20 GHz Antenna Radiation Pattern Obtained From Near-Field Mapping With Electrooptic Probe on a Single Plane

The ability of an electrooptic (EO) sensor to perform near-field mapping of a 20 GHz pyramidal horn antenna without disturbance on the radiation behavior is demonstrated. The electric field is scanned on a plane close to the horn aperture with spatial resolution less than 0.1λ
₀
. The dynamic range reaches more than 40 dB. The measured magnitudes and phases of near-field pixels enable the computation of the far-field radiation pattern. The results are in excellent agreement with theory, numerical simulations and actual far-field measurement. The different approaches lead to the same antenna gain with a confidence interval lower than 1 dB. Furthermore, the behavior of the electromagnetic wave from reactive to radiative region is investigated. The weak invasiveness of the probe is also analyzed.