TABLE OF CONTENTS Section 18.9 presents a survey of a number of techniques used for RF and MW measurements upon dielectric materials. However, there are many practical features that these techniques have in common and we consider some of them together briefly here. The details are covered in much greater detail in the Good Practice Guide [1].
At MW frequencies it is common practice to use automatic network analysers (ANAs) connected to dielectric measurement cells as source/detector combinations. ANAs [15, 16, 36, 37] are the 'workhorses' of microwave laboratories and are described in detail in other chapters. ANAs can be used both for measuring S-parameters of reflection/transmission cells (as in Figure 18.3) and for measuring frequency changes and Q-factors of resonance cells or cavities. Some ANA models have a synthesised time domain facility as one of their features [38]. This can be useful in a number of techniques for gating or de-embedding the S-parameters of a specimen from any mismatched components and imperfect transmission lines that lie between it and the ANA. ANAs can also be used at RF, but at lower frequencies, say below 100 MHz, and especially where the dielectric measurement cells are significantly mismatched to 50 ?, it is often better to use Impedance Analysers, 'Materials Analysers', Admittance or Impedance Bridges or Frequency Response Analysers (FRAs) [39, 40] as they can be more accurate and sensitive. Some FRAs can work down to frequencies...
