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

摘要

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 RFI. Presented here are the sensitivity and frequency response of a test probe measured over 3-30 MHz under near-field conditions.