Interference cancellation repeater incorporating a non-linear element

• US 8,553,610 B2
• Filed: 05/12/2011
• Issued: 10/08/2013
• Est. Priority Date: 05/12/2011
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gainey, Kenneth M., Proctor, James A. Jr.
• Primary Examiner(s): ROSE, KERRI M
• Application Number:
  US13/106,656
• Publication Number:
  US 20120287968A1
• Time in Patent Office: 880 Days
• Field of Search: 370315-317, 370/201, 370/278, 370/282, 370286-290, 455/24, 455/283, 455/284, 455/296, 455/298, 455/299, 455303-312
• US Class Current: 370/317
• CPC Class Codes: H04B 7/15585 by interference cancellation

Abstract

A wireless repeater employing echo cancellation uses a non-linear element in digital baseband to compress the digital transmit signal waveform, thereby allowing distortions in the transmitter circuit as well as interference to be cancelled. In one embodiment, the repeater applies non-linear baseband compression to the digital transmit signal in the digital domain to reduce the peak-to-average amplitude of the digital transmit signal prior to digital-to-analog conversion and prior to over-the-air transmission and prior to sampling of the digital transmit signal for use as the reference signal for echo cancellation. The intentionally introduced non-linear distortion in the transmit signal improves echo cancellation and stability of the repeater. In one embodiment, the non-linear compression is applied only when the digital transmit signal is at or exceed a given power level or a given gain level.

Claims

1. A wireless repeater having a first antenna and a second antenna to receive an input signal and transmit an amplified signal, the input signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the first antenna and the second antenna, the repeater comprising:

a first receiver circuit coupled to the first antenna to receive the input signal and to generate a digital input signals at baseband frequency;

a first transmitter circuit coupled to generate the amplified signal to transmit on the second antenna, the amplified signal being generated from a compressed digital transmit signal at baseband frequency; and

a repeater digital baseband block configured to receive the digital input signal from the first receiver circuit and to generate the compressed digital transmit signal for the first transmitter circuit, the repeater baseband block operative to access a feedback signal estimate, to cancel the feedback signal estimate from the digital input signal to generate an echo cancelled signal, to delay the echo cancelled signal to generate a delayed signal, and to amplify and process the delayed signal to generate a first digital transmit signal, the repeater digital baseband block further configured to apply non-linear baseband compression of the first digital transmit signal to generate the compressed digital transmit signal,

wherein the repeater baseband block is configured to access a feedback signal estimate using the compressed digital transmit signal as a reference signal.

2. The wireless repeater of claim 1, wherein the repeater digital baseband block is configured to apply non-linear baseband compression of the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal to generate the compressed digital transmit signal.

3. The wireless repeater of claim 1, wherein the repeater digital baseband block is configured to apply non-linear baseband compression of the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal when the first digital transmit signal is at or exceed a predetermined power level.

4. The wireless repeater of claim 1, wherein the repeater digital baseband block is configured to apply non-linear baseband compression of the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal when the first digital transmit signal is at or exceed a predetermined gain level.

5. The wireless repeater of claim 1, wherein the repeater digital baseband block comprises a non-linear element configured to apply the non-linear baseband compression.

6. The wireless repeater of claim 5, wherein the non-linear element implements a digital limiter function.

7. The wireless repeater of claim 5, wherein the repeater digital baseband block comprises a transmit filter configured to filter the first digital transmit signal, the non-linear element being provided before the transmit filter.

8. The wireless repeater of claim 5, wherein the repeater digital baseband block comprises a transmit filter configured to filter the first digital transmit signal, the non-linear element being provided after the transmit filter.

9. A method in an echo cancellation repeater comprising:

receiving an input signal at a first antenna of the repeater, the input signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the first antenna and a second antenna;

digitizing the input signal to generate a digital input signal at baseband frequency;

cancelling a feedback signal estimate from the digital input signal to generate an echo cancelled signal;

delaying the echo cancelled signal to generate a delayed signal;

amplifying and processing the delayed signal to generate a first digital transmit signal;

applying non-linear baseband compression to the first digital transmit signal to generate a compressed digital transmit signal;

sampling the compressed digital transmit signal as a reference signal to access a feedback channel estimate of the feedback channel;

generating the feedback signal estimate using at least the feedback channel estimate and the reference signal, the feedback signal estimate being used to cancel a feedback signal component of the digital input signal;

generating an amplified signal from the compressed digital transmit signal; and

transmitting the amplified signal on the second antenna of the repeater.

