Multiple-input multiple-output radio transceiver

• US 6,728,517 B2
• Filed: 10/11/2002
• Issued: 04/27/2004
• Est. Priority Date: 04/22/2002
• Status: Active Grant

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: Cognio, Inc. (Cisco Systems, Inc.)
• Inventors: Rahn, David G., Sugar, Gary L., Masucci, Robert M.
• Primary Examiner(s): Vuong, Quochien B.
• Application Number:
  US10/065,388
• Publication Number:
  US 20030203743A1
• Time in Patent Office: 564 Days
• Field of Search: 455/73, 455/76, 455/78, 455/83, 455/84, 455/86, 455/101, 455/132, 455/133, 455/137, 455/269, 455/272, 455/273, 455/266, 455/324, 455/340, 455/552.1, 455/553.1, 370/276, 370/277, 370/278, 375/219
• US Class Current: 455/73
• CPC Class Codes: H03D 2200/0025 Gain control circuits
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/0057 using diplexing or multiplexing filters for selecting the desired band
• CPC Class Codes: H04B 1/006 using switches for selecting the desired band H04B1/0057 takes precedence
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes

Abstract

A MIMO radio transceiver to support processing of multiple signals for simultaneous transmission via corresponding ones of a plurality of antennas and to support receive processing of multiple signals detected by corresponding ones of the plurality of antennas. The radio transceiver provides, on a single semiconductor integrated circuit, a receiver circuit or path for each of a plurality of antennas and a transmit circuit or path for each of the plurality of antennas. Each receiver circuit downconverts the RF signal detected by its associated antenna to a baseband signal. Similarly, each transmit path upconverts a baseband signal to be transmitted by an assigned antenna.

Claims

1. A multiple-input multiple-output (MIMO) radio transceiver comprising:

a. a receiver comprising at least first and second receiver circuits each to process a signal from a corresponding one of first and second antennas,

i. the first receiver circuit comprising;

1. a first downconverter coupled to the first antenna to downconvert a first receive signal detected by the first antenna to produce a first baseband signal; and

2. a first lowpass filter coupled to the first downconverter that lowpass filters the first baseband signal;

ii. the second receiver circuit comprising;

1. a second downconverter coupled to the second antenna to downconvert a second receive signal detected by the second antenna to produce a second baseband signal; and

2. a second lowpass filter coupled to the second downconverter that lowpass filters the second baseband signal;

b. a transmitter comprising at least first and second transmitter circuits each of which processes a signal to be transmitted by a corresponding one of the first and second antennas,

i. the first transmitter circuit comprising;

1. a first upconverter that upconverts a first baseband analog signal to generate a first RF signal;

2. a first bandpass filter coupled to the output of the first upconverter that filters the first RF signal; and

3. a first power amplifier coupled to the output of the bandpass filter that amplifies the filtered RF signal to produce a first amplified signal that is coupled to the first antenna for transmission;

ii. the second transmitter circuit comprising;

1. a second upconverter that upconverts a second baseband analog signal to generate a second RF signal;

2. a second bandpass filter coupled to the output of the second upconverter that filters the second RF signal; and

3. a second power amplifier coupled to the output of the second bandpass filter that amplifies the second filtered RF signal to produce a second amplified signal that is coupled to the second antenna for transmission.

2. The radio transceiver of claim 1, wherein the first receiver circuit and the second receiver circuit process the first and second receive signals substantially simultaneously to allow for combining of signals resulting from processing by the first and second receiver circuits.

3. The radio transceiver of claim 1, wherein the first transmitter circuit and the second transmitter circuit process the first and second analog baseband signals for transmission substantially simultaneously.

4. The radio transceiver of claim 1, and further comprising a frequency synthesizer that produces an RF local oscillator signal that is coupled to each of the first and second downconverters to be mixed with the first and second receive signals, respectively, wherein the RF local oscillator signal may be at any frequency within one or more discrete radio frequency bands.

5. The radio transceiver of claim 4, wherein the frequency synthesizer couples the RF local oscillator signal to the first and second upconverters to upmix the first and second baseband analog signals, respectively.

6. The radio transceiver of claim 1, wherein the first and second receiver circuits and the first and second transmitter circuits are implemented on a single semiconductor integrated circuit.

