基于CPLD的开关电容组式跟踪滤波器设计与实现

Design and implementation of the switch-capacitor-group-style tracking filter based on CPLD

针对大动态范围高灵敏度短波接收机射频前端信号处理需要,提出并实现了一种基于CPLD的开关电容组式跟踪滤波器与变容二极管电调谐滤波器串联方案,并对该滤波器性能进行了评估。实验结果表明,该滤波器可以工作于1MHz^30MHz频段,带宽易调,设计简单,且具有稳定的带宽和很高的温度稳定性。实测的滤波器3dB带宽为300kHz^700kHz,Q值为11.8dB^25dB,通带增益为2.5~4.5,能很好地满足接收机设计指标。

According to the RF fi＇ont-end needs of the large dynamic range and high sensitivity shortwave receiver, this paper proposes a design method of the switch-capacitor-group-style tracking filter based on CPLD and the varactor electric tuned filter in series. Then it makes a performance evaluation of the tracking filter. The experimental results indicate that the tracking filter can work well on the frequency band between 1 MHz to 30 MHz. The experiment also shows that the design provides a stable band width and higher temperature stability. The observed data of the filter shows that the 3 dB bandwidth is 300 kHz to 700 kHz, with high Q value of 11.8 dB to 25 dB, and the passband gain is 2.5 to 4.5. The experimental results can meet the design indicators of the receiver very well.