Microwave Filters for Communication Systems: Fundamentals, Design and Applications

CHAPTER 20

HIGH-POWER CONSIDERATIONS IN MICROWAVE FILTER NETWORKS

This last chapter is devoted to an overview of high-power considerations for microwave filters and multiplexing networks in terrestrial and space applications. Emphasis is placed on the practical aspects in the design of high-power filter networks.

20.1 BACKGROUND

Microwave breakdown in gases under various physical conditions is a well-known and well-studied problem. A classical summary of relevant results is given by MacDonald [1]. Another phenomenon, which is dormant under normal pressures, shows up when the gas pressure is reduced to values approaching near vacuum. This is called multipaction. A summary of this is presented by Kudsia et al. [2]. Just as significant is the phenomenon of passive intermodulation (PIM) in high-power equipment. It depends on the materials used in the equipment, mechanical design features, and the standards of work quality. Novel microwave structures and topologies, and continuing demands for higher power, give rise to new situations and parameter regimes where previous results are no longer applicable. The problem is further compounded by the use of new materials in the implementation of microwave components. Above all, when it comes to the practical aspects of high-power breakdown, passive intermodulation and the operating environment, it seems that each generation of microwave engineers tends to repeat the mistakes of the past before coming to grips with such issues. In this chapter, ...