On the Wheeler cap measurement of the efficiency of microstrip antennas

The Wheeler cap method for measuring the efficiency of microstrip antennas is revisited. First, we show that the parallel RLC model is a more appropriate model to use than a series one for the microstrip antennas under consideration. Our results are verified by numerical simulation using ENSEMBLE. Second, the role of the interior cavity modes is investigated and a reduced-height Wheeler cap is proposed. Finally, the Wheeler cap method is applied to measure the efficiency of miniaturized microstrip antennas designed using genetic algorithms.