing section stores phase-shifted amounts Φ

1(k) through Φ

n(k) (n is the number of antenna elements, and k is the number of phase-shifted amount updating operations), respectively, which are set in the phase shifting section;

said second phase-shifted amount storing section stores phase-shifted amounts Φ

1′

(k) through Φ

n′

(k), respectively, which are calculated by increasing said Φ

1(k) through Φ

n(k) by a predetermined angle, respectively;

said third phase-shifted amount storing section stores phase-shifted amounts Φ

1″

(k) through Φ

n″

(k), respectively, which are calculated by decreasing said Φ

1(k) through Φ

n(k) by a predetermined angle, respectively;

said phase-shifted amount setting section sets a phase-shifted amount, which is stored in any one of said first phase-shifted amount storing section, said second phase-shifted amount storing section and said third phase-shifted amount storing section, in each of said plurality of phase shifting sections;

said first error signal strength storing section stores said first error signal strength Qi′

detected by said error signal strength detecting section while Φ

1(k), Φ

2(k), . . . , Φ

i−

1(k), Φ

i′

(k), Φ

i+1(k), . . . , Φ

n(k) (1≦

i≦

n) are set in said phase shifting section, respectively;

said second signal strength storing section stores said second error signal strength Qi″

detected by said error signal strength detecting section while Φ

1(k), Φ

2(k), . . . , Φ

i−

1(k), Φ

i″

(k), Φ

i+1(k), . . . , Φ

n(k) are set in said phase shifting section, respectively;

said phase-shifted amount operating sections calculate a new phase-shifted amount Φ

i(k+1), which is obtained by increasing said Φ

i(k) by a value in proportion to a difference between said first and second error signal strengths Qi′ and

Qi″

, to input the calculated phase-shifted amount to Φ

1(k) of said first phase-shifted amount storing section; and

said initial value storing section stores initial values Φ

1(0) through Φ

n(0) of said phase-shifted amount, respectively, and inputs the initial values Φ

1(0) through Φ

n(0) of said phase-shifted amount to Φ

1(k) through Φ

n(k) of said first phase-shifted amount storing section, respectively, when said phase-shifted amount control section is first operated.

6. An adaptive array antenna as set forth in claim 1, wherein said adaptive array antenna comprises:

a plurality of antenna elements;

a plurality of signal cut-off sections which pass or interrupt received signals, which are received by said antenna elements, in accordance with control signals inputted from the outside, respectively;

a plurality of phase shifting sections which control a phase of the received signals, which pass through said signal cut-off sections, in accordance with phase-shifted amounts which are set, respectively;

a combining section which combines the received signals which are phase-controlled by said plurality of phase shifting sections;

a signal strength detecting section which detects the strength of the received signal combined by said combining section; and

a phase-shifted amount control section which calculates a phase-shifted amount on the basis of the strength of the received signal detected by said signal strength detecting section, and for setting the calculated phase-shifted amount in each of said plurality of phase-shifting sections, and

said phase-shifted amount control section comprises;

a signal selecting section which selectively switches said plurality of signal cut-off sections so as to set two of said plurality of signal cut-off sections on a pass side and the rest of said plurality of signal cut-off sections on a cut-off side;

a phase-shifted amount operating section which calculates a phase-shifted amount, which minimizes a strength (P) of the received signal detected by the signal strength detecting section, on the basis of said strength (P) while two of said plurality of signal cut-off sections are set on said pass side and the rest of said plurality of signal cut-off sections are set on said cut-off side; and

a phase-shifted amount setting section which sets the phase-shifted amount, which is calculated by said phase-shifted amount operating section, in one of said plurality of phase shifting sections, which is connected to said signal cut-off sections set on said pass side by said signal selecting section.

