Radio receiver

• US 20030021367A1
• Filed: 05/14/2002
• Published: 01/30/2003
• Est. Priority Date: 05/15/2001
• Status: Active Grant

• Current Assignee: Finesse Wireless, LLC
• Original Assignee: Francis J. Smith
• Inventors: Smith, Francis J.
• Granted Patent: US 7,346,134 B2
• Time in Patent Office: Days
• 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 bitstream, 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 ore 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; and

canceling out one or more inband intermodulation products using the estimate of the intermodulation products.

2. The method defined in claim 1 wherein canceling out the one or more intermodulation products is performed simultaneously.

3. The method defined in claim 1 wherein the received passband is at an intermediate frequency (IF).

4. The method defined in claim 1 wherein the decimating filters are software controlled filters.

5. The method defined in claim 1 wherein over-sampling the received passband comprises a sigma delta A/D converter processing the received signals at an IF frequency.

6. The method defined in claim 1 wherein over-sampling the received passband is performed by a flash A/D converter.

7. The method defined in claim 1 wherein the decimating filters provide down conversion.

8. The method defined in claim 1 wherein the decimating filters operate as band select filters.

9. The method defined in claim 1 wherein over-sampling the passband of the received signals comprises oversampling digitizing the received signal at a first resolution and providing the signals of interest within the passband at a second resolution higher than a 1 bit resolution of a corresponding sample in the bitstream.

10. The method defined in claim 1 further comprising selecting bandwidth of the signals of interest and out of band rejection for the signals of interest via software selection.

12. The method defined in claim 1 further comprising down converting the receive band to a common IF using one of a plurality of mixers, wherein the one mixer is associated with one frequency band.

13. The method defined in claim 12 wherein each frequency band is associated with a communication standard, and the communication standard comprises one selected from a group consisting of mobile telephony, CDMA IS-95, CDMA IS-98, CDMA 2000 IX, CDMA 2000 2X, CDMA 2000 3X, AMPS, TDMA, GSM, GPRS, UMTS, WCDMA, 802.11a, 802.1b, 802.11g, and Bluetooth.

14. The method defined in claim 1 wherein the estimations of the isolated interfering signals comprise estimations of inter-modulation products falling in band of the signals of interest.

15. The method defined in claim 14 further comprising performing phase and amplitude adjustment on the estimations of the intermodulated product interfering signals in a closed loop manner.

16. The method defined in claim 15 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.

17. The method defined in claim 14 further comprising generating the estimations of the intermodulation product interfering signals and cancellation signals corresponding to the estimations of the isolated interfering signals.

18. The method defined in claim 17 wherein the cancellation signals are not generated if the source of the intermodulation product interfering signals corresponding to the estimations of the isolated interfering signals no longer causes interferences.

19. The method defined in claim 1 further comprising searching the receive band for source signals that result in intermodulation products that fall within band of the signals of interest.

20. The method defined in claim 19 wherein searching the receive band is performed using discrete Fourier transforms (DFTs).

21. The method defined in claim 19 wherein searching the receive band is performed using Fast Fourier Transforms (FFTs).

22. The method defined in claim 19 wherein searching the receiver band comprises isolating source signals to a very coarse level, filtering the source signals with filters and then multiplying the filtered signals in the time domain to generate estimates of the in-band intermodulation products.

23. The method defined in claim 1 wherein isolating signals of interest and interfering signals comprising bandpass filtering multiple copies of the bit stream.

24. The method defined in claim 23 wherein filtering and canceling are not performed on the in-phase (I) and quadrature (Q) signals.

25. The method defined in claim 23 further comprising decomposing signals into I and Q channels digitally after band pass filtering and performing interference cancellation to result in perfect quadrature and reduce amplitude imbalance problems.

26. The method defined in claim 1 further comprising extracting a transmitter feed thru signal and canceling impact of the transmitter feed thru signal on the received passband.

118. The apparatus of claim 117 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.

119. The apparatus of claim 118 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-mod estimates.

120. The apparatus of claim 118 wherein the compensation units delays the estimates of the intermodulation products by full samples for a macro adjustment of the phase.

121. The apparatus of claim 118 wherein the compensation unit delays the estimates of the intermodulation products on a sub-sample basis for a micro adjustment of the phase.

122. An apparatus of claim 118 wherein the compensation unit continually updates the phase and amplitude of the intermodulation estimate is continually updated and the estimates of the IIP and IIP3.

11. The method defined in claim I wherein the signals of interest and interfacing signals are coherent after isolation.

27. An apparatus comprising:

means for over-sampling, at a desired frequency, a passband of received signals to create a bitstream, 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; and

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

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

28. The apparatus defined in claim 27 further comprising means for performing phase and amplitude adjustment on the estimations of the intermodulated product interfering signals in a closed loop manner.

