Semi-Empirical Equation for a Semi-Circular PIFA

Abstract

This article introduces a newly proposed Equation for the calculation of the optimal radius of the semicircular structure of the Planar Inverted-F Antenna (PIFA), derived by equating the area of the equivalent rectangular structure and the area of the given structure. The Equation was tested using HFSS simulation at operating frequencies of 2.4 GHz, 5.2 GHz, and 5.8 GHz with substrate materials of relative permittivity 2.55, 3.2, and 4.4. To further examine the Equation’s reliability under practical scenarios, three antenna prototypes were implemented on the FR4 substrate (  = 4.4) at the same frequencies. The measured S11 showed clear resonance minima at the corresponding operating frequencies that matched the theoretical values and simulation results. The strong agreement of the theoretical results with the simulation results and the experimentally measured results, supported by a Pearson’s correlation coefficient of 0.999, validates the proposed Equation’s usability for designing a compact semicircular PIFA structure.