程控滤波器

Digital programmable filter

为了适应工程应用中幅度和频率变化范围很宽的信号,设计了一种增益、频响特性和截止频率可程控的程控滤波器。系统以单片机和FPGA为控制核心,由可控增益放大、程控滤波、椭圆滤波、频率特性测试4部分组成。其中,可控增益放大部分以AD603为核心,级联三路固定增益放大;程控滤波部分巧妙地将两个二阶状态变量滤波级联,并将DAC等效为数控电阻,使得截止频率可调。实验结果表明,整个系统工作稳定,可以很好的实现程控滤波的功能。

In order to adapt the signals in the engineering applications which has the wide range of changes in the amplitude and frequency ,the programmable filter whose frequency response and cutoff frequency can be programmed is designed. The system uses microcontroller and FPGA as the control core, the controllable gain amplifier, programmable filter, the ellipse lowpass filter and the frequency characteristics of the test consists of three parts.Among them, the controllable gain amplifier uses the part of AD603 as the core, and cascades three-way fixed-gain amplifier, programmable filtering part cascades two second-order state variable filter cleverly and resistance of the DAC is equivalent to NC resistance, making the cutoff frequency programmable.Experimental results show that the system is stable, achieving very good programmable filtering functions.