29. The apparatus defined in claim 28 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.

30. An apparatus comprising:

a sampling unit to sample, at a desired frequency, a passband of received signals to create a bitstream, wherein the received signals include signals of interest and interference generating signals, the interference generating signals capable of generating inter-modulation products inband of the signals of interest;

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

a cancellation unit to cancel out isolated interference generated signals using estimations of the intermodulation products generated by the isolated interfering signals.

31. The apparatus defined in claim 30 wherein the received passband is at an intermediate frequency (F).

32. The apparatus defined in claim 30 wherein the decimating filters are software controlled filters.

33. The apparatus defined in claim 30 wherein sampling unit comprises a sigma delta A/D converter to process the received signals at an IF frequency.

34. The apparatus defined in claim 30 wherein one or more filters comprise one or more bandpass filters.

35. The apparatus defined in claim 30 wherein the one or more filters are implemented in software and select bandwidth of the signals of interest and out of band rejection for the signals of interest via software.

36. The apparatus defined in claim 30 wherein the signals of interest and interference generating signals are coherent after isolation.

37. The apparatus defined in claim 30 further comprising a down converter to down convert the receive band to a common IF using one of a plurality of mixers, wherein the one mixer is associated with one frequency band.

38. The apparatus defined in claim 30 wherein the estimations of the isolated interfering signals comprise estimations of inter-modulation products falling in band of the signals of interest.

39. The apparatus defined in claim 38 further comprising a phase and amplitude adjuster to phase and amplitude adjust the estimations of the isolated interfering signals in a closed loop manner.

40. The apparatus defined in claim 39 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.

41. The apparatus defined in claim 30 wherein at least one filter of the one or more filters generates the estimations of the isolated interfering signals and further comprising an intermodulation cancellation signal generator to generate cancellation signals corresponding to the estimations of the isolated interfering signals.

42. The apparatus defined in claim 41 wherein the cancellation signals are not generated if the source of the isolated interfering signals corresponding to the estimations of the isolated interfering signals no longer causes interferences.

43. The apparatus defined in claim 30 further comprising a search unit to search the receive band for source signals that result in intermodulation products that fall within band of the signals of interest.

44. The apparatus defined in claim 43 wherein the search unit searches the receive band using discrete Fourier transforms (DFTs).

45. The apparatus defined in claim 30 further comprising an output to decompose signals into I and Q channels digitally after band pass filtering and performing interference cancellation to result in perfect quadrature and amplitude balance.

46. A method comprising digitizing a full pass band into a bit stream;

and

sending a copy of the bit stream to each of a plurality of filters to process multiple high resolution, narrow band, time coherent signals simultaneously.

47. The method defined in claim 46 wherein the plurality of filters are programmable.

48. The method defined in claim 47 wherein the plurality of filters are programmed to process frequency hopped signals.

49. The method defined in claim 48 wherein a first of the plurality of filters is switched out and programmed to a next hop frequency while a second of the plurality of filters processes a signal in at a current hop frequency.

50. The method defined in claim 46 further comprising:

multiplying signals from the plurality of filters together to generate a result; and

filtering the result to a baseband of the signal of interest to create an estimate of an intermodulation product.

51. An apparatus comprising:

means for digitizing a full pass band into a bit stream; and

means for sending a copy of the bit stream to each of a plurality of filters to process multiple high resolution, narrow band, time coherent signals simultaneously.

52. A method comprising:

outputting a pair of identical digital samples from a Sigma Delta A/C converter after sampling an IF signal with the Sigma Delta A/D converter;

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 inter-modulation products;

applying a second decimating filter to the other of the 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 inter-modulation products;

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

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

53. The method defined in claim 52 wherein the first and second decimating filters comprise FIR filters.

54. The method defined in claim 53 wherein the first and second FIR filters are fractionally spaced FIR filters.

55. The method defined in claim 52 wherein a sampling rate of the Sigma Delta A/D converter is at a rate five or more times a rate of a final sampling rate.

56. The method defined in claim 52 wherein the first and second FIR filters are applied at a rate at which the Sigma Delta A/D converter is applied.

57. The method defined in claim 52 wherein generating an estimate of in-band interference is based on IIP2 and IIP3.

58. The method defined in claim 57 further comprising continuously generating updated IIP2 and IIP3 values.

59. The method defined in claim 57 wherein generating an estimate of in-band interference is further based on other non-linear attributes.

