A Wideband Single-Port Differential-Fed Linear Antenna Array With Low Side Lobe Level and Symmetric Radiation Patterns

Abstract

A single-port differential-fed 12-element linear antenna array is developed for wideband millimeter-wave (mmWave) communication systems, with the 28-GHz band as the primary target providing wide frequency bandwidth (FBW), high gain, low side lobe level (SLL), and highly symmetric radiation characteristics. A wideband stacked-patch antenna element is first developed using a driven patch and a parasitic patch separated by an optimized air gap. Unlike conventional designs, the proposed element is implemented on a cost-effective RO4003 substrate while maintaining broad bandwidth. To suppress side lobes, the four central elements are excited with twice the power of the outer eight elements. The array is then divided into two subarrays fed by conventional 1-to-4 and 1-to-8 corporate power dividers. The two subarrays are combined through a compact backside-fed T-junction, with their 180° phase difference established by the designed feed-path offset, thereby achieving a highly symmetric E-plane radiation pattern without requiring dual-port excitation, external phase shifters, unequal power dividers, or multilayer feeding structures. The proposed 12-element antenna array was fabricated and experimentally characterized. Experimental characterization confirms a FBW of 20.1% (25.0–30.6 GHz), a maximum realized gain of 18.5 dBi, a first SLL of −16.5 dB, and a boresight cross-polarization level below −40 dB. The proposed array provides an attractive combination of wide bandwidth, high radiation performance, and low-complexity implementation for 5G and future 6G mmWave systems.