1 School of Information and Communications Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
2 Department of Electrical and Computer Engineering, Concordia University, Montreal, QC H3G 1M8, Canada.

Dense direct-current (DC) bias routing and numerous radio-frequency (RF) choke inductors pose major challenges to the practical implementation of phase-shifter-free beam steering using PIN-controlled phase switching. To address this issue, a compact vertical DC biasing network is proposed, in which most DC bias lines are routed beneath the ground plane. The DC signals are fed to the PIN diodes through vertical bias lines passing through metallized vias in the dielectric substrate. This arrangement reduces routing congestion and simplifies array-level bias integration. The number of required RF choke inductors is decreased from 112 to 22 per dual-polarized element while preserving the required beam-steering functionality. For experimental validation, a 1 × 3 prototype operating at 3.5 GHz is fabricated and measured. The measured beam directions of -14°, 0°, and +14° agree well with simulations, confirming that the proposed bias network provides the phase control required for beam steering. The proposed network, therefore, offers a compact, low-complexity, and practical solution for scalable phase-shifter-free beam-steering systems.