Systems and methods for interference cancellation

• US 20100159866A1
• Filed: 12/23/2008
• Published: 06/24/2010
• Est. Priority Date: 12/23/2008
• Status: Active Grant

• Current Assignee: L-3 Communications Integrated Systems LP (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Integrated Systems LP (L3Harris Technologies, Inc.)
• Inventors: Kusmanoff, Antone L., Fudge, Gerald L., Bland, Ross E.
• Granted Patent: US 8,078,130 B2
• Time in Patent Office: Days
• US Class Current: 455/302
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H

Abstract

Systems and methods for interference cancellation in which a first signal having a first frequency may be cancelled with a second frequency having a second and different (e.g., lower) frequency by employing sampling to cancel the first signal with the separate signal at the sample instances.

Claims

1. An interference cancellation system configured to receive an analog input RF signal, said interference cancellation system comprising:

cancel path circuitry comprising cancel path signal sampling circuitry and signal isolation circuitry; and

signal path circuitry comprising signal path signal sampling circuitry;

wherein said cancel path signal sampling circuitry is coupled to sample said analog input RF signal to produce an analog or digital cancel path selected sample IF signal, and wherein said signal isolation circuitry is coupled to receive said cancel path selected sample IF signal and to isolate a signal within said cancel path analog selected sample IF signal and to output said isolated signal as an analog cancellation IF signal having a different frequency than said analog input RF signal; and

wherein said signal path circuitry is coupled to combine said analog input RF signal with said analog cancellation IF signal to create a modified analog input signal, wherein said signal path signal sampling circuitry is coupled to sample said modified analog input signal to produce a signal path analog or digital selected sample signal.

2. The system of claim 1, wherein said cancel path signal sampling circuitry comprises cancel path RF sampler circuitry and cancel path image select filter circuitry;

wherein said signal path signal sampling circuitry comprises signal path RF sampler circuitry and signal path image select filter circuitry;

wherein said cancel path RF sampler circuitry is coupled to sample said analog input RF signal to produce a cancel path sampled analog signal including multiple folded signal images of at least a portion of said analog input RF signal, wherein said cancel path image select filter circuitry is coupled to receive said cancel path analog sample RF signal and to select a desired folded signal image from said multiple folded signal copies of said cancel path analog sample RF signal, wherein said cancel path signal sampling circuitry is configured to output said selected desired signal image as said analog or digital cancel path selected sample IF signal, and wherein said signal isolation circuitry is coupled to receive said cancel path analog or digital cancel path selected sample IF signal and to isolate a signal within said cancel path analog or digital cancel path selected sample IF signal and to output said isolated signal as an analog cancellation IF signal having a different frequency than said analog input RF signal; and

wherein said signal path circuitry is coupled to combine said analog input RF signal with said analog cancellation IF signal to create a modified analog input signal, wherein said signal path RF sampler circuitry is coupled to sample said modified analog input signal to produce a signal path sampled analog signal including multiple folded signal images of at least a portion of said modified analog input signal, and wherein said signal path image select filter circuitry is coupled to receive said signal path sampled analog signal and to select a desired folded signal image from said multiple folded signal copies of said signal path sampled analog signal and to output said selected desired signal image as a signal path analog selected sample signal.

3. The system of claim 2, wherein said analog input RF signal comprises at least one desired signal in the presence of at least one interfering signal;

wherein said cancel path analog sample RF signal includes multiple folded signal images of said interfering signal and at least a portion of said desired signal;

wherein said cancel path analog or digital cancel path selected sample IF signal includes a selected folded signal image of said interfering signal and at least a portion of said desired signal;

wherein said analog cancellation IF signal includes said interfering signal in the absence of said desired signal and is effective to at least partially cancel said at least one interfering signal in said analog input RF signal when combined with said analog input RF signal by said signal path circuitry so as to produce said modified analog input signal; and

wherein said modified analog input signal includes at least a portion of said desired signal.

4. The system of claim 3, further comprising anti-alias filter circuitry coupled to filter out one or more frequencies of said analog input RF signal prior to said signal path circuitry and said cancel path circuitry.

5. The system of claim 3, wherein said signal path circuitry further comprises time delay circuitry coupled to delay said analog input RF signal prior to combining said analog input RF signal with said analog cancellation IF signal to create said modified analog input signal, said time delay circuitry configured to delay said analog input RF signal for a period of time that is sufficient to allow said analog cancellation IF signal to be provided and combined with said analog input RF signal so as to at least partially cancel said at least one interfering signal in said analog input RF signal and produce said modified analog input signal.

