Electromagnetic Field Sensor Research Articles

Light-emitting diode as radio-frequency detector: development of RFI-free electromagnetic field sensor

A unique RFI-free electromagnetic field sensing technique using an LED as an RF detector is described. A double heterojunction (AlGaAs/GaAs) LED is used as an RF rectifier coupled to an EM probe; it delivers proportional light output with significant efficiency even at low (rectified) drive currents. DC biasing of the LED to the threshold of conduction can be achieved by an optically powered photodiode pair. Use of fibre-optic links from the detector to the receiver and in the optically powered bias arrangement eliminates the possibilities of RF1. Presented here are the sensitivity and frequency response of a test probe measured over 3–30 MHz under near-field conditions.

On-fiber sensor and modulator

A technique is presented in which part of an optical fiber is used as an electromagnetic-field sensor and modulated. The basic principle used in this technique is the replacement of the passive cladding material surrounding a short section of the fiber core with an active material that is sensitive to electromagnetic fields. The theory is given, and a description is given of a device fabricated using a nematic liquid crystal at the active modified cladding. >