Formulation of Resonant frequency for Compact Microstrip Antennas

A slot cut inside the microstrip antenna (MSA) gives compact MSA configurations like C-shaped MSA and rectangular ring MSA. The approximate equations to predict the resonant frequency of these MSAs have been reported in previous studies. In this paper, modified equations are presented which yields better accuracy in the frequency for different slot dimensions. These equations are obtained by studying the surface current distributions generated using ensemble software. A rectangular MSA (RMSA) of length (L) = 6 cm and width (W) = 4 cm, simulated using IE3D software on RT-duroid substrate (epsiv_r = 2.33, h = 0.159 cm, and tan delta = 0.001) has TM₁₀ mode resonance frequency of 1.607 GHz. The slot of different size was cut inside this RMSA to realize C-shaped and rectangular ring MSA