Self-adaptive digital RF bandpass and bandstop filter architecture

• US 8,385,483 B2
• Filed: 11/11/2008
• Issued: 02/26/2013
• Est. Priority Date: 11/11/2008
• Status: Active Grant

• Current Assignee: ISCO International LLC
• Original Assignee: ISCO International Inc.
• Inventors: Abdelmonem, Amr, Cordone, Sean S.
• Primary Examiner(s): Liu, Shuwang
• Assistant Examiner(s): TAYONG, HELENE E
• Application Number:
  US12/268,996
• Publication Number:
  US 20100118921A1
• Time in Patent Office: 1,568 Days
• Field of Search: 375/148, 375/350, 375/206, 375/346, 375/316, 455/296, 455/278, 455/306, 370/335, 327/310, 327/384, 327/551
• US Class Current: 375/346
• 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
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 2001/1072 by tuning the receiver frequency
• CPC Class Codes: H04J 11/0023 Interference mitigation or co-ordination direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 43/16 Threshold monitoring
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points

Abstract

A system and method provides adaptive digital front end control of an incoming radio frequency (RF) signal to identify RF characteristics in that signal, such as interference or desired data signals and adaptively control digital filter elements to selectively tune only portions of the RF signal to produce a filtered output signal, on a per cycle basis, prior to communicating the RF signal to an underlying wireless communication device, such as a base station in cellular network, cellular phone, wireless router base station, cognitive radio, or other wireless communication device. Each digital filter element may be tuned in frequency and bandwidth of operation and collectively the elements form an adaptive filter stage with elements configurable into both bandpass and bandstop filters for cascaded operation.

Claims

1. A method, comprising:

searching, by a communication device, for available spectrum in a particular radio frequency spectrum;

selecting, by the communication device, a portion of available spectrum in the particular radio frequency spectrum independent of there being interference in the available spectrum;

scanning, by the communication device, a wideband communication signal in the selected portion of spectrum at least once to determine a corresponding signal strength for each of a plurality of narrowband channels for each scan;

determining, by the communication device, a corresponding correlation factor for each of the plurality of narrowband channels by correlating the corresponding signal strengths from the plurality of times each narrowband channel has been scanned;

each scan, identifying, by the communication device, from the corresponding correlation factors for the plurality of narrowband channels, any of the plurality of narrowband channels that contain narrowband interference; and

in response to an identification of at least one of the plurality of narrowband channels as containing narrowband interference, generating, by the communication device, tuning coefficient data to tune a filter frequency and a filter bandwidth of an adaptive digital filter apparatus for filtering the narrowband interference from the wideband communication signal.

2. The method of claim 1, wherein the scanning of the wideband communication signal comprises scanning the wideband communication signal m times, where m is an integer equal to 1 or greater, the method further comprising tuning at the adaptive digital filter apparatus every m scans.

3. The method of claim 2, wherein m=1.

4. The method of claim 1, wherein the adaptive digital filter apparatus comprises a plurality of filter elements.

5. The method of claim 4, wherein the plurality of filter elements are arranged in parallel.

6. The method of claim 4, wherein the plurality of filter elements are arranged in a cascaded configuration.

7. The method of claim 4, wherein each filter element is tuned to filter a different one of the plurality narrowband channels.

8. The method of claim 4, wherein the adaptive digital filter apparatus comprises a bandpass filter and a notch filter in a cascaded configuration, the method further comprising:

filtering a portion of the wideband communication signal by passing it through the bandpass filter;

communicating the filtered portion of the wideband communication signal to the notch filter; and

in the notch filter, filtering the narrowband interference from the filtered portion of the wideband communication signal.

9. The method of claim 4, wherein the generating of the tuning coefficient data comprises generating a corresponding frequency coefficient and a corresponding bandwidth coefficient for each of the plurality of filter elements.

10. The method of claim 9, wherein any of the plurality of filter elements can be configured into a notch filter or a bandpass filter in response to the tuning coefficient data.

11. The method of claim 1, further comprising:

filtering the narrowband interference from the wideband communication signal to create a filtered wideband communication signal;

passing the filtered wideband communication signal to a bandpass filter for producing a passband portion of the wideband communication signal; and

identifying un-used frequency bands within the passband portion.

12. The method of claim 1, further comprising:

filtering the narrowband interference from the wideband communication signal to create a filtered wideband communication signal; and

identifying un-used frequency bands within the filtered wideband communication signal.

