A Rat-Race-Fed Rectangular Microstrip Loop Antenna

A novel-fed rectangular microstrip loop antenna is presented. The proposed antenna is fed by a quasi rat-race coupler otherwise known as hybrid-ring coupler. The resonator is located in between the flat parallel plates of the current-carrying conductors. The proposed rat-race feed is configured in a balanced-mode arrangement, and as such, the input signal at the source input was split into two waves traveling in opposite directions with equal magnitude but 180° out of phase. Three resonance frequencies were excited, and hence, triple frequency bands. The antenna estate area is 0.53 λ
₀
×0.53 λ
₀
at center frequency of 5.3 GHz with a gain of 9.11 dBi for 5.31 GHz, whereas it is 7.04 and 5.66 dBi for 7.0 and 8.0 GHz, respectively. The proposed antenna is compact in size and suitable for multiple integrated services applications as a result of multiband characteristics.