New methodology of conceiving stacked proximity feed antenna

Proximity coupled microstrip antenna is a noncoplanar feed structure using at least two layers. Coupling between the patch and the microstrip feeding line is capacitive in nature. The coupling capacitor is in series with the R-C-L resonant circuit representing the patch. The capacitance is designed for impedance matching. The radiating patch being placed on the double layer gives a larger bandwidth. Iterative method is commonly used to determine the correct position and dimension of each element. Investigating a methodology to calculate the optimal dimension and position of both radiating patch and feeding line will be a useful tool to conceive proximity-coupled microstrip antennas. In this paper, an easy methodology to calculate and to conceive a stacked proximity feed antenna was presented. The methodology is confirmed for a compact rectangular microstrip antenna used for wireless local area networks (WLAN) application. The proposed method suggests fixing the feeding line length at (0.4. λg), the location of the feeding point at 5 Ohms antenna input impedance position and the width of the line is determine to provide the sufficient capacitance to acquire good matching impedance. This method tested for different frequencies led to an optimal antennas characteristics; a gain of 4.65 dB was attained for 2.45 GHz, 3.29 dB for 915 MHz and 4.74 dB for 5 GHz antenna.