US 5,852,386 AGranted

Apparatus and method for microwave field strength stabilization in cell type atomic clocks

AssigneeNorthrop Grumman Corporation

InventorsPeter J. Chantry, Carlo F. Petronio

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Abstract

The microwave field intensity of a cell type atomic clock is stabilized through time division feedback control of the power of the microwave signal implemented by a microcontroller. The depth of the microwave dip is calculated from differences in measurements of the optical signal when the microwave signal is dithered around the atomic transition frequency of the active medium, and measurements taken when the optical signal is dithered around the optical wavelength of the active medium while the microwave signal is adjusted to produce no microwave absorption, either by reducing the microwave power to zero or by detuning it from the atomic transition frequency of the active medium. RF synthesizers suitable for regulating microwave power include a synthesizer using a step recovery diode for frequency multiplication and having the power to a driver amplifier or the bias applied to the diode regulated. A digital synthesizer can also be used to generate a regulated microwave signal.

Claims24

Dependent claims

A cell type atomic clock comprising:

a cell containing an active medium;
optical pumping means generating an optical signal which is passed through said cell to optically pump said active medium;
microwave means generating a microwave signal;
means coupling said microwave signal to said active medium;
means measuring the optical signal passed through said active medium as a measured optical signal;
control means comprising microwave frequency control means controlling said microwave signal generating means to adjust said microwave signal to produce a microwave dip in said measured optical signal, means calculating said microwave dip from said measured optical signal and means controlling said microwave signal generating means to adjust power of said microwave signal to regulate said microwave dip;
and wherein said microwave frequency control means comprises means alternately adjusting said microwave signal to produce maximum absorption of said microwave signal by said active medium, and substantially no absorption of said microwave signal by said active medium, and wherein said means calculating said microwave dip uses measurements of said measured optical signal when said microwave signal is adjusted to produce maximum absorption and when said microwave signal is adjusted to produce substantially no absorption to calculate said microwave dip.

4 more elements

A method of stabilizing microwave field intensity in a cell type atomic clock in which an active medium contained in a cell is optically pumped by an optical signal passed through the active medium, said method comprising:

(a) during a first interval applying a microwave signal to a resonator to generate a microwave field coupled to said active medium in said cell, said microwave signal being dithered around a frequency which produces maximum absorption of said microwave signal by said active medium;
(b) generating first measurements of said optical signal passed through said active medium during said first interval;
(c) during a second interval, adjusting said microwave signal so that there is substantially no absorption of said microwave signal by said active medium and dithering said optical signal;
(d) generating second measurements of said optical signal passed through said active medium during said second interval;
(e) sequentially repeating steps (a) through (d);
and
controlling power of said microwave signal to maintain a specified relationship between said first and second measurements.

4 more elements

Dependencies are inferred from the claim text.