MITIGATION OF TRANSMITTER PASSIVE AND ACTIVE INTERMODULATION PRODUCTS IN REAL AND CONTINUOUS TIME IN THE TRANSMITTER AND CO-LOCATED RECEIVER

• US 20110075754A1
• Filed: 08/05/2010
• Published: 03/31/2011
• Est. Priority Date: 09/06/2007
• Status: Active Grant

• Current Assignee: Finesse Wireless, LLC
• Original Assignee: Francis J. Smith
• Inventors: Smith, Francis J.
• Granted Patent: US 9,548,775 B2
• Time in Patent Office: Days
• US Class Current: 375/285
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input

Abstract

A transmitter channel interference mitigation processing method for cancellation of intermodulation products are described. In one embodiment, a method comprising generating continuous and real time IMP cancellation signals (ICS) in the baseband digital signal set of the transmitter based on a transmitter signal set, combining digital IMP cancellation signals with a digital baseband transmitter signal set such that the digital cancellation signals, when converted to analog signals and transmitted as part of an analog transmitter signal set, are cancelled by and so cancel the IMPs generated by the non-linear components in the analog transmitter hardware, including digitally generating the IMP cancellation signals using a process based on a power series description of a non-linear process generating the IMPs, generating 3^rd order IMP cancellation signals by digitally multiplying two or three signals of the transmitter signal set to create 3^rd order IMP cancellation signals, generating 5^th order IMP cancellation signals by digitally multiplying two or three or five signals of the transmitter signal set to create 5^th order IMP cancellation signals, generating 7^th order IMP cancellation signals by digitally multiplying two or three or five or seven signals of the transmitter signal set to create 7^th order IMP cancellation signal, generating odd order IMP cancellation signals (ICS) by digitally multiplying an odd number of digital signals and combining multiplied digital signals with the transmitter baseband digital signals, creating IMP cancellation signals in the receiver, and cancelling one or both of active and passive IMPs generated in a transmitter path that fall within a receiver passband.

Claims

1. A method for cancelling passive and or active intermodulation products (IMP) in a transmitter and a co-located receiver, the method comprising:

generating continuous and real time IMP cancellation signals (ICS) in the baseband digital signal set of the transmitter based on a transmitter signal set,

combining digital IMP cancellation signals with a digital baseband transmitter signal set such that the digital cancellation signals, when converted to analog signals and transmitted as part of an analog transmitter signal set, are cancelled by and so cancel the IMPs generated by the non-linear components in the analog transmitter hardware, including

digitally generating the IMP cancellation signals using a process based on a power series description of a non-linear process generating the IMPs,

generating 3^rd order IMP cancellation signals by digitally multiplying two or three signals of the transmitter signal set to create 3^rd order IMP cancellation signals,

generating 5^th order IMP cancellation signals by digitally multiplying two or three or five signals of the transmitter signal set to create 5^th order IMP cancellation signals,

generating 7^th order IMP cancellation signals by digitally multiplying two or three or five or seven signals of the transmitter signal set to create 7^th order IMP cancellation signal,

generating odd order IMP cancellation signals (ICS) by digitally multiplying an odd number of digital signals and combining multiplied digital signals with the transmitter baseband digital signals,

creating IMP cancellation signals in the receiver;

cancelling one or both of active and passive IMPs generated in a transmitter path that fall within a receiver passband.

2. The method defined in claim 1 further comprising sampling an output of a transmitter chain, detecting residual IMPs and using detected residual IMPs to process a control signal to adjust the phase and amplitude of the digital IMP cancellation signal(s) to reduce the residual active and passive IMPs at the transmitter output.

3. The method defined in claim 2 wherein the sampling is performed by a co-located receiver.

4. The method defined in claim 1 further comprising sending a digital copy of the transmitter signal set to a co-located receiver, the receiver generating the digital IMP cancellation signals, continuously and in real time cancelling the passive and active IMPs falling within the receiver passband.

