Homodyne radio receiver having DC compensation

• US 6,654,596 B1
• Filed: 01/27/2000
• Issued: 11/25/2003
• Est. Priority Date: 01/27/1999
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Stenström, Sven Erik Niklas, Jakobsson, Jan Peter
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Mehrpour, Naghmeh
• Application Number:
  US09/492,381
• Time in Patent Office: 1,398 Days
• Field of Search: 455/324, 455/278.1, 455/317, 455/208, 455/202, 455/214, 455/222, 455/228, 455/234.2, 455/236.1, 455/251.1, 455/256, 455/277.2, 455/284, 455/305, 375/319, 375/322, 375/340, 329/300, 329/304
• US Class Current: 455/324
• CPC Class Codes: H03D 3/008 Compensating DC offsets
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

A homodyne radio receiver apparatus receives radio frequency signal bursts containing a number of symbols and generates digital samples of at least a complex base band signal (I and Q) of each signal burst. A DC compensator comprises an average calculator (8,8′), which determines an average DC-level of said samples, and a signed square sum calculator (9,9′), which calculates a signed square sum of a plurality of said samples and weights the square sum by a compensation factor. Correction means (10,10′) subtracts the square sum from an output of said average calculator means for forming the DC-level estimate.

Claims

1. A homodyne radio receiver apparatus, comprising a homodyne radio receiver device (1,2,3,4,5,5′

) for receiving radio frequency signal bursts of a number of symbols and generating digital samples of at least a complex base band signal (I and Q) of each signal burst, and DC compensation means (7) operatively connected to said homodyne radio receiver device (1,2,3,4,5,5′

) for determining a DC-level estimate of said samples, wherein said DC compensation means (7) comprises average calculator means (8,8′

) for calculating an average DC-level of said samples, characterized in that said DC compensation means (7) further comprises signed square sum calculator means (9,9′

) for calculating a signed square sum of a plurality of said samples and weighting said square sum by a compensation factor (A), and correction means (10,10′

) for subtracting an output of said square sum calculator means (9,9′

) from an output of said average calculator means (8,8′

) for forming said DC-level estimate.

2. A homodyne radio receiver apparatus according to claim 1, characterized in that said compensation factor (A) is −

1 to −

3.

6. A homodyne radio receiver apparatus according to claim 1, characterized in that said DC compensation means (7;

17) is a digital signal processing device.

7. A homodyne radio receiver apparatus according to claim 1, characterized in that said homodyne radio receiver device comprises signal receiver means (1,2,3;

11,12,13) operatively connected to a quadrature down-converter (4;

14) for down-converting said signal burst to at least a complex base band signal (I and Q), and an analog-to-digital converter (5,5′

;

15,15′

) for generating said samples.

8. A homodyne radio receiver apparatus according to claim 1, characterized in that said correction means (10,10′

;

20,20′

) is adapted to subtract said DC-level estimate from each sample.

3. A homodyne radio receiver apparatus, comprising a homodyne radio receiver device (11,12,13,14,15,15′

) for receiving radio frequency signal bursts containing a number of symbols and generating digital samples of at least a complex base band signal (I and Q) of each signal burst, and DC compensation means (17) operatively connected to said homodyne radio receiver device (11,12,13,14,15,15′

) for determining a DC-level estimate of said samples, wherein said DC compensation means (17) comprises average calculator means (18,18′

) for calculating an average DC-level of said samples, characterized in that said DC compensation means (7) further comprises signed sum calculator means (19,19′

) for calculating a signed sum or a plurality of said samples and weighting said sum by a compensation factor, and correction means (20,20′

) for subtracting an output of said signed sum calculator means (19,19′

) from an output of said average calculator means (18,18′

) for forming said DC-level estimate.

4. A homodyne radio receiver apparatus according to claim 3, characterized in that said samples having an amplitude value of at least 40% of the amplitude of said modulating signal.

5. A homodyne radio receiver apparatus according to claim 4, characterized in that said compensation factor is 0.0055-0.0065.

9. A signal processor for compensating a DC-level of a radio frequency signal bursts received in a homodyne radio receiver, comprising signal receiving means for receiving digital samples of at least a complex base band signal (I and Q) generated by said homodyne radio receiver, DC compensation means (7) for determining a DC-level estimate of said samples, average calculator means (8,8′

) for calculating an average DC-level of said samples, characterized by signed square sum calculator means (9,9′

) for calculating a signed square sum of a plurality of said samples and weighting said square sum by a compensation factor, and correction means (10,10′

) for subtracting an output of said square sum calculator means (9,9′

) from an output of said average calculator means (8,8′

) for forming said DC-level estimate.

10. A signal processor according to claim 9, characterized in that said compensation factor is −

1 to −

3.

14. A signal processor according to claim 9 characterized in that said homodyne radio receiver device comprises signal receiver means (1,2,3;

11,12,13) operatively connected to a quadrature down-converter (4;

14) for down-converting said signal burst to at least a complex base band signal (I and Q), and an analog-to-digital converter (5,5′

;

15,15′

) for generating said samples.

15. A signal processor according to claim 9, characterized in that said correction means (10,10′

;

20,20′

) is adapted to subtract said DC-level estimate from each sample.

11. A signal processor for compensating a DC-level of a radio frequency signal bursts received in a homodyne radio receiver, comprising signal receiving means for receiving digital samples of at least a complex base band signal (I and Q) generated by said homodyne radio receiver, DC compensation means (17) for determining a DC-level estimate of said samples, average calculator means (18,18′

) for calculating an average DC-level of said samples, characterized by signed sum calculator means (19,19′

) for calculating a signed sum of a plurality of said samples and weighting said sum by a compensation factor, and correction means (20,20′

) for subtracting an output of said signed sum calculator means (19,19′

) from an output of said average calculator means (18,18′

) for forming said DC-level estimate.

12. A signal processor according to claim 11, characterized in that said samples having an amplitude value of at least 40% of the amplitude of said modulating signal.

13. A signal processor according to claim 12, characterized in that said compensation factor is 0.0055-0.0065.

16. A method of DC-level estimation in a homodyne radio receiver apparatus, wherein a radio frequency signal burst containing a number of symbols is received in the apparatus, digital samples of at least a complex base band signal (I and Q) of each signal burst are generated, and an average DC-level estimate of said samples is determined, characterized by the further steps of:

determining a signed square sum of a plurality of said samples and weighting said square sum by a compensation factor, and subtracting said signed square sum from said average DC-level for forming said DC-level estimate.

17. A method according to claim 16, characterized in that said compensation factor is −

1 to −

3.

18. A method of DC level estimation in a homodyne radio receiver apparatus, wherein a radio frequency signal burst containing a number of symbols is received in the apparatus, digital samples of at least a complex base band signal (I and Q) of each signal burst are generated, and an average DC-level estimate of said samples is determined, characterized by the further steps of:

determining a signed sum of a plurality of said samples and weighting said signed sum by a compensation factor, and subtracting said weighted signed sum from said averaged DC-level for forming said DC-level estimate.

19. A method according to claim 18, characterized in that said compensation factor is 0.0055-0.0065.

20. A method according to claim 18, characterized in that said compensation factor is 0.006.