Radio receiver

• US 7,346,134 B2
• Filed: 05/14/2002
• Issued: 03/18/2008
• Est. Priority Date: 05/15/2001
• Status: Active Grant

• Current Assignee: Finesse Wireless, LLC
• Original Assignee: Finesse Wireless, Inc.
• Inventors: Smith, Francis J.
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US10/146,358
• Publication Number:
  US 20030021367A1
• Time in Patent Office: 2,135 Days
• Field of Search: 375/346, 375/284, 375/285, 375/350, 375/316, 375/348, 375/349, 455/63.1, 455/501, 455/296
• US Class Current: 375/346
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H

Abstract

Various apparatuses and methods are described to reduce interference in signals subject to intermodulation products and high power narrow band interfering signals on lower power wideband signals. Apparatuses and methods described herein also provide the capability for supporting multi-standards, multi-modes and multi-bands in wireless and wired applications with a single receiver or a receiver with minor variations. The receiver described herein samples the entire band in which there can be signals of interest or signals that can generate interference. All of these signals are sampled in one bit stream and the bit stream is processed to isolate signals of interest and interfering signals. The isolated interfering signals are then cancelled out of the signals of interest.

Claims

1. A method comprising:

over-sampling, at a desired frequency, a passband of received signals to create a bit stream, wherein the received signals include signals of interest and interference generating signals, the interference generating signals capable of generating intermodulation products inband of the signals of interest;

isolating signals of interest in the bit stream using one or more decimating filters;

isolating source signals that generate one or more intermodulation products inband of the signal of interest using one or more decimating filters;

computing an estimate of each of the one or more intermodulation products from the source signals that generate the one or more intermodulation products;

cancelling out one or more inband intermodulation products using the estimate of the intermodulation products; and

performing phase and amplitude adjustment on estimations of the intermodulation product interfering signals in a closed loop manner, wherein performing phase and amplitude adjustment of the estimations comprises performing sub-sample phase shifts to make a phase adjustment on the estimations of the intermodulation product interfering signals.

2. An apparatus comprising:

means for over-sampling, at a desired frequency, a passband of received signals to create a bit stream, wherein the received signals include signals of interest and interference generating signals, the interference generating signals capable of generating intermodulation products inband of the signals of interest;

means for isolating signals of interest in the bit stream using one or more decimating filters;

means for isolating source signals that generate one or more intermodulation products inband of the signal of interest using one or more decimating filters;

means for computing an estimate of each of the one or more intermodulation products from the source signals that generate the one or more intermodulation products;

means for canceling out one or more inband intermodulation products using the estimate of the intermodulation products; and

means for performing phase and amplitude adjustment on estimations of the intermodulation product interfering signals in a closed loop manner, wherein the means for performing phase and amplitude adjustment of the estimations comprises means for performing sub-sample phase shifts to make a phase adjustment on the estimations of the intermodulation product interfering signals.

3. An apparatus comprising:

a sampling unit to sample, at a desired frequency, a passband of received signals to create a bit stream, wherein the received signals include signals of interest and interference generating signals, the interference generating signals capable of generating intermodulation products inband of the signals of interest;

one or more filters to isolate signals of interest and interfering signals in the bit stream;

a cancellation unit to cancel out isolated interference generated signals using estimations of the intermodulation products generated by the isolated interfering signals, wherein the estimations of the isolated interfering signals comprise estimations of intermodulation products falling inband of the signals of interest; and

a phase and amplitude adjuster to adjust the phase and amplitude of estimations of the isolated interfering signals in a closed loop manner, wherein the phase and amplitude adjuster performs phase and amplitude adjustment of the estimations by making sub-sample phase shifts to make a phase adjustment on the estimations of the isolated interfering signals.

4. A method comprising:

outputting a pair of identical digital samples from a sigma delta analog to digital converter (ADC) after sampling an intermediate frequency signal with the sigma delta ADC;

applying a first decimating filter to one of the pair to perform a bandpass operation to obtain a signal of interest with in-band interference intermodulation products, wherein the first decimating filter comprises a finite impulse response (FIR) filter;

applying a second decimating filter to the other pair to perform a band reject operation for the signal of interest to create out of band signals that are a source of the in-band interference intermodulation products, wherein the second decimating filter comprises a FIR filter;

generating an estimate of in-band intermodulation interference based on the out of band signals; and

adding an inverted version of the estimate of in-band intermodulation interference to the signal of interest having the in-band interference intermodulation products to cancel interference caused thereby and create a resulting signal, wherein the first and second FIR filters are applied at a rate at which the sigma delta ADC is applied.

5. A method comprising:

outputting a pair of identical digital samples from a sigma delta analog to digital converter (ADC) after sampling an intermediate frequency signal with the sigma delta ADC;

applying a first decimating filter to one of the pair to perform a bandpass operation to obtain a signal of interest with in-band interference intermodulation products;

applying a second decimating filter to the other pair to perform a band reject operation for the signal of interest to create out of band signals that are a source of the in-band interference intermodulation products;

generating an estimate of in-band intermodulation interference based on the out of band signals, wherein generating an estimate of in-band interference is based on second and third order input intercept points (IIP2 and IIP3); and

adding an inverted version of the estimate of in-band intermodulation interference to the signal of interest having the in-band interference intermodulation products to cancel interference caused thereby and create a resulting signal.