60. The method defined in claim 52 further comprising:

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

61. The method defined in claim 60 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.

62. The method defined in claim 61 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.

63. The method defined in claim 62 wherein the adaptive algorithm is a zero forcing minimizing algorithm.

64. The method defined in claim 63 wherein the minimizing algorithm comprises a zero forcing algorithm.

65. An apparatus comprising:

means for outputting a pair of identical digital samples from a Sigma Delta A/C converter after sampling an IF signal with the Sigma Delta A/D converter;

means for 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 inter-modulation products;

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

means for generating an estimate of in-band inter-modulation interference based on the out of band signals; and

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

66. The apparatus defined in claim 65 further comprising:

means for 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.

67. An apparatus, comprising:

a sampling rate multiplier to sample a signal at a first sampling rate that is greater than a second sampling rate of a subsequent digital down conversion;

one or more decimating filters coupled to the sampling rate multiplier to filter digital data samples taken from the signal at the second sampling rate; and

a compensation cell coupled to the one or more decimating filters to reduce interference in a signal of interest prior to the subsequent digital down conversion.

68. The apparatus of claim 67, wherein the signal comprises a sampled intermediate frequency (IF) signal to be digitally downconverted to baseband.

69. The apparatus defined in claim 67 wherein the one or more decimating filters comprise impulse response filters.

70. The apparatus of claim 69, wherein at least one of the impulse response filters comprises a finite impulse response (FIR) filter.

71. The apparatus of claim 70 wherein the compensation cell compensates for intermodulation products of jammers.

72. The apparatus of claim 70, wherein at least one of the FIR filters has programmable tap weights selected to cause filtering for jammer rejection.

73. The apparatus of claim 67 wherein the compensation cell comprises an intermodulation compensator to reduce interference in the signal of interest based upon estimations of system non-linearities.

74. The apparatus of claim 73, wherein the intermodulation compensator inverts estimations of interfering intermodulation signals and applies inverted estimations of interfering intermodulation to a decimated sample from the signal of interest to reduce interference in the sampled SOI digital data samples.

75. The apparatus of claim 73, wherein the intermodulation compensator phase adjusts the estimations of interfering intermodulation signals to reduce interference in the sampled digital data samples.

76. The apparatus of claim 73, wherein the intermodulation compensator adjusts amplitude of the estimations of interfering intermodulation signals to reduce interference in the sampled digital data samples.

77. The apparatus of claim 67, wherein the sampling rate multiplier comprises a Sigma Delta analog to digital (A/D) converter.

78. The apparatus of claim 67, wherein the sampling rate multiplier comprises a Sigma Delta cell and a flash A/D cell.

79. The apparatus of claim 67, wherein the first sampling rate is at least five times greater than the second sampling rate.

80. The apparatus of claim 67, further comprising a digital down-converter to digitally down-convert the signal of interest independent of modulation type.

81. The apparatus of claim 80, wherein the modulation type can be selected from one in a group consisting of amplitude modulation, frequency modulation, and pulse modulation, and combinations of the amplitude, frequency and pulse modulations and spread spectrum signals.

82. The apparatus of claim 67, further comprising an image reject filter coupled to the sampling rate multiplier with a passband matched to a range of bandwidths containing the signal of interest.

83. An apparatus comprising:

a converter to generate a pair of identical bit streams;

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;

a low pass filter coupled to the decimating filter to filter the digital samples output from the decimating filter; and

an in-band interference compensation unit coupled to the low pass filter.

84. The apparatus of claim 83 wherein at least one decimating filter comprises at least one FIR filter.

85. The apparatus of claim 83, wherein the FIR filter is a fractionally spaced FIR filter.

86. The apparatus of claim 83, wherein spacing in the FIR filter is programmable.

87. The apparatus of claim 83, further comprising a sampling rate multiplier coupled to the decimating filter.

88. The apparatus of claim 83, further comprising a compensation unit coupled to the decimating filter.

89. The apparatus of claim 83, further comprising:

a Sigma Delta A/D converter coupled to the decimating filter.

90. The apparatus of claim 89, wherein the Sigma Delta A/D converter creates two copies of the sampled digital data samples.

91. The apparatus of claim 83, wherein at least one decimating filter further comprises:

a band pass filter to generate an in-band signal that includes an in-band interference signal; and

a band reject filter to generate an out-of-band signals by removing a signal of interest from one of the pair of identical bitstreams.

92. The apparatus of claim 91, wherein the compensation unit generates estimations of interfering intermodulation signals from the out-of-band signals.

93. The apparatus of claim 91, wherein the compensation unit inverts estimations of interfering intermodulation signals and adds the inverted estimations to the in-band signal that includes the in-band interference signal.

94. The apparatus of claim 91, wherein the intermodulation compensator phase adjusts estimations of interfering intermodulation signals and adds the phase adjusted estimations to the signal of interest to reduce interference in the sampled digital data samples.

95. The apparatus of claim 91, wherein the intermodulation compensator amplitude adjusts estimations of interfering intermodulation signals and adds the amplitude adjusted estimations to the signal of interest to reduce interference in the sampled digital data samples.

