一种适用于IEEE802.15.4协议的全集成CMOS复数滤波器

A Fully Integrated CMOS Complex Filter for IEEE802.15.4 Standard

复数滤波器是低中频结构接收机中的一个重要模块,起到镜像抑制的作用。该文针对IEEE802.15.4的低功耗要求,提出了一种可以灵活配置共模反馈模块的伪差分结构OTA,该OTA具有内部共模前馈和共模检测功能,适用于级联应用。基于该OTA结构实现了一个3阶巴特沃斯Gm-C复数滤波器,中心频率在1MHz,带宽1.3MHz,带内群延时波动小于0.16μs,镜像抑制能力满足IEEE802.15.4协议要求。该文还提出了一种频率调节方法,用于控制复数滤波器的中心频率,与传统的锁相环结构相比,该调谐电路结构简单,适合在低功耗应用场合。

Complex filter is one of the major parts in low-if receiver to reject imagine signal.Considering the low-power requirement of IEEE802.15.4 standard,this paper presents a pseudo OTA with flexible configuration of common mode feedback block,which is suitable to use in cascade systems for its inner common mode feed-forward and common mode detection.A third-order Butterworth Gm-C complex filter is designed based on this OTA,its center frequency locate at 1 MHz,with a 1.3 MHz bandwidth,the in-band group delay ripple is less than 0.16 μs,its IRR（Imagine Rejection Ratio） can satisfy IEEE802.15.4 standard＇s requirements.A frequency tuning method is also presented in this paper,it is simple and power efficiency comparing to traditional PLL tuning method.