| Although commercial vector network analyzers are widely used, sampled-line (six-port or five-port) reflectometer is an alternative network analyzer for s-parameter measurements and other potential applications due to its unique advantages, such as compact size, low cost, and simpler structures.;In this dissertation, sampled-line reflectometers at two frequency bands (50-75 GHz, and 270-390 GHz) are designed, tested, and characterized. Initially in the first sampled-line reflectometer (V-band, 50-75 GHz), using it directly as a VSWR meter is introduced. Afterwards, different calibration methods were introduced and compared for both first and second-step five-port calibrations. Measurement results on a prototype reflectometer have shown performance that is in close agreement with data obtained from a commercial vector network analyzer. Measurements were also taken to measure the mismatch between two adjacent stages in a frequency multiplier chain, so as to provide designers with a diagnostic tool that can be used for studying the behavior of multipliers as well as a guide for adjusting external operating parameters (such as bias conditions and drive power levels).;A sampled-line reflectometer at WR-2.8 (270-390 GHz) was built on a single chip. The calibration and verification results were given and compared to HP8510C network analyzer measurements and HFSS simulation. The comparison shows the results agree well, indicating the potential applications of the five-port reflectometer.;Finally, two methods based on reflection measurement to characterize materials are presented, as applications of the sampled-line reflectometers. In the first method, a capillary quartz tube accommodating fluid materials under test was inserted into a waveguide. In this method, deionized water was chosen to be the material under test. The permittivity of the deionized water obtained by this method is compared to Barthel's data. In the second method, a waveguide shim of a certain solid material is inserted into a waveguide. In this method, a silicon wafer was chosen to be the material under test. Generally, the results obtained generally agree with ones from other methods and hence imply that the potential application of sampled-line reflectometers in the field of materials characterization at millimeter wave and submillimeter wave. |