6. The system of claim 3, wherein said at least one interfering signal is a periodic signal;

wherein said signal path circuitry and said cancel path circuitry is configured such that said analog input RF signal is not delayed prior to combining said analog input RF signal with said analog cancellation IF signal to create said modified analog input signal; and

wherein said interference cancellation circuitry further comprises phase tuning circuitry coupled to control sampling of at least one of said signal path RF sampler circuitry or said cancel path RF sampler circuitry to achieve phase inversion between said cancel path sampling and said signal path sampling such that said analog cancellation IF signal at least partially cancels said at least one interfering signal in said analog input RF signal when said analog cancellation IF signal is combined with said analog input RF signal to produce said modified analog input signal.

7. The system of claim 3, wherein said cancel path signal sampling circuitry further comprises cancel path analog to digital converter (ADC) circuitry;

wherein said cancel path signal isolation circuitry comprises digital signal processing (DSP) circuitry, IF digital to analog converter (DAC) circuitry, and amplifier circuitry;

wherein said cancel path ADC circuitry is coupled to produce a digital selected sample IF signal including said interfering signal and said at least a portion of said desired signal;

wherein said DSP circuitry is coupled to receive said digital selected sample IF signal and to isolate said interfering signal to produce a processed digital cancel path IF signal including said interfering signal in the absence of said desired signal;

wherein said IF DAC circuitry is configured to convert said processed digital cancel path IF signal to an analog cancel path IF signal; and

wherein said amplifier circuitry is configured to inversely amplify said analog cancel path IF signal to substantially match an amplitude of said analog input RF signal to produce said analog cancellation IF signal.

8. The system of claim 3, wherein said cancel path RF sampler circuitry is configured to produce an analog selected sample IF signal;

wherein said signal isolation circuitry comprises tunable filter circuitry and amplifier circuitry;

wherein said tunable filter circuitry is coupled to receive said analog selected sample IF signal and is controlled to selectably pass said interfering signal frequency in the absence of said desired signal to produce said analog cancel path IF signal; and

wherein said amplifier circuitry is configured to amplify said analog cancel path IF signal to substantially match an amplitude of said analog input RF signal to produce said analog cancellation IF signal.

9. The system of claim 3, further comprising at least one sample clock circuit coupled to synchronize said sampling performed by said signal path RF sampler circuitry with said sampling performed by said cancel path RF sampler circuitry.

10. The system of claim 3, further comprising modulated frequency clock circuitry and wideband filter circuitry;

said frequency modulated RF clock circuitry coupled to control sampling by each of said signal path RF sampler circuitry and said cancel path RF sampler circuitry to provide non-uniform sampling for signals within multiple Nyquist zones to induce frequency modulation on signals dependent on a Nyquist zone of origin; and

said wideband filter circuitry coupled to filter said analog input RF signal prior to said signal path circuitry and said cancel path circuitry, said wideband filter circuitry having a center frequency within a frequency range of interest and having a bandwidth less than or equal to the frequency range of interest and wide enough to cover multiple Nyquist zones associated with said modulated frequency clock.

11. The system of claim 3, further comprising signal path analog to digital converter (ADC) circuitry coupled to sample said desired signal in said signal path analog selected sample signal to produce a substantially clean digital image of said desired signal in a digital output signal.

12. The system of claim 1, wherein said cancel path signal sampling circuitry comprises direct RF sampling ADC circuitry;

wherein said signal path signal sampling circuitry comprises signal path RF sampler circuitry and signal path image select filter circuitry;

wherein said cancel path signal isolation circuitry comprises digital signal processing (DSP) circuitry, IF digital to analog converter (DAC) circuitry, and amplifier circuitry;

wherein said cancel path direct RF sampling ADC circuitry is coupled to produce a digital selected sample IF signal including said interfering signal and said at least a portion of said desired signal;

wherein said DSP circuitry is coupled to receive said digital selected sample IF signal and to isolate said interfering signal to produce a processed digital cancel path IF signal including said interfering signal in the absence of said desired signal;

wherein said IF DAC circuitry is configured to convert said processed digital cancel path IF signal to an analog cancel path IF signal; and

wherein said amplifier circuitry is configured to inversely amplify said analog cancel path IF signal to substantially match an amplitude of said analog input RF signal to produce said analog cancellation IF signal; and

wherein said signal path is coupled to combine said analog input RF signal with said analog cancellation IF signal to create a modified analog input signal, wherein said signal path RF sampler circuitry is coupled to sample said modified analog input signal to produce a signal path sampled analog signal including multiple folded signal images of at least a portion of said modified analog input signal, and wherein said signal path image select filter circuitry is coupled to receive said signal path sampled analog signal and to select a desired folded signal image from said multiple folded signal copies of said signal path sampled analog signal and to output said selected desired signal image as a signal path analog selected sample signal.

