说明：  滤波器广泛应用于数字信号处理、通信、自动控制领域,但设计可变宽频带有源滤波器则比较困难。利用单片机控制参数可编程的双二阶通用开关电容有源滤波器,精确设置有源滤波器的中心频率f，品质因数Q及有源滤波器的工作方式。本系统主要分为两个部分:即程控滤波器和程控放大器。程控放大器电压增益为40dB，通过单片机控制DA进行分压，可精确实现要求的10dB步进，误差小于0.5 ，通带为100Hz-500KHz，输入电压峰－峰值范围为10mV，在输入范围内无明显失真。由MAX264为核心的滤波器，可设置为高通、低通滤波器。通过单片机直接给出控制频率，使-3dB截止频率在1KHz-20KHz内可调，步进1KHz，误差小于1 。整个系统以52单片机为控制核心，电路简单，性能稳定，且具有较高精度，滤波参数调节通过单片机控制，较为方便。
(Filters are widely used in digital signal processing, communications, automatic control area, but the design variable wideband active filter is more difficult. Control parameters using single-chip programmable universal switched-capacitor biquad active filter, active filter accurately set the center frequency f, quality factor Q and the active filter works. The system is mainly divided into two parts: the program-controlled filters and programmable amplifiers. Programmable amplifier voltage gain of 40dB, the DA through the partial pressure of single-chip control, can accurately achieve the required 10dB step, the error is less than 0.5 , passband to 100Hz-500KHz, input voltage peak- the range of 10mV, the input range no significant distortion. By the MAX264 as the core of filter can be set to high pass, low pass filter. Given directly by the microcontroller controls the frequency, the-3dB cutoff frequency at 1KHz-20KHz adjustable, step 1KHz, error is less than 1 . The entire system for)