96. The apparatus of claim 91 further comprising an antenna coupled to the converter to receive signals wirelessly.

97. The apparatus of claim 91 further comprising an input coupled to the converter to receive signals from a non-wireless source.

98. The apparatus of claim 96 wherein the wirelessly received signals are communicated in a system employing a technique selected from the group consisting of CDMA, AMPS, TDMA, GSM WCDMA, EDGE, and GPRS.

99. The apparatus of claim 83 wherein the identical bit streams are from wireless LAN and the in-band interface compensation unit compensates for co-existence interference between WLAN 802.11b/g and Bluetooth.

100. The apparatus of claim 83 wherein the identical bit streams are from wireless PAN and the in-band interface compensation unit compensates for co-existence interference between PAN 802.11b/g and Bluetooth.

101. The apparatus of claim 96 wherein the converter, the at least one decimating filter, the low-pass filter and compensation unit are used in a WLAN.

102. The apparatus of claim 96 wherein the converter, the at least one decimating filter, the low-pass filter and compensation unit are used in a PAN.

103. The apparatus of claim 96 wherein the converter, the at least one decimating filter, the low-pass filter and compensation unit are used in a 802.11b/g.

104. The apparatus of claim 96 wherein the converter, the at least one decimating filter, the low-pass filter and compensation unit are used in a 802.11a.

105. The apparatus of claim 96 wherein the converter, the at least one decimating filter, the low-pass filter and compensation unit are used in a Bluetooth.

106. The apparatus of claim 97 wherein the converter, the at least one decimating filter, the low-pass filter and the compensation unit are used in wire-line applications to include cables modems and DSL.

107. The apparatus of claim 96 wherein the converter, the at least one decimating filter, the low-pass filter and the compensation unit are used in a Terrestrial microwave applications.

108. The apparatus of claim 107 wherein the Terrestrial microwave application includes one of the applications selected from a group of LMDS, MMDS and other last mile applications.

109. The apparatus of claim 96 wherein the Terrestrial satellite applications include multicarrier transponders.

110. The apparatus of claim 83 wherein a single over-sampled bit stream is processed by multiple decimating filters to process signals of different bandwidths.

111. The apparatus defined in claim 110 wherein the signals of different bandwidths are selected from one of a group consisting of Telephony CDMA, AMPS , TDMA, GSM WCDMA, EDGE, GPRS, 802.11a/b/g and Bluetooth.

112. The apparatus of claim 83 wherein the IF filter reduces out of band blocking signals prior to converter and wherein the bit stream comprises a flash A/D 4 bit low resolution bit stream used to search the receive band for source signals and generate the estimates of the intermodulation products.

113. The apparatus of claim 83 wherein the converter comprises a low bit resolution flash A/D converter to over-sample the passband and further comprising a transform to identify frequency blocks where in source signals exist, which produces intermodulation products inband of the signal of interest.

114. The apparatus defined in claim 113 wherein the transform comprises a DFT.

115. The apparatus defined in claim 113 wherein the transform comprises a FFT.

116. The apparatus of claim 112 further comprising a second module to pass the frequency bands with source signals to a filter function, wherein the low resolution bits stream from the flash A/D is narrow-band filtered to isolate the source signals with fairly wide filters.

117. The apparatus of claim 116 wherein the filter function provides on the order of 5 to 10 times the width of the source signals.

123. A method comprising:

subjecting a wideband low amplitude signal to interference from a high amplitude narrow band signal; and

isolating the narrow band signal by digital filters and using the isolated narrow band to cancel the interference in the low amplitude wideband signal.

124. The method of claim 123 wherein the narrow band signal is a frequency hopped signal and the phase and amplitude of each hopped frequency are stored and used when said each hopped frequency is used.

125. The method of claim 124 further comprising adjusting the phase and amplitude of the narrowband signal to cause the interference to be reduced and storing the values for each frequency hop for use when said each frequency hop is used.

126. The method of claim 124 a transmitter baseband processor providing the sequence of frequency hops, and a receiver using programmable digital decimating filters to isolate the wideband low amplitude signal and the narrow band high amplitude frequency hopped signals from the same over sampled bit stream of the receive band.

127. The method of claim 126 further comprising using the isolated narrowband signal to process one service and using the signal to cancel the interference of the narrowband signal in the wideband signal.

128. The method of claim 123 further comprising processing 802.11b/g and Bluetooth simultaneously and canceling the interference of the Bluetooth signal on the 802.11b/g.

129. An apparatus comprising:

means for subjecting a wideband low amplitude signal to interference from a high amplitude narrow band signal; and

means for isolating the narrow band signal by digital filters and using the isolated narrow band to cancel the interference in the low amplitude wideband signal.