Wideband co-site interference reduction apparatus

• US 6,693,971 B1
• Filed: 02/29/2000
• Issued: 02/17/2004
• Est. Priority Date: 02/29/2000
• Status: Expired due to Term

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Kowalski, Anthony M.
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US09/515,803
• Time in Patent Office: 1,449 Days
• Field of Search: 375/132, 375/133, 375/138, 375/140, 375/141, 375/135, 375/146, 375/284, 375/285, 375/296, 379/406, 379/410, 379/411, 379/392, 370/286, 370/289, 370/291, 455/114, 455/109, 455/67.3, 455/63, 455/501
• US Class Current: 375/285
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10

Abstract

An interference cancellation system for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath. This interference cancellation system includes a frequency hopped radio adapted to operate in a dispersion environment. This frequency hopped radio has an instantaneously limited bandwidth communication channel operating over a substantially larger bandwidth. Transmission of a signal from the frequency hopped radio is via a directly coupled reference path and a received coupled path. A delay means is used for variably adjusting the phase slope delay of the signal in one path relative to the other path. The system employs an amplitude slope means for variably adjusting the amplitude slope of the signal in one path relative to the other path. A digital controlling means, associated with the delay means and the amplitude slope means, provides improved matching of the signal in each path, thereby enhancing the performance of the co-site interference reduction system.

Claims

1. An interference cancellation system for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath comprising:

a frequency hopped radio adapted to operate in dispersion environment, said radio having an instantaneously limited bandwidth communication channel operating over a substantially larger bandwidth;

transmission means, associated with said radio, for transmitting the signal having a phase slope delay over the bandwidth via a directly coupled reference path and a received coupled path and wherein said transmission means has a dead time;

delay means for variably adjusting the phase slope delay of the signal in one path relative to the other path to provide matching between said paths, thereby enhancing the performance of said radio.

2. The interference cancellation system of claim 1 wherein said delay means filter comprises control means for adjusting the delay of the signal in real-time.

3. The interference cancellation system of claim 2 wherein said delay means is implemented in said directly coupled reference path.

4. The interference cancellation system of claim 2 wherein said delay means is implemented in said received path.

5. The interference cancellation system of claim 2 wherein said delay means further comprises a plurality of electrical path lengths of differing path lengths, with each of said electrical paths individually selectable by said control means.

6. The interference cancellation system of claim 2 wherein said delay means further comprises an N-tap tapped delay line having N selectable outputs, with each of said outputs individually selectable by said control means.

7. The interference cancellation system of claim 2 wherein said delay means further comprises a component having an electrically controllable delay connected to said control means wherein said radio can be adjusted to insert a delay in one of said paths such that said paths will match.

8. The interference cancellation system of claim 1 further comprising calibration means for injecting a calibration signal having an expected transmission frequency into said system.

9. The interference cancellation system of claim 8 wherein said calibration means further comprises two tones spaced equidistant from the expected transmit frequency.

10. The interference cancellation system of claim 8 wherein said calibration signal is injected into said system during the dead time of said transmission means.

11. The interference cancellation system of claim 8 wherein said calibration means further comprises a fast-response, low-power vector modulator weight signal.

12. The interference cancellation system of claim 8 wherein said calibration means further comprises a slow response high-dynamic-range variant adapted for nulling.

13. An interference cancellation system for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath comprising:

a frequency hopped radio adapted to operate in dispersion environment, said radio having an instantaneously limited bandwidth communication channel operating over a substantially larger band;

transmission means, associated with said radio, for transmitting the signal having an amplitude slope over the band via a directly coupled reference path and a received coupled path;

amplitude slope means for variably adjusting the amplitude slope of the signal in one path relative to the other path to provide matching between said paths, thereby enhancing the performance of said radio.

14. The interference cancellation system of claim 13 wherein said amplitude slope means further comprises control means for adjusting the variable amplitude slope of the signal in real-time.

15. The interference cancellation system of claim 14 wherein said amplitude slope means is implemented in said directly coupled reference path.

