Radiation Characteristics of a Metaloop Antenna

A dual-band counter-circularly polarized (CP) square loop antenna is investigated. This loop antenna has a single feed point, and the loop arm is composed of numerous segments with capacitive and inductive elements that generate a negative phase constant. When the loop is wound in the counterclockwise direction from the feed point, a left-handed (LH) CP wave is obtained below the balanced frequency (3 GHz), and a right-handed (RH) CP wave is obtained above the balanced frequency. Such counter CP radiation cannot be obtained using a conventional single-feed loop antenna. The LHCP and RHCP radiation patterns are compared, and the frequency bandwidths for the axial ratio and gain are revealed. The VSWR within these CP radiation bands is small, as desired. The experimental results validate the theoretical results.