7. The radio transceiver of claim 1, wherein the first receiver circuit further comprises a first sample-and-hold circuit coupled to the output of the first lowpass filter and the second receiver circuit further comprises a second sample-and-hold circuit coupled to the output of the second lowpass filter.

8. The radio transceiver of claim 1, wherein the first and second downconverters comprise a single stage mixing process to downconvert the first and second receive signals directly to baseband.

9. The radio transceiver of claim 1, wherein the first and second downconverters comprise a two stage mixing process to downconvert the first and second receive signals to first and second intermediate frequency signals at a common intermediate frequency, and then to first and second baseband signals.

10. The radio transceiver of claim 9, and further comprising a frequency synthesizer that supplies an RF local oscillator signal and an IF local oscillator signal to the first and second downconverters, wherein the IF local oscillator signal is derived from the RF local oscillator signal that is also supplied to the first and second downconverters.

11. The radio transceiver of claim 1, wherein the first lowpass filter of the first receiver circuit and the second lowpass filter of the second receiver circuit are variable lowpass filters that are responsive to a bandwidth control signal so as to pass a portion of a radio frequency band or substantially the entire radio frequency band.

12. The radio transceiver of claim 1, wherein the first upconverter and the second upconverter comprise first and second lowpass filters to filter the first and second baseband analog signals, respectively, prior to upconversion, wherein the first and second lowpass filters are variable lowpass filters that are responsive to a bandwidth control signal so as to filter the first and second baseband analog signals for transmission in a portion of the radio frequency band, or in substantially the entire radio frequency band.

13. The radio transceiver of claim 1, wherein the first downconverter comprises first and second RF mixers, wherein the first RF mixer down-mixes the first receive signal to an intermediate frequency signal when the first receive signal is in a first radio frequency band and the second RF mixer down-mixes the first receive signal to an intermediate frequency signal when the first receive signal is in a second radio frequency band, and wherein the second downconverter comprises first and second RF mixers, wherein the first RF mixer down-mixes the second receive signal to an intermediate frequency signal when the second receive signal is in a first radio frequency band and the second RF mixer down-mixes the second receive signal to an intermediate frequency signal when the second receive signal is in the second radio frequency band.

14. A multiple-input multiple-output (MIMO) radio transceiver comprising:

a. a receiver comprising at least first and second receiver circuits each to process a signal from a corresponding one of first and second antennas,

i. the first receiver circuit comprising;

1. a first downconverter coupled to the first antenna to downconvert a first receive signal detected by the first antenna to produce a first in-phase baseband signal and a first quadrature baseband signal; and

2. first and second lowpass filters coupled to the first downconverter that lowpass filter the first in-phase baseband signal and the first quadrature baseband signal, respectively;

ii. the second receiver circuit comprising;

1. a second downconverter coupled to the second antenna to downconvert a second receive signal detected by the second antenna to produce a second in-phase baseband signal and a second quadrature baseband signal; and

2. third and fourth lowpass filters coupled to the second downconverter that lowpass filter the second in-phase baseband signal and the second quadrature baseband signal, respectively;

b. a transmitter comprising at least first and second transmitter circuits each of which processes a signal to be transmitted by a corresponding one of the first and second antennas,

i. the first transmitter circuit comprising;

1. a first upconverter that upconverts a first in-phase baseband analog signal and a first quadrature baseband analog signal to generate a first RF signal;

2. a first bandpass filter coupled to the output of the first upconverter that filters the first RF signal; and

3. a first power amplifier coupled to the output of the first bandpass filter that amplifies the first filtered RF signal to produce a first amplified signal that is coupled to the first antenna for transmission;

ii. the second transmitter circuit comprising;

1. a second upconverter that upconverts a second in-phase baseband analog signal and a second quadrature baseband analog signal to generate a second RF signal;

2. a second bandpass filter coupled to the output of the second upconverter that filters the second RF signal; and

3. a second power amplifier coupled to the output of the second bandpass filter that amplifies the second filtered RF signal to produce a second amplified signal that is coupled to the second antenna for transmission.

15. The radio transceiver of claim 14, wherein the first downconverter comprises first and second RF mixers, wherein the first RF mixer down-mixes the first receive signal to an intermediate frequency signal when the first receive signal is in a first radio frequency band and the second RF mixer down-mixes the first receive signal to an intermediate frequency signal when the first receive signal is in a second radio frequency band, and wherein the second downconverter comprises first and second RF mixers, wherein the first RF mixer down-mixes the second receive signal to an intermediate frequency signal when the second receive signal is in a first radio frequency band and the second RF mixer down-mixes the second receive signal to an intermediate frequency signal when the second receive signal is in the second radio frequency band.

