Shunt posts in microstrip transmission lines

Shunt posts in microstrip transmission lines are analyzed by employing the planar waveguide model. A multiple expansion method with greatly enhanced efficiency and accuracy has been achieved with the development of very fast algorithms for the computation of Schloemilch-type series. The method applies to perfectly conducting imperfectly conducting, and composite shunt posts. This approach is compared with the standard point matching technique for perfectly conducting posts. The two methods are found to be in excellent agreement in regions of overlapping applicability. A fairly wide range of computed data is utilized to develop the tools needed to incorporate the post into various microstrip circuit applications. As one application, a procedure is developed for using this post to obtain effective short-circuiting qualities over a broad frequency range. As a second application, the possibility of creating filtering devices is explored using both multiple metallic post structures and single dielectric posts