Method and system for reducing amplitude modulation (AM) noise in AM broadcast signals

Abstract

A computer-implemented method for reducing a noise signal added to an amplitude modulated (AM) broadcast signal while travelling from a broadcasting antenna to a receiving antenna is provided. The method includes capturing a signal representative of the AM broadcast signal corrupted by the noise signal via the receiving antenna, inverting the captured signal, and determining a carrying frequency of the AM broadcast signal and delaying the inverted waveform by a fraction of a cycle of the carrying frequency. The method further includes generating a difference signal by subtractively combining the captured signal and the delayed inverted signal, generating an estimate noise signal by reducing an amplitude of the generated difference signal using a noise-reduction control multiplier, and minimizing the corrupting noise signal component of the captured signal by subtractively combining the captured signal and the generated estimate noise signal.

What is claimed is:  
     
       1. A computer-implemented method for reducing an externally generated noise signal imposed on an amplitude modulated (AM) broadcast signal, the AM broadcast signal travelling from a broadcasting antenna to a receiving antenna, the method comprising:
 capturing, via the receiving antenna, a signal representative of the AM broadcast signal corrupted by the externally generated noise signal; 
 shifting the phase of the captured signal by 180 degrees; 
 determining a carrying frequency of the AM broadcast signal and delaying the phase-shifted waveform by a fraction of a cycle of the carrying frequency, the delaying of the waveform occurring after the phase shifting of the captured signal; 
 generating a difference signal by combining the captured signal and the delayed phase-shift signal; 
 generating an estimate noise signal by reducing an amplitude of the generated difference signal using a noise amplifier control multiplier, wherein the generated estimate noise signal represents an estimate of the corrupting noise signal; 
 minimizing the corrupting noise signal component of the captured signal by combining the captured signal and the generated estimate noise signal so as to compensate for the externally generated noise signal imposed on the AM broadcast signal; and 
 wherein shifting the phase, determining the carrier frequency, generating a difference signal, generating an estimate noise signal, and minimizing the corrupting noise signal component, are performed on a continuous basis operating on complete cycles of the captured signal and without down-conversion of the signal. 
 
     
     
       2. The computer-implemented method of  claim 1 , wherein a fraction of a cycle is equal to about a half cycle. 
     
     
       3. The computer-implemented method of  claim 1 , further comprising filtering captured signal prior to the signal inversion. 
     
     
       4. The computer-implemented method of  claim 1 , further comprising processing the captured signal through a low noise amplifying unit. 
     
     
       5. The computer-implemented method of  claim 1 , further comprising processing the captured signal through an analog to digital converting unit to generate a digital version of the captured signal prior to the signal inversion. 
     
     
       6. The computer-implemented method of  claim 1 , wherein the noise amplifier control multiplier is equal to a rational number 1/n with n being a number that is greater than a first value equal to one (1) and is less than a second value equal to two (2). 
     
     
       7. A system for reducing an externally generated noise signal imposed on an amplitude modulated (AM) broadcast signal, the AM broadcast signal travelling from a broadcasting antenna to a receiving antenna, the system comprising:
 a receiving unit for capturing, by the receiving antenna, a signal representative of the AM broadcast signal corrupted by the externally generated noise signal; 
 a signal inverting unit for shifting the phase of the captured signal by 180 degrees; 
 a signal frequency determining unit for determining a carrying frequency of the AM broadcast signal and delaying the phase-shifted waveform, using a delay circuit, by a fraction of a cycle of the carrying frequency, the signal inverting unit disposed in a signal processing path before the delay circuit; 
 a first signal differentiating unit for generating a difference signal by combining the captured signal and the delayed phase-shifted signal; 
 a signal amplitude reducing unit for reducing an amplitude of the generated difference signal using a noise amplifier control multiplier to generate an estimate noise signal, wherein the generated estimate noise signal represents an estimate of the corrupting noise signal; 
 a second signal differentiating unit for minimizing the corrupting noise signal component of the captured signal by combining the captured signal and the generated estimate noise signal so as to compensate for the externally generated noise signal imposed on the AM broadcast signal; and 
 wherein the signal inverting unit for shifting the phase, the signal frequency determining unit for determining the carrier frequency, the first signal differentiating unit for generating the difference signal, the signal amplitude reducing unit for generating an estimate noise signal, and the second signal differentiating unit for minimizing the corrupting noise signal component, continuously operate on complete cycles of the captured signal and without down-conversion of the signal. 
 
