Digital decoder and applications thereof
View Patent ↗A decoder includes a sample rate conversion module, a decoding module, and an error sensing module. The sample rate conversion module is operably coupled to convert, based on an error feedback signal, rate of an encoded signal from a first rate to a second rate to produce a rate adjusted encoded signal. The decoding module is operably coupled to decode the rate adjusted encoded signal to produce a decoded signal. The error sensing module is operably coupled to produce the error feedback signal based on the decoded signal.
1. A decoder comprising:
at least one radio processor which converts a received radio signal into a digital radio encoded baseband signal;
a sample rate converter operably coupled to convert, based on an error feedback signal, rate of the digital radio encoded baseband signal from a first rate to a second rate to produce a digital radio rate adjusted encoded baseband signal;
a digital decoder operably coupled to decode the digital radio rate adjusted encoded baseband signal to produce a decoded radio composite signal;
a channel separator operably coupled to separate a left channel signal and a right channel signal from the decoded radio composite signal; and
an error sensor operably coupled to produce the error feedback signal based on the decoded radio composite signal, wherein the error sensor functions to:
determine a period of the decoded radio composite signal based on a known property of the decoded radio composite signal;
compare the period of the decoded radio composite signal with an ideal period; and generate the error feedback signal based on a difference between the period of the decoded radio composite signal and the ideal period.
2. The decoder of claim 1 further comprising:
a sampler operably coupled to sample an input signal at first rate to produce the digital radio encoded baseband signal.
3. The decoder of claim 1 , wherein the known property of the decoded radio composite signal comprises at least one of:
auto correlation;
cross correlation;
a pilot tone; and
a training sequence.
4. The decoder of claim 1 , wherein the error sensor comprises:
a mixer operably coupled to mix the decoded radio composite signal with a digital reference oscillation to produce a mixed signal, wherein the digital reference oscillation corresponds to a known property of the decoded radio composite signal;
a low pass filter operably coupled to filter the mixed signal to produce a near-DC feedback error signal;
a comparator operably coupled to compare offset of the near-DC feedback error signal with a DC reference; and
a feedback filter operably coupled to produce the offset to produce the error feedback signal.
5. The decoder of claim 4 , wherein the low pass filter comprises:
a multiple order cascaded integrated comb filter having a 2 N downsampling factor.
6. The decoder of claim 4 , wherein the feedback filter comprises:
a state variable filter operably coupled to filter the offset to produce a filtered offset; and
a sigma-delta modulator operably coupled to quantize the filtered offset to produce the error feedback signal.
7. A digital radio signal decoder comprising:
a low noise amplifier operably coupled to amplify a received radio signal to produce an amplified radio signal;
a first mixer operably coupled to convert the amplified radio signal into a low intermediate frequency (IF) signal based on a local oscillation;
an analog to digital converter operably coupled to convert the low IF signal into a digital low IF signal;
a digital baseband converter operably coupled to convert the digital low IF signal into a digital baseband signal;
a sample rate converter operably coupled to adjust the digital baseband signal from a first rate to a second rate based on a feedback error signal to produce a digital radio encoded signal;
a demodulator operably coupled to demodulate the digital radio encoded signal to produce a digital radio composite signal;
a channel separator operably coupled to separate a left channel signal and a right channel signal from the digital radio composite signal; and
an error sensor operably coupled to produce the feedback error signal based on the digital radio composite signal, wherein said error sensor functions to:
determine a period of the decoded radio composite signal based on a known property of the decoded radio composite signal;
compare the period of the decoded radio composite signal with an ideal period; and generate the error feedback signal based on a difference between the period of the decoded radio composite signal and the ideal period.
8. The digital radio decoder of claim 7 , wherein the known property of the decoded radio composite signal comprises at least one of:
auto correlation;
cross correlation;
a pilot tone; and
a training sequence.
9. The digital radio decoder of claim 7 , wherein the error sensor comprises:
a second mixer operably coupled to mix the decoded radio composite signal with a digital reference oscillation to produce a mixed signal, wherein the digital reference oscillation corresponds to a known property of the decoded signal;
a low pass filter operably coupled to filter the mixed signal to produce a near-DC feedback error signal;
a comparator operably coupled to determine an offset of the near-DC feedback error signal with a DC reference; and
a feedback filter operably coupled to produce the offset to produce the error feedback signal.
10. The digital radio decoder of claim 9 , wherein the low pass filter comprises:
a multiple order cascaded integrated comb filter having a 2 N downsampling factor.
11. The digital radio decoder of claim 9 , wherein the feedback filter comprises:
a state variable filter operably coupled to filter the offset to produce a filtered offset; and
a sigma-delta modulator operably coupled to quantize the filtered offset to produce the error feedback signal.
12. A digital decoder comprising:
at least one radio processor which converts a received radio signal into a digital radio encoded baseband in-phase signal and a digital radio encoded baseband quadrature signal;
first sample rate converter operably coupled to convert, based on an error feedback signal, rate of the digital radio encoded baseband in-phase signal from a first rate to a second rate to produce a rate adjusted in-phase digital radio encoded baseband signal and a rate adjusted delta-in-phase digital radio encoded baseband signal;
second sample rate converter operably coupled to convert, based on the error feedback signal, rate of the digital radio encoded baseband quadrature signal from the first rate to the second rate to produce a rate adjusted quadrature digital radio encoded baseband signal and a rate adjusted delta-quadrature digital radio encoded baseband signal;
a demodulator operably coupled to demodulate the rate adjusted in-phase radio encoded baseband signal, the rate adjusted delta-in-phase radio encoded baseband signal, the rate adjusted quadrature radio encoded baseband signal, and the rate adjusted delta-quadrature radio encoded baseband signal to produce a composite digital radio baseband signal;
a channel separator operably coupled to separate a left channel signal and a right channel signal from the composite digital radio baseband; and
an error sensor operably coupled to produce the error feedback signal based on the composite digital radio baseband signal, wherein said error sensor functions to:
determine a period of the decoded radio composite signal based on a known property of the decoded radio composite signal;
compare the period of the decoded radio composite signal with an ideal period; and
generate the error feedback signal based on a difference between the period of the decoded radio composite signal and the ideal period.
13. The digital decoder of claim 12 further comprises comprising:
a first sampler operably coupled to sample an input in-phase signal at first rate to produce the digital radio encoded baseband in-phase signal; and
a second sampler operably coupled to sample an input quadrature signal at first rate to produce the digital radio encoded baseband quadrature signal.
14. The digital decoder of claim 12 , wherein the known property of the composite digital radio baseband signal comprises at least one of:
auto correlation;
cross correlation;
a pilot tone; and
a training sequence.
15. The digital decoder of claim 12 , wherein the error sensor comprises:
a mixer operably coupled to mix the decoded composite digital radio baseband signal with a digital reference oscillation to produce a mixed signal, wherein the digital reference oscillation corresponds to a known property of the decoded composite digital radio baseband signal;
a low pass filter operably coupled to filter the mixed signal to produce a near-DC feedback error signal;
a comparator operably coupled to compare offset of the near-DC feedback error signal with a DC reference; and
a feedback filter operably coupled to produce the offset to produce the error feedback signal.
16. The digital decoder of claim 15 , wherein the low pass filter comprises:
a multiple order cascaded integrated comb filter having a 2 N downsampling factor.
17. The digital decoder of claim 16 , wherein the feedback filter comprises:
a state variable filter operably coupled to filter the offset to produce a filtered offset; and
a sigma-delta modulator operably coupled to quantize the filtered offset to produce the error feedback signal.