Next-generation communications systems like Long Term Evolution Advanced (LTE-A) are feeding the need for RF/Microwave Switch Matrices for reliable automatic-test-equipment (ATE) instrumentation. Such matrices must cover DC to 6 GHz while providing fast responses and repeatable performance. Aside from routing high-frequency signals, they also may contain signal-conditioning components. Yet most important among all these features is that the switch be configured to fit the architecture. To balance all of these aspects, the switch matrix usually has to be custom designed. In a white paper titled, "Current Trends in RF/Microwave Switch Matrices," Renaissance Electronics Corp. explores the challenges involved in designing a custom switch matrix as well as other trends and technology options.
The 16-page document offers ample graphics to illustrate the information provided. It begins by listing the six main challenges that are faced by engineers designing a custom switch matrix: RF/microwave design, mechanical design, DC power and control hardware, software control, servicing plan, and documentation. RF/microwave design, for example, is defined as the signal-routing and signal-conditioning design and testing to fulfill specification demands for instance isolation or rejection, power handling, spurious levels, and IM harmonics. These aspects go beyond the obvious criteria, such as minimizing loss and voltage standing wave ratio (VSWR) over any input-to-output path.
A technology overview notes that a switch matrix can be designed in either a blocking or nonblocking style, depending on the architecture. It then describes the choice of switch technologies: coaxial electromechanical, solid state, and RF microelectromechanical systems (MEMS). Much of the document is then devoted to examples of switch matrices based on the firm's actual products. These examples underscore how the design and complexity of these matrices varies with the application. With the growth of the wireless industry, there also is an increasing need for application-specific switch matrices.