Active Vector Modulator Design for Self-Interference Cancellation in STAR Systems

Simultaneous transmit and receive (STAR) systems require effective methods of self-interference cancellation for proper functionality. A common method involves the use of RF cancellers in the direct interference path between the transmitting and receiving antennas of a multi-antenna system. This work presents a novel vector modulator prototype circuit to be used in a multi-tap RF canceller. In-phase and quadrature components are individually controlled to produce any gain magnitude over a full 360° tuning range. The prototype demonstrates between 40 and 50 dB of gain over its 6:1 operational bandwidth from 400 to 2400 MHz. The device’s output 1-dB compression point and third-order intercept were also measured and demonstrate excellent performance across its operating frequency range, proving it suitable for in-band full-duplex (IBFD) systems.