Simplified Digital Predistortion in a Time-Domain Duplexed Transceiver

• US 20080144539A1
• Filed: 12/14/2006
• Published: 06/19/2008
• Est. Priority Date: 12/14/2006
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Copeland, Gregory C., Sperlich, Roland
• Granted Patent: US 7,783,263 B2
• Time in Patent Office: Days
• US Class Current: 370/278
• CPC Class Codes: H04L 25/0286 Provision of wave shaping within the driver wave shaping per se H04L25/03834
• CPC Class Codes: H04L 27/368 adaptive predistortion
• CPC Class Codes: H04L 5/1469 using time-sharing

Abstract

A transceiver for time-domain duplexed (TDD) communications, for example in connection with wireless broadband data communications, is disclosed. The transceiver includes digital predistortion compensation circuitry, which compensates the digital signals to be transmitted based on feedback signals from the output of the power amplifier, in order to linearize the output from the power amplifier. The feedback signals from the power amplifier are coupled back to the digital predistortion circuitry over part of the same receive path as the received signals from the wireless communications channel. The shared path includes analog-to-digital converters that are used both in the transmit period of the TDD cycle to convert the feedback signals from the power amplifier output, and in the receive period of the TDD cycle to convert the analog received signals.

Claims

1. A transceiver for time-domain duplexed (TDD) communications, comprising:

baseband processing circuitry;

digital predistortion circuitry, having an input coupled to the baseband processor to receive digital signals to be transmitted, the digital predistortion circuitry for adjusting the values of the digital signals to be transmitted;

a first digital-to-analog converter, having an input coupled to the digital predistortion circuitry, the first digital-to-analog converter for converting the compensated digital signals to analog signals;

a power amplifier, having an input coupled to an output of the first digital-to-analog converter, for amplifying the analog signals for transmission over a communications channel;

receive circuitry, for receiving signals from the communications channel;

a first analog-to-digital converter, having an input coupled to the receive circuitry and also having an input coupled to the output of the power amplifier, for converting analog signals received at its input to digital signals, and having an output coupled to the baseband processor and coupled to the digital predistortion circuitry; and

a switch for isolating the output of the power amplifier from the input to the first analog-to-digital converter during receive periods of a TDD cycle, and for coupling the output of the power amplifier to the input to the first analog-to-digital converter during transmit periods of the TDD cycle.

2. The transceiver of claim 1, wherein the switch is also for coupling the receive circuitry to the input of the first analog-to-digital converter during receive periods of the TDD cycle.

3. The transceiver of claim 2, further comprising:

at least one local oscillator; and

a receive mixer, having an input coupled to the switch, having an input coupled to receive a periodic signal from one of the at least one local oscillators, and having an output coupled to the input of the first analog-to-digital converter.

4. The transceiver of claim 3, further comprising:

a band-pass filter, having an input coupled to the output of the receive mixer and having an output coupled to the input of the first analog-to-digital converter;

a bypass switch, having an input coupled to the output of the receive mixer and having an output coupled to the input of the first analog-to-digital converter, the bypass switch controlled to be closed during transmit periods of the TDD cycle.

5. The transceiver of claim 3, further comprising:

a transmit mixer, having an input coupled to the output of the first digital-to-analog converter, having an input coupled to receive a periodic signal from one of the at least one local oscillators, and having an output coupled to the input of the power amplifier.

6. The transceiver of claim 5, wherein the receive mixer and the transmit mixer are each coupled to receive a periodic signal from the same one of the at least one local oscillators.

7. The transceiver of claim 2, wherein the receive circuitry comprises:

a first band-pass filter; and

an amplifier, connected in series with the first band-pass filter.

8. The transceiver of claim 2, further comprising:

a second digital-to-analog converter, having an input coupled to the digital predistortion circuitry, the second digital-to-analog converter for converting, to analog signals, compensated digital signals associated with a signal component orthogonal in phase to the digital signals converted by the first digital-to-analog converter, the second digital-to-analog converter having an output coupled to an input of the power amplifier; and

a second analog-to-digital converter, having an input coupled to the switch, for converting, to digital signals, analog signals received at its input associated with a signal component orthogonal in phase to the analog signals converted by the first analog-to-digital converter, and having an output coupled to the baseband processor and coupled to the digital predistortion circuitry.

