Near-field antenna pattern measurements at 94 GHz using synchronized photoconductive sampling

Summary form only given. Coherent detection of free-space GHz- and THz radiation is important for the characterization of free-radiating systems. Most methods reported to date have relied on coherent generation, for instance through photomixing of two laser frequencies, to ensure a fixed phase between detector and source. At this time, such systems cannot provide the power levels required to measure spatially large systems. Here, we use an alternative method, developed by Loffler et al., which uses photoconductive sampling to coherently detect a signal generated by a free-running source. We demonstrate this in a real-life application, namely the measurement of the near-field radiation pattern of a large-aperture antenna at 94 GHz.