Method and apparatus for implementing a digital signal quality metric
View Patent ↗A method for detecting a digital radio signal includes the steps of receiving the digital radio signal including a series of symbols, developing a correlation waveform having a peak that corresponds to a symbol boundary, normalizing the correlation waveform, and calculating a peak value of the normalized correlation waveform, wherein the peak value represents the quality of the received digital radio signal. A receiver that performs the method is also provided.
1. A method for detecting the quality of a digital radio signal, the method comprising the steps of:
receiving a digital radio signal including a series of symbols;
developing a correlation waveform having a peak that corresponds to a symbol boundary;
normalizing the correlation waveform; and
calculating a peak value of the normalized correlation waveform, wherein the peak value represents the quality of the received digital radio signal, 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 , further comprising the steps of:
comparing the peak values of the normalized upper and lower sideband correlation waveforms to a first predetermined threshold, and
comparing the sum of the peak values of the normalized upper and lower sideband correlation waveforms to a second predetermined threshold.
6. The method of claim 4 , further comprising the steps of:
determining a peak index of the normalized upper sideband correlation waveform and a peak index of the normalized lower sideband correlation waveform; and
calculating a peak index delta representative of the difference between the peak indices for the normalized upper and lower sideband correlation waveforms.
7. The method of claim 6 , further comprising the steps of:
comparing the sum of the peak values of the normalized upper and lower sideband correlation waveforms to a first predetermined threshold; and
comparing the peak index delta to a second predetermined threshold.
8. The method of claim 1 , further comprising the step of:
comparing the peak value of the normalized correlation wavefoiin to a predetermined threshold.
9. 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.
10. The method of claim 9 , wherein the amplitudes of the leading and trailing portions of the orthogonal frequency division multiplexed symbols are tapered.
11. The method of claim 1 , wherein the symbols comprise orthogonal frequency division multiplexed symbols and the correlation waveform is based on a cyclic prefix applied to the symbols.
12. A method for detecting the quality of a digital radio signal, the method comprising the steps of:
receiving a digital radio signal including 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, wherein the peak value represents the quality of the received digital radio signal; and
setting a status flag to indicate if the received digital radio signal exceeds a predetermined quality threshold.
13. The method of claim 1 , wherein the digital radio signal includes upper and lower sidebands, and the symbols received on the upper and lower sidebands are processed separately.
14. The method of claim 13 , further comprising the step of:
filtering each sideband in the digital radio signal prior to the step of developing a correlation waveform.
15. The method of claim 14 , wherein the filtering step is performed using a finite impulse response filter.
16. A method for detecting the quality of a digital radio signal, the method comprising the steps of:
receiving a digital radio signal including 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, wherein the peak value represents the quality of the received digital radio signal, wherein the step of developing a correlation waveform is performed for upper and lower sidebands of the digital radio signal to produce an upper sideband correlation waveform and a lower sideband correlation waveform; and
calculating a frequency offset difference for the correlation waveforms for the upper and lower sidebands.
17. The method of claim 16 , further comprising the step of comparing the frequency offset difference to a predetermined threshold.
18. A receiver for detecting a digital radio signal, the receiver comprising:
an input for receiving a digital radio signal including a series of symbols; and
a processor for calculating a peak value that corresponds to a symbol boundary of a normalized correlation waveform, wherein the peak value represents the quality of the received digital radio signal, wherein the digital radio signal includes a sideband, and the symbols are received on the sideband.
19. The receiver of claim 18 , wherein the digital radio signal includes 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.
20. The receiver of claim 19 , wherein the processor compares at least one of the peak values of the normalized upper and lower sideband correlation waveforms to a predetermined threshold.
21. The receiver of claim 19 , wherein the processor compares the peak values of the normalized upper and lower sideband correlation waveforms to a first predetermined threshold and compares the sum of the peak values of the normalized upper and lower sideband correlation waveforms to a second predetermined threshold.
22. The receiver of claim 19 , wherein the processor determines 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.
23. The receiver of claim 22 , wherein the processor compares the sum of the peak values of the normalized upper and lower sideband correlation waveforms to a first predetermined threshold and the peak index delta to a second predetermined threshold.
24. The receiver of claim 18 , wherein the digital radio signal includes upper and lower sidebands, and the samples received on the upper and lower sidebands are processed separately.
25. The receiver of claim 24 , further comprising:
a filter for filtering each sideband in the digital radio signal prior to the processor calculating the peak value of a normalized correlation waveform.
26. The receiver of claim 25 , wherein the filter comprises a finite impulse response filter.
27. The receiver of claim 18 , wherein the correlation waveform is based on amplitudes of samples of leading and trailing portions of orthogonal frequency division multiplexed symbols.
28. The receiver of claim 27 , wherein the amplitudes of the leading and trailing portions of the symbols are tapered.
29. The receiver of claim 18 , wherein the symbols comprise orthogonal frequency division multiplexed symbols and the correlation waveform is based on a cyclic prefix applied to the symbols.
30. A receiver for detecting a digital radio signal, the receiver comprising:
an input for receiving a digital radio signal including a series of symbols; and
a processor for calculating a peak value that corresponds to a symbol boundary of a normalized correlation waveform, wherein the peak value represents the quality of the received digital radio signal, and wherein the processor sets a status flag to indicate that the received digital radio signal exceeds a predetermined quality threshold.
31. A receiver for detecting a digital radio signal, the receiver comprising:
an input for receiving a digital radio signal including a series of symbols;
a processor for calculating a peak value that corresponds to a symbol boundary of a normalized correlation waveform, wherein the peak value represents the quality of the received digital radio signal;
wherein the digital radio signal includes 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; and
wherein the processor calculates a frequency offset difference for the correlation waveforms for the upper and lower sidebands.
32. The method of claim 31 , wherein the processor compares the frequency offset difference to a predetermined threshold.