Wideband multi-protocol wireless radio transceiver system

• US 20020080728A1
• Filed: 10/29/2001
• Published: 06/27/2002
• Est. Priority Date: 11/03/2000
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cognio, Inc. (Cisco Systems, Inc.)
• Inventors: Seed, William R., Sugar, Gary L.
• Granted Patent: US 6,526,264 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 1/001 Channel filtering, i.e. selecting a frequency channel within the SDR system multiplexing of multicarrier modulation signals being represented by different frequencies H04L5/06; multiplexing of multicarrier modulation signals H04L5/023
• CPC Class Codes: H04B 1/0017 Digital filtering H04B1/001 takes precedence; digital filters per se H03H17/00
• CPC Class Codes: H04B 1/0021 Decimation, i.e. data rate reduction techniques H04B1/0025 takes precedence
• CPC Class Codes: H04B 1/0092 using a wideband front end
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A wideband radio transceiver system that features a wideband RF section and a flexible and scalable baseband signal processing section. The transceiver system architecture has configurable baseband processing to process signals for multiple communication protocol standards, or multiple instances of the same communication protocol standard, that operate over the same frequency band. Optional additional features include a transmit carrier suppressor and transmit interference canceller to suppress the effects of a transmit signal on receive signal processing when signals are being transmitted and received simultaneously.

Claims

1. A wideband radio transceiver system for full-duplex communication of signals associated with one or more wireless communication protocols operating in a common frequency band, the system comprising:

at least one receive signal path section for connection to a receive antenna, the receive signal path section comprising;

a downconverter coupled to the receive antenna that downconverts a signal detected by the receive antenna representing a spectrum of said frequency band to an intermediate frequency signal;

an analog-to-digital converter (ADC) coupled to the downconverter that converts the intermediate frequency signal to a digital intermediate frequency signal;

a downconverter bank including one or more downconverters coupled to the ADC, each downconverter associated with a communication protocol, which downconverts the digital intermediate frequency signal to generate a baseband signal for each communication protocol;

a decimator bank including one or more decimators coupled the bank of downconverters, each decimators associated with a corresponding communication protocol, and which decimates a corresponding baseband signal to a convenient sampling rate for a corresponding communication protocol to generate a complex baseband signal for each communication protocol;

a detector bank including one more detectors coupled to the bank of decimators, associated with a corresponding communication protocol, and which demodulates a corresponding complex baseband signal to recover data therefrom;

a transmit signal path section coupled to a transmit antenna, the transmit signal path section comprising;

a modulator bank including one or more modulators, associated with a corresponding communication protocol, coupled to receive data to be transmitted using the communication protocol, each modulator generating a complex baseband signal corresponding to a communication protocol;

an interpolator bank including one or more interpolators coupled to the bank of modulators, associated with a corresponding communication protocol, each modulator increases a sampling rate of a corresponding complex baseband signal;

an upconverter bank including one or more upconverters, coupled to the bank of interpolators, each associated with a corresponding communication protocol and which upconverts an output of a corresponding interpolator to generate an intermediate frequency signal having a desired offset position in the frequency band;

a summer coupled to the output of the upconverter bank to sum each intermediate frequency signal output by the upconverter bank to generate a composite intermediate frequency signal;

a digital-to-analog converter coupled to the summer that converts the composite intermediate frequency signal to a composite analog signal;

an upconverter coupled to the digital-to-analog converter that upconverts the composite analog signal to a frequency range of the frequency band to generate a composite transmit signal;

a power amplifier coupled between the upconverter and the transmit antenna to amplify the composite transmit signal and couple the composite transmit signal to the transmit antenna for transmission;

wherein the receive signal path section and the transmit signal path section are operable to simultaneously process at least one receive signal and at least one transmit signal associated with one or more communication protocols in the frequency band.

2. The system of claim 1, and further comprising two receive antennas that are physically separated to enable the benefits of spatial diversity under Rayleigh fading conditions to be achieved, and a receive signal path section associated with each receive antenna.

3. The system of claim 1, wherein the downconverter bank, the decimator bank and the detector bank of the receive signal path section, and the modulator bank, the interpolator bank, the upconverter bank and the summer of the transmit signal path section are implemented by one or more digital application specific and/or general purpose processors that execute firmware or software, respectively, to process signals as required by each communication protocol.

4. The system of claim 1, and further comprising a control processor coupled to one or more components in the receive signal path section and the transmit signal path section, wherein the control processor supplies operating frequency information to the downconverter decimator bank of the receive signal path section to control an operating frequency of at least one downconverter in the downconverter bank to coincide with changes to the carrier frequency of a communication protocol.

