A Simple Compact Wideband Microstrip Antenna Consisting of Three Staggered Patches

Abstract

This letter proposes a simple compact microstrip antenna with enhanced bandwidth. The antenna is composed of three narrow rectangular patches: one middle patch and two side patches. The side patches are staggered longitudinally with respect to the middle patch and connected using short strips. The antenna is printed on a thin single-layer dielectric substrate with a ground plane and fed by a coaxial probe at the center of the middle patch. By staggering the side patches with respect to the middle patch, two resonant modes are excited at two close frequencies and a wide bandwidth is obtained. The antenna has a compact size of 0.31 λ 0 × 0.29 λ 0 × 0.027 λ 0 (where λ 0 is the center operating wavelength in the free space) and a measured impedance bandwidth of 6.8% (return loss > 10 dB), which is approximately 2.3 times wider than that of a conventional square microstrip antenna on the same substrate. The antenna has a stable gain varying from 5.8 to 7.5 dBi and a low cross-polarization level less than −15 dB within the impedance bandwidth. The radiation characteristics are nearly constant over the entire impedance bandwidth.