16. The radio transceiver of claim 15, wherein the first downconverter further comprises a pair of quad mixers coupled to the output of the first and second RF mixers to further down-mix the intermediate frequency signal to the first in-phase and quadrature baseband signals representative of the first receive signal, and the second downconverter further comprises a pair of quad mixers coupled to the output of the first and second RF mixers to further down-mix the intermediate frequency signal to the second in-phase and quadrature baseband signals representative of the second receive signal.

17. The radio transceiver of claim 16, and further comprising an RF frequency synthesizer that generates an RF local oscillator signal for the RF mixers in the first and second downconverters and wherein an intermediate frequency local oscillator signal used by the quad mixers in the first and second downconverters is derived from the RF local oscillator signal.

18. The radio transceiver of claim 17, and further comprising a divide-by-four circuit that divides the frequency of the RF local oscillator signal to generate the intermediate frequency local oscillator signal that is coupled to the quad mixers in the first and second downconverters.

19. The radio transceiver of claim 16, and further comprising an RF frequency synthesizer that generates an RF local oscillator signal for the RF mixers and an intermediate frequency synthesizer that generates an intermediate frequency local oscillator signal for the quad mixers in the first and second downconverters.

20. The radio transceiver of claim 14, wherein the first downconverter comprises a pair of quad mixers that down-mix the first receive signal directly to the first in-phase and quadrature baseband signals, and the second downconverter comprises a pair of quad mixers that down-mix the second receive signal directly to the second in-phase and quadrature baseband signals.

21. The radio transceiver of claim 20, wherein the first and second receiver circuits each further comprise a variable amplifier coupled to amplify an intermediate frequency signal before it is supplied to their quad mixers.

22. The radio transceiver of claim 14, wherein the first upconverter comprises a pair of quad mixers that up-mix the first baseband in-phase and quadrature signals to an intermediate frequency signal, the second upconverter comprises a pair of quad mixers that up-mix the second baseband in-phase and quadrature signals to an intermediate frequency signal.

23. The radio transceiver of claim 22, wherein the first upconverter further comprises an RF mixer coupled to the output of the quad mixers that up-mixes the intermediate frequency signal to a first RF signal, and the second upconverter further comprises an RF mixer coupled to the output of the quad mixers that up-mixes the intermediate frequency signal to a second RF signal.

24. The radio transceiver of claim 23, wherein the first and second transmitter circuits each further comprises a variable amplifier coupled to amplify the intermediate frequency signal before it is supplied to their RF mixers.

25. The radio transceiver of claim 23, wherein the first and second transmitter circuits further comprise first and second bandpass filters coupled to the output of their RF mixers, that are dedicated to bandpass filtering signals to be transmitted in a first radio frequency band, and third and fourth bandpass filters coupled to the RF mixers to filter signals to be transmitted in a second radio frequency band.

26. The radio transceiver of claim 14, wherein the first receiver circuit comprises first and second sample-and-hold circuits that are connected to the first and second lowpass filters, respectively, to couple the first in-phase baseband signal and the first quadrature baseband signal to an analog-to-digital converter, and the second receiver circuit comprises third and fourth sample-and-hold circuits that are connected to the third and fourth lowpass filters, respectively, to couple the second in-phase baseband signal and the second quadrature baseband signal to an analog-to-digital converter.

27. The radio transceiver of claim 14, wherein the receiver and the transmitter are implemented on a single semiconductor integrated circuit.

28. The radio transceiver of claim 14, wherein the first receiver circuit and the second receiver circuit process the first and second signals substantially simultaneously to allow for combining of signals resulting from processing by the first and second receiver circuits.

29. The radio transceiver of claim 14, wherein the first transmitter circuit and the second transmitter circuit process the first and second analog baseband signals for transmission substantially simultaneously.

30. The radio transceiver of claim 14, wherein the first, second, third and fourth lowpass filters are variable lowpass filters that are responsive to a bandwidth control signal so as to pass a portion of a radio frequency band or to pass substantially the entire radio frequency band.

