Research On Fast Algorithms For The Cylindrically Conformal Microstrip Structure

In this paper, the cylindrically conformal microstrip structures and the relevant analysis methods are the research objects. And the cylindrically conformal microstrip antennas are analyzed using the Method of Moment and the Wave Concept Iterative Procedure, which are based on the integral equation and the transmission line modeling, respectively.In the first instance, the spectral-domain Green's functions for cylindrically stratified media are deduced from the vector wave equation in cylindrical coordinate system. By utilizing the generalized pencil of function (GPOF) technique, the Green's functions are fitted in the spectral domain. While in the spatial domain, they are represented in the closed form via the Sommerfeld identity and the large argument approximation of the Hankel functions. When the source point and the field point are lying on the same cylindrical interface, the amount of the high-order harmonics of the spectral-domain Green's functions becomes large and the convergence behavior of the infinite integral becomes bad. Considering the situation that the computational efficiency for the spatial-domian Green's functions can't meet the demand, the spectral-domain MoM is employed for analyzing the cylindrically conformal microstrip antennas. The tangential components of the spectral–domain Green's functions, which are practicable for calculations, are detailedly derived for the superstrate-loaded cylindrically conformal microstrip antennas. And the transverse components of the incident electric fields due to the current on the thin probe are given in a specific form. The convergence behaviors of the infinite series and integrals in the impedance matrix's elements are guaranteed due to the full-domain basis functions. After the surface currents of the patch have been obtained by the Method of Moment, the calculation formulae for the input impedance of the thin probe are given explicitly. Because the thickness of the dielectric substrate is far small compared to the radii of the cylindrical structure and the operating wavelength, one can neglect the curvature reasonably and suppose the probe to be inserted to a planar stratified structure for simplifying the process of calculations. By analyzing the numerical results for the probe-fed cylindrically conformal microstrip antennas with superatrates, such as input impedance and radiation pattern, the effects of the superstrate to the characteristics of the antenna are discussed. The novel Wave Concept Iterative Procedure (WCIP) which is used for the fast analysis of microstrip structure is presented. Based on the transmission line modeling (TLM) method and the fast mode transform (FMT) theory, this kind of method accelerates the process of the calculation by introducing the concept of the transverse electromagnetic waves instead of the transverse fields considered in the traditional algorithm. By avoiding the inversion of the large matrices and the complicated derivative process of the Green's functions, the iterative procedure improves the efficiency of the analysis significantly. In the process of the interface modeling, for avoiding the large number of cells arising in the course of the uniform meshing, the non-uniform meshes could be utilized to handle the large disparities between the dimensions of different components. Ultimately, the WCIP is extended to cylindrical coordinate system. By matching the boundary condition on each cylindrical interface in the spectral domain, the specific forms of the modal admittance and the spectral reflection operator are deduced. The input impedance of the cylindrically conformal microstrip antenna fed by means of a microstripline is calculated via the iterative procedure. And the radiation pattern can also be gained by introducing the cylindrical Green's functions.