Own Transmitter Interference Tolerant Transceiver and Receiving Methods

• US 20100159837A1
• Filed: 12/19/2008
• Published: 06/24/2010
• Est. Priority Date: 12/19/2008
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Mattisson, Sven, Dent, Paul Wilkinson
• Granted Patent: US 7,995,973 B2
• Time in Patent Office: Days
• US Class Current: 455/63.100
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

Circuits and methods are disclosed for reducing interference from transmitter leakage in a radio transceiver. An exemplary method for reducing interference from transmitter leakage in a radio transceiver comprises downconverting, filtering, and sampling a radio frequency signal comprising a desired signal and a transmitter leakage signal to obtain a sampled signal of interest. The method further comprises generating a sampled distortion signal estimate that estimates one or more distortion products of the transmitter leakage signal, such as a squared amplitude obtained from a square-law device or corresponding digital function. Further, the method comprises dividing the sampled distortion signal estimate and the sampled signal of interest into a plurality of frequency channels. Finally, for a selected number of frequency channels, the method comprises combining the sampled distortion signal estimate for a frequency channel with the corresponding sampled signal of interest for the same frequency channel to obtain interference-reduced signal samples for the frequency channel.

Claims

1. A radio transceiver, comprising:

a receiver unit configured to downconvert, filter, and sample a radio frequency signal comprising a desired signal and a transmitter leakage signal to obtain a sampled signal of interest;

a distortion estimation unit configured to generate a sampled distortion signal estimate of one or more distortion products of the transmitter leakage signal;

first and second transform units to divide the sampled signal of interest and the sampled distortion signal estimate, respectively, into a plurality of frequency channels; and

an interference subtraction unit configured to combine the sampled distortion signal estimate for each of a selected number of frequency channels with the corresponding sampled signal of interest for each of the same frequency channels to obtain interference-reduced signal samples for each of said selected number of frequency channels.

2. The radio transceiver of claim 1, wherein the receiver comprises one of a homodyne downconverter and an intermediate frequency downconverter for downconverting the radio frequency signal.

3. The radio transceiver of claim 1, wherein the transmitter leakage signal has a modulation bandwidth, and wherein the receiver unit is configured to downconvert the radio frequency signal to an intermediate frequency less than the modulation bandwidth of the transmitter leakage signal.

4. The radio transceiver of claim 1, wherein the distortion estimation unit comprises one or more analog non-linear components configured to produce estimates of non-linear products of the transmitter leakage from a transmitter signal and an analog-to-digital converter to produce the sampled distortion signal estimate from the non-linear products.

5. The radio transceiver of claim 1, wherein the distortion estimation unit comprises a digital distortion processor configured to generate the sampled distortion signal estimate.

6. The radio transceiver of claim 1, wherein the distortion estimation unit further comprises one or more filters matched to one or more receive filters in the receiver unit.

7. The radio transceiver of claim 1, wherein the first and second transform units comprise first and second discrete Fourier transform units.

8. The radio transceiver of claim 1, wherein the interference subtraction unit comprises:

a first correlator configured to correlate the sampled signal of interest for each of said selected number of frequency channels with the corresponding sampled distortion signal estimate for each of the same frequency channels to obtain a first factor for each of said selected number of frequency channels;

a second correlator configured to correlate the sampled distortion signal estimate for each of said selected number of frequency channels with itself to obtain a second factor for each of said selected number of frequency channels;

a scaling unit configured to scale the sampled distortion signal estimate for each of a second selected number of frequency channels based on the first and second factors; and

a subtracting unit configured to subtract the scaled sampled distortion signal estimate for each of said second selected number of frequency channels from the corresponding sampled signal of interest for each of the same second selected number of frequency channels to obtain the interference-reduced signal samples for each of said second selected number of frequency channels.

9. The radio transceiver of claim 8, wherein the interference subtraction unit further comprises:

a first averaging unit to average the first factor for each of said selected number of frequency channels over a plurality of OFDM symbol periods;

a second averaging unit to average the second factor for each of said selected number of frequency channels over a plurality of OFDM symbol periods; and

a divider to divide the averaged first and second factors generated for each of said selected number of frequency channels to generate a scaling factor for each of said selected number of frequency channels.

