Decoupling Structure for High-Bandwidth Multiport Monopole Antennas in K-Band and 5G Applications

This paper introduces a multiport monopole antenna featuring high isolation and a broad operating bandwidth, specifically designed for K-band and 5 G applications. The proposed antenna configuration comprises four antenna elements assembled to achieve a compact design. A 0.254 mm thick Rogers RT-5880 substrate is used, with an overall size of 24 × 22 mm. Each antenna element is supported by a truncated ground plane, and four symmetrical slots are introduced into the radiating structures. As a result, the proposed multiport antenna covers a frequency band of approximately 18–27 GHz, based on the -10 dB criterion, providing a wide bandwidth of nearly 9 GHz. The separation between the antenna elements is about 4.5 mm. Additionally, a decoupling structure is inserted between the radiating elements to enhance isolation within the desired band, also resulting in a minor improvement in the operating bandwidth. Several performance metrics, including total active reflection coefficient (TARC), diversity gain (DG), envelope correlation coefficient (ECC), and channel capacity loss (CCL), are evaluated and show satisfactory performance within the operating bandwidth. The proposed antenna achieves more than 75% radiation efficiency. The overall performance of the multiport antenna indicates its potential for K-band and 5 G applications.