Adaptive array antenna

• US 20020057219A1
• Filed: 06/15/2001
• Published: 05/16/2002
• Est. Priority Date: 06/16/2000
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Obayashi, Shuichi
• Granted Patent: US 6,466,165 B2
• Time in Patent Office: Days
• US Class Current: 342/372
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays

Abstract

An active array antenna system comprises a plurality of element antennas and radio frequency circuits connected to the element antennas. The radio frequency circuits comprises first frequency converters provided to correspond to the element antenna and converts the frequency between a carrier-wave frequency and a first intermediate-frequency by using a carrier-wave frequency band local signal, second frequency converters provided to correspond to the element antenna and converts the frequency between the first intermediate-frequency signal and a second intermediate-frequency which is lower than the first intermediate frequency by using an intermediate-frequency band local signal, and a variable phase shifter circuit for individually controlling the phases of the intermediate-frequency local signals which are supplied to the second frequency converters. A variable phase shifter circuit for beam scan can be constituted at a low cost so that an active array antenna system which can be realized at a low cost is provided.

Claims

1. An active array antenna system comprising:

a plurality of element antennas; and

radio frequency circuits connected to the plural element antennas and comprising

frequency converting circuits provided for each of said element antennas and performing a frequency conversion by using local signals, and

a variable phase shifter circuit for controlling phases of the local signals which are supplied to said frequency converting circuits.

2. The active array antenna system according to claim 1, wherein

each of said frequency converting circuits comprises:

a plurality of first frequency converters provided to correspond to said element antennas and converting a frequency between a carrier-wave frequency and a first intermediate-frequency by using a carrier-wave frequency band local signal, and

a plurality of second frequency converters provided to correspond to each of said element antennas and converting a frequency between the first intermediate-frequency and a second intermediate-frequency which is lower than the first intermediate-frequency by using the local signal, and

said variable phase shifter circuit comprises a variable phase shifter for controlling phases of the local signals which are supplied to said second frequency converters.

3. The active array antenna system according to claim 1, wherein said each of said frequency converting circuits comprises a local signal generator for generating the local signal having a variable frequency.

4. The active array antenna system according to claim 1, further comprising:

a gain control circuit for controlling a gain of an intermediate signal for each of said element antennas.

5. The active array antenna system according to claim 1, wherein an input frequency band F_in(min) to F_in(max) of each of said frequency converting circuits and frequency F_LO of the local signal satisfy the conditions that F_LO<

F_in(min)/2 and F_LO<

(F_in(min)/(n+1)) or F_LO>

(F_in(max)/(n+1)) regarding to all integers n which are not smaller than two.

6. The active array antenna system according to claim 1, wherein said variable phase shifter circuit comprises a plurality of quadrature modulators provided to correspond to said element antennas and receiving the local signal and a phase shift control signal.

7. The active array antenna system according to claim 1, wherein said variable phase shifter circuit comprises a variable phase shifter comprising:

two bridge circuits receiving the local signal in the form of a differential signal and having two capacitors disposed on two opposite sides and two resistors disposed on other two opposite sides, resistance values of the capacitors and the resistors being different from one another, and

a selector for selectively outputting either output of the two bridge circuits in response to a phase shift control signal.

8. The active array antenna system according to claim 1, wherein said variable phase shifter circuit comprises a plurality of variable delay circuits, a delay time each of which is controlled in response to a phase shift control signal.

9. The active array antenna system according to claim 1, wherein said radio frequency circuit comprises one of a divider for dividing a signal allowed to pass between the frequency converting circuit and the element antenna to the radio frequency circuit in another active array antenna system, and an adder for adding the signal allowed to pass between the frequency converting circuit and the element antenna and a signal supplied from the radio frequency circuit in the other active array antenna system.

