Asynchronous near-field measurement and far-field characterization using electrooptic probes in the millimeter-wave band

We show the principle and setup of an electric field visualization system based on an asynchronous measurement technique, which visualizes the spatial distributions of electric near-fields three-dimensionally without plugging a cable to the radio frequency (RF) source to be measured. Although the measurement system is a so-called spectrum analyzer type, not only the amplitude but also the phase distribution can be mapped. Antenna characterizations based on a near-field to far-field transformation at millimeter-wave region are demonstrated. We also demonstrate that our system can reveal the nearfield distribution of the millimeter-wave car radar would be distorted by car bumper placement. We believe that the presented technique is a promising inspection technique for not only radars but also the on-chip antenna devices.