Theory and experiment on horizontally inhomogeneous rectangular microstrip antenna

Abstract

Theoretical investigation on horizontally inhomogeneous rectangular microstrip antenna is presented here. The dielectric inhomogeneity is introduced by adding two different substrate materials side by side to increase the degrees of freedom by 2 (arm ratio and relative permittivity of newly added material). TE and TM both modes are used here for theoretical investigations. The transcendental equation is derived here to predict the resonant frequency for different modes. Closed‐form analytical expressions are also given to predict the far‐zone electric fields for different HEM modes. Theoretical results are compared with published results as found in the open literature, data obtained using commercially available numerical three‐dimensional electromagnetic simulator high‐frequency structure simulator, and the authors’ own experimental data to show the accuracy of their theory. The additional horizontal dielectric segment gives more flexibility to the antenna designer, leading to wider tuning range over conventional homogeneous RMA. Advantages of this novel antenna structure are also discussed in detail. The authors’ theory can be used (or extended) to investigate log‐periodic antenna using RMAs, fractal‐shaped RMAs etc.