13. The method of claim 1, wherein the adaptive digital filter is a notch filter.

14. The method of claim 1, wherein the wideband communication signal is a direct sequence spread spectrum signal.

15. The method of claim 14, wherein the direct sequence spread spectrum signal is a code division multiple access (CDMA) signal.

16. The method of claim 1, wherein the wideband communication signal is an Orthogonal Frequency-Division Multiple Access (OFDMA) signal.

17. The method of claim 1, wherein the wideband communication signal is a Groupe Special Mobile (GSM) signal.

18. The method of claim 1, wherein the wideband communication signal is Universal Mobile Telecommunications System (UMTS) signal.

19. The method of claim 1, wherein determining the corresponding correlation factor for each of the plurality of narrowband channels comprises using a subset of the corresponding signal strengths.

20. The method of claim 19, wherein the subset of the plurality of the corresponding signal strengths observed are a most recent of the corresponding signal strengths.

21. The method of claim 1, wherein identifying any of the plurality of narrowband channels containing narrowband interference further comprises comparing each corresponding correlation factor to a threshold correlation factor.

22. The method of claim 21, further comprising:

upon each scan of the wideband communication signal, determining a group of narrowband channels that have a highest of signal strengths during the scan; and

determining if any of the group of narrowband channels is present in groups of channels having the highest signal strengths in at least two subsequent scans of the wideband communication signal.

23. The method of claim 21, wherein identifying narrowband channels that contain narrowband interference comprises:

calculating an average signal strength for each scan of the wideband communication signal; and

identifying narrowband channels having corresponding signal strength above the average signal strength by at least a first threshold amount.

24. The method of claim 1, wherein the communication device is adapted to communicate using multiple communication standards.

25. The method of claim 24, wherein the communication device is adapted to recognize a difference between at least two communication standards.

26. The method of claim 25, wherein the adaptive digital filter apparatus is adapted to filter at least one of the two communication standards.

27. The method of claim 25, wherein the adaptive digital filter apparatus is adapted to generate two outputs wherein a first output of the two outputs corresponds to a first communication standard and wherein a second output of the two outputs corresponds to a second communication standard.

28. The method of claim 1, wherein the adaptive digital filter apparatus is adapted to received header information about the wideband communication signal.

29. The method of claim 28, wherein the adaptive digital filter apparatus is adapted to generate tuning coefficient data based on the received header information.

30. A method, comprising:

selecting, by a wireless communication device, a portion of a wideband spectral region in a particular radio frequency spectrum independent of there being interference in the portion of the wideband spectral region;

scanning, by the wireless communication device, an incoming radio frequency (RF) signal in the selected portion of the wideband spectral region to identify at least one RF characteristic in the incoming RF signal, wherein the at least one RF characteristic includes an interference signal within a narrowband frequency region of the incoming RF signal;

determining, by the wireless communication device, tuning coefficients in response to the identification of the RF characteristic, the tuning coefficients containing frequency data and bandwidth data identifying the at least one RF characteristic;

applying, by the wireless communication device, the tuning coefficients to an adaptive filter stage to tune the adaptive filter stage to filter the at least one RF characteristic from the incoming RF signal to form a filtered RF signal; and

processing, by the wireless communication device, messages in the incoming RF signal according to the filtered RF signal while operating over at least the portion of the wideband spectral region containing to the incoming RF signal.

31. The method of claim 30, wherein the at least one RF characteristic comprises a plurality of RF characteristics, at least two of which have different frequencies or frequency bands, the method further comprising tuning the adaptive filter stage to filter each of the plurality of RF characteristics.

32. The method of claim 30, further comprising:

scanning the incoming RF signal a plurality of times to determine a corresponding signal strength for each of a plurality of frequency bands within the RF signal for each scan;

determining a corresponding correlation factor for each of the plurality of frequency bands by correlating the corresponding signal strengths from the plurality of times each frequency band has been scanned;

each scan, identifying from the corresponding correlation factors for the plurality of frequency bands, any of the plurality of frequency bands that contain narrowband interference; and

in response to an identification of at least one of the plurality of frequency bands as containing narrowband interference, generating the tuning coefficients.

33. The method of claim 32, wherein identifying any of the plurality of frequency bands containing narrowband interference further comprises comparing each corresponding correlation factor to a threshold correlation factor.

34. The method of claim 33, further comprising:

upon each scan of the incoming RF signal, determining a group of frequency bands that have the highest signal strengths during the scan; and

determining if any of the group of frequency bands is present in groups of frequency bands having a highest of signal strengths in at least two subsequent scans of the incoming RF signal.

