Compact frequency-reconfigurable microstrip antenna based on hybrid inverted T and L-shapes for WiMAX, 5G, Wi–Fi 5/6 applications sub-6 GHz

Abstract

This article presents a compact, reconfigurable frequency microstrip antenna for sub-6 GHz multi-standard wireless communication systems. The proposed structure is a hybrid combination of two inverted T and L shaped radiating elements, separated by a slot that allows frequency reconfiguration via a PIN diode model SMP1340-079LF. A partial ground plane with a rectangular stub is etched onto the bottom layer of the substrate. Bias circuits for the PIN diode, including a DC blocking capacitor (Cblock) and choke inductors (Lchoke), are integrated into the top layer to isolate the RF signal from the DC signal. The antenna operates in two modes: ON (PIN diode conducting) and OFF (PIN diode blocking). In ON mode, the antenna operates on three distinct frequency bands, with resonances at 2.88 GHz (WiMAX), 4 GHz (5 G, n77), and 5.6 GHz (Wi–Fi 5/6, n46). In OFF mode, it offers broadband operation centered around 3.82 GHz (5 G, n77) with FBW of 62%. A prototype was fabricated on a low-cost FR-4 substrate with a thickness of 1.6 mm and a relative permittivity εr=4.4 and was validated through experimental testing. The results obtained are consistent with simulations, confirming the reliability of the design. The antenna achieves a maximum radiation efficiency of 80%, a maximum gain of 3.82 dBi, and exhibits measured S11 values below −30 dB across all operating bands, indicating proper impedance matching. The antenna has compact overall dimensions (38 × 35 × 1.6 mm3), and its design uses a single PIN diode for reconfiguration, enabling multiband operation in the sub-6 GHz range.