5. The system of claim 4, wherein the control processor supplies operating frequency information to the upconverter bank of the transmit signal path section to control an operating frequency of at least one upconverter in the upconverter bank to coincide with changes to the carrier frequency of a communication protocol.

6. The system of claim 4, wherein the downconverter bank, the decimator bank, the detector bank, the interpolator bank, the upconverter bank and the modulator bank are each capable of processing of signals according to one or more of the Bluetooth™

communication protocol and versions thereof, the IEEE 802.11 communication protocol and versions thereof, and the HomeRF communication protocol and versions thereof.

7. The system of claim 1, wherein the downconverter in the receive signal path section comprises a zero-IF quadrature downconverter and a lowpass filter.

8. The system of claim 7, wherein the analog-to-digital converter is a dual channel analog-to-digital converter that generates at least 80 million complex samples per second.

9. The system of claim 1, wherein the downconverter in the receive signal path comprises a real downconverter that converts to a non-zero intermediate frequency of at least 40 MHz.

10. The system of claim 9, wherein the analog-to-digital converter in the receive signal path section comprises a single channel analog-to-digital converter operating at a sampling rate of at least 160 MHz.

11. The system of claim 1, and further comprising a transmit interference canceller coupled between the summer after the output of the upconverter bank and an output of the receive antenna, the transmit interference canceller comprising:

a coupled signal path estimator coupled to receive as input the composite intermediate frequency signal output by the summer, the coupled signal path estimator comprising one or more of the following elements to operate on the composite intermediate frequency signal;

a multiplier for multiplying the composite intermediate frequency signal by phase and attenuation factors, a filter having a filter function, a non-linear distortion processing element having a non-linear distortion function, and an adder for adding a complex additive constant, values for the phase and attenuation factors, the filter function, the non-linear distortion function and the complex additive constant being generated using an iterative algorithm to minimize an error signal that is digitized by the analog-to-digital converter in the receive signal path section, and to produce as output a digital signal that represents, at baseband, a transmit signal coupled to the receive signal path, adjusted for one or more of phase, amplitude, frequency distortion, non-linear distortion and carrier leakage/DC offset associated with the coupled signal path;

a digital-to-analog converter coupled to the output of the coupled signal path estimator to convert the output thereof to an analog signal;

an upconverter coupled to the output of the digital-to-analog converter to upconvert the analog signal to a radio frequency of the receive signal thereby producing a signal that is a replica of the reflected transmit signal; and

an adder coupled between the output of the receive antenna and an input to the downconverter in the receive signal path section to subtract the signal output by the upconverter from energy detected by the receive antenna, thereby suppressing the transmit signal that is being transmitted at the same time the receive signal path section is processing one or more receive signals.

12. The system of claim 11, and further comprising a processor coupled to receive the error signal and the composite intermediate frequency signal, and generating values for the phase and attenuation factors, the filter function, the non-linear distortion function and the complex added constant.

13. The system of claim 1, and further comprising a transmit interference canceller coupled between the summer after the output of the upconverter bank and an output of the receive antenna, the transmit interference canceller comprising:

a coupled signal path estimator coupled to receive as input the composite intermediate frequency signal output by the summer, the coupled signal path estimator comprising one or more of the following elements to operate on the composite intermediate frequency signal;

a multiplier for multiplying the composite intermediate frequency signal by phase and attenuation factors, a filter having a filter function, a non-linear distortion processing element having a non-linear distortion function, and an adder for adding a complex additive constant, values for the phase and attenuation factors, the filter function, the non-linear distortion function and the complex additive constant being generated using an iterative algorithm to minimize an error signal that is digitized by the analog-to-digital converter in the receive signal path section, and to produce as output a digital signal that represents, at baseband, a transmit signal coupled to the receive signal path, adjusted for one or more of phase, amplitude, frequency distortion, non-linear distortion and carrier leakage/DC offset associated with the coupled signal path;

a digital-to-analog converter coupled to the output of the coupled signal path estimator to convert the output thereof to an analog signal;

an adder coupled between the output of the downconverter and the input to the analog-to-digital converter in the receive signal path section to subtract the analog signal output by the digital-to-analog converter of the transmit interference canceller from the output of the downconverter, thereby suppressing the transmit signal that is being transmitted at the same time the receive signal path section is processing one or more receive signals.