10. The active array antenna system according to claim 1, wherein a phase shift amount of said variable phase shifter circuit is controlled such that a period of the phase shift is smaller than an inverse of a transmission baud rate of a received signal or a transmission signal and the phase shift is varied in synchronization with a synchronization signal which varies at a time interval which is shorter than a time obtained by multiplying an inverse of the number of the received signals or the transmission signals and the inverse of the transmission baud rate of the received signal or the transmission signal, and

said variable phase shifter circuit comprises a demultiplexer for dividing the received signal or the transmission signal at timing delayed from the synchronization signal by a predetermined time.

11. The active array antenna system according to claim 2, wherein each of said second frequency converters comprises a local signal generator for generating the local signal having a variable frequency.

12. The active array antenna system according to claim 2, further comprising:

a gain control circuit for controlling a gain of the second intermediate-frequency signal for each of said element antennas.

13. The active array antenna system according to claim 2, wherein an input frequency band F_in(min) to F_in(max) of each of said second frequency converters and frequency F_LO of the local signal satisfy the conditions that F_LO<

F_in(min)/2 and F_LO<

(F_in(min)/(n+1)) or F_LO>

(F_in(max)/(n+1)) regarding to all integers n which are not smaller than two.

14. The active array antenna system according to claim 2, wherein said variable phase shifter circuit comprises a plurality of quadrature modulators provided to correspond to said element antennas and receiving the local signal and a phase shift control signal.

15. The active array antenna system according to claim 2, wherein each of said radio frequency circuits comprises one of a divider for dividing a signal allowed to pass between the frequency converting circuit and the element antenna to the radio frequency circuit in another active array antenna system, and an adder for adding the signal allowed to pass between the frequency converting circuit and the element antenna and a signal supplied from the radio frequency circuit in the other active array antenna system.

16. The active array antenna system according to claim 2, wherein a phase shift amount of said variable phase shifter circuit is controlled such that a period of the phase shift is smaller than an inverse of a transmission baud rate of a received signal or a transmission signal and the phase shift is varied in synchronization with a synchronization signal which varies at a time interval which is shorter than a time obtained by multiplying an inverse of the number of the received signals or the transmission signals and the inverse of the transmission baud rate of the received signal or the transmission signal, and

said variable phase shifter circuit comprises a demultiplexer for dividing the received signal or the transmission signal at timing delayed from the synchronization signal by a predetermined time.

19. The active array antenna system according to claim 18, wherein said variable phase shifter circuit comprises a first variable phase shifter for a reception radio frequency circuit and a second variable phase shifter for a transmission radio frequency circuit, and the phase shift of each of the first and second variable phase shifters is controlled such that the phases of local signals which are output are complex conjugate each other.

20. The active array antenna system according to claim 19, wherein said transmission/reception element antennas comprise a plurality of transmission antennas and a plurality of reception antennas, and said first and second variable phase shifter circuits commonly use phase shift control signals corresponding to the transmission antennas and the reception antennas disposed symmetrically to each other with respect to a center of said transmission/reception element antennas.

17. An active array antenna system comprising:

a plurality of element antennas; and

radio frequency circuits connected to the plural element antennas and comprising

frequency converting circuits provided to correspond to each of said element antennas and performing a frequency conversion between a carrier-wave frequency and an intermediate frequency, and

a variable phase shifter circuit provided to correspond to each of said element antennas and controlling a phase of a received signal or a transmission signal of each of said element antennas, the variable phase shifter circuit having a quadrature modulator.

18. An active array antenna system comprising:

a plurality of transmission/reception element antennas;

a reception radio frequency circuit supplied with a received signal from said transmission/reception element antennas; and

a transmission radio frequency circuit for supplying a transmission signal to said transmission/reception element antennas, wherein each of said transmission radio frequency circuit and said reception radio frequency circuit comprises;

a frequency converting circuit provided to correspond to each of said transmission/reception element antennas and performing a frequency conversion by using a local signal, and

a variable phase shifter circuit for controlling a phase of the local signal which is supplied to the frequency converting circuit.