Abstract: The impedance of coax-fed arbitrary shape microstrip patch antenna is investigated by the moment method. The two-level discrete complex image method is used to compute the spatial Green's Function, and thus improves the speed to compute Green's function compared with the direct integral method. The simplified additional mode is introducted to simulate the current distribution near the probe-to-patch junction with the complexity decreased. The intut impedance of two different shape microstrip patch antennas is computed and the numerical result agrees well with the experimental result.

Key words: microstrip antenna, input impedance, two-level discrete complex image method