10. The method of claim 9, wherein applying non-linear baseband compression to the first digital transmit signal to generate a compressed digital transmit signal comprises:

applying non-linear baseband compression to the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal.

11. The method of claim 9, wherein applying non-linear baseband compression to the first digital transmit signal to generate a compressed digital transmit signal comprises:

applying non-linear baseband compression to the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal when the first digital transmit signal is at or exceed a predetermined power level.

12. The method of claim 9, wherein applying non-linear baseband compression to the first digital transmit signal to generate a compressed digital transmit signal comprises:

applying non-linear baseband compression to the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal when the first digital transmit signal is at or exceed a predetermined gain level.

13. The method of claim 9, wherein applying non-linear baseband compression to the first digital transmit signal to generate a compressed digital transmit signal comprises:

applying a digital limiter function as the non-linear baseband compression.

14. The method of claim 9, further comprising filtering the first digital transmit signal before applying non-linear baseband compression to the first digital transmit signal.

15. The method of claim 9, further comprising filtering the first digital transmit signal after applying non-linear baseband compression to the first digital transmit signal.

16. A wireless repeater having a first antenna and a second antenna to receive an input signal and transmit an amplified signal, the input signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the first antenna and the second antenna, the repeater comprising:

first means coupled to the first antenna for receiving the input signal and to generate a digital input signals at baseband frequency;

second means for generating the amplified signal to transmit on the second antenna, the amplified signal being generated from a compressed digital transmit signal at baseband frequency; and

third means for receiving the digital input signal from the first means and generating the compressed digital transmit signal for the second means, the third means for accessing a feedback signal estimate, canceling the feedback signal estimate from the digital input signal to generate an echo cancelled signal, delaying the echo cancelled signal to generate a delayed signal, and amplifying and processing the delayed signal to generate a first digital transmit signal, the third means further for applying non-linear baseband compression of the first digital transmit signal to generate the compressed digital transmit signal,

wherein the third means is configured for accessing a feedback signal estimate using the compressed digital transmit signal as a reference signal.

17. The wireless repeater of claim 16, wherein the third means is configured for applying non-linear baseband compression of the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal to generate the compressed digital transmit signal.

18. The wireless repeater of claim 16, wherein the third means is configured for applying non-linear baseband compression of the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal when the first digital transmit signal is at or exceed a predetermined power level.

19. The wireless repeater of claim 16, wherein the third means is configured for applying non-linear baseband compression of the first digital transmit signal to compress a peak-to-average amplitude ratio of the first digital transmit signal when the first digital transmit signal is at or exceed a predetermined gain level.

20. A computer readable medium having stored thereon computer executable instructions for performing at least the following acts:

receiving an input signal at a first antenna of an echo cancellation repeater, the input signal being a sum of a remote signal to be repeated and a feedback signal resulting from a feedback channel between the first antenna and a second antenna of the repeater;

digitizing the input signal to generate a digital input signal at baseband frequency;

cancelling a feedback signal estimate from the digital input signal to generate an echo cancelled signal;

delaying the echo cancelled signal to generate a delayed signal;

amplifying and processing the delayed signal to generate a first digital transmit signal;

applying non-linear baseband compression to the first digital transmit signal to generate a compressed digital transmit signal;

sampling the compressed digital transmit signal as a reference signal to access a feedback channel estimate of the feedback channel;

generating the feedback signal estimate using at least the feedback channel estimate and the reference signal, the feedback signal estimate being used to cancel a feedback signal component of the digital input signal;

generating an amplified signal from the compressed digital transmit signal; and

transmitting the amplified signal on the second antenna of the repeater.