5. The method defined in claim 1 wherein, given three signals S₁, S₂ and S₃, the 3^rd order IMP cancellation signals are generated by digitally multiplying S₁×

S₁×

S₂, S₁×

S₂×

S₂, S₁×

S₂×

S₃, S₁×

S₁×

S₃, S₂×

S₂×

S₃, S₁×

S₃×

S₃, and S₂×

S₃×

S₃ and further comprising filtering the digital IMPs to selectively produce required 3^rd order IMP cancellation signals.

6. The method defined in claim 1 wherein, given up to a set of 5 signals, S1, S2, S3, S4, and S5, wherein different combinations of signals in the set of signals up to 5 signals, some duplicated, are multiplied together digitally and filtered to selectively create required 5th order IMP cancellation signals.

7. The method defined in claim 1 wherein, given up to a set of 7 signals, S₁, S₂, S₃, S₄, S₅, S₆, and S₇, wherein different combinations of signals in the set of signals up to 7 signals, some duplicated, are multiplied together digitally and filtered to selectively create required 7^th order IMP cancellation signals.

8. The method defined in claim 1 wherein generating odd order IMP cancellation signals comprises digitally multiplying an odd number of digital signals, up to “

n”

in number, from the transmitter signal set, some duplicated, and filtering results of the digitally multiply to selectively create required n^th odd order passive and or active IMP cancellation signals.

9. The method defined in claim 1 wherein, with the a priori knowledge of a transmitter signal set, active and/or passive IMPs generated in the transmitter are cancelled in the transmitter and a co-located receiver by a digital process based on a power series description of the non-linear process in a transmitter hardware chain using one or more ICSs in one or both of the transmitter and the receiver.

10. A method comprising:

digitally multiplying a full passband of a composite digital transmitter signal set a number of times, sample by sample, in real and continuous time to create a composite ICS signal with a number of required transmitter IMPs; and

filtering the composite ICS signal to selectively pass one or both of active and passive digital ICSs in an output band of a transmitter.

11. The method defined in claim 10 further comprising digitally summing the composite ICS signal with a transmitter digital signal so that the composite ICS signal set selectively cancels and is so cancelled by the one or both active and passive IMPs.

12. The method defined in claim 10 wherein the full passband of a composite digital transmitter signal set is digitally multiplied in a co-located receiver, to create the composite ICS signal with all of one or both passive and active transmitter IMPs, which is then filtered to selectively pass ICSs to an IMP cancellation process to selectively cancel one or both of the passive and active IMPs in a passband of the receiver.

13. The method defined in claim 12, digitally and selectively canceling one or both of the passive and active IMPs from the transmitter, using the composite ICS is used in the receiver.

14. The method defined in claim 11 further comprising digitally cross-correlating one or both of the digitally sampled residual active and passive IMPs at the transmitter output in a transmitter baseband process and adjusting the phase and amplitude of the composite ICSs to reduce cross correlation between one or both of sampled residual active and passive IMPs and the ICSs generated digitally from a transmitter signal set.

15. The method defined in claim 10 wherein further comprising adjusting each individual digital baseband IMP cancellation signal individually in phase and amplitude to reduce cross correlation between one or both of the residual active and passive IMPs generated in the analog transmitter components and the IMP cancellation signals generated from a selected set of signals from a transmitter signal set.

16. The method defined in claim 10 further comprising individually adjusting each individual digital baseband IMP cancellation signals in phase and amplitude to reduce cross correlation between one or both of residual active and passive IMPs generated in a transmitter and the IMP cancellation signals generated from a set of signals from a transmitter signal set.

17. The method defined in claim 11 further comprising generating multiple individual ICS signals;

individually and simultaneously selectively cancelling one or both of active and passive IMPs generated in a transmitter chain.

18. The method defined in claim 17 further comprising individually adjusting each of the individual digital baseband IMP cancellation signals in phase and amplitude to reduce cross correlation between one or both of residual active and passive IMPs generated in the transmitter and the IMP cancellation signals generated from a set of signals from a transmitter signal set.

19. The method defined in claim 12 further comprising generating multiple individual ICS signals;

individually and simultaneously selectively cancelling passive IMPs generated in a transmitter chain with cancellation in a co-located receiver.

