Spread spectrum adaptive antenna interference canceller

• US 4,670,885 A
• Filed: 02/26/1985
• Issued: 06/02/1987
• Est. Priority Date: 02/26/1985
• Status: Expired due to Term

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Signatron, Inc.
• Inventors: Parl, Steen A., Pierce, John N.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US06/705,613
• Time in Patent Office: 826 Days
• Field of Search: 455/273, 455/276, 455/278, 455/279, 455/283, 455/284, 455/137, 455/138, 455/206, 343/368, 343/371, 343/372, 343/379, 343/380, 343/381, 343/850, 343/852, 343/853, 333/117, 333/121, 375/1, 375/99, 375/102
• US Class Current: 375/148
• CPC Class Codes: H01Q 3/2617 Array of identical elements
• CPC Class Codes: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10

Abstract

An adaptive power equalizer circuit for use in a spread spectrum receiver system which includes an antenna system 12, 13 and a receiver 11, the circuit comprising adaptive power inversion circuitry 15 for producing a first signal having a minimized power level and a second signal having a substantially higher power level than that of the first signal. Such signals are supplied to a power equalizer circuitry 16 which equalizes the power levels thereof, such equalized power level signals then being combined in a suitable combiner circuit 30 for producing an output receiver output signal for the receiver 11.

Claims

1. An adaptive power equilizer means for use in a spread spectrum signal receiver system which includes at least two antenna means, each of which receives at least two incoming signals from unknown directions, one of said incoming signals having a higher power level than the other, and receiver means, said adaptive power equalizer means comprising

adaptive means responsive to said incoming antenna signals for producing a first signal in which the signal having the higher power level has been effectively cancelled and for producing a second signal;

power equalizer means responsive to said first and second signals for causing the power levels of said first and second signals to be substantially equal; and

means for combining said substantially equalized power level signals for providing an output receiver signal for use by said receiver means.

2. An adaptive power equalizer means in accordance with claim 1 wherein said incoming signals include a spread spectrum signal and at least one interference signal having a power level higher than that of said spread spectrum signal,

said adaptive means producing said first signal comprising primarily said spread spectrum signal, said interference signal being effectively cancelled therein, and producing said second signal comprising said interference signal and said spread spectrum signal;

and

said combining means providing an output signal comprising said spread spectrum signal and said interference signal, the power levels of each being substantially equal.

3. An adaptive power equalizer means in accordance with claim 1 wherein said antenna means comprises two antennas and said adaptive means is an adaptive power inversion circuit which comprises

at least one weighting loop circuit for multiplying the incoming signal received at one of said antennas by a weighting factor to provide a weighted signal;

a hybrid coupler means responsive to said weighted signal and to the incoming signal received at the other of said antennas for providing said first signal at a difference port thereof and said second signal at a sum port thereof.

4. An adaptive power equalizer means in accordance with claim 3 wherein said weighting loop circuit includes

complex multiplier means;

complex correlator means;

means responsive to the incoming signal received at said one of said antennas for supplying said incoming signal to said complex multiplier means and to one input of said complex correlator means;

means responsive to said first signal for supplying said first signal to the other input of said complex correlator means;

said complex correlator means thereby producing a correlated output signal;

filter means responsive to said correlated output signal for providing a filtered weighting signal;

said complex multipler being responsive to said filtered weighting signal and to the incoming signal from said one of said antennas to provide said weighted signal.

5. An adaptive means circuit in accordance with claim 4 wherein said correlated output signal and said filtered weighting signal each has in-phase and quadrature components.

6. An adaptive power equalizer means in accordance with claim 1 wherein said power equalizer means comprises

means responsive to said second signal for controllably attenuating the power level of said second signal;

control means responsive to said first signal and to said second signal for supplying a control signal to said attenuating means so as to controllably attenuate the power level of said second signal in a manner so as to be equal to the power level of said first signal;

said combining means being responsive to said first signal and to the controllably attenuated second signal for providing said output receiver signal.

7. An adaptive power equalizer means in accordance with claim 6 wherein said combining means is a summation circuit.

8. An adaptive power equalizer means in accordance with claim 1 wherein said power equalizer means comprises

first automatic gain control circuitry responsive to said first signal for providing a first gain controlled signal having a selected power level;

second automatic gain control circuitry responsive to said second signal for providing a second gain controlled signal having substantially the same said selected power level;

said combining means being responsive to said first and second gain controlled signals for providing said output receiver signal.

9. An adaptive power equalizer means in accordance with claim 1 wherein said antenna means comprises two antennas and said adaptive means is an adaptive power inversion circuit which comprises

a pair of weighted loop circuits, one of said weighted loop circuits being responsive to the incoming signal from one of said antennas and to said first signal for providing a first weighted signal and the other of said weighted loop circuits being responsive to the incoming signal time delayed by a selected time period and to said first signal for providing a second weighted signal;

means for combining said first and second weighted signals for providing an overall weighted signal;

hybrid complex means responsive to said overall weighted signal and to the incoming signal received at the other of said antennas for providing said first signal at a difference port thereof and said second signal at a sum port thereof.