     
     
       8. The system of  claim 7 , wherein a fraction of a cycle is equal to about a half cycle. 
     
     
       9. The system of  claim 7 , further comprising a filtering unit for filtering captured signal prior to the signal inversion. 
     
     
       10. The system of  claim 7 , further comprising a low noise amplifying unit for amplifying a low noise component of the captured signal. 
     
     
       11. The system of  claim 7 , further comprising an analog to digital converting unit for generating a digital version of the captured signal prior to the signal inversion. 
     
     
       12. The system of  claim 7 , wherein the noise-reduction control multiplier is equal to a rational number 1/n with n being a number that is greater than a first value equal to one (1) and is less than a second value equal to two (2). 
     
     
       13. A non-transitory computer readable storage medium having stored therein instructions executable by a computing element to cause the computing element to perform functions to reduce an externally generated noise signal imposed on an amplitude modulated (AM) broadcast signal, the AM broadcast signal travelling from a broadcasting antenna to a receiving antenna, the functions comprising:
 capturing, by the receiving antenna, a signal representative of the AM broadcast signal corrupted by the externally generated noise signal; 
 shifting the phase of the captured signal by 180 degrees; 
 determining a carrying frequency of the AM broadcast signal and delaying the phase-shifted waveform by a fraction of a cycle of the carrying frequency, the delaying of the waveform occurring after the phase-shifted of the captured signal; 
 generating a difference signal by combining the captured signal and the delayed phase-shifted signal; 
 generating an estimate noise signal by reducing an amplitude of the generated difference signal using a noise-reduction control multiplier, wherein the generated estimate noise signal represents an estimate of the corrupting noise signal; 
 minimizing the corrupting noise signal component of the captured signal by subtractively combining the captured signal and the generated estimate noise signal so as to compensate for the externally generated noise signal imposed on the AM broadcast signal; and 
 wherein shifting the phase, determining the carrier frequency, generating a difference signal, generating an estimate noise signal, and minimizing the corrupting noise signal component, are performed on a continuous basis operating on complete cycles of the captured signal and without down-conversion of the signal. 
 
     
     
       14. The non-transitory computer readable storage medium of  claim 13 , wherein a fraction of a cycle is equal to about a half cycle. 
     
     
       15. The non-transitory computer readable storage medium of  claim 13 , further comprising filtering captured signal prior to the signal inversion. 
     
     
       16. The non-transitory computer readable storage medium of  claim 13 , further comprising processing the captured signal through a low noise amplifying unit. 
     
     
       17. The non-transitory computer readable storage medium of  claim 13 , further comprising processing the captured signal through an analog to digital converting unit to generate a digital version of the captured signal prior to the signal inversion. 
     
     
       18. A computing system comprising:
 at least one memory unit for storing program instructions for reducing a noise signal imposed on an amplitude modulated (AM) broadcast signal, the AM broadcast signal travelling from a broadcasting antenna to a receiving antenna, and 
 at least one processing unit for executing the program instructions; and 
 wherein the program instructions comprise:
 capturing, via the receiving antenna, a signal representative of the AM broadcast signal corrupted by the externally generated noise signal; 
 shifting the phase of the captured signal by 180 degrees; 
 determining a carrying frequency of the AM broadcast signal and delaying the phase-shifted waveform by a fraction of a cycle of the carrying frequency, the delaying of the waveform occurring after the inverting of the captured signal; 
 generating a difference signal by subtractively combining the captured signal and the delayed inverted signal; 
 generating an estimate noise signal by reducing an amplitude of the generated difference signal using a noise-reduction control multiplier, wherein the generated estimate noise signal represents an estimate of the corrupting noise signal; 
 minimizing the corrupting noise signal component of the captured signal by subtractively combining the captured signal and the generated estimate noise signal so as to compensate for the externally generated noise signal imposed on the AM broadcast signal; and 
 wherein shifting the phase, determining the carrier frequency, generating a difference signal, generating an estimate noise signal, and minimizing the corrupting noise signal component, are performed on a continuous basis operating on complete cycles of the captured signal and without down-conversion of the signal. 
 
 
     
     
       19. The computing system of  claim 18 , wherein a fraction of a cycle is equal to about a half cycle. 
     
     
       20. The computing system of  claim 18 , further comprising filtering captured signal prior to the signal inversion.