Modified re-configurable quadrature balanced power amplifiers for half and full duplex RF front ends

Abstract

An RF front-end (RFFE) architecture for dual-mode half and full duplex operation, employing a modified quadrature balanced power amplifier (QBPA), is proposed, where the receive channel is connected to the QBPA transmit isolated output. In this RFFE, the receive signal is reconstructed from inherent output reflections of the two internal power amplifiers employed in the modified QBPA. Re-configurable transmit signal isolation at the receive port enables safe LNA operation at half-duplex and relaxed RF self-interference cancellation (SIC) requirements for full-duplex operation. The S-parameter signal flow diagram of the proposed RFFE is described and analyzed, yielding transmit-receive transfer functions of interest in the presence of antenna back-reflected transmit signal. Transmit-receive isolation compensation for antenna reflections is analytically derived. Circuit simulations of the proposed topology verify the model and theoretical analysis.