14. The system of claim 1, and further comprising:

a coupled signal path estimator coupled to receive as input the composite intermediate frequency signal output by the summer, the signal path estimator comprising one or more of the following elements to operate on the composite intermediate frequency signal;

a multiplier for multiplying the composite intermediate frequency signal by phase and attenuation factors, a filter having a filter function, a non-linear distortion processing element having a non-linear distortion function, and an adder for adding a complex additive constant, values for the phase and attenuation factors, the filter function, the non-linear distortion function and the complex added constant being generated using an iterative algorithm to minimize an error signal that is digitized by the analog-to-digital converter in the receive signal path section;

a predistortion look up table that stores values to predistort the composite intermediate frequency signal output by the summer in order to compensate for non-linear distortion generated by the power amplifier in the transmit signal path section, values for the predistortion look up table being generated to minimize a weighted mean-square distortion between the composite intermediate frequency signal and a signal which is the sum of the output of the coupled signal path estimator and the output of the analog-to-digital converter in the receive signal path section.

15. The system of claim 14, and further comprising a processor coupled to receive the signal which is the sum of the output of the coupled signal path estimator and the output of the analog-to-digital converter in the receive signal path section, and the composite intermediate frequency signal to generate values for the predistortion look up table.

16. The system of claim 15, wherein the processor generates values which are weighted so as to provide distortion adjustment across a spectrum only where energy associated when a transmitted signal exists.

17. The system of claim 1, wherein the receive signal path section processes energy detected by the receive antenna in the frequency band simultaneously with the transmit signal path section processing signals that are transmitted in the frequency band.

18. The system of claim 1, and further comprising a transmit carrier suppressor comprising a low pass filter coupled to the output of the analog-to-digital converter in the receive signal path section and an accumulator coupled to the output of the low pass filter, the accumulator having a large time constant relative to a transmit packet duration so as to suppress leakage of energy associated with a transmit carrier, wherein an output of the accumulator is subtracted from the composite intermediate frequency signal before input to the digital-to-analog converter in the transmit signal path section.

19. The system of claim 1, wherein the downconverter bank, the decimator bank and the detector bank of the receive signal path section, and the modulator bank, the interpolator bank, the upconverter bank and the summer of the transmit signal path section comprise a sufficient number of elements to process signals associated with two or more communication protocols in the frequency band.

20. The system of claim 1, wherein the receive antenna and the transmit antenna are spatially separated a sufficient distance from each other to suppress coupling of a transmit signal into the receive signal path section.

21. A method for full-duplex communication of signals associated with one or more wireless communication protocols operating in a common frequency band, comprising steps of:

downconverting energy detected by a receive antenna representing a spectrum of energy in substantially all of said frequency band to an intermediate frequency signal;

converting the intermediate frequency signal to a digital intermediate frequency signal;

for each of one or more communication protocols, downconverting the digital intermediate frequency signal to generate a baseband signal associated with each communication protocol;

decimating each baseband signal to a convenient sampling rate for a corresponding communication protocol to generate a plurality of complex baseband signals;

demodulating each complex baseband signal to recover data contained therein;

modulating data to be transmitted using the plurality of communication protocols to generate a complex baseband signal for each communication protocol;

increasing a sampling rate of each complex baseband signal to a sampling rate convenient for each communication protocol thereby producing an up-sampled signal for each communication protocol;

upconverting each up-sampled to an intermediate frequency signal having a desired offset position in the frequency band;

adding together each intermediate frequency signal to produce a composite intermediate frequency signal;

converting the composite intermediate frequency signal to a composite analog signal;

upconverting the composite analog signal to a frequency range of the frequency band to produce a composite transmit signal.

22. The method of claim 21, and further comprising steps of:

processing the composite intermediate frequency signal to adjust for one or more of phase distortion, amplitude distortion, frequency distortion, non-linear distortion, and carrier leakage/DC offset associated with a coupled signal path of the transmit signal to the receive antenna to produce a digital signal that represents, at baseband, the transmit signal as affected by the coupled signal path;

converting the digital signal to an analog signal;

upconverting the analog signal to a radio frequency to produce a signal that is a replica of the reflected transmit signal from the receive signal path; and

subtracting the replica signal from the energy detected by the receive antenna thereby suppressing the transmit signal that is being transmitted at the same time one or more receive signals are being processed.

23. The method of claim 22, wherein the step of processing the composite intermediate frequency signal comprises generating values for the phase distortion, amplitude distortion, frequency distortion, non-linear distortion, and carrier leakage/DC offset using an iterative algorithm to minimize an error signal that is derived from the digital intermediate frequency signal.

24. The method of claim 21, and further comprising steps of:

processing the composite intermediate frequency signal to adjust for one or more of phase distortion, amplitude distortion, frequency distortion, non-linear distortion, and carrier leakage/DC offset associated with a coupled signal path of the transmit signal to the receive antenna to produce a digital signal that represents, at baseband, the transmit signal as affected by the coupled signal path;

converting the digital signal to an analog signal;

subtracting the analog signal from the digital intermediate frequency signal thereby suppressing the transmit signal that is being transmitted at the same time one or more receive signals are being processed.

