Hexagonal CSRR Based Broadband Monopole Antenna at UHF-Band

Abstract

: In this work, complementary split ring resonators (CSRR) based broadband monopole antenna is proposed. A variety of geometrical shapes are studied as a radiator to find out the radiator with the highest possible return loss bandwidth potential. It has been found that the semi-circularly shaped resonator has the widest VSWR<3 bandwidth. Therefore, a monopole antenna constructed by a semi-circularly shaped microstrip radiator which is excited with a 50-ohm microstrip line is proposed. It has been seen that a semi-circularly shaped microstrip radiator does not have adequate broadband performance in terms of VSWR<2 bandwidth. Therefore, CSRR structures that are shaped like hexagons are employed in order to enhance the VSWR<2 bandwidth of the proposed antenna. It has been seen that a single CSRR only influences a limited frequency range. In order to make the proposed monopole antenna operate within a much larger frequency bandwidth and achieve return loss enhancement along the whole frequency band, multiple equilateral hexagonal CSRRs are utilized. The ground plane of the monopole antenna is modified such that three CSRR structures having different dimensions are inserted behind the 50-ohm feeding line. The resulting manufactured monopole antenna operates from 320 MHz to 1100 MHz while having an average gain of 3.05 dBi gain. Moreover, the total efficiency of 94% is achieved along the operating frequency band.