Input impedance of a probe-fed cylindrical annular-ring microstrip antenna

An analysis using a generalized transmission line model (GTLM) for a probe-fed cyclindrical annular-ring microstrip antenna is presented. The equivalent circuit elements for the microstrip antenna modeled as a transmission line loaded with wall admittances are derived and the expression for the input impedance is given. Numerical results for the antenna excited at the TM12 mode are also calculated and compared with the measured ones, and the effects of different feed positions and cylinder radii on the input impedance are analyzed. Good agreement of the GTLM solutions with the experimental results is observed. (C) 1997 John Wiley & Sons, Inc.