25. The method of claim 21, and further comprising steps of:

processing the composite intermediate frequency signal to adjust for one or more of phase, attenuation, non-linear distortion, and carrier leakage/DC offset associated with a coupled signal path of the transmit signal to the receive antenna to produce a digital signal that represents, at baseband, the transmit signal as affected by the coupled signal path;

storing in a predistortion look up table values to predistort the composite intermediate frequency signal in order to compensate for non-linear distortion generated by a power amplifier used for transmitting the composite transmit signal; and

generating the values for the predistortion look up table to minimize a weighted mean-square distortion between the composite intermediate frequency signal and a signal which is the sum of the digital signal that represents, at baseband, the transmit signal as affected by the coupled signal path and the digital intermediate frequency signal.

26. The method of claim 25, wherein the step of generating values comprises weighting the values so as to provide distortion adjustment across a spectrum only where energy associated when a transmitted signal exists.

29. The transmit interference canceller of claim 28, and further comprising:

an upconverter coupled to the output of the digital-to-analog converter to upconvert the analog signal to a radio frequency of the receive signal; and

a summer coupled to the output of the receive antenna to subtract from the receive signal the output of the upconverter thereby suppressing the transmit signal that is transmitted at the same time the receiver is processing a receive signal.

30. The transmit interference canceller of claim 28, and further comprising:

a summer coupled to subtract the from a downconverted and intermediate frequency version of the receive thereby suppressing the transmit signal that is transmitted at the same time the receiver is processing a receive signal.

27. A software product stored on a processor readable memory containing instructions that, when executed by a processor, causes the processor to perform steps of:

for each of a plurality of communication protocols, downconverting a digital intermediate frequency signal derived from energy detected by a receive antenna representing a spectrum of a frequency band to generate a baseband signal associated with each communication protocol;

decimating each baseband signal to a convenient sampling rate for a corresponding communication protocol to generate a plurality of complex baseband signals;

demodulating each complex baseband signal to recover data contained therein;

modulating data to be transmitted using the plurality of communication protocols to generate a complex baseband signal for each communication protocol;

increasing a sampling rate of each complex baseband signal to a sampling rate convenient for each communication protocol thereby producing an up-sampled signal for each communication protocol;

upconverting each up-sampled to an intermediate frequency signal having a desired offset position in the frequency band; and

adding together each intermediate frequency signal to produce a composite intermediate frequency signal that can be converted to an analog signal and upconverted to a radio frequency for transmission.

28. A transmit interference canceller useful to cancel energy associated with a signal transmitted by a transmitter of a communication device that is detected by a receive antenna and coupled to a receiver in the communication while the receiver is otherwise receiving a signal, the transmit interference canceller comprising:

a coupled signal path estimator coupled to receive as input an intermediate frequency signal representing information to be transmitted, the coupled signal path estimator comprising one or more of the following elements to operate on the intermediate frequency signal;

a multiplier for multiplying the intermediate frequency signal by phase and attenuation factors, a filter having a filter function, a non-linear distortion processing element having a non-linear distortion function, and an adder for adding a complex additive constant, values for the phase and attenuation factors, the filter function, the non-linear distortion function and the complex added constant being generated to adjust the intermediate frequency signal for effects caused by a coupled signal path between components in the transmitter, an air-interface between the transmitter and receiver, and components in the receiver; and

a digital-to-analog converter coupled to the output of the signal path estimator to convert the output thereof to an analog signal.

31. A predistorter useful to predistort a signal representing information to be transmitted by a communication device having a transmitter and a receiver, the transmitter having a power amplifier, the predistorter comprising:

a coupled signal path estimator coupled to receive as input an intermediate frequency signal representing information to be transmitted, the coupled signal path estimator comprising one or more of the following elements to operate on the intermediate frequency signal;

a multiplier for multiplying the intermediate frequency signal by phase and attenuation factors, a filter having a filter function, a non-linear distortion processing element having a non-linear distortion function, and an adder for adding a complex additive constant, values for the phase and attenuation factors, the filter function, the non-linear distortion function and the complex added constant being generated to adjust the intermediate frequency signal for effects caused by a coupled signal path between components in the transmitter, an air-interface between the transmitter and receiver, and components in the receiver; and

a predistortion look up table that stores values to predistort the intermediate frequency signal output by the summer in order to compensate for non-linear distortion generated by the power amplifier in the transmit signal path section, values for the predistortion look up table being generated to minimize a weighted mean-square distortion between the intermediate frequency signal and a signal which is the sum of the output of the signal path estimator and an intermediate frequency signal in the receiver derived from a received signal.

32. The predistorter of claim 31, and further comprising a processor that generates values for the look up table which are weighted so as to provide distortion adjustment across a spectrum only where energy associated when a transmitted signal exists.