7. An adaptive array antenna as set forth in claim 1, wherein said adaptive array antenna comprises:

a plurality of antenna elements;

a plurality of signal cut-off sections which pass or interrupt received signals, which are received by said antenna elements, in accordance with control signals inputted from the outside, respectively;

a plurality of phase shifting sections which control a phase of the received signals, which pass through said signal cut-off sections, in accordance with phase-shifted amounts which are set, respectively;

a combining section which combines the received signals which are phase-controlled by said plurality of phase shifting sections;

a signal strength detecting section which detects the strength of the received signal combined by said combining section; and

a phase-shifted amount control section which calculates a phase-shifted amount on the basis of the strength of the received signal detected by said signal strength detecting section, and for setting the calculated phase-shifted amount in each of said plurality of phase-shifting sections, and

said phase-shifted amount control section comprises;

a first signal strength storing section which stores a first strength (P1) of a received signal detected by said signal strength detecting section while desired waves and interference waves exist;

a second signal strength storing section which stores a second strength (P2) of a received signal detected by said signal strength detecting section which interference waves exist;

a signal selecting section which sets two of said plurality of signal cut-off sections on a pass side and the rest of said plurality of signal cut-off sections on a cut-off side;

a phase-shifted amount operating section which calculates a phase-shifted amount, which minimizes a difference (P1-P2) between said first strength (P1) and second strengths (P2), on the basis of said first strength (P1) and second strengths (P2) while two of said plurality of signal cut-off sections are set on said pass side and the rest of said plurality of signal cut-off sections is set on said cut-off side; and

a phase-shifted amount setting section which sets the phase-shifted amount, which is calculated by said phase-shifted amount operating section, in one of said plurality of phase shifting sections, which is connected to said signal cut-off sections set on said pass side by said signal selecting section.

8. An adaptive array antenna as set forth in claim 1, wherein said adaptive array antenna comprises:

a distributing section which distributes transmitted signals;

a plurality of phase shifting sections which control a phase of the transmitted signals, which are distributed by said distributing section, in accordance with phase-shifted amounts, which are set, respectively;

a plurality of signal cut-off sections which pass or interrupt the transmitted signals, which are phase-controlled by said plurality of phase shifting sections, to circuits in the subsequent stage in accordance with control signals inputted from the outside;

antenna elements which transmit the transmitted signals passing through said plurality of signal cut-off sections;

a phase-shifted amount control section which calculates a phase-shifted amount on the basis of input information and which sets the calculated phase-shifted amount in each of said phase shifting sections; and

a signal strength detecting section which detects the signal strength of the signals received in a foreign station communicating with a self-station, on the basis of the notice from said foreign station, and

said phase-shifted amount control section comprises;

a signal selecting section which sets two of said plurality of signal cut-off sections on a pass side and the rest of said plurality of signal cut-off sections on a cut-off side;

a phase-shifted amount operating section which calculates a phase-shifted amount, which minimizes a strength (P) of the received signal detected by said signal strength detecting section, on the basis of said strength (P) while two of said plurality of signal cut-off sections are set on said pass side and the rest of said plurality of signal cut-off sections are set on said cut-off side; and

a phase-shifted amount setting section which sets the phase-shifted amount, which is calculated by said phase-shifted amount operating section, in one of said plurality of phase shifting sections, which is connected to said signal cut-off sections set on said pass side by said signal selecting section.

9. An adaptive array antenna as set forth in claim 1, wherein said adaptive array antenna comprises:

a distributing section which distributes transmitted signals;

a plurality of phase shifting sections which control a phase of the transmitted signals, which are distributed by said distributing section, in accordance with phase-shifted amounts, which are set, respectively;

a plurality of signal cut-off sections which pass or interrupt the transmitted signals, which are phase-controlled by said plurality of phase shifting sections to circuits in the subsequent stage in accordance with control signals inputted from the outside;

antenna elements which transmit the transmitted signals passing through said plurality of signal cut-off sections;

a phase-shifted amount control section which calculates a phase-shifted amount on the basis of input information and for setting the calculated phase-shifted amount in each of said phase shifting sections; and

a signal strength detecting section which detects the signal strength of the signals received in a foreign station communicating with a self-station, on the basis of the notice from said foreign station, and

said phase-shifted amount control section comprises;

a first signal strength storing section which stores a first strength (P1) of a received signal detected by said signal strength detecting section while signals are transmitted from said antenna elements;

