Bandwidth Enhancement of a Microstrip Line-Fed Printed Wide-Slot Antenna With a Parasitic Center Patch

A printed wide-slot antenna with a parasitic patch for bandwidth enhancement is proposed and experimentally investigated. A simple 50-Ω microstrip line is used to excite the slot. A rotated square slot resonator is considered as reference geometry. The rotated square slot antenna exhibits two resonances (f₁ : lower resonant frequency, f₂: higher resonant frequency). By embedding a parasitic patch into the center of the rotated square slot, the lower resonant frequency is decreased and the higher resonant frequency is increased. Thus, broadband characteristic of the wide-slot antenna is achieved. The measured results demonstrate that this structure exhibits a wide impedance bandwidth, which is over 80% for |S₁₁| ≤ -10 dB ranging from 2.23 to 5.35 GHz. Also, a stable and omnidirectional radiation pattern is observed within the operating bandwidth. In this design, a smaller ground plane is considered compared to the reference antenna (rotated square slot antenna without the parasitic center patch).