System and method for synchronous processing of analog and digital pathways in a digital radio receiver
A method of processing a digital radio broadcast signal in a digital radio receiver includes: receiving baseband signal samples at a first sample rate; adjusting the sample rate of the baseband signals based on a difference between a receiver clock and a transmitter clock to produce adjusted baseband signal samples at a second sample rate; filtering the adjusted baseband signal samples to separate a digital component of the samples and an analog component of the samples, wherein the digital component and the analog component are synchronous; and separately demodulating the digital component and the analog component to produce a digital output signal and an analog output signal. A receiver that uses the method is also provided.
1. A method of processing a digital radio broadcast signal in a digital radio receiver comprising:
receiving baseband signal samples at a first sample rate;
using an asynchronous sample rate converter to adjust the sample rate of the baseband signal samples based on a sample rate correction value derived from both a sample slip and a sample rate offset between a receiver and a transmitter to produce adjusted baseband signal samples at a second sample rate to drive both the sample slip and the sample rate offset to zero;
filtering the adjusted baseband signal samples to separate a digital component of the samples and an analog component of the samples, wherein the digital component and the analog component are synchronous; and
separately demodulating the digital component and the analog component to produce a digital output signal and an analog output signal.
2. The method of claim 1 , wherein the step of using an asynchronous sample rate converter to adjust the sample rate of the baseband signal samples further comprises:
resampling the baseband signal samples using the asynchronous sample rate converter.
3. The method of claim 1 , further comprising:
using a Kalman filter to estimate the sample slip and the sample rate offset.
4. The method of claim 3 , wherein a linear quadratic regulator (LQR) algorithm is used to determine the correction value.
5. The method of claim 1 , wherein the step of filtering the adjusted baseband signal samples to separate a digital component of the samples and an analog component of the samples is implemented in an isolation filter.
6. The method of claim 1 , further comprising:
using a symbol time adjustment module during an initial phase of tracking to drive the sample slip toward zero.
7. The method of claim 6 , wherein:
the symbol time adjustment module adjusts samples of only the digital component.
8. The method of claim 1 , further comprising:
detecting a loss of the digital radio broadcast signal;
stopping the step adjusting the sample rate of the baseband signal samples;
detecting a come back of the digital radio broadcast signal; and
restarting the step adjusting the sample rate of the baseband signal samples using a reset tracking algorithm.
9. A receiver for processing a digital radio broadcast signal, the receiver comprising;
a processing system including an asynchronous sample rate converter, an isolation filter, an OFDM demodulator, and an analog demodulator configured to receive baseband signal samples at a first sample rate; adjust the sample rate of the baseband signal samples based on a sample rate correction value derived from both a sample slip and a sample rate offset between a receiver and a transmitter to produce adjusted baseband signal samples at a second sample rate and to drive both the sample slip and the sample rate offset to zero; filter the adjusted baseband signal samples to separate a digital component of the samples and an analog component of the samples, wherein the digital component and the analog component are synchronous; and separately demodulate the digital component and the analog component to produce a digital output signal and an analog output signal.
10. The receiver of claim 9 , wherein the processing system is further configured for adjusting the sample rate of the baseband signal samples including resampling the baseband signal samples.
11. The receiver of claim 10 , wherein the processing system uses a Kalman filter to estimate the sample slip and the sample rate offset.
12. The receiver of claim 11 , wherein the processing system uses a linear quadratic regulator (LQR) algorithm to determine the correction value.
13. The receiver of claim 9 , wherein the processing system further comprises a symbol time adjustment module configured to drive the sample slip toward zero during an initial phase of tracking.
14. The receiver of claim 13 , wherein the symbol time adjustment module adjusts samples of only the digital component.
15. An article of manufacture comprising a computer readable storage medium containing executable instructions adapted to a cause a processing system to execute the method of claim 1 .