A 1-2-GHz Quadrature Balanced N-Path Receiver for Frequency Division Duplex Systems

The implementation of fully integrated frequency division duplexing (FDD) transceivers imposes many challenges, such as receiver (RX) desensitization by the transceiver (TX), reciprocal mixing, and sensitivity, to antenna voltage standing wave ratio (VSWR) variations. Here, we present the quadrature balanced N-path receiver (QBNR) architecture. The QBNR is composed of a quadrature hybrid and two identical mixers, presenting a short circuit and 50- \Omega matching in the TX and RX bands, respectively. The TX power reflects at the mixers and reconstructs in-phase at the antenna, while the RX signal from the antenna can be reconstructed in phase at the baseband RX port. This architecture provides wideband FDD functionality while providing TX noise and local oscillator phase noise cancelation and antenna VSWR tunable compensation. Our implementation measurement results for an equalized configuration show more than 55-dB TX to RX isolation at frequencies of 1-2 GHz and for antenna VSWR of 2:1, with 3-dB TX loss and 4-dB RX loss, RX IP 1 dB of 5 dBm and TX IP 1 dB of 16 dBm, and receiver {B_{1\,\text {dB}}} of 10 dBm.