An efficient computation of impedances of dipoles over cylindrical structure by using a spectrum of 2D solutions with asymptotic waveform evaluation

Many antennas can be modeled as three-dimensional (3D) excitation elements in the vicinity of two-dimensional (2D) cylindrical structures. For this type of problem, a spectrum of 2D solutions (S2DS) is a very efficient method to find the radiation or scattering characteristics. This paper extends our previous work (Yang, J. and Kildal, P.-S., IEEE Trans. Antennas and Propag., 2004). We apply the asymptotic waveform evaluation (AWE) method to S2DS by expanding the boundary currents in term of the spectral variable, k, in the complex plane in order to calculate the near fields. Therefore, much fewer spectral 2D field solutions are needed than otherwise in order to perform the inverse Fourier transform. For the examples presented, only seven 2D solutions are needed in order to obtain accurately the impedance of a dipole in the vicinity of a cylindrical structure. Thereby, the speed of the calculation has been accelerated by an order of magnitude compared with using the S2DS method directly.