4.10: Summary

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The use of modules has become increasingly important in microwave engineering. A wide variety of passive and active modules are available and high-performance systems can be realized enabling many microwave systems of low-to-medium volumes to be realized cost effectively and with stellar performance. Module vendors are encouraged by the market to develop competitive modules that can be used in a wide variety of applications. The challenge is to develop a module with high performance and adaptability. Many modules have matched \(50\:\Omega\) input and output impedances so that modules can be freely interconnected. Many integrated systems are first prototyped using vendor-supplied modules that are, perhaps, gradually replaced by higher-performance monolithically integrated implementations. Doing so is only justified when unit volumes are very high. The availability of evaluation boards with coaxial connectors for many modules makes it easy to do early design trade-offs. The great majority of RF and microwave engineers either develop modules or use modules to realize RF systems.

The most important part of a system design is achieving the desired functionality largely arrived at by choosing a suitable topology, usually cascaded subsystems, and appropriate functional units (i.e., modules). Then the major concern in design is managing noise, distortion, DC power consumption, cost, and size. The noise and distortion concerns can be combined together as dynamic range and then the objective is maximizing dynamic range while controlling DC power consumption and using affordable modules. Systems must also be concerned with distortion that originates in supposedly linear elements. Something as simple as a termination can produce PIM through heating and thus resistance changes.