31. The radio transceiver of claim 30, wherein the first and second variable lowpass filters receive as input the first in-phase baseband analog signal and the first quadrature baseband analog signal, respectively, and the third and fourth lowpass filters receive as input the second in-phase baseband analog signal and the second quadrature baseband analog signal, respectively, to filter these signals for transmission in a portion of the radio frequency band, or in substantially the entire radio frequency band.

32. The radio transceiver of claim 14, wherein the first transmitter circuit comprises first and second variable lowpass filters to filter the first in-phase and quadrature signals prior to upconversion and the second transmitter circuit comprises third and fourth variable lowpass filters to filter the second in-phase and quadrature signals prior to upconversion, wherein the first, second, third and fourth variable lowpass filters in the first and second transmitter circuits are variable lowpass filters that are responsive to a bandwidth control signal so as to filter the first and second baseband analog signals for transmission in a portion of a radio frequency band, or in substantially the entire radio frequency band.

33. The radio transceiver of claim 14, wherein the first downconverter and the second downconverter downconvert the first and second receive signals, respectively, directly to baseband in a single stage downconversion process.

34. In combination, the radio transceiver of claim 14, and further comprising:

a. an analog-to-digital converter (ADC);

b. a digital-to-analog converter (DAC); and

c. a digital multiplexer coupled to the ADC and to the DAC;

d. wherein the ADC receives as input one of;

an analog transmit power level signal, first or second quadrature baseband analog signal, first or second in-phase baseband analog signal; and

wherein the DAC receives as input one of;

first or second digital quadrature transmit signal, first or second digital in-phase transmit signal, digital receiver gain control signal, and wherein the digital multiplexer directs signals from the ADC to their appropriate destination and directs appropriate ones of the signals to the DAC for digital-to-analog conversion.

35. The combination of claim 34, and further comprising a first switch having first and second input terminals and an output terminal, the output terminal of the first switch being coupled to the input of the ADC, the first and second input terminals of the first switch being coupled to any two signals of:

the analog transmit power level signal, first or second quadrature baseband analog signal, and the first or second in-phase baseband analog signal, and a second switch having first and second output terminals and an input terminal, the input terminal of the second switch being coupled to the output of the DAC, and wherein the digital multiplexer directs one of the following signals to the input of the DAC;

the first or second digital quadrature transmit signal, first or second digital in-phase transmit signal, and the digital receiver gain control signal.

36. In combination, the radio transceiver of claim 14, and a radio front-end section comprising:

a. a first transmit/receive switch to be coupled to the first antenna and a second transmit/receive switch to be coupled to the second antenna, wherein the first and second transmit/receive switches each comprise an antenna terminal to be coupled to the first and second antenna, respectively, a receive output terminal and a transmit input terminal, the transmit input terminals of the first and second transmit/receive switches being coupled to the output of the first and second transmitter circuits, respectively, wherein the first and second transmit/receive switches are responsive to a control signal to select one of the two output terminals; and

b. first and second bandpass filters, the first bandpass filter coupled to the receive output terminal of the first transmit/receive switch and the second bandpass filter coupled to the receive output terminal of the second transmit/receive switch, the first and second bandpass filters filter the signals detected by the first and second antennas, respectively, to produce the first and second receive signals.

37. The combination of claim 36, wherein the first and second bandpass filters are dedicated to filtering signals in a first radio frequency band, and further comprising:

a. third and fourth bandpass filters dedicated to filtering signals in a second radio frequency band;

b. first and second band select switches, the first and second band selection switches having an input terminal coupled to the receive output terminals of the first and second transmit/receive switches, respectively, and each having a first output terminal coupled to the first and second bandpass filters, respectively, and a second output terminal coupled to the third and fourth bandpass filters, respectively.

38. The combination of claim 37, wherein the radio front-end section further comprises third and fourth band select switches, each having first and second input terminals, and an output terminal, the output terminal of the third and fourth band select switches being coupled to the transmit input terminals of the first and second transmit/receive switches.

39. The combination of claim 38, wherein the radio front-end section further comprises first and second lowpass filters dedicated to filtering signals to be transmitted in the first radio frequency band, the outputs of the first and second lowpass filters being connected to the first input terminals of the third and fourth band select switches, respectively, and third and fourth lowpass filters dedicated to filtering signals to be transmitted in the second radio frequency band, the outputs of the third and fourth lowpass filters being connected to the second input terminals of the third and fourth band select switches.

