L-band bandpass filter with high out-of-band rejection based on CMOS active series and shunt inductors

An active 7-stage L-band bandpass filter with high out-of-band rejection is presented. The LC equivalent prototype of the bandpass filter is designed and optimized to absorb parasitic capacitances introduced by the active inductors. The active filter employs active shunt and series inductors. To the best of our knowledge, it is the first time that active series inductors are used for wideband bandpass filter design. The bandpass filter is fabricated in a standard 0.13 μm CMOS process. The measured 3 dB bandwidth is from 1 GHz to 2 GHz and the out-of-band rejection is better than 40 dB below 0.7 GHz and above 2.24 GHz. A common mode suppression of 30 dB is also achieved over the full measured frequency range. The measured input referred 1 dB compression point is -21 dBm. The filter consumes 25 mA at 1.2 V and the core area is 0.18 mm².