A Fully Integrated CMOS Active Bandpass Filter for Multiband RF Front-Ends

In this paper, design techniques for an integrated RF bandpass filter are discussed. A novel wide-tuning high-$Q$ active bandpass filter utilizing the active inductors is presented. Issues of the active inductor related to $Q$-enhancement, noise, linearity, and stability are considered. The circuit has been fabricated in an 0.18-$mu$m CMOS process, and the filter occupies the active area of 150$,times,$ 200 $mu$m $^{2}$. Measurement results show that the filter centered at 3.82 GHz with about 36-MHz bandwidth (3-dB) is tunable in frequency from about 1.92 to 3.82 GHz, and it exhibits $-$ 15- to 1-dB compression point at 2.44 GHz with approximately 60-MHz bandwidth while the dc power consumes 10.8 mW.