Characterizing ingress noise

1. A method for characterizing ingress noise in a cable network, the method comprising:

(a) identifying a first frequency band of a cable signal at a first location in the cable network;

(b) obtaining a time trace of a first parameter of the cable signal in the first frequency band identified in step (a);

(c) computing an autocorrelation function of the time trace, wherein a first autocorrelation peak at a first non-zero time delay identifies a first repetitive noise component of the ingress noise;

(d) repeating steps (b) and (c);

(e) averaging the autocorrelation functions computed in the repeated step (c) to compute an averaged autocorrelation function; and

(f) determining a first repetition frequency of the first repetitive noise component from a time delay of a peak in the averaged autocorrelation function of step (e).

2. The method of claim 1 , wherein the first parameter includes an amplitude of the cable signal at the first location.

3. The method of claim 2 , wherein step (a) is performed by identifying a noise peak in a frequency spectrum of the cable signal at the first location, and selecting the first frequency band to include a central frequency of the noise peak.

4. The method of claim 3 , wherein the frequency spectrum is measured by a spectrum analyzer module coupled to the first location, wherein the time trace of step (b) is obtained by dwelling the spectrum analyzer module at the first frequency band for a dwelling time, and capturing an output signal of the spectrum analyzer module.

5. The method of claim 1 , wherein step (b) includes

(b1) demodulating the cable signal; and

(b2) obtaining a symbol error vector of the demodulation of step (b1);

wherein the first parameter includes the symbol error vector of step (b2).

6. The method of claim 1 , wherein in step (b), the time trace is captured when at least one of the first parameter and a time derivative of the first parameter exceeds a predefined threshold.

7. The method of claim 6 , wherein in step (b), the time trace is captured when the first parameter is within a predefined parameter range.

8. A method for characterizing ingress noise in a cable network, the method comprising:

(a) identifying a first frequency band of a cable signal at a first location in the cable network;

(b) obtaining a time trace of a first parameter of the cable signal in the first frequency band identified in step (a); and

(c) computing an autocorrelation function of the time trace, wherein a first autocorrelation peak at a first non-zero time delay identifies a first repetitive noise component of the ingress noise; wherein step (c) further comprises a summation analysis of the computed autocorrelation function, the summation analysis comprising;

(i) summing up N values of the autocorrelation function at multiples of a time interval Δt to obtain a value S(Δt), wherein N is an integer ≧2;

(ii) repeating step (i) at a different value of Δt; and

(iii) out of the Δt values of steps (i) and (ii), selecting a value Δt of the different values of Δt that corresponds to a maximum value of S(Δt).

9. The method of claim 8 , wherein in steps (i) and (ii), the Δt values are selected to correspond to periods of known types of periodic interference.

10. A method for characterizing ingress noise in a cable network, the method comprising:

(a) identifying a first frequency band of a cable signal at a first location in the cable network;

(b) obtaining a time trace of a first parameter of the cable signal in the first frequency band identified in step (a);

(c) computing an autocorrelation function of the time trace, wherein the autocorrelation function comprises first and second autocorrelation peaks at first and second non-zero time delays, respectively, identifying respective first and second repetitive noise components of the ingress noise, the second autocorrelation peak being smaller than the first autocorrelation peak;

(d) processing the time trace to remove signal peaks corresponding to the first autocorrelation peak; and

(e) computing an autocorrelation function of the time trace processed in step (d) to find the second autocorrelation peak.

11. The method of claim 1 , further comprising:

(g) displaying a frequency spectrum of the cable signal at the first cable network location, the frequency spectrum having a first peak in the first frequency band due to the first repetitive noise component; and

(h) displaying the first repetition frequency of the first repetitive noise component.

12. A method for characterizing ingress noise in a cable network, the method comprising:

(a) identifying a first frequency band of a cable signal at a first location in the cable network;

(b) obtaining a time trace of a first parameter of the cable signal in the first frequency band identified in step (a);

(c) computing an autocorrelation function of the time trace, wherein the autocorrelation function comprises first and second autocorrelation peaks at first and second non-zero time delays, respectively, indicative of first and second repetitive noise components of the ingress noise, respectively; and determining first and second repetition frequencies of the first and second repetitive noise components from the first and second time delays of the first and second autocorrelation peaks, respectively;

(d) displaying a frequency spectrum of the cable signal at the first cable network location, the frequency spectrum having first and second peaks in the first frequency band due to the first and second repetitive components, respectively; and

(e) displaying the first and second repetition frequencies of the first repetitive component;

wherein the first peak includes first and second distinctly colored or shaded areas corresponding to the first and second repetitive noise components, respectively;

wherein a relative size and/or position of the colored or shaded areas corresponds to a relative magnitude of the first and second repetitive noise components; and

wherein step (e) includes displaying the first and second repetition frequencies and their representative colors or shades.

13. The method of claim 11 , wherein in step (h), at least one repetition frequency of the frequency peak is displayed on a common frequency axis graph disposed proximate to, or superimposed with, the frequency spectrum displayed in step (g).

14. The method of claim 1 , wherein in step (c), the autocorrelation function includes a cyclic autocorrelation function.

15. The method of claim 1 , further comprising proceeding to a second cable network location associated with the first repetition frequency determined in step (c).

16. A device to characterize ingress noise in a cable network, the device comprising:

an input terminal to couple to a first cable network location; and

a hardware processor coupled to the input terminal, the hardware processor to:

identify a first frequency band of a cable signal at the first location in the cable network;

obtain time traces of a first parameter of the cable signal in the identified first frequency band;

compute an autocorrelation function for each of the time traces, wherein a first autocorrelation peak at a first non-zero time delay identifies a first repetitive noise component of the ingress noise;

average the autocorrelation functions computed for the time traces to compute an averaged autocorrelation function; and

determine a first repetition frequency of the first repetitive noise component from a time delay of a peak in the averaged autocorrelation function.

17. The device of claim 16 , wherein the hardware processor comprises a RF front end coupled to the input terminal, and an ADC coupled to the RF front end, for digitizing an output signal of the RF front end.

18. The device of claim 16 , wherein the hardware processor comprises at least one of a FPGA, a digital signal processor, and a microprocessor.