An analysis and optimum method of a microstrip probe is presented. The input impedance is derived through the dyadic Green's function in a dielectric loaded waveguide. A wideband impedance match optimum process is employed to realize good return loss and insert loss of the microstrip probe. A Ka‐band microstrip probe has been designed and tested. Experiment shows good coupling efficiency and return loss. © 1995 John Wiley & Sons, Inc.