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

This paper demonstrates transmit rejection with a quarter-wave $(\lambda/4)$ 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 I-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.

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