Null processing receiver apparatus and method

• US 4,734,701 A
• Filed: 03/12/1986
• Issued: 03/29/1988
• Est. Priority Date: 03/12/1986
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Magnavox Government and Industrial Electronics Company
• Inventors: Grobert, Paul H.
• Primary Examiner(s): Blum, Theodore M.
• Assistant Examiner(s): CAIN, DAVID C
• Application Number:
  US06/838,920
• Time in Patent Office: 748 Days
• Field of Search: 342/378, 342/379, 342/380, 342/382, 342/383
• US Class Current: 342/380
• CPC Class Codes: H01Q 3/2617 Array of identical elements

Abstract

A null processing receiver apparatus that receives and combines together a number of modulated information signals in such a fashion that an interference or jamming signal superimposed on each received signal is substantially eliminated from the combined signal. The apparatus first demodulates each received signal to baseband, to produce a primary demodulated signal and one or more auxiliary demodulated signals. The apparatus then appropriately weights the one or more auxiliary signals and sums together the weighted signals with the primary signal to produce a sum signal in which the interference is substantially nulled out. The weighting is based on a cross-correlation of the sum signal with the baseband signals themselves.

Claims

1. Signal processing receiver apparatus comprising:

demodulator means for demodulating a plurality of modulated signals to produce a primary information signal and one or more related auxiliary information signals, all of the information signals containing an interference signal;

weighting means for operating on the one or more auxililary information signals, to produce a corresponding number of intermediate signals; and

summing means for summing together the primary information signal and the one or more intermediate signals to produce a sum signal in which the interference signal is substantially nulled out;

wherein the weighting means includes

correlation means responsive to the one or more auxiliary information signals for producing a corresponding number of weighting signals, said correlation means including means for correlating the sum signal with each of the one or more auxiliary information signals to produce the corresponding number of weighting signals, and

multiplier means for multiplying the one or more auxiliary information signals by their corresponding weighting signals to produce the one or more intermediate signals;

at least one of the primary and one or more information signals, the one or more weighting signals, the one or more intermediate signals and the sum signal being a baseband digital code signal.

2. Signal processing apparatus as defined in claim 1, wherein the correlation means includes:

means for multiplying the sum signal by each of the one or more auxiliary information signals to produce a corresponding number of product signals; and

means for integrating each of the one or more product signals to produce the one or more weighting signals.

3. Signal processing apparatus as defined in claim 1, wherein:

the demodulator means includes means for multiplying each of the modulated signals by a pair of orthogonal carrier signals, to produce a pair of primary information signals and one or more pairs of related auxiliary information signals;

the weighting means includes means for operating on each of the one or more pairs of auxiliary information signals, to produce a pair of intermediate signals for each;

the summing means sums together one signal of the pair of primary information signals with one signal of each pair of intermediate signals and further sums together the other signal of the pair of primary information signals with the other signal of each pair of intermediate signals, to produce a pair of sum signals;

the correlation means is responsive to the pair of sum signals and the one or more pairs of intermediate signals to produce a corresponding number of pairs of weighting signals; and

the multiplier means includes means for multiplying each signal in the one or more pairs of auxiliary information signals by its corresponding weighting signal, to produce the one or more pairs of intermediate signals.

4. Signal processing apparatus as defined in claim 1, wherein:

the plurality of modulated signals are received from a corresponding plurality of antenna elements, each modulated signal each includes a carrier signal modulated by a predetermined digital code signal; and

the demodulator means includes

means for multiplying each modulated signal by a common local oscillator signal to produce a corresponding plurality of modulated intermediate-frequency signals, and

means for multiplying each modulated intermediate frequency signal by a common, locally-generated replica of the predetermined digital code signal, to remove the digital code signal therefrom, and for producing the primary and auxiliary information signals.

5. Signal processing apparatus as defined in claim 4, wherein:

the apparatus further includes duty cycle means for alternately enabling and not enabling the correlation means to adjust the weighting signals; and

the demodulator means includes means for substituting a non-replica of the predetermined digital code signal for the signal replica whenever the duty cycle means enables the correlation means to adjust the weighting signals.

6. Signal processing apparatus as defined in claim 1, wherein the weighting means is configured such that the sum signal produced by the summing means has a minimum output power.

7. Signal processing apparatus as defined in claim 1, wherein the primary and one or more auxiliary information signals, the one or more weighting signals, the one or more intermediate signals, and the sum signal are all baseband digital code signals.

8. Signal processing apparatus as defined in claim 1, wherein:

the weighting means further includes means for operating on the primary information signal to produce a weighted primary information signal; and

the summing means includes means for summing together the weighted primary information signal and the one or more intermediate signals to produce the sum signal.

