In-band full-duplex technology for VDES applications

This paper presents an approach that integrates in-band full-duplex technology with the VDES frequency band. This integration is designed to address the pressing challenge of scarce spectrum resources and the significant upstream and downstream conflicts that arise in VHF data exchange systems. The key technology for resolving the issue of system self-interference, which significantly impairs the reception of useful signals, is to enhance the isolation between the transceiver links. A varactor diode and LC resonant circuit are used to construct an impedance mismatch circuit, the input impedance of which is changed to regulate the amplitude and phase of the reflected signal from the circulator, and finally the reflected signals and the direct leakage signals are superimposed and cancelled to achieve the isolation improvement. The final physical test conducted in the 160 MHz band with a 5 MHz bandwidth demonstrated an isolation of approximately 50 dB and a relative bandwidth of 3.125%.