35. The method of claim 34, wherein identifying frequency bands that contain narrowband interference comprises:

calculating an average signal strength for each scan of the incoming RF signal; and

identifying frequency bands having corresponding signal strength above the average signal strength by at least a first threshold amount.

36. The method of claim 30, comprising scanning the incoming RF signal m times, where m is an integer equal to 1 or greater.

37. The method of claim 36, wherein m=1.

38. The method of claim 30, wherein the adaptive filter stage comprises a plurality of filter elements.

39. The method of claim 38, the method further comprising configuring the plurality of filter elements into a parallel configuration.

40. The method of claim 38, the method further comprising configuring the plurality of filter elements arranged into a cascaded configuration.

41. The method of claim 38, the method further comprising tuning each of the filter elements to filter a different one of the at least one RF characteristics.

42. The method of claim 30, the method further comprising tuning the adaptive filter stage to provide a bandpass filtering of a portion of the incoming RF signal.

43. The method of claim 30, further comprising tuning the adaptive filter stage to provide a bandstop filtering of the least one RF characteristic.

44. The method of claim 43, further comprising tuning the adaptive filter stage to provide a bandpass filtering of at least a portion of the RF characteristic overlapping with the filtered at least one RF characteristic.

45. The method of claim 30, further comprising an RF tuner to identify unused frequency bands within the filtered RF signal.

46. The method of claim 30, wherein the adaptive filter stage comprises a notch filter.

47. The method of claim 30, wherein the incoming RF signal is a direct sequence spread spectrum signal.

48. The method of claim 30, wherein the incoming RF signal is an Orthogonal Frequency-Division Multiple Access (OFDMA) signal.

49. The method of claim 30, wherein the incoming RF signal is a Groupe Special Mobile (GSM) signal.

50. The method of claim 30, wherein the incoming RF signal is Universal Mobile Telecommunications System (UMTS) signal.

51. The method of claim 30, wherein the incoming RF signal is a code division multiple access (CDMA) signal.

52. The method of claim 30, wherein the wireless communication device is to communicate using multiple communication standards.

53. The method of claim 52, wherein the wireless communication device is to recognize a difference between at least two communication standards.

54. The method of claim 53, wherein the adaptive filter stage is to filter at least one of the two communication standards.

55. The method of claim 53, further comprising filtering the incoming RF signal into a first RF signal corresponding to a first communication standard and a second RF signal corresponding to a second communication standard.

56. The method of claim 30, further comprising identifying information in the incoming RF signal that indicates a type of data in that incoming RF signal.

57. The method of claim 56, further comprising generating tuning coefficient data based on the identified information.

58. An apparatus comprising:

a memory storing instructions; and

a controller coupled to the memory, wherein execution of the instructions by the controller, causes the controller to perform operations, comprising;

causing a radio frequency (RF) receiver to scan for available spectrum in a particular radio frequency spectrum;

selecting a portion of available spectrum in the particular radio frequency spectrum independent of there being interference in the available spectrum;

causing the RF receiver to receive an incoming RF signal in the available spectrum that is converted to an incoming digital RF signal;

analyzing the incoming digital RF signal;

determining at least one RF characteristic within the incoming digital RF signal;

producing tuning coefficient data according to the at least one RF characteristic for tuning an adaptive filter stage from which the adaptive filter stage is to produce a tuned RF signal; and

causing the adaptive filter stage filter the incoming digital RF signal in response to the tuning coefficient data to produce the tuned RF signal, wherein the adaptive filter stage comprises a plurality of filter stages each filter stage being configurable into a bandpass filter or a bandstop filter in response to the tuning coefficient data, wherein the tuning coefficient data contains frequency coefficient and bandwidth coefficient pairs to collectively tune the plurality of filter stages, each filter stage being capable of filtering the incoming digital RF signal in response to the tuning coefficient data.

59. The apparatus of claim 58, further comprising:

a first RF sampler to sample the incoming digital RF signal and to identify the RF characteristic within the incoming digital RF signal to the controller; and

a second RF sampler to sample the tuned RF signal and to identify a presence or absence of the RF characteristic to the controller.

60. The apparatus of claim 58, further comprising wherein the tuning coefficient data is to tune the adaptive filter stage such that each of the plurality of filter stages filters at a different frequency and over a different bandwidth.

