Accuracy Improvement of Cavity Model Effective Patch Dimensions using a Single Full-Wave Iteration

An accuracy improvement procedure for microstrip patch antenna design is presented. The classical cavity model of a patch antenna is discussed with emphasis on the fringe fields and the compensation for these fringe fields in the form of effective patch dimensions. The effective patch dimensions are improved using a single full-wave simulation, drastically increasing accuracy at the cost of only a small increase in computation time. Using the input impedance of the patch antenna determined via a full-wave simulator, effective patch dimensions are adjusted for each single mode, matching the cavity model results to the full-wave results. It is found that adjustment of non-resonant modes cause a shift in amplitude of the input impedance and a adjustment of a resonant mode results in a shift in frequency. The error in predicted impedance decreases from 75% to 5%. An example is given where an exotic input impedance is required, to match the antenna directly to a nonlinear system. This shows that this method results in fast, efficient, reliable and optimal microstrip patch antenna design.