A compact wideband printed inverted-F antenna for smart-card-sized IoT devices

Abstract

A compact printed Inverted-F antenna (PIFA) with a wide impedance bandwidth is proposed for integration into smart-card–sized IoT devices. The antenna occupies only 14 × 31.1 mm² and achieves a wide impedance bandwidth by introducing an F-shaped parasitic stub, which generates a controlled dual-resonant response. A prototype was fabricated on a single-layer FR-4 substrate (ε_r = 4.3, thickness of 1 mm) using standard PCB etching. Measurements show a −10 dB bandwidth of 540 MHz (2.12–2.66 GHz), which agrees well with simulations and validates the robustness of the dual-mode mechanism. The antenna exhibits a peak gain of 3.69 dBi and a radiation efficiency of 93.7% at 2.4 GHz. Compared with recent PIFA and parasitic-element-based structures in the literature, the proposed design provides competitive or superior bandwidth while maintaining a simple planar profile and extremely compact footprint without using defected ground structures, multilayer substrates, tunable components, or metamaterial loading. These characteristics make the proposed antenna suitable for cost-effective and space-constrained IoT terminals operating in the 2.4 GHz band.