9. The transceiver of claim 1, further comprising:

at least one local oscillator; and

a receive mixer, having an input coupled to the receive circuitry, having an input coupled to receive a periodic signal from one of the at least one local oscillators, and having an output coupled to the input of the first analog-to-digital converter; and

a second mixer, having an input coupled to the output of the power amplifier, having an input coupled to receive a periodic signal from one of the at least one local oscillators, and having an output coupled to the switch;

wherein the switch is coupled between the output of the second mixer and the input of the first analog-to-digital converter.

10. The transceiver of claim 9, further comprising:

a band-pass filter, having an input coupled to the output of the receive mixer and having an output coupled to the input of the first analog-to-digital converter.

11. The transceiver of claim 10, wherein the receive circuitry comprises:

a first band-pass filter; and

an amplifier, connected in series with the first band-pass filter.

12. The transceiver of claim 9, wherein the second mixer and the transmit mixer are each coupled to receive a periodic signal from the same one of the at least one local oscillators.

13. The transceiver of claim 9, further comprising:

a second digital-to-analog converter, having an input coupled to the digital predistortion circuitry, the second digital-to-analog converter for converting, to analog signals, compensated digital signals associated with a signal component orthogonal in phase to the digital signals converted by the first digital-to-analog converter, the second digital-to-analog converter having an output coupled to an input of the power amplifier; and

a second analog-to-digital converter, having an input coupled to the switch, for converting, to digital signals, analog signals received at its input associated with a signal component orthogonal in phase to the analog signals converted by the first analog-to-digital converter, and having an output coupled to the baseband processor and coupled to the digital predistortion circuitry.

14. The transceiver of claim 1, further comprising:

an antenna; and

a duplexer, coupled to the output of the power amplifier, to the receive circuitry, and to the antenna, for selectively coupling and isolating the output of the power amplifier and the receive circuitry to and from the antenna.

15. A method of transmitting signals over a time-domain duplexed (TDD) communications channel, comprising:

receiving a datastream of digital signals to be transmitted;

applying digital predistortion compensation values to the datastream of digital signals;

converting the compensated digital signals to analog signals;

amplifying the analog signals using a power amplifier, for transmission over the communications channel during a transmit period of a TDD cycle;

during the transmit period of the TDD cycle, converting analog feedback signals from the output of the power amplifier to digital signals using a first analog-to-digital converter;

determining digital predistortion compensation values responsive to the converted feedback signals;

during a receive period of the TDD cycle, isolating the output of the power amplifier from the first analog-to-digital converter; and

during the receive period of the TDD cycle, converting analog signals received from the communications channel to digital signals, using the first analog-to-digital converter.

16. The method of claim 15, further comprising:

operating at least one local oscillator to generate at least one periodic signal; and

during the transmit period of the TDD cycle, before the step of converting analog feedback signals, mixing the analog feedback signals with a periodic signal from one of the at least one local oscillators using a first receive mixer.

17. The method of claim 16, further comprising:

before the amplifying step, mixing the analog signals with a periodic signal from one of the at least one local oscillators.

18. The method of claim 17, wherein the steps of mixing the analog feedback signals and mixing the analog signals use a periodic signal from the same one of the at least one local oscillators.

19. The method of claim 17, further comprising:

during the receive period of the TDD cycle, before the step of converting analog signals received from the communications channel, mixing the received analog signals with a periodic signal from one of the at least one local oscillators using the first receive mixer.

20. The method of claim 19, further comprising:

band-pass filtering the mixed received analog signals before the step of converting analog signals received from the communications channel using a band-pass filter; and

during the transmit period of the TDD cycle, bypassing the band-pass filter so that the mixed analog feedback signals are not band-pass filtered.

21. The method of claim 17, further comprising:

during the receive period of the TDD cycle, before the step of converting analog signals received from the communications channel, mixing the received analog signals with a periodic signal from one of the at least one local oscillators using a second receive mixer.

22. The method of claim 16, further comprising:

before the compensating step, digitally upconverting the digital signals to be transmitted to produce first and second datastreams corresponding to orthogonal phase components;

wherein the step of converting the compensated digital signals to analog signals converts signals from both of the first and second datastreams;

wherein the step of mixing the analog feedback signals generates first and second orthogonal phase analog feedback signal components;

wherein the step of converting analog signals received from the communications channel to digital signals is performed using a first pair of analog-to-digital converters;

and wherein the step of converting analog signals received from the communications channel to digital signals is also performed using the first pair of analog-to-digital converters.