Design of HIS-backed Miniaturized Cross Slotted Antenna for Circular Polarization Using Modal Analysis: A Novel Approach

Abstract

This work presents a novel design technique of a circularly polarized miniaturized cross slotted antenna backed by a High Impedance Surface using substructure based Characteristic Mode analysis. The electromagnetic behavior of the antenna and the HIS is studied while the two structures are in close vicinity, with no air gap isolation between them. Such problem of proximity induced near field interaction of the finite HIS with the antenna has rarely been systematically attempted in literature. The chosen operating frequency of the cross slotted antenna is synchronized with the frequency of high impedance operation of the HIS by analysing the structure. This work explains how the characteristics of HIS can be determined when placed at the near electromagnetic field of an antenna. Circularly polarized radiation is obtained at 2.45 GHz with a 3-dB axial ratio bandwidth close to 1.46% with a 10-dB impedance bandwidth of 4.4%. The overall size of the designed antenna is 0.23 Llambda_0 x 0.23 lamba_0 x 0.039 lambda_0 including the substrate dimensions at 2.45 GHz (lambda_0 is the free space wavelength). The area reduction of the complete antenna and only the slotted patch is achieved as 78% and 88% respectively, as compared to the fundamental mode half wavelength antenna at this frequency.