Echo preventing circuit and digital signal processing circuit

回波防止电路及数字信号处理电路

Abstract

回波防止电路,具备将第1数字信号变换成第2及第3数字信号的滤波器电路,将第2数字信号变换成第1模拟信号的第1DAC,将第3数字信号变换成第2模拟信号的第2DAC,进行第1模拟信号的输出或第3模拟信号的输入的输入输出端子,输出从第1及第3模拟信号中减去第2模拟信号的第4模拟信号的减法电路,将第4模拟信号变换成第4数字信号的ADC。滤波器电路,设定第4模拟信号为从第1及第3模拟信号中只除去或衰减第1模拟信号的信号的滤波器系数,使从减法电路输出的第4模拟信号,作为对应第3模拟信号的输出信号被输出。本发明在有效地防止回波的同时,实现成本削减及消耗电能的降低。
An echo preventing circuit comprises a filter that is inputted with a first digital signal and outputs a second and a third digital signals; a first DA converter that converts the second digital signal into a first analog signal and outputs the first analog signal; a second DA converter that converts the third digital signal into a second analog signal and outputs the second analog signal; an input/output terminal that outputs the first analog signal or that is inputted with a third analog signal; a subtracting circuit that outputs a fourth analog signal obtained by subtracting the second analog signal from a signal formed by combining the first analog signal and the third analog signal; and an AD converter that converts the fourth analog signal into a fourth digital signal, wherein the filter sets filter coefficients for which the fourth analog signal is a signal formed by removing or attenuating the first analog signal from a signal formed by combining the first analog signal and the third analog signal, and wherein the fourth analog signal outputted from the subtracting circuit is outputted as an output signal corresponding to the third analog signal. The present invention can effectively prevent echoes and can reduce the cost and the power consumption thereof.

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