Equivalence between circular and rectangular posts in guiding structures

An accurate approximation is obtained for the impedance of a circular-post diode mount in a millimeter-wave guiding structure. The circular-post diode mount driving-point impedance is determined for the general case of a post embedded in a homogeneous dielectric between parallel conducting planes, as found in H-guide, groove-guide, and shielded image-guide diode mounts. The technique employed in this study is based on the determination of the equivalence between a circular post and a rectangular post. Theoretical calculations are found to be in very good agreement with experimental measurements. The primary advantage of this technique is the ease of calculation, together with the applicability of the technique to a broad class of guiding structures.