A magnetic‐free in‐band full‐duplex RF front‐end with antenna balancing structure. Issue 6 (16th March 2021) - Jeong, Junhyung
Abstract: In this article, a design of magnetic‐free in‐band full‐duplex (IBFD) RF front‐end with antenna balancing structure is presented. The proposed magnetic‐free IBFD RF front‐end consists of 3 dB hybrid couplers, a Wilkinson power divider, two transmitter (Tx) antennas, and two receiver (Rx) antennas. The proposed IBFD RF front‐end can be implemented and integrated at high frequencies because all the components used in the circuit are non‐magnetic devices. Proposed IBFD RF front‐end eliminated the 3‐dB Tx insertion‐loss of the Balun and transformer in conventional IBFD RF front‐ends using antenna balancing structure. Moreover, there is no noise figure degradation at Rx because it realized only a passive circuit. The mathematical analysis of the cancellation characteristics between two different signals with magnitude and phase difference variations according to the normalized frequencies is presented. Accordingly, the broadband out‐of‐phase balancing power splitter and the antenna balancing structure are adopted to achieve broadband SIC. In order to verify the electrical performances of the proposed magnetic‐free IBFD RF front‐end, it was implemented at the 2.5 GHz WiMax frequency band. When the fabricated IBFD RF front‐end was operated with antenna balancing structure, the measurement results show that the 60 dB SIC bandwidth and maximum SIC were 113 MHz (2.446 ‐ 2.559 GHz) and 75.6 dB, respectively.