1. A method of calibrating a signal filter comprising the steps of:
applying a sinusoidal test tone to a replica filter in the transition band of the replica filter;
calibrating the replica filter amplitude at the test tone frequency and producing replica filter calibration values;
using the replica filter calibration values to calibrate the signal filter.
2. The method of claim 1 further comprising the steps of:
determining the parametric tracking relationship between the signal filter and the replica filter;
programming the signal filter using the filter calibration values and the tracking relationship.
3. The method of claim 1 further comprising the steps of:
measuring the temperature of the signal filter; and
detecting a change in temperature and performing a new calibration of the signal filter if the temperature change exceeds a predetermined value.
4. The method of claim 1 wherein the replica filter is continuously calibrated and the signal filter is calibrated when the replica filter calibration values change.
5. An integrated circuit filter with calibration comprising:
a main signal path filter with programmable characteristics;
a replica filter with programmable characteristics, wherein the replica filter tracks parameter changes occurring in the main signal path filter;
a sinusoidal test tone generator that injects a tone into the replica filter in the transition band;
a detector for detecting the amplitude output of the replica filter and setting a programmable characteristic of the replica filter; and
means for setting the main signal path filter programmable characteristics with settings used for the replica filter.
6. The integrated circuit filter of claim 5 further comprising:
a temperature sensor wherein calibration of the main signal path filter is performed if the temperature changes by a predetermined amount.
7. The integrated circuit filter of claim 5 wherein the test tone generator has an adjustable frequency.
8. A method of calibrating a programmable filter used in a tuner to a desired frequency band, the method comprising the steps of:
generating a sinusoidal test signal, the test signal frequency selected to be in the transition region of the desired frequency band;
applying the test signal to the programmable filter;
applying the test signal to an attenuator;
comparing amplitudes of the outputs of the programmable filter and the attenuator;
adjusting the programmable filter corner frequency to cause the filter output level to match the attenuator output level.
9. The method of claim 8 wherein the programmable filter is a replica filter and calibration values for the replica filter are used to program a signal filter.
10. The method of claim 8 wherein the programmable filter is a main filter.
11. The method of claim 8 wherein the attenuator has a programmable attenuation level.
12. The method of claim 8 wherein the test signal frequency is programmable.
13. The method of claim 8 further comprising the steps of:
measuring the filter temperature;
initiating a calibration if the temperature changes by more than a predetermined amount.
14. The method of claim 13 wherein the step of adjusting the programmable filter corner frequency starts at the filter frequency programmed when calibration begins and the corner frequency is adjusted in the direction determined by the temperature change direction.
15. A calibrator for a programmable filter used in a tuner to set a desired frequency band, the calibrator comprising:
a frequency generator for generating a sinusoidal test signal, the test signal frequency selected to be in the transition region of the desired frequency band;
the test signal coupled to the programmable filter;
the test signal coupled to an attenuator;
a comparing circuit that compares the amplitude output of the programmable filter and the attenuator; and
a control circuit that adjusts the programmable filter corner frequency to cause the filter output level to match the attenuator output level.
16. The calibrator of claim 15 further comprising a temperature sensor that initiates a filter calibration when the temperature changes by more than a predetermined amount.
17. The calibrator of claim 15 wherein the attenuator is programmable.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method comprising:
receiving, at a receiver, an input signal from a transmitter, wherein the input signal has been encoded in the transmitter with an underlying quadrature amplitude modulation (QAM) constellation that is unknown to the receiver;
selecting, by candidate selector circuitry at the receiver, a current candidate QAM constellation from a plurality of candidate QAM constellations, wherein the plurality of candidate QAM constellations comprises the underlying QAM constellation with which the received input signal was encoded, and wherein each QAM constellation comprises a plurality of points;
computing, by error computing circuitry, an error for a signal responsive to the input signal based on the current candidate QAM constellation; and
comparing, by error comparison circuitry, the error to a threshold error value.
2. The method of claim 1 further comprising:
selecting a previous candidate QAM constellation from the plurality of candidate QAM constellations; and
identifying the previous candidate QAM constellation as a recovered QAM constellation based on a result of the comparing.
3. The method of claim 2 wherein the identifying occurs if the computed error is substantially greater than the threshold error value.
4. The method of claim 2 wherein the selecting the current candidate QAM constellation comprises setting a candidate QAM constellation index to a number corresponding to the current candidate QAM constellation.
5. The method of claim 1 further comprising comparing a measured occurrence rate of the signal responsive to the input signal at a selected point in the current candidate QAM constellation to an occurrence threshold value.
6. The method of claim 5 wherein the comparing the measured occurrence rate to the occurrence threshold value occurs if the computed error is substantially less than the threshold error value.
7. The method of claim 5 further comprising setting a next threshold error value to be substantially equal to the computed error.
8. The method of claim 1 further comprising selecting a next candidate QAM constellation if the computed error is substantially less than the threshold error value.
9. The method of claim 1 further comprising setting the threshold error value to be substantially equal to infinity.
10. Circuitry for receiving an input signal, the circuitry comprising:
a receiver for receiving an input signal from a transmitter, wherein the input signal has been encoded in the transmitter with an underlying quadrature amplitude modulation (QAM) constellation that is unknown to the receiver;
candidate selector circuitry at the receiver operable to select a current candidate QAM constellation from a plurality of candidate QAM constellations, wherein the plurality of candidate QAM constellations comprises the underlying QAM constellation with which the received input signal was encoded, and wherein each QAM constellation comprises a plurality of points;
error computing circuitry responsive to the candidate selector circuitry and operable to compute an error of a signal responsive to the input signal based on the current candidate QAM constellation; and
error comparison circuitry responsive to the error computing circuitry and operable to compare the computed error to a threshold error value.
11. The circuitry of claim 10 further comprising identification circuitry responsive to the error comparison circuitry and operable to identify a previous candidate QAM constellation from the plurality of candidate QAM constellations as a recovered QAM constellation based on a result of the error comparison circuitry, wherein the candidate selector circuitry is further operable to select the previous candidate QAM constellation.
12. The circuitry of claim 11 wherein the identification circuitry is operable to identify the previous candidate QAM constellation as the recovered QAM constellation if the computed error is substantially greater than the threshold error value.
13. The circuitry of claim 11 wherein the candidate selector circuitry is further operable to set a candidate QAM constellation index to a number corresponding to the current candidate QAM constellation.
14. The circuitry of claim 10 further comprising occurrence rate comparison circuitry responsive to the computed error comparison circuitry and operable to compare a measured occurrence rate of the signal responsive to the input signal at a selected point in the current candidate QAM constellation to an occurrence threshold value.
15. The circuitry of claim 14 wherein the occurrence rate comparison circuitry is operable to compare the measured occurrence rate to the occurrence threshold value if the computed error is substantially less than the threshold error value.
16. The circuitry of claim 14 further comprising threshold setting circuitry responsive to the occurrence rate comparison circuitry and operable to set a next threshold error value to be substantially equal to the computed error.
17. The circuitry of claim 10 wherein the candidate selector circuitry is responsive to the error comparison circuitry and is further operable to select a next candidate QAM constellation if the computed error is substantially less than the threshold error value.
18. The circuitry of claim 10 further comprising threshold setting circuitry operable to set the threshold error value to be substantially equal to infinity, wherein the error circuitry is further responsive to the threshold setting circuitry.
19. A media player comprising the circuitry of claim 10.
20. A phone comprising the circuitry of claim 10.