Resonances Loss in Integrated Microwave Circuits

The dielectric loss in microstrip or suspended microstrip transmission lines is an important parameter in the design of hybrid integrated circuits which require small attenuation. This loss can be calculated if one knows the loss tangent of the dielectric substrate and the electric field distribution inside the substrate. Electric field computations are usually complicated and not practical for design purposes. It is therefore important to find a simple and accurate method for calculating the dielectric loss from other well known properties of the microstrip transmission line. The results of dielectric loss computations for microstrips, which have been made by other authors, are quoted in many recent papers on hybrid integrated circuit design. 1-6 It can be shown that these results are applicable only if the boundaiy between the dielectric substrate and air is parallel to an electric field line. This paper presents general design equations valid for all microstrip transmission lines provided that the propagating mode can be approximated by a T E M mode. 2325