A Broadband Low Profile Patch Antenna of Compact Size With Three Resonances

An E-shaped patch antenna fed by a folded L-shaped probe is proposed. The shorted wall loading is employed to make the antenna compact, and the lateral size is only 0.196 lambda_L times 0.221 lambda_L, where lambda_L is wavelength at the lower cutoff frequency of the measured operating bandwidth in the free space. Three adjacent resonances are utilized to achieve a broad band while keeping the antenna very low profile. The air substrate is only 4 mm (i.e., 0.029 lambda_L) thick, and the measured impedance bandwidth is about 19.8% (with a central frequency of 2.378 GHz). The procedure of optimal design is also described.