A λ/4-Inverted N-Path Filter in 45-nm CMOS SOI for Transmit Rejection with Code Selective Filters

This paper demonstrates transmit rejection with a quarter-wave (λ/4) transformer that inverts the response of a shunt N-path filter to break the inherent N-path trade-offs between switch resistance and rejection. A 45-nm CMOS SOI filter supports both frequency and code selective filtering modes. The chip consumes a power of 9.37 mW from 1-V and 1.8-V supplies at frequency of 0.9–1.1 GHz and the chip area is 1.77mm². The transmit rejection is 21.9 dB with 3.3 dB insertion loss. The in-band third-order-intercept point (IIP3) is 22.6 dBm.