A simple asymptotical model for analyzing wire antenna with different radius

In this research letter, a simple asymptotical model is present for analyzing wire antenna with different radius. Method of moments (MoM) based on sinusoidal basis function is used to give the analysis. In the process of using MoM for different radius, if we neglect the monopole along normal axis at the joint part, the different consideration of endpoint charges will make the final results different for conventional methods, and final results are also different with the results from HFSS and measurement results. In view of that, a simple asymptotical model is present to approximately deal with the joint part at the position of different radius. One advantage for the introduction of the present model is that the final results will be the same and independent of conventional methods. The other advantage is that the final results based on the present model have better agreement with HFSS and measurement results. Fabricated loop antennas with different radius are given as practical examples to show the advantages of the present model.