A Hybrid Transformer-Based CMOS Duplexer With a Single-Ended Notch-Filtered LNA for Highly Integrated Tunable RF Front-Ends

A hybrid transformer-based CMOS tunable duplexer with a single-ended blocker-tolerant low-noise amplifier (LNA) is proposed for a highly integrated reconfigurable RF front-end architecture. The proposed LNA adopts $Q$ -enhanced $LC$ notch filter at the source of the cascode device and $LC$ bandpass filter at the load. It improves the blocker tolerance and linearity of the receiver by rejecting unwanted out-of-band blockers and transmitter (TX) leakage signals. The duplexer with the notch-filtered LNA was fabricated in a 65-nm CMOS process. It has a voltage gain of 24.2 dB from the antenna to the LNA output with 28-dB notch filtering, cascaded noise figure of 6.4 dB, TX insertion loss of 3.8 dB, and IIP3FD of 52.4 dBm. It can also cover a mid-band range from 1.6 to 2.2 GHz in cellular applications. It draws an average current of 8 mA from a supply voltage of 1.2 V and has an active area of 1.19 mm2.