Bandwidth Enhancement of a Differential-Fed Equilateral Triangular Patch Antenna via Loading of Shorting Posts

Abstract

A comprehensive study on the mechanism of bandwidth enhancement for an equilateral triangular microstrip patch antenna (MPA) under differential excitation is presented in this paper. Attributing to the way of differential excitation, the radiation directivity of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode in such a patch has been improved a lot, and field distributions for both TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes are found to be simultaneously excited for radiation. Next, two shorting posts are introduced to this MPA so as to generate an additional mode, i.e., zero mode, which resonates in a frequency between TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes. With the proper arrangement of these three modes in proximity to each other, a wide bandwidth for radiation can be satisfactorily achieved. To demonstrate the validity of the proposed concept, a prototype antenna is finally designed and fabricated. As theoretically expected, the impedance bandwidth of the final designed patch antenna has been increased to 50.46% and the gain is around 6.5 dBi. Both simulated and measured results exhibit wide bandwidth and good performance of radiation.