基于FPGA的程控滤波器的设计

Design of a programmable filter based on FPGA

以单片机和可编程逻辑器件（FPGA）为控制核心,设计了一个程控滤波器,实现了小信号程控放大、程控调整滤波器截止频率和幅频特性测试的功能。其中放大模块由可变增益放大器AD603实现,最大增益60 dB,10 dB步进可调,增益误差小于1%。程控滤波模块由MAX297低通滤波、TLC1068高通滤波及椭圆低通滤波器构成,滤波模式用模拟开关选择。本系统程控调整有源滤波的-3 dB截止频率,使其在1~30 kHz范围内可调,误差小于1.5%。此外,采用有效值采样芯片AD637及12位并行A/D转换器MAX120实现了对扫频信号幅度的测量。

Using microcontroller and FPGA as the operation core,a programmable filter was designed,which has the function of small signal amplification,cut-off frequency adjustment and amplitude measurement.The amplifier module is achieved by using variable gain amplifier AD603,the biggest gain can reach 60dB,with 10dB gain adjustable,and the gain error is less than 1%.The programmable filter module consists of a MAX297 lowpass filter,a TLC1068 highpass filter and an elliptic lowpass filter,and the filtered mode is chosen by using the analog switch.The system can adjust the active filters＇-3dB cut-off frequency from 1kHz to 30kHz,and the error is less than 1.5%.Besides,the amplitude measurement is achieved by using RMS sampling chip AD637 and 12-bit parallel ADC MAX120.