Over-the-Air Characterization Techniques for Antenna-Coupled Direct-Detectors at Terahertz Frequencies

The continuous advancements in the coverage and sensitivity of terahertz direct-detector imagers places increasing constraints on the test benches needed for characterization. Already, relative differences on the order of a few decibels are observed between simulated and measured performance in the state-of-the-art literature. This contribution elaborates on our experimental strategies to maximize the characterization accuracy and precision of terahertz direct-detection imagers using a broadband, over-the-air measurement procedure. As a demonstration, four elements within a dense detector array were characterized in the WR2.2 band. By optimizing the modulation frequency in the setup for minimal impact of low-frequency noise and interference, a measurement dynamic range up to 30 dB was achieved, including the path loss over 20 cm. The hardware-to-model agreement of the characterized array is below 1 dB between 325 and 450 GHz.