Design of a broadband U-slot loaded E-shaped patch antenna using characteristic mode analysis

Abstract

This article introduces a characteristic mode analysis (CMA) based broadband and high gain microstrip patch antenna by embedding U-slot into an E-shaped patch in a single-layer radiating structure. The design and analysis of the antenna utilize the CMA to obtain the inherent modal currents induced in the E-shaped radiator. Out of possible radiating intrinsic modes, an undesired higher-order mode (HOM), adjacent to the upper band of the E-shaped patch, is efficiently excited with a secondary radiating slot (U-slot) to increase the bandwidth. Additionally, the U-slot creates another HOM with proper polarization and broadside radiation. Consequently, the overlapping of these new excited modes with the primary operating band of the E-shaped patch exhibits a broader bandwidth of 64.7% (4.7–9.2 GHz) and a peak gain of 10.6 dBi with an overall dimension of 1.4λ0×1.4λ0×0.1λ0 (λ0 being the free-space wavelength at a centre frequency of ≃ 7 GHz). The fabricated prototype agrees well with the simulation results, and the radiation patterns remain consistent over the entire bandwidth. Due to planar and broadband features, the proposed antenna is suitable for low-cost WLAN, Wi-Max, Wi-Fi 6E, and sub-6 GHz applications.