Fm analog demodulator compatible with iboc signals

Abstract

A method is disclosed which comprises receiving a radio signal; sampling and filtering the radio signal to isolate the FM portion; demodulating the FM portion of the received signal; applying a sliding window to the first, second, and third samples; and, adjusting the value of the second sample if the product of the second sample times the sum of the first and third samples is less than a threshold value. In various embodiments, an apparatus may be provided which comprises an input for receiving a radio signal and processing circuitry for performing various methods described herein.

What is claimed is: 
     
         1 . A method comprising:
 receiving a radio signal;   sampling and filtering the radio signal to isolate the FM portion;   demodulating the FM portion of the received signal;   applying a sliding window to the first, second, and third samples; and   adjusting the value of the second sample if the product of the second sample times the sum of the first and third samples is less than a threshold value.   
     
     
         2 . The method of  claim 1 , wherein the value of the second sample is adjusted to an average of the values of the first and third samples. 
     
     
         3 . The method of  claim 1 , wherein the value of the second sample is adjusted to the magnitude of the larger of the first or third sample. 
     
     
         4 . The method of  claim 1 , wherein the threshold is adjusted as a function of a sample rate. 
     
     
         5 . An apparatus comprising:
 an input for receiving a radio signal; and   processing circuitry for:
 sampling and filtering the radio signal to isolate the FM portion, 
 demodulating the FM portion of the received signal, 
 applying a sliding window to the first, second, and third samples, and adjusting the value of the second sample if the product of the second sample times the sum of the first and third samples is less than a threshold value. 
   
     
     
         6 . The apparatus of  claim 5 , wherein the value of the second sample is adjusted to an average of the values of the first and third samples. 
     
     
         7 . The apparatus of  claim 5 , wherein the value of the second sample is adjusted to the magnitude of the larger of the first or third sample. 
     
     
         8 . The apparatus of  claim 5 , wherein the threshold is adjusted as a function of a sample rate.