A closed-form expression for the resonant frequency of rectangular microstrip antennas

A new and accurate expression for the edge extension in accurately predicting the resonant frequency of electrically thin and thick rectangular microstrip antennas is presented. First, a closed form model for the edge extension is constructed by utilizing a differential evolution algorithm, the resonant frequency of rectangular microstrip antennas is then calculated by means of this edge extension expression. The calculations were carried out on 46 antennas with a range of different dimensions built on various substrates. The resonant frequency results presented in this letter show the better agreement with the experimental results as compared with those reported by the several researchers. A comparison between calculated and experimental resonant frequencies demonstrates that the edge extension model provides less than 0.7% errors on average. (c) 2007 Wiley Periodicals, Inc.