Compact Multiband Microstrip Antenna Using Inverted-L- and T-Shaped Parasitic Elements

By placing inverted-L- and T-shaped parasitic elements at both the radiating apertures of a microstrip patch antenna, a low-profile, compact single-layer multiband microstrip antenna operable in various bands has been developed. These bands include LTE TDD No. 34 (2.0175 GHz), WLAN (2.45 GHz), and WiMAX (3.5 GHz) bands. The antenna has dimensions of 0.26 λ_L ×0.25 λ_L ×0.03 λ_L, where λ_L is the free-space wavelength at 2.0175 GHz, and resonance in the parasitic elements occurs through coupling and perturbations to the microstrip patch. In each band, the measured -10-dB bandwidths cover the required bandwidths at 28 MHz (1.39%), 91 MHz (3.71%), and 255 MHz (7.29%). Within each of the designed bands, a broadside radiation pattern is observed.