Pilot tracking module operable to adjust interpolator sample timing within a handheld audio system
View Patent ↗A processing module including an interpolator, a demodulator, and a tracking module. The interpolator applies a feedback signal to a first digitized signal having a first data rate to produce a second digitized signal having a second data rate. The demodulator processes the second digitized signal to produce a digital composite signal having a timing component. The tracking module mixes the digital composite signal with a reference signal and produces the feedback signal. The tracking module may include a mixer, a filter, a comparator, a loop filter and a quantizer. The mixer and filter mixes an input signal with a reference signal to provide a filtered timing error signal. The comparator compares the timing error signal with a reference signal and produces an offset signal. The loop filter processes the offset signal to produce a filtered offset. The quantizer processes the filtered offset to produce the feedback signal.
1. A pilot tracking module operable to produce a feedback signal used to adjust an input signal, comprising:
a mixer, operable to mix an the input signal containing a timing component with a reference signal;
a filter operably coupled to the mixer, wherein the filter is operable to filter a timing error signal from an output of the mixer;
a comparator operably coupled to the filter, wherein the comparator is operable to compare the timing error signal with a null signal and produce an offset signal;
a loop filter operably coupled to the comparator, wherein the loop filter processes the offset signal to produce a filtered offset; and wherein the loop filter further comprises: a first gain module;
a second gain module, wherein the first and second gain modules receive an output of the comparator;
an integrator operably coupled to the second gain module, wherein the integrator receives an output of the second gain module;
a first summing module, operably coupled to the first gain module and integrator, and wherein the first summing module is operable to sum an output of the first gain module and an output of the integrator; and
a second summing module operably coupled to the first summing module, wherein the second summing module sums an output of the first gain module and a level signal, and wherein the second summing module normalizes an output of the loop filter for the quantizer; and
a quantizer operably coupled to the loop filter, wherein the quantizer receives and processes the filtered offset to produce the feedback signal used to adjust the input signal.
2. The pilot tracking module of claim 1 , further comprising:
an interpolator operable to receive the feedback signal and a first digitized near baseband signal having a first data rate, wherein the interpolator applies the feedback signal to the received first digitized near baseband signal to produce a second digitized signal having a second data rate; and
a demodulator operably coupled to the interpolator, wherein the demodulator is operable to process the second digitized signal to produce the input signal containing the timing component.
3. The pilot tracking module of claim 1 , wherein the feedback signal is based on a comparison of the timing component and the reference signal.
4. The pilot tracking module of claim 1 , wherein the timing component corresponds to a known property of the input signal and the reference signal comprises a digital reference oscillation.
5. The pilot tracking module of claim 1 , wherein the timing component is a 19K tone and the reference signal comprises a digitized 19k tone.
6. The pilot tracking module of claim 1 , wherein the filter comprises:
a cascaded integrated cone (CIC) filter;
down sampling by N module; and
a leaky bucket integrator, wherein the CIC filter, down sampling by N module and leaky bucket integrator are coupled in series.
7. The pilot tracking module of claim 2 , wherein the digitized near baseband signal comprises a digitized frequency modulated composite signal.
8. A method of operating a pilot tracking module to produce a feedback signal used to adjust an input signal, comprising:
mixing a reference signal with the input signal which has a timing component and providing a timing error signal;
filtering the timing error signal and providing a filtered error signal;
comparing the filtered error signal with a null signal and providing an offset signal;
processing the offset signal and providing a filtered offset; wherein said processing the offset signal comprises: receiving, by a first gain module, the offset signal and providing a first output; receiving, by a second gain module, the offset signal and providing a second output; integrating the second output and providing a third output; summing the first output and the third output and providing a fourth output; and summing the fourth output with a timing difference signal.
quantizing the filtered offset and providing a feedback signal; and using the feedback signal to adjust the input signal.
9. The method of claim 8 , further comprising:
applying the feedback signal to a first digitized near baseband signal having a first data rate and providing a second digitized signal having a second data rate; and
processing the second digitized signal and providing the input signal.
10. The method of claim 9 , wherein said applying the feedback signal to a first digitized near baseband signal comprises applying the feedback signal to a digitized frequency modulated composite signal.
11. The method of claim 8 , wherein said providing the feedback signal is based on comparing the timing component with the reference signal.
12. The method of claim 8 , wherein said mixing the input signal comprises mixing a known timing component with a digital reference oscillation.
13. The method of claim 8 , wherein said mixing the input signal comprises mixing a 19K tone with a digitized 19k tone.
14. The method of claim 8 , wherein said filtering comprises:
filtering using a cascaded integrated cone (CIC) filter and providing a first output;
down sampling using a down sampling by N module and providing a second output; and
integrating the second output using a leaky bucket integrator.