一种低功耗自动频率修正的复数滤波器设计

采用当前主流的0.18μm RFCMOS工艺,设计实现了一款低功耗五阶OTA-C复数滤波器电路,该电路应用于低中频结构的GPS射频前端芯片中。滤波器的频率修正电路没有采用基于锁相环的常规结构,而是设计了一种带有频率修正功能的自偏置电流基准,来补偿工艺、温度变化的影响。滤波器的带宽为3MHz,中心频率为4.092MHz,镜像抑制大于30dB,10MHz频率处的阻带抑制大于40dB。滤波器的通带增益为10dB,消耗的总电流为0.8mA,工作电压为1.8V。理论仿真结果和测试结果能够很好地符合。

A Low Power Complex Filter Design with Automatic Frequency Tuning

A low power fifth-order OTA-C complex filter for a low-IF GPS receiver is implemented in a mainstream 0.18 μm RFCMOS process.The frequency tuning scheme is different from the conventional one based on phased-locked loop.To compensate for process and temperature variations,a self-biased current reference is designed playing the role of frequency tuning.The filter bandwidth is 3 MHz and is centered at 4.092 MHz.Image is attenuated by more than 30 dB,and the stop-band attenuation at 10 MHz is at least 40 dB.The pass-band gain of the filter is 10 dB,and it dissipates 0.8 mA from a 1.8 V supply.The theoretical and experimental results are in good agreement.