The Groove-Guide Oscillator

Abstract

The groove guide, a low-loss waveguide consists of two separate parallel plates whose separation distance can be adjusted, thereby affecting the frequency of operation of the guide itself. The standing waves in a groove guide along the direction of propagation are commonly obtained by either total reflection at both ends or by forming a closed loop. A negative resistance has to be implemented to induce oscillations of the groove guide resonator. It is desirable to induce oscillations directly inside the groove region therefore the negative resistance must be placed inside the groove. A Gunn element was selected to provide this negative resistance. A standard heterodyne system may be realized in order to use the groove-guide oscillator for distance or permittivity measurements. The groove-guide oscillator works as an active sensor in the X-band. The accuracy with which the resonant frequency is determined depends on the bias stability of the Gunn element, the phase noise of the local oscillator, and the error of the frequency counter.