Low-Loss Integrated Passive CMOS Electrical Balance Duplexers With Single-Ended LNA

A tunable integrated electrical balanced duplexer (EBD) is presented as a compact alternative to multiple bulky surface acoustic wave (SAW) and bulk acoustic wave (BAW) duplexers in third-generation (3G)/fourth-generation (4G) cellular transceivers. A balancing network creates a replica of the transmitter (TX) signal for cancellation at the input of a single-ended low-noise amplifier (LNA) to isolate the receive path from the TX. The proposed passive EBD is based on a cross-connected transformer topology without the need of any extra baluns at the antenna side. The balancing network enables a single-ended LNA with reliable high TX power operation up to 22 dBm by alleviating the common-mode coupling. The duplexer achieves around 50-dB transmitter-receiver (TX-RX) isolation within a 1.6-2.2-GHz range. The cascaded noise figure (NF) of the duplexer and LNA is 6.5 dB, and TX insertion loss (TXIL) of the duplexer is about 3.2 dB. The duplexer and LNA are implemented in a 0.18-μm CMOS process and occupy an active area of 0.35 mm
²
.