SDR for Metrology at Microwave and Submillimeter-Wave Frequencies

This thesis explores the practicality of using commercial off-the-shelf (COTS) software-defined radio (SDR) hardware to implement metrology equipment, specifically a vector network analyzer (VNA). Although SDRs are flexible general purpose instruments, their performance typically falls short of dedicated measurement instruments. A software framework has been developed to facilitate high performance collection and processing of SDR data, interface with scientific libraries, and interchangeably connect to various radio frequency (RF) instruments. A low frequency prototype was constructed and thoroughly tested to assess its performance metrics and to identify limitations when using SDR as the underlying backend, enabling future projects to avoid pitfalls and optimize performance. Furthermore, SDR has been used as a back-end for submillimeter wave (sub-mmWave) experiments utilizing VNA frequency extenders. This work not only demonstrates the current feasibility of using SDRs as metrology instruments, particularly VNAs, but also outlines strategies for future advancements. To my knowledge, this is the most detailed characterization of a SDR-based VNA performed yet and is the first to describe using a SDR as a backend for sub-mmWave VNA measurements.