10. The radio transceiver of claim 9, wherein the selected number of frequency channels comprises all of the plurality of frequency channels, and wherein the second selected number of frequency channels equals the selected number of frequency channels.

11. The radio transceiver of claim 9, wherein the selected number of frequency channels comprises a subset of the plurality of frequency channels comprising fewer than the plurality of frequency channels.

12. The radio transceiver of claim 11, wherein the scaling unit is configured to scale the sampled distortion signal for each of the selected number of frequency channels using the scaling factor generated for each of the same frequency channels and to reuse the determined scaling factors to scale the sampled distortion signal for the remaining frequency channels.

13. A method for reducing interference from transmitter leakage in a radio transceiver, the method comprising:

downconverting, filtering, and sampling a radio frequency signal comprising a desired signal and a transmitter leakage signal to obtain a sampled signal of interest;

generating a sampled distortion signal estimate of one or more distortion products of the transmitter leakage signal;

dividing each of the sampled signal of interest and the sampled distortion signal estimate into a plurality of frequency channels; and

combining the sampled distortion signal estimate for each of a selected number of frequency channels with the corresponding sampled signal of interest for each of the same frequency channels to obtain interference-reduced signal samples for each of said selected number of frequency channels.

14. The method of claim 13, wherein downconverting, filtering, and sampling the radio frequency signal comprises downconverting the radio frequency signal to one of a baseband frequency and an intermediate frequency.

15. The method of claim 13, wherein downconverting, filtering, and sampling the radio frequency signal comprises downconverting the radio frequency signal to an intermediate frequency less than a modulation bandwidth of the transmitter leakage signal.

16. The method of claim 13, wherein generating the sampled distortion signal estimate comprises producing estimates of non-linear products of the transmitter leakage from a transmitter signal, using one or more analog non-linear components, and sampling the non-linear products to produce the sampled distortion signal estimate.

17. The method of claim 13, wherein generating the sampled distortion signal estimate comprises generating the sampled distortion signal estimate from a digital transmitter modulation signal.

18. The method of claim 13, further comprising filtering the sampled distortion signal estimate using one or more filters configured to match the response of one or more filters in the receiver circuit.

19. The method of claim 13, wherein dividing each of the sampled signal of interest and the sampled distortion signal estimate into a plurality of frequency channels comprises applying a discrete Fourier transform to each of the sampled signal of interest and the sampled distortion signal estimate.

20. The method of claim 13, wherein combining the sampled distortion signal estimate with the sampled signal of interest comprises:

correlating the sampled signal of interest for each of said selected number of frequency channels with the corresponding sampled distortion signal estimate for each of the same frequency channels to obtain a first factor for each of said selected number of frequency channels;

correlating the sampled distortion signal estimate for each of said selected number of frequency channels with itself to obtain a second factor for each frequency of said selected number of frequency channels;

scaling the sampled distortion signal estimate for each of a second selected number of frequency channels based on the first and second factors; and

subtracting the scaled sampled distortion signal estimate for each of said second selected number of frequency channels from the corresponding sampled signal of interest for each of the same second selected number of frequency channels to obtain the interference-reduced signal samples for each of said second selected number of frequency channels.

21. The method of claim 20, further comprising:

averaging the first factor for each of said selected number of frequency channels over a plurality of OFDM symbol periods;

averaging the second factor for each of said selected number of frequency channels over a plurality of OFDM symbol periods; and

dividing the averaged first and second factors generated for each of said selected number of frequency channels to generate a scaling factor for each of said selected number of frequency channels.

22. The method of claim 21, wherein the selected number of frequency channels comprises all of the plurality of frequency channels, and wherein the second selected number of frequency channels equals the selected number of frequency channels.

23. The method of claim 21, wherein the selected number of frequency channels comprises a subset of the plurality of frequency channels comprising fewer than the plurality of frequency channels.

24. The method of claim 23, wherein scaling the sampled distortion signal comprises scaling the sampled distortion signal for each of the selected number of frequency channels using the scaling factor generated for each of the same frequency channels and reusing the determined scaling factors to scale the sampled distortion signal for the remaining frequency channels.