Log‑Periodic Patch Array with Coupled T‑Probes for Broadband Dual‑Polarized Antenna‑on‑Display

Abstract

This paper proposes a log-periodic patch array with coupled T-probes for broadband dual-polarized antenna-on-display applications. The antenna is implemented as thin-metal meshes on a low-profile substrate (≤ 0.01λ 0 ), ensuring optical transparency. The array consists of three square patches, each rotated by 45° and fed at two lower edges by T-shaped proximity probes, which excite two orthogonal slant polarizations. The edge lengths of the patches are logarithmically scaled to achieve multiple resonant frequencies, resulting in a broad matching bandwidth. The coupled T-probe structure facilitates efficient feeding of the patches without the need for additional precise tuning, allowing for uniform impedance matching independent of patch length. Since the log-periodic patches radiate primarily at their resonant frequencies, the total radiating fields remain consistent across a wide frequency range, producing flat gains. In addition, the proposed design achieves lower cross-polarization levels due to the cancellation of currents induced in the T-probe on the opposite side. To validate the design approach, a 3 × 1 array with a feeding network was fabricated and tested. The measured −10-dB impedance bandwidth is 23.7% (24.9−31.6 GHz), and the 3-dB gain bandwidth is 21.1% (24.6−30.4 GHz) with a peak gain of 7.65 dBi at 27.7 GHz. The proposed design is then extended to a 3 × 4 array, demonstrating a 3-dB gain bandwidth of 20% (24.7−30.2 GHz) with a peak gain of 11.2 dBi at 25.4 GHz.