Versatile radiofrequency sensor

Abstract

A miniature, monolithic radiofrequency sensor operating with MESFET circuitry in the GHz range is able to detect a wide variety of magnetic, metallic and dielectric materials via the losses induced in the sensitive volume around a coil. Application of the sensor to detect plastic and metal gearwheels and falling liquid drops is illustrated; the signal-to-noise ratio falls off as the inverse distance from the coil to the liquid drop.