6. The method defined in claim 5 further comprising continuously generating updated IIP2 and IIP3 values.

7. The method defined in claim 5 wherein generating an estimate of in-band interference is further based on other non-linear attributes.

8. further A method comprising:

outputting a pair of identical digital samples from a sigma delta analog to digital converter (ADC) after sampling an intermediate frequency signal with the sigma delta ADC;

applying a first decimating filter to one of the pair to perform a bandpass operation to obtain a signal of interest with in-band interference intermodulation products;

applying a second decimating filter to the other pair to perform a band reject operation for the signal of interest to create out of band signals that are a source of the in-band interference intermodulation products;

generating an estimate of in-band intermodulation interference based on the out of band signals;

adding an inverted version of the estimate of in-band intermodulation interference to the signal of interest having the in-band interference intermodulation products to cancel interference caused thereby and create a resulting signal; and

cross-correlating the resulting signal with the estimate of the in-band interference.

9. The method defined in claim 8 further comprising:

adjusting phase and amplification of the inverted estimate of the in-band interference prior to adding the inverted estimate of in-band inter-modulation interference to the signal of interest.

10. The method defined in claim 9 wherein adjusting phase and amplitude of the inverted estimate of the in-band interference is controlled by an adaptive algorithm to produce results of cross-correlating the resulting signal with the estimate of the in-band interference.

11. The method defined in claim 10 wherein the adaptive algorithm is a zero forcing minimizing algorithm.

12. The method defined in claim 11 wherein the minimizing algorithm comprises a zero forcing algorithm.

13. An apparatus comprising:

a converter to generate a pair of identical bit streams, wherein the bit stream comprises a flash analog to digital converter (ADC) 4 bit low resolution bit stream used to search the receive band for source signals and generate the estimates of the intermodulation products;

at least one decimating filter coupled to the converter to filter the bit streams from an intermediate frequency (IF) signal prior to application of a digital down conversion, wherein the IF filter reduces out of band blocking signals prior to converter;

a lowpass filter coupled to the decimating filter to filter the digital samples output from the decimating filter;

an in-band interference compensation unit coupled to the lowpass filter; and

a second module to pass the frequency bands with source signals to a filter function, wherein the low resolution bit stream from the flash ADC is narrow-band filtered to isolate the source signals with fairly wide filters.

14. The apparatus of claim 13 wherein the filter function provides on the order of 5 to 10 times the width of the source signals.

15. The apparatus of claim 14 wherein the in-band interfere compensation unit multiplies isolated source signals together in the time domain to generate estimates of the intermodulation products and filters the result to pass only those intermodulation products that fall inband of the signal of interest.

16. The apparatus of claim 15 wherein only those frequency blocks with source signals, with such as relationship as to generate intermodulation products inband of the signal of interest, are isolated and filtered and used to generate inter modulation product estimates.

17. The apparatus of claim 15 wherein the compensation unit delays the estimates of the intermodulation products by full samples for a macro adjustment of the phase.

18. The apparatus of claim 15 wherein the compensation unit delays the estimates of the intermodulation products on a sub-sample basis for a micro adjustment of the phase.

19. The apparatus of claim 15 wherein the compensation unit continually updates the phase and amplitude of the intermodulation estimate and the estimates of the input intercept points (IIP2 and IIP3).

20. A method comprising:

receiving a signal comprising a signal of interest and one or more source signals;

generating a sampled data stream by oversampling the received signal over a receiver bandwidth at a low resolution;

recovering one or more of the source signals from the sampled data stream;

using a digital process to estimate an intermodulation product in real time using the one or more recovered source signals;

generating an intermodulation cancellation signal in real time from the estimate of the intermodulation product; and

using the intermodulation cancellation signal to cancel the intermodulation product in a bandwidth of the signal of interest.

21. The method of claim 20, wherein recovering the one or more source signals from the sampled data stream comprises:

copying the sampled data stream;

filtering the copies of the sampled data stream with a plurality of programmable passband filters.

22. The method of claim 20, wherein the one or more source signals are recovered by sampling a full passband of the receiver at radio frequency (RF), intermediate frequency (IF), or baseband (BB) using a flash analog to digital converter.

23. The method of claim 20, wherein the one or more source signals are recovered by sampling a full passband of the receiver at radio frequency (RF), intermediate frequency (IF), or baseband (BB) using a sigma delta analog to digital converter.

24. The method of claim 20, wherein the intermodulation cancellation signal is generated using a digital process comprising multiplying, sample by sample, two or more recovered source signals.

