USING POWER DETECTORS TO MEASURE SCATTERING COEFFICIENTS OF MICROWAVE DEVICES

Abstract

The inherent attraction of the six-port technique is that it is possible to obtain the (complex) scattering coefficients of microwave devices from some (scalar) power measurements. The objective of the present project, therefore, is to develop a systematic study of such measurement system (Chapter 3) so as to explore how this simple and yet innovative concept can be further extended. Arising from the study, three novel measurement techniques that only require power detectors have been proposed – two-detector technique (Chapter 4), multi-detector technique (Chapters 5-6) and four-detector technique (Chapter 7). Various new instruments based on the proposed techniques have been successfully constructed and tested, e.g. four-port reflectometer, three-state network analyser, four-state network analyser and nine-port network analyser. All of the measurement results obtained by each of these prototype instruments have been compared with the readings taken by the heterodyne-based HP8510C automatic network analyser. Good agreement has been found between the corresponding sets of measurement results, hence verifying the feasibility of the proposed techniques. Also included in the investigations are two ancillary problems that arose during the conduct of the project, viz. 180° phase ambiguities in transmission-coefficient measurements of rectangular waveguide devices and calibration accuracies for waveguide measurements near cut-off frequency.