A Gain Boosted N-Path Filter with Improved Out of Band Rejection

This paper proposes a gain boosted N-path filter with improved out of band (OOB) rejection. The proposed filter contains two stages. The first stage contains a gain boosted N-path filter where two switches in each path are driven by the same clock phase. The second stage contains a two-port passive N-path filter where two switches in each path are driven by clocks of 180 degrees out of phase. The proposed design removes the limitation on OOB rejection due to switch resistance, which saves dynamic power consumption. A four path differential bandpass filter tunable from 0.2–1.2 GHz with a bandwidth of 16 MHz is implemented in 65nm CMOS technology. It achieves a maximum gain of 19.5 dB with a minimum noise figure of 2.3 dB. The maximum OOB rejection achieved is 65 dB. The minimum in-band IIP3 recorded is −4.5 dBm. The minimum third and fifth order harmonic rejection achieved is 20 dB and 27 dB, respectively. The proposed filter draws a maximum power of 16 mW from 1.2 V supply at 1.2 GHz tuning frequency.