Antenna with electro-optical modulator

Abstract

A wideband, passive detector of electromagnetic fields in free space is disclosed. The apparatus is especially designed to minimize amplitude perturbations of the electromagnetic field being monitored. The apparatus includes an electro-optic modulator having first and second surfaces with electrodes attached thereto and a third and fourth surfaces intersecting an optical path. An electrically small dipole or loop antenna has a first electrode connected to the first electrode of the modulator and a second electrode connected to the second electrode of the modulator, for converting electromagnetic fields intercepted in free space to a voltage signal to be applied to the first and second electrodes of the modulator. A loading resistor may be added in parallel with the electrodes to improve system bandwidth. A light source is located along the optical path, for transmitting light into the modulator through the third surface. The modulator modulates the light entering through the third surface, as it traverses the modulator, with the voltage signal impressed upon the first and second surfaces by the antenna means. An optical detector is located along the optical path for detecting the modulated light along the optical path as it exits from the modulator through the fourth surface. In this manner, weak electromagnetic fields may be detected and their amplitude, phase and frequency measured with a minimal perturbation due to a lack of metallic wires attached to the antenna as in conventional field measurement systems.

Dependencies are inferred from the claim text.