Low-Profile, Broadband, Wide-Angle Electronically Scanning Transmitarray Based on SIW Slot-Coupled Near-Field Feeding

This letter proposes a low-profile, broadband, and wide-angle electronically scanning transmitarray (TA) based on substrate integrated waveguide (SIW) slot-coupled near-field feeding, which theoretically overcomes the challenge of achieving low-profile design for far-field fed antenna arrays. First, a high efficiency reconfigurable transmitarray (RTA) element is constructed based on Fabry-Pérot cavity theory. The RTA element integrates orthogonally polarized metallic gratings and a “double-arrow” shaped polarization converter with a pair of PIN diodes. It achieves 1-bit transmission phase control while maintaining a cross-polarization transmission amplitude above -1 dB over a 20.7% fractional bandwidth (7.46–9.18 GHz). Furthermore, we design an 8×8 slot antenna array, fed by the 1:8 SIW power divider, exhibits a measured -10 dB impedance bandwidth of 22.9% (7.39–9.3 GHz), which fully covers the operational bandwidth of the phase-shifting layer. Finally, a low-profile RTA with an effective physical aperture of 200×200 mm² and an overall profile of only 0.38λ0 at 8.3 GHz is fabricated and measured. Measurement results show that the proposed RTA achieves a peak aperture efficiency of 18.9% with a 3-dB gain bandwidth of 15.6% and a working bandwidth (|S11| < -10 dB) of 22.9% (7.42–9.34 GHz), while demonstrating wide-angle beam scanning capability of ±60° in both the E- and H-planes.