10. An adaptive power equalizer means in accordance with claim 9 wherein each of said weighted loops includes

complex correlator means responsive to said first signal and to other incoming signal supplied thereto for providing a correlated output signal;

filter means responsive to said correlated output signal for providing a filtered weighting signal; and

multiplier means responsive to said filtered weighting signal and to the incoming signal supplied thereto for providing the weighted signal therefrom.

11. An adaptive power equalizer means in accordance with claim 1 wherein said antenna means comprises four antennas and said adaptive means includes

a plurality of adaptive power inversion circuits comprising

a first said circuit responsive to the incoming signals received at two of said antennas for producing first difference and sum signals therefrom;

a second said circuit responsive to the incoming signals received at the other two of said antennas for producing second difference and sum signals therefrom;

a third said circuit responsive to said first and second difference signals for producing third difference and sum signals;

a fourth said circuit responsive to said first and second sum signals for producing fourth difference and sum signals;

a fifth said circuit responsive to said third sum signal and to said fourth difference signals for producing fifth difference and sum signals;

a sixth said circuit response to said third difference signal and to said fifth difference signal for producing sixth difference and sum signals; and

further wherein

said power equalizer means is responsive to said sixth difference signal, said sixth sum signal, said fifth sum signal and said fourth sum signal for equalizing the power levels thereof; and

said combining means combines said equalized power level signals to provide an output receiver signal for said receiver means.

12. An adaptive power equalizer means in accordance with claim 1 wherein said antenna means comprises N antennas and said adaptive means includes a plurality of N(N-1)/2 adaptive power inversion circuits said adaptive power inversion circuits being responsive to the incoming signals received at said N antennas for producing a difference output signal and (N-1) sum output signals;

and further wherein

said power equalizer means is responsive to said difference output signal and to said (N-1) sum output signals for equalizing the power levels thereof; and

said combining means combines said equalized power level signals to provide said output receiver signal.

13. An adaptive power equalizer means in accordance with claim 1 wherein said antenna means comprises four antennas and said receiver means comprises two receivers, said adaptive power equalizer means including a pair of adaptive power equalizer means in accordance with claim 1, one of said adaptive power equalizer means being responsive to the incoming signals at one pair of said four antennas for providing an output receiver signal for one of said receivers and the other of said adaptive power equalizer means being responsive to the incoming signals received at the other pair of said four antenna means for providing an output receiver signal for the other of said receivers.

14. A spread spectrum communications receiving system for use in reducing the effects of at least one interference signal on the reception of a transmitted spread spectrum communications signal received by said receiver system, said system comprising

antenna means for receiving said transmitted spread spectrum signal and said at least one interference signal from unknown directions, said at least one interference signal having a higher power level than said spread spectrum signal;

at least one adaptive power equalizer means in accordance with claim 1 responsive to the spread spectrum signal and the at least one interference signal received at said antenna means for providing a spread spectrum receiver output signal in which the effects of said at least one interference signal is reduced,

the adaptive means of said at least one adaptive power equalizer means being responsive to the signal received at said antenna means for producing a first signal in which said at least one interference signal has been effectively cancelled and a second signal which includes said spread spectrum signal and said at least one interference signal,

the power equalizer means of said adaptive power equalizer means being responsive to said first and second signals for causing the power levels of said first and second signals to be substantially equal; and

the combining means of said adaptive power equalizer means combining said substantially equalized power level signals for producing a spread spectrum output receiver signal; and

receiver means for receiving said spread spectrum output receiver signal.

15. An adaptive power equalizer means in accordance with claim 1 wherein said incoming signals include a spread spectrum signal and at least one interference signal, said spread spectrum signal having a power level higher than that of said at least one interference signal,

said adaptive means producing said first signal comprising primarily said interference signal, said spread spectrum signal being effectively cancelled therein, and producing said second signal comprising said spread spectrum signal and said at least one interference signal;

and

said combining means providing an output signal comprising said spread spectrum signal and said at least one interference signal, the power levels of each being substantially equal.

16. A spread spectrum communications receiving system for use in reducing the effects of at least one interference signal on the reception of a transmitted spread spectrum communications signal received by said receiver system, said system comprising

antenna means for receiving said transmitted spread spectrum signal and said at least one interference signal from unknown directions, said spread spectrum signal having a higher power level than said at least one interference signal;

at least one adaptive power equalizer means in accordance with claim 1 responsive to the spread spectrum signal and the at least one interference signal received at said antenna means for providing a spread spectrum receiver output signal in which the effects of said spread spectrum signal is reduced,

the adaptive means of said at least one adaptive power equalizer means being responsive to the signals received at said antenna means for producing a first signal in which said spread spectrum signal has been effectively cancelled and a second signal which includes said spread spectrum signal and said at least one interference signal,

the power equalizer means of said adaptive power equalizer means being responsive to said first and second signals for causing the power levels of said first and second signals to be substantially equal; and

the combining means of said adaptive power equalizer means combining said substantially equalized power level signals for producing a spread spectrum output receiver signal; and

receiver means for receiving said spread spectrum output receiver signal.