Compact Frequency-Reconfigurable Microstrip Antenna for Sub-6 GHz applications

Abstract

This article describes the design of a compact, frequency-reconfigurable microstrip antenna for Sub-6 GHz band. Frequency agility is achieved through two PIN diodes, which dynamically modify the current paths on the patch, providing access to four operating states. Each operating state of the antenna produces one or more resonance frequencies in the $1.8-5.45 \mathrm{GHz}$ range, while preserving stable radiation patterns. The antenna was designed and analyzed using CST Microwave Studio with an emphasis on performance parameters such as VSWR, S11, patterns, and efficiency, as well as the underlying physical mechanisms revealed by surface current distributions. The results obtained confirm the effectiveness of impedance matching and the accurate definition of resonance bands for each configuration. Surface current analysis shows how PIN diodes modify current paths and thus the electrical length of the antenna. It is important to note that radiation patterns remain largely consistent across different operating modes. Generally, the proposed design offers a good compromise between compact antenna size, electromagnetic performance, and frequency reconfigurability making it suitable for Sub-6 GHz wireless applications, such as WLAN and IoT systems.