Compact mixer-based 1-12 GHz reflectometer

Compact, broadband, and low-cost reflectometry is important for array-based microwave imaging and sensing applications in biology and medicine. To achieve broadband performance, we use cascaded bridged-T attenuators incorporating mixers to replace directional couplers in a new reflectometer design. In this letter, we present the design of the reflectometer and the associated calibration technique. We evaluate the performance of the reflectometer in characterizing two different load impedances and compare results favorably with those of a commercial vector network analyzer.