Patent ID: 8036376
Filing Date: 2011-10-11
Classification: H04B

Abstract:
1. An echo prevention circuit for an earphone microphone comprising: an input terminal into which a first input signal corresponding to voice output from an external communication device is received; a first FIR filter into which the first input signal is input through the input terminal; a second FIR filter into which the first input signal is input at the same time as into the first FIR filter; an input/output terminal to which an output signal of the first FIR filter is output and a second input signal output from the earphone microphone is input; a first subtracter that subtracts an output signal of the second FIR filter from a combined signal of the output signal of the first FIR filter and the second input signal; an adaptive digital filter into which the output signal of the first FIR filter is input; a second subtracter that subtracts an output signal of the adaptive digital filter from an output signal of the first subtracter; and an output terminal to which an output signal of the second subtracter is output, wherein