Evaluation of Efficient Closed-Form Green’s Function in a Cylindrically Stratified Medium

An efficient technique is proposed for the removal of the spatial singularity for a z-directed current source in a cylindrically layered structure by decomposing the spectral domain Green's function into the particular and homogeneous parts. The particular part with the singularity is converted into the spatial domain using Sommerfeld's identity, while the DCIM with general pencil of function technique is applied on the spectral domain homogeneous part. The use of the ratio form of the reflection/transmission matrices, the Debye approximation, and the subsequent envelope extraction for the treatment of the spatial domain singularity is thus avoided. In addition, a very significant reduction in the number of modes required for convergence is also achieved. The technique is applied for evaluating the input impedance of several antennas in the cylindrical multilayer structure together with a coupling configuration for the excitation of the multilayer structure.