Impulse noise mitigation under out-of-band interference conditions

• US 8,488,663 B2
• Filed: 09/22/2010
• Issued: 07/16/2013
• Est. Priority Date: 09/23/2009
• Status: Active Grant

• Current Assignee: Maxlinear Incorporated
• Original Assignee: Maxlinear Incorporated
• Inventors: Lo, Andy, Kang, Sugbong
• Primary Examiner(s): Ahn, Sam K
• Assistant Examiner(s): Wong, Linda
• Application Number:
  US12/924,185
• Publication Number:
  US 20110069798A1
• Time in Patent Office: 1,028 Days
• Field of Search: 375229-236, 37524002-24007, 37524026-24029, 375/284, 375/285, 375/259, 375/295, 375/316, 375/354, 375/219, 375/211, 375/220, 375/221, 375/222, 375/254, 375/296, 375/299, 375346-350, 708322-400
• US Class Current: 375/229
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H

Abstract

A noise abatement method and system for impulse noise in an RF receiver where the RF analog signal is converted to a digital signal prior to being connected to a demodulator. Two filters are used to detect impulse noise signals even under out-of-band interferer conditions, and prevent the impulse noise from reaching the input to the demodulator. A first of the two filters detects impulse noise using signals lower than the frequency bandwidth of the desired signal, and a second of the two filters detects impulse noise using signals higher the frequency bandwidth of the desired signal. A mean magnitude of the signal is detected over a predetermined time T and is used to select which filter to use for noise abatement.

Claims

1. A method for impulse noise mitigation, comprising:

a) forming an impulse noise mitigation circuit;

b) forming two complex high pass filters within the impulse noise mitigation circuit;

c) setting a cut-off frequencies of the two complex high pass filters to bound a frequency bandwidth of a desired signal, wherein a first of the two complex high pass filters allows frequencies higher than the frequency bandwidth of the desired signal, and wherein a second of the two complex filters allows frequencies lower than the frequency bandwidth of the desired signal;

d) measuring a first signal response of the first filter;

e) measuring a second signal response of the second filter;

f) computing and storing a mean magnitude separately for the first signal response of the first filter and the second signal response of the second filter;

g) selecting the first filter for impulse noise mitigation if the mean magnitude of the second filter is greater than the mean magnitude of the first filter; and

h) selecting the second filter for impulse noise mitigation if the mean magnitude of the first filter is greater than the second filter.

2. The method of claim 1, wherein measuring the first and second signal response occurs over a predetermined time period.

3. The method of claim 1, wherein computing and storing the mean magnitude and selecting either the first or second filter is controlled by a state machine.

4. The method of claim 1, wherein impulse noise mitigation includes other noise interferers.

5. The method of claim 1, wherein the first and the second filter are integrated together into a single programmable filter, wherein the single programmable filter is initially configured as the first filter to measure the mean magnitude of the first filter and then configured as the second filter to measure the mean magnitude of the second filter, whereupon the mean magnitudes of the first filter and the second filter are compared to select which filter configuration to use to mitigate impulse noise.

6. A system for impulse noise mitigation, comprising:

a) an impulse noise mitigation circuit (INMC) connected to an output of an analog to digital converter (ADC) configured to convert an analog RF signal to a digital signal;

b) the INMC further comprises two complex high pass filters, which bound a bandwidth of a desired RF signal;

c) the INMC is configured to measure a response, to impulse noise, of each of the two complex high pass filters over a predetermined time span, and compute, for each of the two complex high pass filters, a mean magnitude value of the effects of the impulse noise on the output of the ADC;

d) a first filter of the two complex high pass filters is selected to abate impulse noise and other interferer when the mean magnitude value of the second filter of the two complex high pass filters is greater than the mean magnitude value of the first filter of the two complex high pass filters; and

e) the second filter of the two complex high pass filters selected to abate impulse noise and other interferer when the mean magnitude value of the first filter of the two complex high pass filters is greater than the mean magnitude value of the second filter of the two complex high pass filters.

7. The system of claim 6, wherein the first filter operates on frequency components of the RF signal higher than a desired signal frequency band to detect impulse noise.

8. The system of claim 6, wherein the second filter operates on frequency components of the RF signal lower than a desired signal frequency band to detect impulse noise.

9. The system of claim 6, wherein the ADC receives an input from an RF tuner.

10. The system of claim 6, wherein the INMC delivers a digital signal with impulse noise mitigated from the desired signal to a demodulator circuit.

11. The system of claim 6, wherein the two complex high pass filters are integrated together into a single programmable complex high pass filter, wherein the single programmable complex high pass filter is initially configured as the first filter to measure the mean magnitude of the first filter and then configured as the second filter to measure the mean magnitude of the second filter, whereupon the mean magnitudes of the first filter and second filter are compared to select which filter configuration to use to mitigate impulse noise.