Wide-band ultralow-profile compact microstrip antenna loaded by slots

A novel method to extend the operation bandwidth and reduce the size of the ultralow-profile microstrip antenna is presented in this paper. Printed on a dielectric substrate of FR4 with relative permittivity of 4.4, loss tangent of 0.02 and thickness of h = 1 mm (approximate to 0.005 lambda(0), where lambda(0) is the center frequency wavelength at free space), and fed by coaxial probe from the back, the microstrip antenna loaded by slots is demonstrated to generate three closer resonant frequencies of 1.625 GHz, 1.682 GHz and 1.752 GHz to achieved wideband characteristic (1605-1776 MHz, 10.1%). The antenna size is only 23% of the traditional microstrip antenna for the same frequency with the same substrate. Details of the antenna design is presented and discussed in this paper.