Several types of polygonal loop antennas have been investigated theoretically and experimentally and their fundamental properties are demonstrated. Theoretical investigations have been carried out using antenna simulation software Numerical Electromagnetic Code (NEC). Experiments have been performed to measure input impedance, impedance bandwidth, and radiation patterns of these configurations, which tally well with simulation results. To perform these experiments, a new method for matching loop antenna impedance with the 50 ohm source for ISM band using parallel-wire transmission line has been proposed. Design of length and width of the parallel-wire transmission line for various loop configurations of 1λ perimeter at 915 MHz has been presented. Variation of impedance with frequency of these configurations has also been studied. The simulation and experimental results obtained using this method show very good agreement. These investigations provide useful data on design of loop antennas for a specific application. For example, data on input impendence is useful in designing the antenna feeder. Proposed impedance matching method gives wide and symmetrical impedance bandwidth at VSWR = 2.

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Impedance Numerical Electromagnetic Code (NEC)