Impulse noise mitigation under out-of-band interference conditions
An impulse noise mitigation circuit (INMC) may set a cut-off frequency of each of two high pass filters to bound a frequency bandwidth of a desired signal, wherein a first of the two filters allows frequencies higher than the frequency bandwidth of the desired signal, and a second of the two filters allows frequencies lower than the frequency bandwidth of the desired signal. The INMC may compute and store a mean magnitude separately for a first signal response of the first filter and a second signal response of the second filter. The INMC may select the first filter for impulse noise mitigation when the mean magnitude of the second filter is greater than the mean magnitude of the first filter. The INMC may select the second filter for impulse noise mitigation when the mean magnitude of the first filter is greater than the second filter.
1. A system comprising:
a first filter having a first high-pass response, a second filter having a second high-pass response, signal characterization circuitry, a filter selection circuitry, and a comparator, wherein:
said signal characterization circuitry is operable to:
generate a characterization of a first signal output by said first filter in response to a second signal being input to said first filter; and
generate a characterization of a third signal output by said second filter in response to said second signal being input to said second filter;
said filter selection circuit is operable to:
receive said first signal and said third signal; and
select one of said first signal and said third signal based on said characterization of said first signal and said characterization of said third signal; and
said comparator is operable to compare a noise detection threshold and said selected one of said first signal and said third signal.
2. The system of claim 1 , comprising a suppressor that is operable to clip samples of said first signal.
3. The system of claim 2 , wherein an output of said comparator is coupled to a control input of said suppressor.
4. The system of claim 3 , wherein an output of said suppressor is coupled to an input of a demodulator.
5. The system of claim 1 , comprising a suppressor that is operable to null samples of said first signal.
6. The system of claim 5 , wherein an output of said comparator is coupled to a control input of said suppressor.
7. The system of claim 6 , wherein an output of said suppressor is coupled to an input of a demodulator.
8. The system of claim 1 , wherein a cutoff frequency of said first filter is higher than a lowest desired frequency of said second signal, and a cutoff frequency of said second filter is lower than said lowest desired frequency of said second signal.
9. The system of claim 1 , wherein said signal characterization circuitry comprises an accumulator.
10. The system of claim 1 , comprising a tuner and an analog-to-digital converter, wherein:
an output of said tuner is coupled to an input of said analog-to-digital converter; and
said second signal is output by said analog-to-digital converter.
11. A method comprising:
generating, by signal characterization circuitry, a characterization of a first signal output by a first filter in response to a second signal being input to said first filter;
generating, by said signal characterization circuitry, a characterization of a third signal output by a second filter in response to said second signal being input to said second filter;
receiving, by filter selection circuitry, said first signal and said third signal;
selecting, by said filter selection circuitry, one of said first signal and said third signal based on said characterization of said first signal and said characterization of said third signal; and
comparing, by a comparator, a noise detection threshold and an output of said selected one of said first signal and said third signal.
12. The method of claim 11 , comprising clipping, by a suppressor, samples of said first signal.
13. The method of claim 12 , comprising controlling said clipping based on a signal output of said comparator.
14. The method of claim 3 , comprising demodulating, by a demodulator, a signal output by said suppressor.
15. The method of claim 11 , comprising nulling, by a suppressor, samples of said first signal.
16. The method of claim 15 , comprising controlling said nulling based on a signal output by said comparator.
17. The method of claim 16 , comprising demodulating, by a demodulator, a signal output of said suppressor.
18. The method of claim 11 , wherein a cutoff frequency of said first filter is higher than a lowest desired frequency of said second signal, and a cutoff frequency of said second filter is lower than said lowest desired frequency of said second signal.
19. The system of claim 1 , comprising generating said second signal by digitizing, via an analog-to-digital converter, an output of a tuner.