A Study of Composite Microstrip/Coplanar-Waveguide Transmission Line for Miniaturization of Microwave Planar Circuits

A new type of microwave planar transmission line is introduced in this paper, wherein a microstrip line (ML) is superimposed onto a coplanar waveguide (CPW) and connected with copper vias. The new planar line is designated as a composite ML/CPW line that owns a unique feature of dual signal path on a single dielectric slab. By employing meander or zigzagging line sections for the design of RF/microwave circuits such as power divider, the substrate slab area can be significantly reduced when compared with conventional planar transmission lines. Through design examples, this paper demonstrates the effectiveness of the transmission line that is well-suited for RF/microwave circuits miniaturization.