Method and apparatus for reducing audio band noise in a periodic wave signal

Abstract

A triangular waveform generator includes a square waveform clock circuit and an integrating circuit. The integration circuit receives input from the square waveform clock circuit and generates a triangular waveform output. A feedback circuit is operatively connected to the integrating circuit to reduce the audio band noise content in the triangular waveform output. The feedback circuit acts as a DC balance without significant sacrifice in the linearity of the triangular waveform output.

What is claimed is: 
     
         1 . A method for reducing noise in a periodic wave signal using an electronic circuit, said method comprising the steps of:
 receiving from a periodic wave signal generation circuit a first periodic wave signal having a periodic frequency higher than an audio frequency band and comprising a first level of noise in said audio frequency band;   integrating said first periodic wave signal using an integrating circuit to produce a second periodic wave signal;   generating a feedback signal from said second periodic wave signal by applying a transfer function to said second periodic wave signal;   combining said feedback signal with said first periodic wave signal prior to integrating said first periodic wave signal so as to reduce said first level of noise in said audio frequency band.   
     
     
         2 . The method of  claim 1  wherein said transfer function has a first gain in said audio frequency band and a second gain at said periodic frequency, said first gain being greater than said second gain. 
     
     
         3 . The method of  claim 2  wherein said transfer function has a crossover frequency and wherein at least one of said plurality of poles is below said crossover frequency. 
     
     
         4 . The method of  claim 3  wherein at least one of said plurality of poles is above said crossover frequency. 
     
     
         5 . The method of  claim 3  wherein a plurality of said plurality of poles is above said crossover frequency. 
     
     
         6 . The method of  claim 3  wherein a plurality of said plurality of poles is below said crossover frequency. 
     
     
         7 . The method of  claim 3  wherein said transfer function comprises a region of nearly flat gain. 
     
     
         8 . The method of  claim 1  wherein said first periodic wave signal comprises a square wave signal. 
     
     
         9 . The method of  claim 8  wherein said first periodic wave generation circuit comprises a square wave clock circuit. 
     
     
         10 . The method of  claim 8  wherein said second periodic wave signal comprises a triangle wave signal.