25. The method of claim 20, wherein the intermodulation cancellation signal phase and amplitude are adjusted in real time to improve intermodulation product cancellation within a passband of the signal of interest.

26. The method of claim 21, further comprising recovering the signal of interest from the first sampled stream.

27. The method of claim 21, further comprising:

generating a second sampled stream by sampling a second passband of the receiver at a second sampling rate and filtering the resulting second signal with the plurality of programmable passband filters; and

recovering the signal of interest from the second sampled stream.

28. The method of claim 20, further comprising:

filtering the intermodulation cancellation signal to retain only intermodulation products that fall within a passband of the signal of interest.

29. The method of claim 20, further comprising:

cross-correlating the intermodulation cancellation signal with the signal of interest after the cancellation process to determine a residual intermodulation interference; and

improving cancellation by adjusting the intermodulation cancellation signal phase and amplitude based on the residual intermodulation interference.

30. The method of claim 29, further comprising forcing the residual intermodulation interference to approach a minimum.

31. The method of claim 20, further comprising:

updating the estimate of the intermodulation product; and

adapting the intermodulation cancellation signal using the updated estimate of the intermodulation product.

32. The method of claim 20, wherein cancellation of intermodulation products is achieved without substantially changing an energy of the signal of interest.

33. The method of claim 20, wherein a source signal is transmitter feed thru.

34. The method of claim 21, further comprising:

searching the first sampled stream with a fast search algorithm;

identifying frequencies of the source signals; and

using the identified frequencies to predict intermodulation products within a bandwidth of the signal of interest.

35. The method of claim 34, wherein the fast search algorithm is a fast Fourier transform.

36. The method of claim 34, wherein the fast search algorithm is a discrete Fourier transform.

37. The method of claim 34, further comprising:

generating a control signal based on the identified frequencies;

sending the control signal to the programmable passband filters;

adjusting the programmable passband filters based on the control signal; and

recovering the source signals.

38. The method of claim 34, further comprising:

sub-sampling and re-sampling the intermodulation cancellation signal; and

time-aligning the intermodulation cancellation signal and the predicted intermodulation products.

39. The method of claim 21, further comprising filtering hopped signals with programmable digital filters to pass the hopped signals in different portions of the receive band.

40. The method of claim 21, further comprising frequency hopping the intermodulation cancellation signal to align the intermodulation cancellation signal with at least one of the signal of interest and the intermodulation product, wherein at least one of the source signals or the signal of interest is frequency hopped.

41. A receiver comprising:

a sampling rate multiplier to sample an analog signal using an oversampling ratio;

a first finite impulse response (FIR) filter to pass a bandwidth of a signal of interest;

a second FIR filter to reject the bandwidth of the signal of interest;

a first downsampler to downsample a first signal to a sampling frequency;

a second downsampler to downsample a second signal to the sampling frequency; and

an intermodulation compensator,

wherein;

the first FIR filter is coupled to the sampling rate multiplier and to the first downsampler;

the second FIR filter is coupled to the sampling rate multiplier and to the second downsampler; and

the first and second downsamplers are coupled to the intermodulation compensator.

42. The receiver of claim 41, wherein the oversampling ratio of the sampling rate multiplier is between 8 and 100.

43. The receiver of claim 41, wherein the sampling rate multiplier comprises a sigma delta analog to digital converter.

44. The receiver of claim 41, wherein the sampling rate multiplier comprises a flash analog to digital converter.

45. The receiver of claim 41, wherein the sampling rate multiplier is operable to sample the full passband of the receiver at radio frequency (RF), intermediate frequency (IF), or baseband (BB).

46. The receiver of claim 41, wherein the tap weights of each FIR filter are programmable.

47. The receiver of claim 41, wherein the intermodulation compensator is operable to receive a number bit streams from the sampling rate multiplier equal to a number of source signals to be compensated.

48. An intermodulation compensator comprising:

a processor to accept an input signal and to compute expected in-band interfering signals based on second order and third order input intercept points (IIP2 and IIP3) for a receiver;

a finite impulse response (FIR) filter to pass intermodulation products in a bandwidth of a signal of interest;

an adjuster to adjust an intermodulation cancellation signal phase and amplitude;

an inverter to invert the intermodulation cancellation signal; and

an adder to add the inverted intermodulation cancellation signal to another signal,

wherein;

the processor is coupled to the FIR filter;

the controller is coupled to the FIR filter and to the inverter; and

the adder is coupled to the inverter.

49. The intermodulation compensator of claim 48, wherein the adjuster has an input for a control signal.

50. The intermodulation compensator of claim 49, further comprising:

a correlator coupled to the adder output and to the adjuster; and

an adaptive algorithm calculator coupled to the adjuster and to the correlator, wherein the adaptive algorithm calculator is operable to generate the control signal.

51. The intermodulation compensator of claim 50, wherein the adaptive algorithm calculator includes logic to execute an adaptive algorithm to compute the control signal.

52. The intermodulation compensator of claim 48, wherein the processor is configured to accept input intercept point estimate updates.