9. Signal processing receiver apparatus comprising:

antenna means for supplying a plurality of rf signals each including a carrier modulated by a predetermined digital code signal and further including an interference signal;

demodulator means including

means for multiplying each rf signal by a common local oscillator signal to produce a corresponding plurality of first intermediate-frequency signals,

means for multiplying each first intermediate frequency signal by a common, locally-generated replica of the predetermined digital code signal, to remove the digital code signal therefrom and produce a corresponding plurality of second intermediate-frequency signals, and

means for multiplying each of the second intermediate frequency signals by a pair of orthogonal reference carrier signals, to produce a pair of primary information signals and one or more pairs of related auxiliary information signals;

weighting means for operating on each of the one or more pairs of auxiliary information signals, to produce a pair of intermediate signals for each; and

summing means for summing together one signal of the pair of primary information signals with one signal of each pair of intermediate signals and for further summing together the other signal of the pair of primary information signals with the other signal of each pair of intermediate signals, to produce a pair of sum signals in which the interference signal is substantially absent;

wherein the weighting means includes

correlation means for correlating the pair of sum signals with the one or more pairs of intermediate signals to produce a corresponding number of pairs of weighting signals, and

multiplier means for multiplying each signal in the one or more pairs of auxiliary information signals by its corresponding weighting signal, to produce the one or more pairs of intermediate signals.

10. Signal processing apparatus as defined in claim 9, wherein the correlation means includes:

means for multiplying each of the pair of sum signals by each of the one or more auxiliary information signals to produce a corresponding number of pairs of product signals; and

means for integrating each of the one or more pairs of product signals to produce the one or more pairs of weighting signals.

11. Signal processing apparatus as defined in claim 9, wherein:

the apparatus further includes duty cycle means for alternately enabling and not enabling the correlation means to adjust the weighting signals; and

the demodulator means includes means for substituting a non-replica of the predetermined digital code signal for the signal replica whenever the duty cycle means enables the correlation means to adjust the weighting signals.

12. Signal processing apparatus as defined in claim 9, wherein the weighting means is configured such that the pair of sum signals produced by the summing means both have minimum output power.

13. Signal processing apparatus as defined in claim 9, wherein the pair of primary information signals, the one or more pairs of auxiliary information signals, the one or more pairs of weighting signals, the one or more pairs of intermediate signals, and the pair of sum signals are all baseband digital code signals.

14. A signal processing method comprising the steps of:

demodulating a plurality of modulated signals to produce a primary information signal and one or more related auxiliary information signals, all of the information signals containing an interference signal;

weighting the one or more auxiliary information signals, to produce a corresponding number of intermediate signals; and

summing together the primary information signal and the one or more intermediate signals to produce a sum signal in which the interference signal is substantially nulled out;

wherein the step of weighting includes steps of

producing one or more weighting signals in response to the one or more auxilliary information signals, and

multiplying the one or more auxiliary information signals by their corresponding weighting signals to produce the one or more intermediate signals;

at least one of the primary and one or more information signals, the one or more weighting signals, the one or more intermediate signals and the sum signal being a baseband digital code signal.

15. A signal processing method as defined in claim 14, wherein the step of producing includes a step of correlating the sum signal with each of the one or more auxiliary information signals to produce the corresponding number of weighting signals.

16. A signal processing method as defined in claim 15, wherein the step of correlating includes steps of:

multiplying the sum signal by each of the one or more auxiliary information signals to produce a corresponding number of products signals; and

integrating each of the one or more product signals to produce the one or more weighting signals.

17. Signal processing method as defined in claim 14, wherein:

the step of demodulating includes a step of multiplying each of the modulated signals by a pair of orthogonal carrier signals, to produce a pair of primary information signals and one or more pairs of related auxiliary information signals;

the step of weighting includes a step of operating on each of the one or more pairs of auxiliary information signals, to produce a pair of intermediate signals for each;

the step of summing sums together one signal of the pair of primary information signals with one signal of each pair of intermediate signals and further sums together the other signal of the pair of primary information signals with the other signal of each pair of intermediate signals, to produce a pair of sum signals;

the step of producing responds to the pair of sum signals and the one or more pairs of intermediate signals to produce a corresponding number of pairs of weighting signals; and

the step of multiplying includes a step of multiplying each signal in the one or more pairs of auxiliary information signals by its corresponding weighting signal, to produce the one or more pairs of intermediate signals.

18. A signal processing method as defined in claim 14, wherein:

the plurality of modulated signals are received from a corresponding plurality of antenna elements, each modulated signal each includes a carrier signal modulated by a predetermined digital code signal; and

the step of demodulating includes steps of

multiplying each modulated signal by a common local oscillator signal to produce a corresponding plurality of modulated intermediate-frequency signals, and

multiplying each modulated intermediate-frequency signal by a common, locally-generated replica of the predetermined digital code signal, to remove the digital code signal therefrom, and for producing the primary and auxiliary information signals.

19. A signal processing apparatus as defined in claim 18, wherein:

the method further includes steps of alternately enabling and not enabling the step of producing to adjust the weighting signals; and

the step of demodulating includes a step of substituting a non-replica of the predetermined digital code signal for the signal replica whenever the step of alternately enabling enables the step of producing to adjust the weighting signals.

20. A signal processing method as defined in claim 14, wherein the step of weighting is performed such that the sum signal produced in the step of summing has a minimum output power

21. A signal processing method as defined in claim 14, wherein the primary and one or more auxiliary information signals, the one or more weighting signal, the one or more intermediate signal, and the sum signal are all baseband digital code signals.

22. A signal processing method as defined in claim 14, wherein:

the step of weighting further includes a step of weighting the primary information signal to produce a weighted primary information signal; and

the step of summing includes a step of summing together the weighted primary information signal and the one or more intermediate signals to produce the sum signal.