13. A method for canceling interference in an analog input RF signal, comprising:

providing cancel path circuitry comprising cancel path signal sampling circuitry and signal isolation circuitry;

providing signal path circuitry comprising signal path signal sampling circuitry;

providing said analog input RF signal to said signal path circuitry and said cancel path circuitry;

utilizing said cancel path signal sampling circuitry to sample said analog input RF signal to produce an analog or digital cancel path selected sample IF signal;

utilizing said signal isolation circuitry to isolate a signal within said analog or digital cancel path selected sample IF signal and to output said isolated signal as an analog cancellation IF signal having a different frequency than said analog input RF signal;

combining said analog input RF signal with said analog cancellation IF signal to create a modified analog input signal; and

utilizing said signal path signal sampling circuitry to sample said modified analog input signal to produce a signal path analog or digital selected sample signal.

14. The method of claim 13, wherein said cancel path signal sampling circuitry comprises cancel path RF sampler circuitry and cancel path image select filter circuitry;

wherein said signal path signal sampling circuitry comprises signal path RF sampler circuitry and signal path image select filter circuitry; and

wherein said method further comprises;

providing cancel path circuitry comprising cancel path RF sampler circuitry, cancel path image select filter circuitry, and signal isolation circuitry;

providing signal path circuitry comprising signal path RF sampler circuitry and signal path image select filter circuitry;

providing said analog input RF signal to said signal path circuitry and said cancel path circuitry;

utilizing said cancel path RF sampler circuitry to sample said analog input RF signal to produce a cancel path analog sample RF signal including multiple folded signal images of at least a portion of said analog input RF signal;

utilizing said cancel path image select filter circuitry to select a desired folded signal image from said multiple folded signal copies of said cancel path analog sample RF signal and outputting said selected desired signal image from said cancel path signal sampling circuitry as said analog or digital cancel path selected sample IF signal;

utilizing said signal isolation circuitry to isolate a signal within said analog or digital cancel path selected sample IF signal and to output said isolated signal as an analog cancellation IF signal having a different frequency than said analog input RF signal;

combining said analog input RF signal with said analog cancellation IF signal to create a modified analog input signal;

utilizing said signal path RF sampler circuitry to sample said modified analog input signal to produce a signal path sampled analog signal including multiple folded signal images of at least a portion of said modified analog input signal; and

utilizing said signal path image select filter circuitry to select a desired folded signal image from said multiple folded signal copies of said signal path sampled analog signal and to output said selected desired signal image as a signal path analog selected sample signal.

15. The method of claim 14, wherein said analog input RF signal comprises at least one desired signal in the presence of at least one interfering signal;

wherein said cancel path analog sample RF signal includes multiple folded signal images of said interfering signal and at least a portion of said desired signal;

wherein said cancel path analog or digital cancel path selected sample IF signal includes a selected folded signal image of said interfering signal and at least a portion of said desired signal;

wherein said analog cancellation IF signal includes said interfering signal in the absence of said desired signal; and

wherein said method further comprises at least partially canceling said at least one interfering signal in said analog input RF signal by combining said analog cancellation IF signal with said analog input RF signal to produce said modified analog input signal, said modified analog input signal including at least a portion of said desired signal.

16. The method of claim 15, further comprising providing and utilizing anti-alias filter circuitry to filter out one or more frequencies of said analog input RF signal prior to providing said analog input RF signal to said signal path circuitry and said cancel path circuitry.

17. The method of claim 15, further comprising providing and utilizing time delay circuitry to delay said analog input RF signal prior to combining said analog input RF signal with said analog cancellation IF signal to create said modified analog, input signal, a value of said time delay being sufficient to allow said analog cancellation IF signal to be provided and combined with said analog input RF signal so as to at least partially cancel said at least one interfering signal in said analog input RF signal and produce said modified analog input signal.

