Dual-Polarized Microstrip Patch Antenna With Enhanced Bandwidth and Gain Using Mode Perturbation and <i>λ</i> /4 Resonator Coupling

In this paper, a dual-polarized (DP) square microstrip patch antenna (MPA) with enhanced bandwidth and gain is proposed. The antenna operates in modified TM10/TM01-like modes, excited independently via two orthogonal ports, and enabled by four symmetrically placed metallic vias that perturb the field distribution within the substrate. As a result, the antenna becomes electrically larger relative to the wavelength at resonance frequency, leading to an increase in realized gain. To enhance the bandwidth, the proposed MPA is fed by a pair of quarter-wavelength microstrip line resonators, which introduce an additional resonance associated with the feeding structure, and function as an integrated filter. When properly combined with the modified fundamental mode, these resonances result in significant bandwidth enhancement. Although both techniques have been used separately in prior single-polarized designs, their integration in a dual-polarized configuration has not been previously reported. Besides that, as the radiator is integrated with a filter, a study of its performance in a digital communication system was carried out, taking into account the dispersive parameters, particularly group delay, which is a critical aspect of filters, and gain. Following the detailed design process, a prototype was fabricated and measured, exhibiting excellent consistency between simulated and experimental results. The final antenna design achieves a bandwidth of approximately 7.5% (6.93–7.47 GHz) for |Snn|≤-10 dB, where |Snn| denotes the magnitude of the reflection coefficient (S11 or S22) at port n. At the frequency of 7.25 GHz, the antenna exhibits a peak realized gain of 10.3 dBi, port isolation greater than 25.0 dB, and cross-polarization discrimination of 22.2 dB. These results demonstrate that the proposed antenna provides an effective low-profile solution combining wide bandwidth, high gain, and dual-polarization capability.