a second signal strength storing section which stores a second strength (P2) of a received signal detected by said signal strength detecting section which no signals are transmitted from said antenna elements;

a signal selecting section which sets two of said plurality of signal cut-off sections on a pass side and the rest of said plurality of signal cut-off sections on a cut-off side;

a phase-shifted amount operating section which calculates a phase-shifted amount, which minimizes a difference (P1-P2) between said first strength (P1) and second strengths (P2), on the basis of said first strength (P1) and second strengths (P2) while two of said plurality of signal cut-off sections are set on said pass side and the rest of said plurality of signal cut-off sections is set on said cut-off side; and

a phase-shifted amount setting section which sets the phase-shifted amount, which is calculated by said phase-shifted amount operating section, in one of said plurality of phase shifting sections, which is connected to said signal cut-off sections set on said pass side by said signal selecting section.

10. An adaptive array antenna as set forth in claim 1, wherein said adaptive array antenna comprises:

a plurality of antenna elements;

a plurality of real number weighting sections which weight received signals, which are received by said plurality of antenna elements, by real number weights which are set, respectively;

a plurality of individual element signal strength detecting sections which detect the strength of each of the received signals, which are weighted by said plurality of real number weighting sections, as an individual element signal strength;

a combining section which combines the received signals weighted by said plurality of real number weighting sections;

a signal strength detecting section which detects the strength of the received signal, which is combined by said combining section, as a combined signal strength; and

a plurality of real number weight control sections which calculate a real number weight on the basis of the variation in said combined signal strength and said plurality of individual element signal strengths when the sign of the real number weight set in at least one of said plurality of weighting sections is changed, and for repeating a processing for setting the calculated real number weight in each of said plurality of real number weighting sections by a plurality of cycles.

11. An adaptive array antenna as set forth in claim 10, wherein said real number weight control section comprises:

a plurality of initial value storing sections which store initial values W_1(O) through W_n(O) (n is the number of antenna elements) which are set in said plurality of real number weighting sections;

a plurality of real number weight storing sections which store said W_1(O) through W_n(O) as real number weights W_1(k) through W_n(k) (k is the number of real number weight updating operations), which are to be set in each of said plurality of real number weighting sections, when said real number weight control section is first operated;

a plurality of real number weight setting sections which set any one of W_i(k) and −

W_i(k) (1≦

i≦

n) as a real number weight of each of said plurality of real number weighting sections on the basis of W_1(k) through W_n(k) stored in said plurality of real number weight storing sections; and

real number weight operating sections which calculate new real number weights W_i(k+1)=W_i(k)+a*[Px_i(k)+{Py(k)−

Py_i(k)}/4]W_i(k) (a is a constant, and 1≦

i≦

n) to input the calculated new real number weights to W_1(k) through W_n(k) of said plurality of real number weight storing sections, respectively, when the combined signal strengths Py(k) detected by said combined signal strength detecting section while W_1(k) through W_n(k) are set in said plurality of real number weighting sections, respectively, are inputted, respectively, and when the individual element signal strengths Px_1(k) through Px_n(k) detected by said plurality of individual element signal strength detecting sections, respectively, while W_1(k) through W_n(k) are set by said plurality of real number weighting sections, respectively, are inputted, respectively, and when the combined signal strengths Py_i(k) (1≦

i≦

n) detected by said combined signal strength detecting section, respectively, while W_1(k), W_2(k), . . . , W_i−

1(k), −

W_i(k), W_i+1(k), . . . , W_n(k) (1≦

i≦

n) are set in said plurality of real number weighting sections, respectively, are inputted, respectively.

12. An adaptive array antenna as set forth in claim 10, wherein said real number weight control section further comprises an update stopping section which stops the operation of said real number weight control section, on the basis of a predetermined condition.

13. An adaptive array antenna as set forth in claim 12, wherein said update stopping section stops the operation of said real number weight control section after repeating the operation of said real number weight control section predetermined times.

14. An adaptive array antenna as set forth in claim 12, wherein said update stopping section stops the operation of said real number weight control section when a falling amount of a real number weight set in said real number weighting section is a predetermined value or less.

