Removing impulsive noise in a radio

Patent metadata

Field	Value
Publication number	US-9780816-B1
Application number	US-201615086236-A
Country	US
Kind code	B1
Filing date	Mar 31, 2016
Priority date	Mar 31, 2016
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

In one example, an apparatus includes: a delay unit to delay a demodulated signal obtained from an input radio frequency (RF) frequency modulation (FM) signal; a filter to filter the demodulated signal and output a filtered demodulated signal; an impulse detection circuit to receive the filtered demodulated signal and detect presence of an impulse in the demodulated signal; and an impulse removal circuit to remove the detected impulse from the demodulated signal.

First claim

What is claimed is:

1. An apparatus comprising:
a delay unit to delay a demodulated signal obtained from an input radio frequency (RF) frequency modulation (FM) signal;
a filter to filter the demodulated signal and output a filtered demodulated signal;
an impulse detection circuit to receive the filtered demodulated signal and detect presence of an impulse in the demodulated signal; and
an impulse removal circuit to remove the detected impulse from the demodulated signal;
wherein the delay unit comprises:
a plurality of delay elements to receive, delay and output a sample of the demodulated signal; and
a plurality of selectors controllable to substitute a sample output from the filter for a sample of the demodulated signal, responsive to detection of the impulse.

2. The apparatus of claim 1 , wherein the filter comprises a linear phase high pass filter to filter a signal portion of the demodulated signal and output an impulse portion of the demodulated signal.

3. The apparatus of claim 2 , wherein the impulse removal circuit comprises a summer to subtract the impulse portion of the filtered demodulated signal output by the filter from an output of the delay unit to remove the detected impulse.

4. The apparatus of claim 1 , wherein the filter comprises a linear phase low pass filter to receive the demodulated signal and filter the impulse from the demodulated signal and output the filtered demodulated signal.

5. The apparatus of claim 4 , wherein the impulse removal circuit is to substitute the filtered demodulated signal for an output of the delay unit to remove the detected impulse.

6. The apparatus of claim 1 , wherein the impulse detection circuit is to detect the presence of the impulse when the filtered demodulated signal exceeds a threshold value.

7. The apparatus of claim 6 , wherein the impulse detection circuit comprises:
a first power detector to detect an instantaneous power of the filtered demodulated signal;
a second power detector to detect an average power of the filtered demodulated signal; and
a controller to detect the impulse based on the instantaneous power and the average power.

8. The apparatus of claim 7 , wherein the impulse detection circuit is to detect the impulse if the instantaneous power exceeds a product of the average power and a coefficient.

9. The apparatus of claim 1 , wherein the filter comprises a first filter portion to sum an output of a first subset of the plurality of delay elements and a second filter portion to sum an output of a second subset of the plurality of delay elements.

10. The apparatus of claim 9 , wherein the plurality of selectors are coupled between the first subset of the plurality of delay elements and the second subset of the plurality of delay elements.

11. The apparatus of claim 1 , wherein the plurality of selectors are interposed between at least some of the plurality of delay elements.

12. A non-transitory computer readable medium including instructions that when executed enable a system to:
obtain, in a first filter of a receiver, a first filter sum of a plurality of phase samples of an incoming frequency modulation (FM) signal;
obtain, in a second filter of the receiver, a second filter value based on the first filter sum and a selected phase sample of the plurality of phase samples;
determine, in an impulse detection circuit of the receiver, whether the second filter value exceeds a threshold value; and
responsive to a determination that the second filter value exceeds the threshold value, replace one or more selected phase samples of the plurality of phase samples with the first filter sum.

13. The non-transitory computer readable medium of claim 12 , further comprising instructions that when executed enable the system to obtain the first filter sum as a first average of a first set of phase samples and a second average of a second set of phase samples.

14. The non-transitory computer readable medium of claim 12 , wherein the replacement of the one or more selected phase samples with the first filter sum is to remove an impulse in the incoming FM signal.

15. The non-transitory computer readable medium of claim 12 , further comprising instructions that when executed enable the system to determine the threshold value based on an average value of the second filter value.

16. A system comprising:
a receiver to receive and process a frequency modulation (FM) signal, the receiver comprising:
a delay circuit including a plurality of delay units to delay a plurality of phase samples;
a filter to filter at least some of the plurality of phase samples and generate a filter output;
a detector to determine whether the FM signal includes impulsive noise, based at least in part on the filter output; and
a control circuit to replace one or more of the plurality of phase samples within the delay circuit with the filter output if the detector determines that the FM signal includes the impulsive noise, to remove at least some of the impulsive noise from the FM signal;
wherein the delay circuit comprises:
a plurality of delay elements to receive, delay and output a sample of the plurality of phase samples; and
a plurality of selectors, wherein at least one of the plurality of selectors is controllable to substitute the filter output for a sample of the plurality of phase samples, responsive to detection of the impulsive noise.

17. The system of claim 16 , when the detector comprises:
a first power detector to detect an instantaneous power of the filter output,
a second power detector to detect an average power of the filter output; and
a controller to detect the impulsive noise based on the instantaneous power and the average power.

Assignees

• Silicon Lab Inc

Inventors

• Elenes Javier
• Taipale Dana
• Hakkola Alex

Classifications

• H04L27/14

  Demodulator circuits; Receiver circuits · CPC title

• H04B1/1661 Primary

  Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels · CPC title

• H04B1/10 Primary

  Means associated with receiver for limiting or suppressing noise or interference · CPC title