Design of a metamaterial-inspired size-reduced wideband loop antenna with frequency scanning characteristic

Abstract

A novel metamaterial-inspired loop antenna is proposed towards wideband operation, size reduction and frequency scanning capabilities. The high permeability characteristic of split rings resonators (SRRs) is utilised to reduce the size of a loop antenna. The SRRs also improve the impedance matching of the loop antenna, and thus significantly increase the bandwidth. Moreover, the proposed antenna has a frequency scanning capability because of the existence of SRRs. According to the measured results, the proposed antenna has a 10 dB operating band from 2.3 to 3.8 GHz with the absolute bandwidth of 1.5 GHz and the fractional bandwidth of 50%. Owing to SRRs, the first-order resonant frequency of the antenna shifts from 3.5 to 2.4 GHz, leading to an effective size reduction of 32% against the original loop antenna. The proposed antenna exhibits a continuous frequency scanning capability with the total scanning angle of 135 degrees, sweeping from 75 to -60 degrees.