61. The apparatus of claim 58, wherein the RF characteristic is an interference signal in the incoming RF signal.

62. The apparatus of claim 58, wherein the adaptive filter stage comprises:

a digital down converter;

a bank of infinite impulse response (IIR) filters or finite impulse response (FIR) filters, each of which are adaptable in configuration, frequency, and bandwidth of operation, wherein the digital down converter is coupled to an input end of the bank of IIR or FIR filters;

a controller interface for coupling the adaptive filter stage to the controller and for communicating the tuning coefficients from the controller to the bank of IIR or FIR filters; and

a digital upconverter coupled to an output end of the bank of IIR or FIR filters.

63. The apparatus of claim 58, wherein the adaptive filter stage is implemented entirely within a field programmable gate array.

64. The apparatus of claim 58, further comprising a clock signal coupled to synchronize the controller and the adaptive filter stage.

65. The apparatus of claim 58, wherein the incoming RF signal is a direct sequence spread spectrum signal.

66. The apparatus of claim 58, wherein the incoming RF signal is an Orthogonal Frequency-Division Multiple Access (OFDMA) signal.

67. The apparatus of claim 58, wherein the incoming RF signal is a Groupe Special Mobile (GSM) signal.

68. The apparatus of claim 58, wherein the incoming RF signal is Universal Mobile Telecommunications System (UMTS) signal.

69. The apparatus of claim 58, wherein the adaptive filter stage is to communicate using multiple communication standards.

70. The apparatus of claim 69, wherein the adaptive filter stage is to recognize a difference between at least two communication standards.

71. The apparatus of claim 70, wherein the adaptive filter stage is to filter at least one of the two communication standards.

72. The apparatus of claim 70, wherein the adaptive filter stage is to generate two outputs wherein a first output of the two outputs corresponds to a first communication standard and wherein a second output of the two outputs corresponds to a second communication standard.

73. The apparatus of claim 58, wherein the controller is to identify information in the incoming RF signal that indicates a type of data in the incoming RF signal.

74. The apparatus of claim 73, wherein the controller is to generate tuning coefficient data based on the identified information.

75. An apparatus comprising:

an adaptive filter stage that receives and filters a digital radio frequency (RF) signal in response to tuning coefficient data, wherein the adaptive filter stage contains a plurality of bandpass or bandstop filters that are each separately tunable in frequency and bandwidth to filter selected portions of the digital RF signal; and

a controller coupled to the adaptive filter stage that performs operations comprising;

causing an RF receiver to scan for available spectrum in a particular radio frequency spectrum;

selecting a portion of available spectrum in the particular radio frequency spectrum independent of there being interference in the available spectrum;

causing the RF receiver to receive an incoming RF signal in the available spectrum that is converted to an incoming digital RF signal;

analyzing the digital RF signal, to determine at least one RF characteristic within the digital RF signal; and

producing the tuning coefficient data according to the at least one RF characteristic for tuning the adaptive filter stage, from which the adaptive filter stage is to produce a tuned RF signal,

wherein the adaptive filter stage is tuned to identify and filter RF characteristics in a first wireless communication band when the apparatus is operating in a second wireless communication band, and wherein the adaptive filter stage is tuned to identify and filter RF characteristics in the second wireless communication band;

when the, apparatus is operating in the first wireless communication band.

76. The apparatus of claim 75, wherein the first wireless communication band is a Groupe Special Mobile (GSM) band and wherein the second wireless communication band is a Universal Mobile Telecommunications System (UMTS) band.

77. The apparatus of claim 76, wherein the RF characteristic is a GSM data signal when the apparatus is operating in the UMTS band or a UMTS signal when the apparatus is operating in the GSM band.

78. The apparatus of claim 75, further comprising:

a first RF sampler to sample the digital RF signal and to identify the RF characteristic within the incoming digital RF signal to the controller; and

a second RF sampler to sample the tuned RF signal and to identify a presence or absence of the RF characteristic to the controller.

79. The apparatus of claim 75, wherein the adaptive filter stage comprises:

a digital down converter;

a bank of infinite impulse response (IIR) filters or finite impulse response (FIR) filters, each of which are adaptable in configuration, frequency, and bandwidth of operation, wherein the digital down converter is coupled to an input end of the bank of IIR or FIR filters;

a controller interface for coupling the adaptive filter stage to the controller and for communicating the tuning coefficients from the controller to the bank of IIR or FIR filters; and

a digital upconverter coupled to an output end of the bank of IIR or FIR filters.

80. The apparatus of claim 79, wherein the adaptive filter stage is implemented entirely within a field programmable gate array.

81. The apparatus of claim 75, wherein the controller is to identify information in the digital RF signal that indicates a type of data in the incoming RF signal and is to produce the tuning coefficient data based on the identified information.