20. The method defined in claim 19 further comprising individually adjusting each of the individual digital baseband IMP cancellation signals in phase and amplitude to reduce cross correlation between one or both of residual passive IMPs generated in a transmitter and the IMP cancellation signals generated from a set of signals from a transmitter signal set in a co-located receiver.

21. A method comprising:

suppressing active intermodulation products generated in a transmitter by isolating digital copies of signals in the transmitter;

using these signals to generate IMP cancellation signals (ICS); and

injecting an inverted ICS into a transmitter signal set to create signals to cancel and be cancelled by the IMPs generated in a transmitter signal path.

22. The method defined in claim 21 further comprising sampling an output of an HPA and cross correlating this sampled signal with the ICS signal to generate control signals which control the phase and the amplitude of the ICS to minimize the cross correlation and maximize the IMP cancellation process.

23. The method defined in claim 21 wherein a full passband of a composite digital transmitter signal set is multiplied some number of times, sample by sample, in real and continuous time to create a composite ICS signal with all of the transmitter IMPs, which is then filtered to pass only the IMPs in the passband of the transmitter.

24. The method defined in claim 21 wherein the ICS generation, inversion and insertion into the transmitter path are performed digitally and then the composite transmitter signal is converted to an analog signal for amplification and transmission and IMP cancellation.

25. The method defined in claim 21 where a timing tone is digitally inserted into the transmit signal set to provide a correlation signal to adjust the rough timing of the transmitter and feedback sampled signal paths.

26. The method define in claim 21 wherein selectable bandpass filters are selected at the output of the sampled signal after an HPA to pass one of three passband signals, the transmitter passband, a receiver passband or the transmitter and receive passband.

27. The method defined in claim 21 wherein an output of a selectable filter after an HPA is sampled to satisfy a Nyquist sampling rate for the selected filter and the filtered passband is then cross correlated with the ICS signal(s).

28. A method where a digital IMP cancellation process is combined with digital AM/AM and AM/PM pre-distortion and digital signal clipping and side lobe suppression filtering to allow transmitters to be operated in the limit of their non-linear range while meeting IMP and out of band emissions requirements.

29. A method wherein an output of a HPA is filtered to recover a copy of a transmitter noise floor feed through and this signal, representing the transmitter noise floor feed through is used to cancel the HPA noise floor feed through in a receiver.

30. A method wherein digital copies of a transmitter signals are used to create passive IMP cancellation signals in a receiver by multiplying the transmitter signals together sample by sample in real and continuous time to create the cancellation signals and then inverting these signals and using them to cancel passive transmitter IMPs in the receiver.

31. The method defined in claim 30 where the output of the receiver cancellation process is sampled and cross correlated with the passive ICS signal(s) and then control signals are generated to adjust the phase and amplitude of the passive ICS signals to minimize the cross correlation and optimize the cancellation process.

32. A method wherein a selected filter at an output of an HPA is selected to pass a passband of a receiver and recover copies of active IMPs which are used in the receiver to cancel transmitter generated passive IMPs.

33. An apparatus comprising the cancellation of passive and or active intermodulation products (IMP) in a transmitter and a co-located receiver,

with a priori knowledge of some set of transmitter signals, generating continuous and real time IMP cancellation signals (ICS) in the baseband digital signal set of the transmitter based on a transmitter signal set,

combing the digital IMP cancellation signals with a digital baseband transmitter signal set such that the digital cancellation signals, when transmitted as part of the analog transmitter signal set, are cancelled by and so cancel the IMPs generated by the non-linear components in the analog transmitter hardware,

in a digital process, generating the IMP cancellation signals by a process based on a power series description of a non-linear process generating the IMPs,

generating 3^rd order IMP cancellation signals by digitally multiplying two or three signals of a transmitter signal set to create a 3^rd order IMP cancellation signals,

generating 5^th order IMP cancellation signals by digitally multiplying two or three or five signals of a transmitter signal set to create a 5^th order IMP cancellation signals,

generating 7^th order IMP cancellation signals by digitally multiplying two or three or five or seven signals of a transmitter signal set to create a 7^th order IMP cancellation signal,

generating odd order IMP cancellation signals (ICS) by digitally multiplying an odd number of digital signals and combining these digital signals with the transmitter baseband digital signals,

with a priori knowledge of a transmitter signal set, creating IMP cancellation signals in the receiver to cancel and be cancelled by the active and or passive IMPs generated in the transmitter path that fall within the receiver passband.

