RESONANCE OF NONAXIAL SYMMETRIC MODES IN CIRCULAR MICROSTRIP DISK ANTENNA

Resonant frequencies of the nonaxial symmetric modes in a microstrip disk are computed using two approaches: Galerkin's method and a perturbative approach. The perturbative approach is good when the substrate of the microstrip disk is thin compared to its radius and when the dielectric constant of the substrate is high. Galerkin's method can be used to compute the resonant frequency to high accuracy but the perturbative approach is more efficient for thin substrate and large dielectric constant. In applying Galerkin's method, the problem is first cast into a vector dual integral equation using vector Hankel transform (VHT). Using VHT, it is also shown that the magnetic-wall model is only good when the substrate is of zero thickness. Using zero-order current distribution on the disk, we also derive the radiation field and radiation pattern. Also, by taking into account the radiation loss, the resonant frequencies are complex. We find discrepancies when we compare our results for the resonant frequency shifts with that obtained by quasistatic approach. © 1980 American Institute of Physics.