Two-dimensional AWE technique in fast calculation of microstrip antennas

The method of moments (MoM) in conjunction with the two-dimensional asymptotic waveform evaluation (AWE) (E.K. Miller, IEEE Antennas and Propag. Mag., vol. 40, no. 1, pp. 40-52, 1998; ibid., vol. 40, no. 2, pp. 51-65, 1998; ibid., vol. 40, no. 3, pp. 49-66, 1998) is applied to calculate both input impedance response in terms of frequency and substrate parameters for a microstrip antenna simultaneously. The hybrid field integral equation of the microstrip patch irradiated by a current source is first converted into a matrix equation using MoM and Green's functions of the substrate. In the AWE method, the derivatives of Green's function are required. A closed form of microstrip Green's function is used for this requirement. Then, the matrix equation of frequency and permittivity derivatives can be obtained from the original matrix equation. With these matrices in hand, coefficients of the two-dimensional Pade polynomial can be obtained by using AWE technique in simultaneous frequency and permittivity extrapolation. Numerical results demonstrate the accuracy and efficiency of this technique.