Ebauches S.a.

Helmuth-Hugo Brandenberger

Giovanni Busca

The invention, which may be used in particular as a frequency standard, seeks to avoid disturbance in the control action in respect of the cavity 10 by a powerful parasite signal due to the line of stimulated emission. Control of the cavity and control of the oscillator 1 on the line of stimulated emission control in a shared-time mode. A control circuit 40 acts on the carrier by way of a programmable synthesizer 43, the carrier than assuming the successive values .omega..sub.+, .omega..sub.H, .omega..sub.-, .omega..sub.H, .omega..sub.+, etc. in stages. .omega..sub.H is centered on the line of stimulated emission; .omega..sub.+ and .omega..sub.- which are symmetrically shifted interrogate the flanks of the emission line. By means of a signal INH, the control circuit 40 periodically suppresses the output of an active filter 42 and thus interrupts the detection action used for controlling the cavity, during the periods in which .omega..sub.Q is equal to .omega..sub.+  or .omega..sub.-. This detection action occurs only when .omega..sub.Q =.omega..sub.H, and after a damping dead time.

Passive masers having alternately operated oscillator and cavity control

The maser of the invention is particularly suitable for forming a frequency standard, by virtue of its excellent degree of frequency stability. The stimulating signal injected into a hydrogen maser cavity 10 is phase modulated at a single modulating frequency from a source 34 by a modulator 2. Nevertheless, the envelope detected signal picked off from the cavity and detected by a detector 13 includes two error signal components which respectively represent the difference between the carrier frequency of the injected signal and the frequency of the stimulated emission and the difference between the resonance frequency of the cavity and the said carrier frequency. These components are distinguished by their phases and phase shifters 42 and 44 and bring them respectively into phase with the modulating signal for detection in detectors 23 and 33 whose integrated outputs are used to control the oscillator 1 (and hence the said carrier frequency) and the cavity tuning respectively.

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Sugiez, Switzerland

Helmuth-Hugo Brandenberger