A Wide Tunable Bandpass Filter Design Based on CMOS Active Inductor

In this paper, a wide tunable bandpass filter based on a proposed active inductor topology is presented. Based on the proposed structure, a prototype Q-enhanced second-order filter is designed and simulated in a 0.18??m CMOS process. A center frequency tuning range from 375 MHz to 2 GHz with a quality factor of at least 40 (phase errors less than 1 degree) is achieved thanks to a new technique of frequency tuning. Having a fine and wide range control of its inductance value, the active inductor topology avoids the usage of external capacitances or on-chip varactors for the fine/coarse adjustment of the operating frequency under a fixed nominal biasing condition. The filter consumes 5mW under a supply voltage of 1.8V, including input and output buffers. Keywords-Active inductor; bandpass filter; inductance simulation; wide tuning.