Chapter 8. Instrumentation for near-field scanning microwave microscopy
Pavel Kabos, Thomas M. Wallis
In the previous chapter, we discussed the underlying physics and theory of operation for near-field scanning microwave microscopes (NSMMs) and related probe-based measurement systems. Here, we consider the practical implementations of such scanning probe systems. In designing an NSMM system, several critical questions must be considered. Will the probe be implemented with a resonant or non-resonant microwave circuit? What type of microwave probe will be used: a sharpened metal tip, a planar structure such as a stripline, or perhaps a resonant cavity with a sub-wavelength aperture? What distance-following mechanism will be used to maintain a constant distance between the probe and the sample under test? Depending on how these questions are addressed, any of a wide variety of NSMM designs may be engineered. In addition, the instrumentation directly impacts calibration techniques, which were described in detail in the preceding chapter. Before proceeding to the detailed discussion of contemporary approaches to NSMM instrumentation, we will briefly review the historical development of near-field microwave probing.