High Isolation CMOS TDD RF Front-End Using Sandwich-Type Concentric Vortical Transformer and Leakage Elimination Technique

This paper presents a 90-nm CMOS radio-frequency (RF) front-end using the proposed sandwich-type concentric vortical transformer (CVT) for transmit/receive (TX/RX) switching in time-division duplexing (TDD) systems. This implementation combined with the TX leakage elimination technique embedded in low-noise amplifier (LNA) circuits is capable of improving the isolation between TX port and RX port. Moreover, the insertion loss (IL) in both TX and RX modes can be improved by about 1 dB as compared with the conventional transformer-based T/R switch topology. The proposed RF frond-end circuits including two separated chips with a pair of differential bonding wires for interconnection was measured using a continuous-wave (CW) signal at 2.6 GHz. It achieves 46.5-dB isolation between the TX port and the RX port, 29.1-dBm peak output power and 42.8% efficiency in TX mode, and 12.4-dB gain and 3.46-dB noise figure (NF) in RX mode, respectively.