16. The interference cancellation system of claim 14 wherein said amplitude slope means is implemented in said received path.

17. The interference cancellation system of claim 14 wherein said amplitude slope means further comprises a variable filter.

18. The interference cancellation system of claim 17 wherein said variable filter is a transversal filter having programmable weights, selectable by said control means, such that the phase and pass band of the band can be adjusted.

19. The interference cancellation system of claim 18 wherein said transversal filter has only two taps.

20. The interference cancellation system of claim 19 further comprising an amplitude tilt network with said transversal filter.

21. The interference cancellation system of claim 20 wherein said amplitude tilt network is balanced.

22. The interference cancellation system of claim 20 wherein said amplitude tilt network is unbalanced.

23. The interference cancellation system of claim 20 wherein said filter has a center frequency, a pass-band envelop, and a main lobe bandwidth that is much greater than the signal bandwidth and wherein the amplitude tilt adjusted is implemented by adjusting the center frequency of said filter causing the instantaneous band to be conditioned by a separate portion of the passband envelope, whereby the performance of said radio is enhanced.

24. The interference cancellation system of claim 13 further comprising calibration means for injecting a calibration signal having an expected transmission into said system.

25. The interference cancellation system of claim 24 wherein said calibration means further comprises two tones spaced equidistant from the expected transmit frequency.

26. The interference cancellation system of claim 24 wherein said calibration signal is injected into said system during a dead time of said transmission means.

27. The interference cancellation system of claim 24 wherein said calibration means further comprises a fast-response, low-power vector modulator weight signal.

28. The interference cancellation system of claim 24 wherein said calibration means further comprises a slow response high-dynamic-range variant adapted for nulling.

29. An interference cancellation system for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath comprising:

a frequency hopped radio adapted to operate in dispersion environment, said radio having an instantaneously limited bandwidth communication channel operating over a substantially larger bandwidth;

transmission means, associated with said radio, for transmitting the signal having a phase slope delay and an amplitude slope over the bandwidth via a directly coupled reference path and a received coupled path;

delay means for variably adjusting the phase slope delay of the signal in one path relative to the other path;

amplitude slope means for variably adjusting the amplitude slope of the signal in one path relative to the other path;

digital controlling means, associated with said delay means and said amplitude slope means, for improving the matching of the signal in each path, thereby enhancing the performance of said radio.

30. The interference cancellation system of claim 29 further comprising calibration means for injecting a calibration signal having an expected transmission into said system.

31. The interference cancellation system of claim 30 wherein said calibration means further comprises two tones spaced equidistant from the expected transmit frequency.

32. The interference cancellation system of claim 30 wherein said calibration signal is injected into said system during a dead time of said transmission means.

33. The interference cancellation system of claim 30 wherein said calibration means further comprises a fast-response, low-power vector modulator weight signal.

34. The interference cancellation system of claim 30 wherein said calibration means further comprises a slow response high-dynamic-range variant adapted for nulling.

35. An interference cancellation system for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath comprising:

a frequency hopped radio adapted to operate in dispersion environment, said radio having an instantaneously limited bandwidth communication channel operating over a substantially larger band;

transmission means, associated with said radio, for transmitting the signal having an amplitude slope over the band via a directly coupled reference path and a received coupled path;

amplitude slope means for variably adjusting the amplitude slope of the signal in one path relative to the other path to provide matching between said paths;

wherein said amplitude slope means further comprises control means for adjusting the variable amplitude slope of the signal in real-time and a transversal filter having only two taps and having programmable weights, selectable by said control means, such that the phase and pass band of the band can be adjusted; and

wherein said filter has a center frequency, a pass band envelope, and a main lobe bandwidth that is substantially greater than the signal bandwidth, and

wherein the amplitude slope adjusted is implemented by adjusting the center frequency of said filter causing the instantaneous band to be conditioned by a separate portion of the pass band envelope, whereby the performance of said radio is enhanced;

an amplitude tilt network associated with said transversal filter;

thereby enhancing the performance of said radio.