A Compact Frequency-Reconfigurable Antenna Using a Single PIN Diode for IoT and Sub-6 GHz Applications

Abstract

This research article introduces a compact, frequency-reconfigurable microstrip radiating element featuring a PIN diode for multiband wireless communications. The proposed radiating element is simulated on an FR-4 substrate measuring 22.5 x 13 x 1.6 mm³ and is designed to operate below 6 GHz. The antenna design features a U-shaped radiating element with additional folded sections to improve current distribution and multiband performance. The arrangement uses a single PIN diode as a dynamic switching device between two operating modes, without complex circuitry. When the switch is OFF, the radiating element resonates at 2.4 GHz and 5 GHz; in the ON state, the frequencies shift to 2.16 GHz and 4.5 GHz, enabling support for multiple operating frequencies for IoT, WLAN, and other modern systems. The suggested antenna shows good impedance matching across all operating frequencies, with S11 values of −22 dB, −37 dB, −32.9 dB, and −16.5 dB at 2.4, 5, 2.16, and 4.5 GHz, respectively. The bandwidths are 300 MHz and 800 MHz in OFF mode and 200 MHz and 600 MHz in ON mode, respectively. VSWR was below 1.5 in all operating modes. The antenna has stable gains of 1.5 to 2.5 dBi and a high efficiency of 86% to 95%. Radiation patterns are mostly bidirectional and omnidirectional in the E-plane and H-plane, respectively, ensuring good communication performance. The findings affirm the claim that the proposed radiator element offers a small, cost-effective, and efficient role for multiband and reconfigurable wireless systems, especially in the IoT and sub-6 GHz bands.