15. An adaptive array antenna as set forth in claim 10, wherein each of said plurality of antenna elements comprises a directional antenna.

16. An adaptive array antenna as set forth in claim 10, wherein each of said plurality of antenna elements comprises an array antenna.

17. An adaptive array antenna comprising:

a plurality of element antennas;

a plurality of high-frequency circuits, each of which is connected to a corresponding one of said element antennas; and

a local signal phase-shifting circuit for varying the phase of a local signal, which is added to a frequency converting circuit in said high-frequency circuit, every one of said high-frequency circuits for each of said element antennas,

wherein each of said plurality of high-frequency circuits has a coupler which branches a part of signals from each of said element antennas, and an orthogonal demodulator for an individual element antenna, to which signals are inputted from said coupler.

18. An adaptive array antenna as set forth in claim 17, wherein said local signal phase circuit has an orthogonal modulator which inputs a local frequency signal and a control signal, as at least a part thereof.

19. An adaptive array antenna as set forth in claim 18, which further comprises:

a phase/amplitude comparator circuit for inputting a demodulated signal from said orthogonal demodulator for the individual element antenna, and for comparing the phase and amplitude of each of the input signals to each other to detect a difference therebetween;

a phase deviation compensating control section which controls an output signal of a phase control signal output circuit so as to compensate a phase deviation due to the detected difference, differences in extending length of an antenna feeding line and another wiring length, and a difference in a pagging phage characteristic of a component provided in the subsequent stage of said coupler which branches a part of signals from each of said antenna elements, on the basis of the compared result of said phase/amplitude comparator circuit; and

a phase shift control signal output circuit which outputs a control signal to said orthogonal modulator of said local signal phase shifter circuit on the basis of at least the output of said phase deviation compensating control section.

20. An adaptive array antenna comprising:

a plurality of antenna elements;

a plurality of high-frequency circuits, each of which is connected to a corresponding one of said antenna elements;

a high-frequency combining circuit for combining the outputs of said plurality of high-frequency circuits;

at least one first RSSI circuit which monitors at least one signal level of RF and IF signals from a plurality of individual antenna elements;

a second RSSI circuit which monitors the signal level of said RF or IF signal after combining signals from said individual antenna elements;

(N−

1) first variable gain circuits which allow the variation in relative levels of all of RF or IF signals of each of individual elements;

a second variable gain circuit which varies the signal level of the RF or IF signal after combining signals from said individual elements; and

a gain control circuit which controls the output signal level after synthesis to be within a predetermined range on the basis of RSSI signals from said first RSSI circuit and second RSSI circuit, and which controls said first variable gain circuit and said second variable gain circuit so as to prevent a high-frequency circuit element for each of said individual elements from being saturated.

21. An adaptive array antenna as set forth in claim 20, which further comprises:

a storing section which stores a predetermined number of past output values of said RSSI circuits; and

a gain changing section which outputs a gain change order to said first variable gain circuit or said second variable gain circuit only when a difference between an input value and a predetermined number of output values stored in said storing section exceeds a certain predetermined value.

22. An adaptive array antenna comprising:

a plurality of antenna elements;

a plurality of high-frequency circuits, each of which is connected to a corresponding one of said antenna elements;

a high-frequency distributing circuit which distributes outputs to the plurality of high-frequency circuits;

an amplitude weighting circuit which weights the amplitude of each of said antenna elements in the high-frequency circuit;

(N−

1) first variable gain circuit which allows the variation in the relative levels of all of RF or IF signals of each of individual antenna elements;

a second variable gain circuit which varies the signal level of an RF or IF signal before distribution to said individual antenna elements; and

a gain control circuit which controls said (N−

1) first variable gain circuit and said second variable gain circuit so that the effective radiation power taking account of the directional gain from said adaptive array antenna, which is presumed on the basis of the output of said amplitude weighting circuit, does not exceed a predetermined value, and which controls said first and second variable gain circuits so that each of said high-frequency circuits of each of said individual antenna elements is not saturated.