Method and apparatus for implementing seek and scan functions for an FM digital radio signal
View Patent ↗A method for detecting a digital radio signal includes the steps of receiving the digital radio signal, developing a correlation waveform having a peak that corresponds to a symbol boundary, normalizing the correlation waveform, calculating a peak value of the normalized correlation waveform, and dwelling on the received digital radio signal when the peak value exceeds a predetermined threshold. A receiver that performs the method is also provided.
1. A method for detecting a digital radio signal, the method comprising the steps of:
receiving a digital radio signal representing a series of symbols;
developing a correlation waveform having a peak that corresponds to a symbol boundary;
normalizing the correlation waveform;
calculating a peak value of the normalized correlation waveform; and
dwelling on the received digital radio signal when the peak value exceeds a predetermined threshold, wherein the digital radio signal includes a sideband, and the symbols are received on the sideband.
2. The method of claim 1 , wherein the digital radio signal includes upper and lower sidebands, and the step of developing a correlation waveform is performed for the upper and lower sidebands of the digital radio signal to produce an upper sideband correlation waveform and a lower sideband correlation waveform.
3. The method of claim 2 , wherein the step of normalizing the correlation waveform is performed for the upper and lower sideband correlation waveforms.
4. The method of claim 3 , wherein the step of calculating the peak value of the normalized correlation waveform is performed for the normalized upper and lower sideband correlation waveforms.
5. The method of claim 4 , wherein the step of dwelling on the received digital radio signal is performed when at least one of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a predetermined threshold.
6. The method of claim 4 , wherein the step of dwelling on the received digital radio signal is performed when:
at least one of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a first predetermined threshold, or
the sum of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a second predetermined threshold.
7. The method of claim 4 , further comprising the steps of:
determining the peak index of the normalized upper sideband correlation waveform and the peak index of the normalized lower sideband correlation waveform;
calculating a peak index delta representative of the difference between the peak indices for the normalized upper and lower sideband correlation waveforms; and
dwelling on the received digital radio signal when:
the sum of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a first predetermined threshold and the peak index delta is less than a second predetermined threshold.
8. The method of claim 1 , wherein the digital radio signal includes upper and lower sidebands, and the samples received on the upper and lower sidebands are processed separately.
9. The method of claim 8 , further comprising the step of:
filtering each sideband in the digital radio signal prior to the step of developing a correlation waveform.
10. The method of claim 9 , wherein the filtering step is performed using a finite impulse response filter.
11. The method of claim 1 , wherein the correlation waveform is based on amplitudes of samples of leading and trailing portions of orthogonal frequency division multiplexed symbols.
12. The method of claim 11 , wherein the amplitudes of the leading and trailing portions of the orthogonal frequency division multiplexed symbols are tapered.
13. The method of claim 1 , wherein the correlation waveform is based on a cyclic prefix applied to orthogonal frequency division multiplexed symbols.
14. A method for detecting a digital radio signal, the method comprising the steps of:
receiving a digital radio signal representing a series of symbols;
developing a correlation waveform having a peak that corresponds to a symbol boundary;
normalizing the correlation waveform;
calculating a peak value of the normalized correlation waveform;
dwelling on the received digital radio signal when the peak value exceeds a predetermined threshold; and
setting a status flag to indicate if the receiver should dwell on the received digital radio signal or tune to another channel.
15. A receiver for detecting a digital radio signal, the receiver comprising:
an input for receiving a digital radio signal representing a series of symbols; and
a processor for calculating the peak value of a normalized correlation waveform having a peak that corresponds to a symbol boundary, and for causing the receiver to dwell on the received digital radio signal when a peak value exceeds a predetermined threshold, wherein the digital radio signal includes a sideband, and the symbols are received on the sideband.
16. The receiver of claim 15 , wherein the digital radio signal has upper and lower sidebands, and the processor calculates the peak values of a normalized upper sideband correlation waveform and a normalized lower sideband correlation waveform.
17. The receiver of claim 16 , wherein the processor causes the receiver to dwell on the received digital radio signal when at least one of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a predetermined threshold.
18. The receiver of claim 16 , wherein the processor causes the receiver to dwell on the received digital radio signal when at least one of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a first predetermined threshold or the sum of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a second predetermined threshold.
19. The receiver of claim 16 , wherein the processor calculates:
a peak index for the normalized upper sideband correlation waveform and a peak index of the normalized lower sideband correlation waveform, and a peak index delta representative of the difference between the peak indices for the normalized upper and lower sideband correlation waveforms; and
wherein the processor causes the receiver to dwell on the received digital radio signal when the sum of the peak values of the normalized upper and lower sideband correlation waveforms exceeds a first predetermined threshold and the peak index delta is less than a second predetermined threshold.
20. The receiver of claim 15 , wherein the digital radio signal includes upper and lower sidebands, and the samples received on the upper and lower sidebands are processed separately.
21. The receiver of claim 15 , wherein the correlation waveform is based on amplitudes of samples of leading and trailing portions of orthogonal frequency division multiplexed symbols.
22. The receiver of claim 21 , wherein the amplitudes of the leading and trailing portions of the orthogonal frequency division multiplexed symbols are tapered.
23. The receiver of claim 15 , wherein the correlation waveform is based on a cyclic prefix applied to orthogonal frequency division multiplexed symbols.
24. The receiver of claim 15 , wherein the predetermined threshold correlates to the sensitivity of the receiver for receiving a digital radio signal.
25. A receiver for detecting a digital radio signal, the receiver comprising:
an input for receiving a digital radio signal representing a series of symbols; and
a processor for calculating the peak value of a normalized correlation waveform having a peak that corresponds to a symbol boundary, and for causing the receiver to dwell on the received digital radio signal when a peak value exceeds a predetermined threshold, wherein the processor sets a status flag to indicate if the receiver should dwell on the received digital radio signal or tune to another channel.
26. A receiver for detecting a digital radio signal, the receiver comprising:
an input for receiving a digital radio signal representing a series of symbols;
a processor for calculating the peak value of a normalized correlation waveform having a peak that corresponds to a symbol boundary, and for causing the receiver to dwell on the received digital radio signal when a peak value exceeds a predetermined threshold; and
a filter for filtering a sideband in the digital radio signal prior to the processor calculating the peak value of a normalized correlation waveform.
27. The receiver of claim 26 , wherein the filter comprises a finite impulse response filter.
28. A receiver for detecting a digital radio signal, the receiver comprising:
an input for receiving a digital radio signal representing a series of symbols; and
a processor for calculating the peak value of a normalized correlation waveform having a peak that corresponds to a symbol boundary, and for causing the receiver to dwell on the received digital radio signal when a peak value exceeds a predetermined threshold, wherein the predetermined threshold correlates to the value of one or more seek-scan status bits.