The current distribution on the feeding probe in an air filled rectangular microstrip antenna

The current distribution on the probe and the input impedance of the rectangular air-filled microstrip antenna are calculated using the electrical-field integral equation (EFIE) formulation. A rigorous model for the coaxial line excitation is adopted which makes the formulation valid for electrically thick microstrip antennas. The EFIE is solved numerically using the moment method with a piecewise linear approximation of the patch current and a polynomial approximation of the probe current. It was found by numerous calculations that operating the microstrip antenna at the resonant frequency of the microstrip patch gives the best results with respect to the sidelobe level and cross-polar level. To validate the calculations, the impedance of the rectangular air-filled microstrip antenna was measured for the case h=6 mm and was found to agree with the calculated impedance.<>