Circuit Miniaturisation for Micro and Millimeter-Wave Frequencies

Next-generation communication systems will exploit the mm-wave frequency bands. So there is need to establish design rules for components to be used at these frequencies. These components will need to be compact, as well as low cost, to be economically viable. Developments in materials for thick film and low-temperature co-fired ceramic (LTTC) circuits have made these technologies viable and attractive options for very high-frequency circuits. It is the investigation of the practical implementation of these technologies for next-generation wireless components that forms the main theme of this book. It presents the approach of circuit miniaturisation at microwave and millimetre-wave frequencies. It includes the techniques for the characterization of dielectric materials, mainly LTCC and barium strontium Titanate (BST), using a free space method at frequencies between 145 and 200 GHz.

A new technique to characterize dual-layer materials is also discussed. Using BST as a distributed varactor, a new, miniature tuneable bandpass filter was developed. The filter performance shows a significant improvement in performance compared to other similar structures, reported elsewhere. Besides, the development of a narrowband bandpass filter at 150 GHz, using a rectangular waveguide as a prototype for an LTCC design is also discussed. In this filter, the design procedures commonly used at lower frequencies were modified to give optimum results at high mm-wave frequencies. The effect of miniaturizing the area occupied by microwave and mm-wave circuits was also investigated. This led to new information on the optimum spacing of circuit interconnections, and on the effectiveness of isolation structures, for both single and multilayer circuits, operating over a given frequency range.