Mechanical load cell based on cavity-controlled microwave oscillators

A device consisting of a rectangular resonator to which two oscillators are coupled at right angles to each other is described. The frequency of each oscillator is controlled by the cavity, and distortions caused by mechanical load change the two frequencies in opposite directions. The detector, which is arranged at an angle of 45 degrees to the probes of the two oscillators, picks up a beat signal whose frequency in the MHz range is linearly related to the mechanical load applied across the cavity. The oscillators using GaAs MESFETs have been designed to detect small distortion in the cavities by a mechanical load. >