L-probe fed multiband microstrip antennas with slots

Adding a U-slot has been found to increase the overall bandwidth of microstrip antenna (MSA). Previous studies focus on broadband operation implemented on slightly thicker substrate using coaxial feeding system. For this paper, the design of a multiband microstrip antenna with U-slots fed by L-probe in thin substrate is presented. The multiband operation is achieved by adding multiple U-slots on typical MSA. The L-probe feeding system provides good return loss characteristics on multiple frequencies. The relationship between key antenna dimensions and overall antenna characteristics are investigated. A test antenna with three U-slots exhibits good antenna characteristics on multiple frequencies. Also, a modified model to U-slot MSA is also presented by varying the slot geometry.