40. In combination, the radio transceiver of claim 14, and a radio front-end section, wherein the radio front end section comprises a first diplexer to be coupled to the first antenna and a second diplexer to be coupled to the second antenna, wherein the first and second diplexers each have first and second branches onto which signals from first and second radio frequency bands, respectively, are coupled for transmission via the first and second antennas, respectively, or are coupled when received by the first and second antennas, respectively.

41. The combination of claim 40, wherein for each diplexer, the radio front-end section further comprises a bandpass filter coupled in the first branch to filter signals received in the first frequency band and a bandpass filter coupled in the second branch to filter signals received in the second frequency band.

42. The combination of claim 41, wherein the radio-front end section further comprises a transmit/receive switch coupled to the bandpass filter in each of the first and second branches for each diplexer, wherein the transmit/receive switch selects either a signal to be transmitted through an antenna coupled to the associated diplexer, or a signal detected by an antenna coupled to the associated diplexer which is coupled to the bandpass filter for that branch.

43. The combination of claim 41, wherein the radio transceiver further comprises a transmit/receive switch coupled to the bandpass filter in each of the first and second branches for each diplexer, wherein the transmit/receive switch selects either a signal to be transmitted through an antenna coupled to the associated diplexer, or a signal detected by an antenna coupled to the associated diplexer which is coupled to the bandpass filter for that branch.

44. The combination of claim 43, wherein the radio front-end section further comprises a quarter wavelength element coupled between the transmit/receive switch and the bandpass filter in each of the first and second branches for each diplexer.

45. A multiple-input multiple-output (MIMO) radio transceiver on a single semiconductor integrated circuit, comprising:

a. a receiver comprising at least first and second receiver circuits each to process a signal from a corresponding one of first and second antennas,

i. the first receiver circuit comprising;

1. a first downconverter coupled to the first antenna to downconvert a first receive signal detected by the first antenna to produce a first baseband signal; and

2. a first lowpass filter coupled to the first downconverter that lowpass filters the first baseband signal;

ii. the second receiver circuit comprising;

1. a second downconverter coupled to the second antenna to downconvert a second receive signal detected by the second antenna to produce a second baseband signal; and

2. a second lowpass filter coupled to the second downconverter that lowpass filters the second baseband signal;

b. a transmitter comprising at least first and second transmitter circuits each of which processes a signal to be transmitted by a corresponding one of the first and second antennas,

i. the first transmitter circuit comprising;

1. a first upconverter that upconverts a first baseband analog signal to generate a first RF signal; and

2. a first bandpass filter coupled to the output of the first upconverter that filters the first RF signal;

ii. the second transmitter circuit comprising;

1. a second upconverter that up converts a second baseband analog signal to generate a second RF signal; and

2. a second bandpass filter coupled to the output of the second upconverter that filters the second RF signal.

46. The radio transceiver of claim 45, wherein the first receiver circuit and the second receiver circuit process the first and second receive signals substantially simultaneously to allow for combining of signals resulting from processing by the first and second receiver circuits.

47. The radio transceiver of claim 45, wherein the first transmitter circuit and the second transmitter circuit process the first and second analog baseband signals for transmission substantially simultaneously.

48. The radio transceiver of claim 45, and further comprising a frequency synthesizer that produces an RF local oscillator signal that is coupled to each of the first and second downconverters to be mixed with the first and second receive signals, respectively, wherein the RF local oscillator signal may be at any frequency within one or more discrete radio frequency bands.

49. The radio transceiver of claim 48, wherein the frequency synthesizer couples the RF local oscillator signal to the first and second upconverters to upmix the first and second baseband analog signals, respectively.

50. The radio transceiver of claim 45, wherein the first and second downconverters comprise a single stage mixing process to downconvert the first and second receive signals directly to baseband.

51. The radio transceiver of claim 50, wherein the first downconverter comprises a pair of quad mixers that down-mix the first receive signal directly to first in-phase and quadrature baseband signals, and the second downconverter comprises a pair of quad mixers that down-mix the second receive signal directly to the second in-phase and quadrature baseband signals.

52. The radio transceiver of claim 45, wherein the first lowpass filter of the first receiver circuit and the second lowpass filter of the second receiver circuit are variable lowpass filters that are responsive to a bandwidth control signal so as to pass a portion of a radio frequency band or substantially the entire radio frequency band.