34. An apparatus defined in claim 33 wherein the output of the transmitter chain is sampled and residual IMPs are detected and used to process a control signal back to the baseband digital process to adjust the phase and amplitude of the digital IMP cancellation signal to minimize the residual active and passive IMPs.

35. An apparatus defined in claim 34 where in a co-located receiver is used to provide the sampling function of the output of the transmitter chain for the detection of residual passive and active IMPs for the generation of the control signals to minimize the transmitter IMPs.

36. An apparatus defined in claim 33 wherein a copy of a transmitter signal set is provided to a co-located receiver and wherein the receiver generates the digital IMP cancellation signals and digitally, continuously and in real time selectively cancels the passive and or active IMPs falling within the receiver passband.

37. An apparatus defined in claim 33 wherein, given three signals S₁, S₂ and S₃, the 3^rd order IMP cancellation signals are generated by multiplying S₁×

S₁×

S₂ and S₁×

S₂×

S₂ and S₁×

S₂×

S₃ and S₁×

S₁×

S₃ and S₂×

S₂×

S₃ and S₁×

S₃×

S₃ and S₂×

S₃×

S₃ and the digital IMPs are filtered to selectively produce the required 3^rd order IMP cancellation signals.

38. An apparatus defined in claim 33 wherein, given up to a set of 5 signals, S₁, S₂, S₃, S₄, and S₅, wherein different combinations of up to 5 signals, some duplicated, are multiplied together digitally and filtered to selectively create the required 5^th order IMP cancellation signals.

39. An apparatus defined in claim 33 wherein, given up to a set of 7 signals, S₁, S₂, S₃, S₄, S₅, S₆, and S₇, wherein different combinations of up to 7 signals, some duplicated, are multiplied together digitally to and filtered to create the required 7^th order IMP cancellation signals.

40. An apparatus defined in claim 33 wherein odd order IMP cancellation signals are generated by digitally multiplying an odd number of digital signals, up to “

n”

in number, from a transmitter signal set, some duplicated, and filtering the results to create the required n^th odd order passive and active IMP cancellation signals.

41. An apparatus defined in claim 33 wherein, with the a priori knowledge of a transmitter signal set, active and passive IMPs, generated in the transmitter are cancelled in the transmitter and a co-located receiver by a digital process based on a power series description of the non-linear process in a transmitter hardware chain.

42. An apparatus defined in claim 33 wherein a full passband of a composite digital transmitter signal set is digitally multiplied some number of times, sample by sample, in real and continuous time to create a composite ICS signal with some number of required transmitter IMPs, which is then filtered to pass the active and or passive digital ICSs in the output band of the transmitter.

43. An apparatus defined in claim 42 where in the composite ICS signal is digitally summed with the transmitter digital signal so that the composite ICS signal set cancels and is so cancelled by the Active and or passive IMPs generated in the analog transmitter chain.

44. An apparatus defined in claim 33 wherein a full passband of a composite digital transmitter signal set is digitally multiplied, in a co-located receiver, some number of times, sample by sample, in real and continuous time to create a composite ICS signal with all of the passive and or active transmitter IMPs, which is then filtered to pass only the passive and or active IMPs in the passband of the receiver.

45. An apparatus defined in claim 44, wherein the composite ICS is used in the receiver to digitally cancel the passive and or active IMPs from the transmitter chain.

46. An apparatus defined in claim 43 wherein the digitally sampled residual active and or passive IMPs at the transmitter output are cross correlated digitally in the transmitter baseband process and the phase and amplitude of the composite ICS signal are adjusted to minimize the cross correlation between the sampled residual active IMPs and the ICS generated digitally from the transmitter signal set.

47. An apparatus defined in claim 33 wherein the each of the individual digital baseband IMP cancellation signals are individually adjusted in phase and amplitude to minimize the cross correlation between the residual active and or passive IMPs generated in the analog transmitter components and the IMP cancellation signals generated from a set of signals from a transmitter signal set.

