Unidirectional printed loop antenna

Abstract

A new type of printed rectangular loop antenna with capacitive loads is proposed for unidirectional radiation pattern production. The arrangement presented here is shown to have a current distribution with balanced magnitude and 90/spl deg/ phase difference on parallel radiating edges of the loop. As a result, the printed loop is equivalent to an array of two dipoles with quarter-wavelength space separation and 90/spl deg/ phase excitation difference. Simulated and measured results for 1 GHz center-frequency operation show that the new unidirectional printed loop antenna can achieve a front-to-back ratio of more than 20 dB, power gain of 4.5 dBi, and can be easily matched.