Analytical Design and Experimental Validation of an SRR-Based High-Impedance Surface Co-Integrated with a Bow-Tie Microstrip Patch Antenna at 2.5 GHz

Abstract

This paper presents a mathematically rigorous analytical synthesis framework for optimising a Split-Ring Resonator (SRR) High-Impedance Surface (HIS) meta-surface co-integrated with a bow-tie microstrip patch antenna at 2.5 GHz. The central optimisation objective is minimisation of the antenna quality factor Q — and consequent maximisation of the 10-dB impedance bandwidth — subject to the resonance-alignment constraint fHIS = fr. The SRR unit cell is modelled as a parallel LC resonator; closed-form expressions for equivalent inductance Ls and capacitance Cs are derived, and the optimum outer radius rout* = 5.5 mm is identified via a parametric sweep with Nicolson–Ross–Weir (NRW) S-parameter extraction confirming the global optimum. Both a reference and the HIS-integrated antenna are fabricated on FR4 (εr = 4.4, tan δ = 0.02, h = 1.6 mm, 45 × 40 mm²) and characterised by Agilent FieldFox VNA with OSLT calibration. Measured results validate the optimisation: 10-dB impedance bandwidth expands from 5.5% to 9.8% (+78%); return loss deepens from −11.76 dB to −15.96 dB; and peak gain increases from 4.82 dBi to 5.64 dBi (+17%).