Self-Interference-Constrained Transmit Beamforming in Interleaved and Displaced In-Band Full-Duplex Arrays: Gain and Isolation Trade-Offs

Paper in proceeding, 2026

This paper investigates the joint impact of array geometry and SI-constrained transmit (Tx) beamforming on in-band full-duplex (IBFD) performance. A maximum-gain Tx beamformer with a pre-described Tx-Rx isolation constraint is applied to interleaved and vertically displaced planar dipole arrays, modeled via full-wave Method-of-Moments simulations. For each configuration, the Tx array gain loss relative to unconstrained beamforming is quantified as the required isolation is swept from 0-100 dB, across varying lateral interleaving percentages and vertical offsets. Results reveal that highly interleaved coplanar configurations suffer rapid gain degradation beyond moderate isolation levels, whereas vertical separation reduces effective coupling, expanding the feasible region where high Tx array gain and stringent isolation coexist. These findings highlight geometry-aware beamforming as a key lever for optimizing compact IBFD array deployments.