53. The radio transceiver of claim 45, wherein the first upconverter and the second upconverter comprise first and second lowpass filters to filter the first and second baseband analog signals, respectively, prior to upconversion, wherein the first and second lowpass filters are variable lowpass filters that are responsive to a bandwidth control signal so as to filter the first and second baseband analog signals for transmission in a portion of the radio frequency band, or in substantially the entire radio frequency band.

54. The radio transceiver of claim 45, and further comprising a first power amplifier in the first transmitter circuit coupled to the output of the first upconverter that amplifies the first RF signal and a second power amplifier in the second transmitter circuit coupled to the output of the second upconverter that amplifies the second RF signal.

55. A multiple-input multiple-output (MIMO) radio transceiver on a single semiconductor integrated circuit, comprising:

a. a receiver comprising at least first and second receiver circuits each to process a signal from a corresponding one of first and second antennas, the first receiver circuit comprising a first downconverter that downconverts a first receive signal detected by the first antenna to produce a first baseband signal, the second receiver circuit comprising a second downconverter that downconverts a second receive signal detected by the second antenna to produce a second baseband signal;

b. a transmitter comprising at least first and second transmitter circuits each of which processes a signal to be transmitted by a corresponding one of the first and second antennas, the first transmitter circuit comprising a first upconverter that upconverts a first baseband analog signal to generate a first RF signal, the second transmitter circuit comprising a second upconverter that upconverts a second baseband analog signal to generate a second RF signal.

56. The radio transceiver of claim 55, and further comprising a first power amplifier in the first transmitter circuit coupled to the output of the first upconverter that amplifies the first RF signal and a second power amplifier in the second transmitter circuit coupled to the output of the second upconverter that amplifies the second RF signal.

57. The radio transceiver of claim 55, and further comprising a first bandpass filter coupled between the output of the first upconverter and an input to the first power amplifier that filters the first RF signal, and a second bandpass filter coupled between the output of the second upconverter and an input to the second power amplifier that filters the second RF signal.

58. The radio transceiver of claim 55, wherein the first receiver circuit and the second receiver circuit process the first and second receive signals, respectively, substantially simultaneously to allow for combining of signals resulting from processing by the first and second receiver circuits.

59. The radio transceiver of claim 55, wherein the first transmitter circuit and the second transmitter circuit process the first and second analog baseband signals, respectively, for transmission substantially simultaneously.

60. The radio transceiver of claim 55, and further comprising a local oscillator that produces an RF local oscillator signal that is coupled to each of the first and second downconverters to be mixed with the first and second receive signals, respectively.

61. The radio transceiver of claim 60, wherein the local oscillator produces an RF local oscillator signal that is coupled to the first and second upconverters to upmix the first and second baseband analog signals, respectively.

62. The radio transceiver of claim 55, wherein the first and second downconverters downconvert the first and second receive signals directly to baseband.

63. The radio transceiver of claim 55, wherein each of the first and second downconverters comprises an RF mixer that down-mixes the first and second receive signals, respectively, to an intermediate frequency signal, and a pair of quad mixers that down-mix the intermediate frequency signal to in-phase and quadrature baseband signals.

64. The radio transceiver of claim 55, wherein each of the first and second receiver circuits further comprises a lowpass filter coupled to the output of the first and second downconverters, respectively, wherein each lowpass filter is a variable lowpass filter that is responsive to a bandwidth control signal so as to pass a portion of a radio frequency band or substantially the entire radio frequency band.

65. The radio transceiver of claim 55, and further comprising first and second lowpass filters, the first lowpass filter having inputs and an output and being shared by the first transmitter circuit and first receiver circuit, to filter either the first baseband analog signal that is output to the first transmitter circuit or to filter the first baseband signal produced by the first receiver circuit, and the second lowpass filter having inputs and an output and being shared by the second transmitter circuit and second receiver circuit to filter either the second baseband analog signal that is output to the second transmitter circuit or to filter the second baseband signal produced by the second receiver circuit, and further comprising a first switch having an output coupled to an input of the first lowpass filter and that couples to the input of the first lowpass filter either the first baseband analog signal or the first baseband signal, and a second switch having an output coupled to an input of the second lowpass filter and that couples to the input of the second lowpass filter either the second baseband analog signal or the second baseband signal.