Magnetic-Less Simultaneous Transmit and Receive Front End using Highly Efficient GaN-Based Quadrature Balanced Amplifier

This paper presents the first-ever high-power magnetic-less simultaneous transmit and receive (STAR) front end based on quadrature-balanced power amplifier (QB-PA). It is originally discovered that the harmonic-tuning and high output reflection of high-power GaN PA can be synergistically co-designed for achieving high TX efficiency and low receive (RX) path loss of the front end. Based on this methodology, a QB-PA-based STAR front end is practically designed using commercial GaN transistors as a proof-of-concept demonstration. The developed prototype experimentally achieves up to 80% PA efficiency at peak transmission power of 42.5 dBm and meanwhile very low receive loss of ≈1.5 dB. Moreover, STAR operation is experimentally conducted using both continuous and modulated TX stimulus at 1.6 GHz, in which a satisfactory reception performance is measured at 1.66 GHz with a very low RX EVM. This design radically outperforms the state-of-the-art by order of magnitude in TX power, together with significantly enhanced PA efficiency and antenna-interface efficiency.