Design of Novel Multilayer Microwave Coupled-Line Structures using Thick- Film Technology

A novel octave band DC block (2.5 -10.5GHz) and a broadband 3dB directional coupler (3-8GHz) have been designed, fabricated and tested using a new multilayer format. The multiple layers of thick-film dielectric and metal were printed on an alumina base and an etching technique used to form the final conductor pattern. The tight coupling required between the coupled lines was realized by overlapping these lines in a multilayer structure. Very good agreement was obtained between measured and simulated data. The results demonstrate that multilayer thick-film techniques provide an efficient method of achieving small size, low cost components having good microwave performance. In particular, the new multilayer approach has been shown to overcome the problem of fabricating very small gaps between coupled lines in a traditional single layer structure.