48. An apparatus defined in claim 33 wherein the each of the individual digital baseband IMP cancellation signals are individually adjusted in phase and amplitude to minimize the cross correlation between the residual active and or passive IMPs generated in the transmitter and the IMP cancellation signals generated from a set of signals from a transmitter signal set.

49. An apparatus defined in claim 34 wherein multiple individual ICS signals are generated and individually and simultaneously cancel Active and or passive IMPs generated in the transmitter chain.

50. An apparatus defined in claim 49 wherein each of the individual digital baseband IMP cancellation signals are individually adjusted in phase and amplitude to minimize the cross correlation between the residual active and or passive IMPs generated in the transmitter and the IMP cancellation signals generated from a set of signals from a transmitter signal set.

51. An apparatus defined in claim 35 wherein where in multiple individual ICS signals are generated and individually and simultaneously cancel passive IMPs generated in a transmitter chain with cancellation in a co-located receiver.

52. An apparatus defined in claim 51 wherein the each of the individual digital baseband IMP cancellation signals are individually adjusted in phase and amplitude to minimize the cross correlation between the residual passive IMPs generated in the transmitter and the IMP cancellation signals generated from a set of signals from a transmitter signal set.

53. An apparatus comprising suppressing active intermodulation products generated in a transmitter by taking digital copies of signals in the transmitter and isolating them and using these signals to generate IMP cancellation signals (ICS) and injecting an inverted ICS into the transmitter signal set to create signals that will cancel and be cancelled by the IMPs generated in the transmitter signal path.

54. An apparatus defined in claim 53 wherein an output of an HPA is sampled and this sampled signal is cross correlated with the ICS signal so that control signals are generated which control the phase and the amplitude of the ICS to minimize the cross correlation and maximize the IMP cancellation process.

55. An apparatus defined in claim 53 wherein a full passband of a composite digital transmitter signal set is multiplied some number of times, sample by sample, in real and continuous time to create a composite ICS signal with all of the transmitter IMPs, which is then filtered to pass only the IMPs in the passband of the transmitter.

56. An apparatus defined in claim 53 wherein the ICS generation, inversion and insertion into the transmitter path are performed digitally and then the composite transmitter signal is converted to an analog signal for amplification and transmission and IMP cancellation.

57. An apparatus defined in claim 53 wherein a timing tone is digitally inserted into the transmit signal set to provide a correlation signal to adjust the rough timing of the transmitter and feedback sampled signal paths.

58. An apparatus define in claim 53 wherein selectable band-pass filters are selected at the output of the sampled signal after an HPA to pass one of three passband signals, the transmitter passband, a receiver passband or the transmitter and receive passband.

59. An apparatus defined in claim 53 wherein an output of a selectable filter after an HPA is sampled to satisfy a Nyquist sampling rate for the selected filter and the filtered passband is then cross correlated with the ICS signal(s).

60. An apparatus wherein a digital IMP cancellation process is combined with digital AM/AM and AM/FM pre-distortion and digital signal clipping and side lobe suppression filtering to allow transmitters to be operated in the limit of their non-linear range while meeting IMP and out of band emissions requirements.

61. An apparatus wherein an output of an HPA is filtered to recover a copy of a transmitter noise floor feed through and this signal, representing the transmitter noise floor is used to cancel the HPA noise floor feed through in a receiver.

62. An apparatus wherein digital copies of a transmitter signals are used to create passive IMP cancellation signals in a receiver by multiplying the transmitter signals together sample by sample in real and continuous time to create the cancellation signals and then inverting these signals and using them to cancel passive transmitter IMPs in the receiver.

63. An apparatus defined in claim 62 where the output of the receiver cancellation process is sampled and cross correlated with the passive ICS signal(s) and then control signals are generated to adjust the phase and amplitude of the passive ICS signals to minimize the cross correlation and optimize the cancellation process.

64. An apparatus wherein a selected filter at an output of an HPA is selected to pass a passband of a receiver and recover copies of active IMPs which are used in the receiver to cancel transmitter generated passive IMPs.