18. The method of claim 15, wherein said at least one interfering signal is a periodic signal;

wherein said analog input RF signal is not delayed by time delay circuitry prior to combining said analog input RF signal with said analog cancellation IF signal to create said modified analog input signal; and

wherein said method further comprises providing and utilizing phase tuning circuitry to control said sampling of at least one of said signal path RF sampler circuitry or said cancel path RF sampler circuitry to achieve phase inversion between said cancel path sampling and said signal path sampling such that said analog cancellation IF signal at least partially cancels said at least one interfering signal in said analog input RF signal when said analog cancellation IF signal is combined with said analog input RF signal to produce said modified analog input signal.

19. The method of claim 15, wherein said cancel path signal sampling circuitry further comprises cancel path analog to digital converter (ADC) circuitry;

wherein said cancel path signal isolation circuitry comprises digital signal processing (DSP) circuitry, IF digital to analog converter (DAC), and amplifier circuitry; and

wherein said method further comprises;

utilizing said cancel path ADC circuitry to produce a digital selected sample IF signal from said analog selected sample IF signal, said digital selected sample IF signal including said interfering signal and said at least a portion of said desired signal;

utilizing said DSP circuitry to isolate said interfering signal and produce a processed digital cancel path IF signal from said digital selected sample IF signal, said processed digital cancel path IF signal including said interfering signal in the absence of said desired signal;

utilizing said IF DAC circuitry to convert said processed digital cancel path IF signal to an analog cancel path IF signal; and

utilizing said amplifier circuitry to produce said analog cancellation IF signal by inversely amplifying said analog cancel path IF signal to substantially match an amplitude of said analog input RF signal.

20. The method of claim 15, wherein said signal isolation circuitry comprises tunable filter circuitry and amplifier circuitry;

and wherein said method further comprises;

utilizing said cancel path RF sampler circuitry to produce an analog selected sample IF signal;

providing said analog selected sample IF signal to said tunable filter circuitry and controlling said tunable filter circuitry to selectably pass said interfering signal frequency in the absence of said desired signal to produce said analog cancel path IF signal; and

utilizing said amplifier circuitry to produce said analog cancellation IF signal by amplifying said analog cancel path IF signal to substantially match an amplitude of said analog input RF signal.

21. The method of claim 15, further comprising providing and utilizing at least one sample clock circuit to generate sampling clock signals to synchronize said sampling performed by said signal path RF sampler circuitry with said sampling performed by said cancel path RF sampler circuitry.

22. The method of claim 15, further comprising:

providing modulated frequency clock circuitry and wideband filter circuitry;

utilizing said frequency modulated RF clock circuitry to control sampling by each of said signal path RF sampler circuitry and said cancel path RF sampler circuitry to provide non-uniform sampling for signals within multiple Nyquist zones to induce frequency modulation on signals dependent on a Nyquist zone of origin; and

utilizing said wideband filter circuitry to filter said analog input RF signal prior to providing said analog input RF signal to said signal path circuitry and said cancel path circuitry, said wideband filter circuitry having a center frequency within a frequency range of interest and having a bandwidth less than or equal to the frequency range of interest and wide enough to cover multiple Nyquist zones associated with said modulated frequency clock.

23. The method of claim 15, further comprising providing and utilizing a signal path analog, to digital converter (ADC) circuitry to sample said desired signal in said signal path analog selected sample signal to produce a substantially clean digital image of said desired signal in a digital output signal.

24. The method of claim 13, wherein said cancel path signal sampling circuitry comprises direct RF sampling ADC circuitry;

wherein said cancel path signal isolation circuitry comprises digital signal processing (DSP) circuitry, IF digital to analog converter (DAC), and amplifier circuitry; and

wherein said method further comprises;

utilizing said cancel path direct RF sampling ADC circuitry to produce a digital selected sample IF signal including said interfering signal and said at least a portion of said desired signal;

utilizing said DSP circuitry to isolate said interfering signal and produce a processed digital cancel path IF signal from said digital selected sample IF signal, said processed digital cancel path IF signal including said interfering signal in the absence of said desired signal;

utilizing said IF DAC circuitry to convert said processed digital cancel path IF signal to an analog cancel path IF signal; and

utilizing said amplifier circuitry to produce said analog cancellation IF signal by inversely amplifying said analog cancel path IF signal to substantially match an amplitude of said analog input RF signal.