BROAD-BAND COMPLEX PERMITTIVITY MEASUREMENTS OF LIQUID-CRYSTALS, MICROEMULSIONS AND POLAR LIQUIDS BY TIME-DOMAIN REFLECTOMETRY

Recent improvements in time-domain reflectrometry (TDR) rendered preci se measurements of complex permittivity possible over a wide frequency range from about 100 kHz to 20 GHz. Developments in sampling techniqu es and digital processing have enhanced enormously the quality of meas urements. Powerful software development has been realized by the intro duction of the total reflection method by Cole. This approach, includi ng complete use of basic transmission line theory and some high freque ncy corrections have made it possible to make complex permittivity mea surement of materials, even with large d.c. conductivity. Application of the TDR technique in the field of liquid crystals, microemulsions a nd polar liquids is discussed.