Method and apparatus for radio receiver equalization
View Patent ↗A method, apparatus and computer program product are configured to provide calibration accuracy in an analog filter. In this regard, a method is provided that includes estimating a cutoff frequency for an analog filter. The method further includes causing a filter tuning word to be modified based on the estimated cutoff frequency for the analog filter. The method also includes determining a residual cutoff frequency mismatch for the analog filter. The method also includes causing an equalizer configuration to be selected for a digital filter based on the determined residual cutoff frequency mismatch.
1. A method comprising:
estimating a cutoff frequency for an analog filter;
causing a filter tuning word to be modified based on the estimated cutoff frequency for the analog filter;
determining a residual cutoff frequency mismatch for the analog filter; and
causing an equalizer configuration to be selected for a digital filter based on the determined residual cutoff frequency mismatch.
2. A method of claim 1 wherein estimating the cutoff frequency further comprises:
causing test tones to be injected at a plurality of test tone frequencies, the test tones to be injected prior to passing through the analog filter; and
measuring the magnitude of the injected test tones at a plurality of test tone frequencies after the injected test tones pass through the analog filter.
3. A method of claim 2 wherein estimating the cutoff frequency further comprises iteratively searching a test tone frequency where gain drops by 3 dB relative to 100 kHz.
4. A method of claim 1 , wherein an equalizer configuration is chosen that best compensates for the determined residual cutoff frequency mismatch.
5. A method of claim 1 further comprises causing the residual cutoff frequency mismatch to be categorized; and causing the equalizer configuration to be selected based on the categorized residual cutoff frequency mismatch.
6. A method of claim 5 , wherein a residual cutoff frequency mismatch o is categorized into at least one of the categories defined by o<15 kHz, −15 kHz<=o<5 kHz, −5 kHz<=o<5 kHz or 15 kHz<=o.
7. A method of claim 1 wherein in an instance in which a gain control word is equal to a predetermined value, then an offset may be added to the categorized residual cutoff frequency mismatch.
8. An apparatus comprising:
a processor and
a memory including software, the memory and the software configured to, with the processor, cause the apparatus to at least:
estimate a cutoff frequency for an analog filter;
cause a filter tuning word to be modified based on the estimated cutoff frequency for the analog filter;
determine a residual cutoff frequency mismatch for the analog filter; and
cause an equalizer configuration to be selected for a digital filter based on the determined residual cutoff frequency mismatch.
9. An apparatus according to claim 8 wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus to:
cause test tones to be injected at a plurality of test tone frequencies, the test tones to be injected prior to passing through the analog filter; and
measure the magnitude of the injected test tones at a plurality of test tone frequencies after the injected test tones pass through the analog filter to estimate the cutoff frequency.
10. An apparatus according to claim 9 wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus to iteratively search a test tone frequency where gain drops by 3 dB relative to 100 kHz.
11. An apparatus according to claim 8 , wherein an equalizer configuration is chosen that best compensates for the determined residual cutoff frequency mismatch.
12. An apparatus according to claim 8 wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus to cause the residual cutoff frequency mismatch to be categorized; and cause the equalizer configuration to be selected based on the categorized residual cutoff frequency mismatch.
13. An apparatus according to claim 12 , wherein a residual cutoff frequency mismatch o is categorized into at least one of the categories defined by o<15 kHz, −15 kHz<=o<5 kHz, −5 kHz<=o<5 kHz or 15 kHz<=o.
14. An apparatus according to claim 8 wherein in an instance in which a gain control word is equal to a predetermined value, then an offset may be added to the categorized residual cutoff frequency mismatch.
15. A computer program product comprising:
at least one computer readable non-transitory memory medium having program code stored thereon, the program code which when executed by an apparatus cause the apparatus at least to:
estimate a cutoff frequency for an analog filter;
cause a filter tuning word to be modified based on the estimated cutoff frequency for the analog filter;
determine a residual cutoff frequency mismatch for the analog filter; and
cause an equalizer configuration to be selected for a digital filter based on the determined residual cutoff frequency mismatch.
16. A computer program product according to claim 15 , further comprising program code instructions to:
cause test tones to be injected at a plurality of test tone frequencies, the test tones to be injected prior to passing through the analog filter; and
measure the magnitude of the injected test tones at a plurality of test tone frequencies after the injected test tones pass through the analog filter to estimate the cutoff frequency.
17. A computer program product according to claim 16 further comprising program code instructions to iteratively search a test tone frequency where gain drops by 3 dB relative to 100 kHz.
18. A computer program product according to claim 15 , wherein an equalizer configuration is chosen that best compensates for the determined residual cutoff frequency mismatch.
19. A computer program product according to claim 15 further comprising program code instructions to cause the residual cutoff frequency mismatch to be categorized; and cause the equalizer configuration to be selected based on the categorized residual cutoff frequency mismatch.
20. A computer program product according to claim 15 wherein in an instance in which a gain control word is equal to a predetermined value, then an offset may be added to the categorized residual cutoff frequency mismatch.