In its digital processing circuit, clock chip with high precision and temperature compensation is uesd as reference clock. High frequency reversible counter is used to count trimmed impulse signal forward or backward and two pathes SAW signals are selected timely by multichannel selector. 数字信号处理电路采用高精度、具有温度补偿的时钟芯片作为基准时钟,采用高频可逆计数器对整形后的脉冲信号进行正向或逆向计数,采用高性能的多路选择器控制两路SAW信号的定时选择。