Automatic material characterization at microwave frequencies

An instrument was assembled to measure complex permittivity at microwave frequencies in an efficient, inexpensive manner. It bridges the gap between traditional, tedious methods of characterization and expensive vector network analyzer techniques. A microcomputer is used to control the operation of a scalar network analyzer. Measurements of the magnitude of the reflection and transmission coefficients are automatically made as a function of frequency and temperature over a range of 2-18 GHz. A theory is developed covering the different regimes of operation: the thin sample, the multiple reflecting sample, and the high insertion loss sample. Sample thickness criteria for accurate measurements are reported. Results are presented for dielectric and semiconductor samples