Apparatus and method for detecting NTSC co-channel interference

1. Apparatus for use in detecting an interfering signal, the apparatus comprising:

a carrier tracking loop for processing a received signal to provide a tracking signal indicative of a possible presence of at least one carrier of an interfering signal; and

a decision device for determining if the interfering signal is present as a function of the tracking signal; wherein the decision device further comprises:

a filter for averaging the tracking signal; and

a comparator for comparing the averaged tracking signal to a predetermined threshold for determining if the interfering signal is present.

2. The apparatus of claim 1 , further comprising a look-up-table for providing a D/U (Desired-to-Undesired) signal power ratio from the averaged tracking signal.

3. The apparatus of claim 2 , wherein the D/U signal power ratio is defined as an average digital vestigial sideband ATSC (Advanced Television Systems Committee) signal power divided by an average NTSC (Nation Television System Committee) peak signal power.

4. The apparatus of claim 1 , wherein the interfering signal is an NTSC (National Television Systems Committee) signal and the at least one carrier is an NTSC video carrier.

5. The apparatus of claim 1 , wherein the interfering signal is an NTSC signal and the at least one carrier is an NTSC chroma carrier.

6. The apparatus of claim 1 , wherein the interfering signal is an NTSC signal and the at least one carrier is an NTSC audio carrier.

7. The apparatus of claim 1 , wherein the carrier tracking loop further comprises:

a bandpass filter for filtering the received signal to provide a bandpass filtered signal, wherein the bandpass filter is centered about the at least one carrier;

a delay/Hilbert filter for filtering the bandpass filtered signal to provide a complex signal; and

a carrier tracking loop operative on the complex signal for providing the tracking signal.

8. The apparatus of claim 7 , wherein the carrier tracking loop further comprises:

a phase detector for processing the tracking signal to provide a phase offset signal indicative of a phase offset in the tracking signal;

a loop filter for filtering the phase offset signal;

a combiner for combining the loop filtered phase offset signal and a frequency offset signal to provide a combined signal, where the frequency offset signal is equal to a frequency of the at least one carrier signal;

a numerically controlled oscillator responsive to the combined signal for providing a phase angle signal;

a sine/cosine table for receiving the phase angle signal and for providing associated sine and cosine values; and

a complex multiplier for multiplying the complex signal by the sine and cosine values provided by the sine/cosine table to provide the tracking signal.

9. A method for use in detecting an interfering signal, the method comprising:

processing a received signal to provide a tracking signal indicative of a possible presence of at least one carrier of an interfering signal; and

determining if the interfering signal is present as a function of the tracking signal; wherein the determining step includes the steps of:

averaging the tracking signal; and

comparing the averaged tracking signal to a predetermined threshold for determining if the interfering signal is present.

10. The method of claim 9 , further comprising the step of providing a D/U (Desired-to-Undesired) signal power ratio from the averaged tracking signal.

11. The method of claim 10 , wherein the D/U signal power ratio is defined as an average digital vestigial sideband ATSC (Advanced Television Systems Committee) signal power divided by an average NTSC (Nation Television System Committee) peak signal power.

12. The method of claim 9 , wherein the interfering signal is an NTSC (National Television Systems Committee) signal and the at least one carrier is an NTSC video carrier.

13. The method of claim 9 , wherein the interfering signal is an NTSC signal and the at least one carrier is an NTSC chroma carrier.

14. The method of claim 9 , wherein the interfering signal is an NTSC signal and the at least one carrier is an NTSC audio carrier.

15. The method of claim 9 , wherein the processing step includes the steps of:

filtering the received signal to provide a bandpass filtered signal, wherein the bandpass filtered signal has a bandwidth centered about the at least one carrier;

filtering the bandpass filtered signal to provide a complex signal; and

processing the complex signal with a carrier tracking loop for providing the tracking signal.

16. The method of claim 15 , wherein the processing the complex signal step includes the steps of:

processing the tracking signal to provide a phase offset signal indicative of a phase offset in the tracking signal;

filtering the phase offset signal to provide a filtered phase offset signal;

combining the filtered phase offset signal and a frequency offset signal to provide a combined signal, where the frequency offset signal is equal to a frequency of the at least one carrier signal;

processing the combined signal to provide a phase angle signal proportional to the frequency of the combined signal;

providing sine and cosine values associated with the provided phase angle; and

multiplying the complex signal by the provided sine and cosine values to provide the tracking signal.

17. The method of claim 9 , further comprising the step of enabling a rejection filter for processing the received signal to remove the interfering signal when the interfering signal is determined to be present.