The broadband microstrip antenna is more commonly realized by cutting the slots at an appropriate position inside the patch. The slot when its length equals either half wave or quarter wave in length then it introduces a mode near the fundamental mode of the patch and yields broader bandwidth. However this simpler approximation of slot length against the wavelength does not give closer results. In this paper, a broadband co-axially fed U-slot cut equilateral triangular microstrip antenna and its compact variation, half U-slot cut half equilateral triangular microstrip antenna is discussed. The analysis to study the effects of slot on the broadband response is presented. It was observed that the slot reduces second order TM11 mode resonance frequency of the patch and along with fundamental TM10 mode yields broadband response. The slot also modifies the surface current directions at TM11 mode in both the slot cut configurations and thereby yields broadside radiation pattern over the complete bandwidth. The proposed analysis gives an insight into the functioning of slot cut broadband microstrip antennas.

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Equilateral Triangular Microstrip Antenna Half Equilateral Triangular Microstrip Antenna Broadband Microstrip Antenna U-slot Half U-slot Higher Order Mode