Cylindrical Near-Field Measurement and Far-Field Characterization of 300-GHz Band Antenna Based on an Electrooptic Measurement Technique

Cylindrical near-field measurements and far-field characterization of a 300 GHz antenna based on photonics technology are demonstrated. The measurement system is based on self-heterodyne and nonpolarimetric frequency down-conversion techniques. The electromagnetic field to be measured is generated using a uni-travelling-carrier photodiode (UTC-PD) and detected by an electrooptic (EO) probe. The EO probe has no metallic components and is made of dielectric material, which minimizes the disturbance to the field. Also, the use of optical fiber significantly reduces scattering from the probe compared to the conventional probe antennas with metal cables or waveguides. A rectangular horn antenna (WR-3.4) with an antenna gain of approximately 25 dBi is used as an antenna under test (AUT). We show here the far-field distribution calculated from the measured cylindrical near-field distribution without any probe compensations agrees well with the results obtained by a direct far-field measurements and simulations.