Fujitsu Corporation

Yoshifumi Nakajima

Yoshito Koyama

Ken Atsumi

Hideyuki Matsuura

Hideo Sumiyoshi

Kazuharu Chiba

Koji Nakamuta

Minoru Sakai

An oscillator controller which optimizes key circuit parameters of an excitation circuit according to the operating condition of a discharge lamp. An excitation circuit energizes a discharge lamp to produce a light beam for pumping atoms, as part of a mechanism of atomic resonance detection. The operation of the excitation circuit is monitored by a start-up voltage monitor, which asserts a voltage monitoring signal when the excitation circuit's start-up voltage is reached. A light amount monitor receives a resonance detection signal from a light sensing device to check the amount of light before and after the discharge lamp lights up. The resultant light amount monitoring signal indicates this information. Based on the two monitoring signals, a bias voltage selector selects an appropriate bias voltage that varies circuit parameters of the excitation circuit.

Oscillator controller and atomic oscillator

A rubidium atom oscillator is not influenced by a circumference noise or the like, and is excellent in the short-term stability and the phase noise characteristic. A crystal oscillator oscillates a fixed frequency as an atomic resonance frequency. A direct digital synthesizer inputs an output of the crystal oscillator as a system clock and also inputs tuned data corresponding to an error signal generated according to a resonance frequency so as to carry out a variable control of an output frequency. A frequency synthesizer synthesizes and multiplies an output of the direct digital synthesizer and applies a phase modulation with a low-frequency signal. An atomic resonator inputs an output of the frequency synthesizer and detects an error signal with respect to a resonance frequency of rubidium atoms. A tuned-data generating circuit inputs the error signal from the atomic resonator so as to generate the tuned data corresponding to the error signal. The output frequency of the direct digital synthesizer is output from the rubidium atom oscillator.

Rubidium atom oscillator generating a stable frequency

In an atomic oscillator, a high-frequency converting circuit converts the output of a standard oscillator into a high frequency signal such that the frequency of the high frequency signal multiplied by a low natural number equals an atomic resonant frequency signal. The high frequency signal is then multiplied by a low natural number in an active, low-natural-number multiplier circuit to convert the output frequency of the standard oscillator into a resonant frequency to be input to the atomic oscillator. The result is that, without using a passive, high-natural-number multiplier circuit, such as a varactor diode, which is expensive, it is possible to convert the output frequency of the standard oscillator into a resonant frequency signal of a rubidium atom, thus downsizing the circuits of the atomic oscillator and reducing the term and cost of manufacture.

Atomic oscillator utilizing a high frequency converting circuit and an active, low-integral-number multiplier

A rubidium atomic oscillator includes a voltage-controlled oscillator (VCO) producing a first microwave signal for an output, and a light source producing pumping light of which the wavelength is externally controlled. The oscillator further includes a division part for dividing the pumping light into a first light and a second light, a wavelength shift part changing a wavelength of the second light to produce a third light, and a cavity resonator, oscillated by a second microwave signal, which absorbs the first light and the third light, the cavity resonator having a resonance cell filled with a rubidium gas. In an electrical control part, the second microwave signal is produced based on the first microwave signal from the VCO, a level of the first light passed through the cavity resonator is detected, and a frequency of the VCO is controlled so that the first light is maximally absorbed in the cavity resonator. In an optical control part, a level of the third light passed through the cavity resonator is detected and the wavelength of the light source is controlled so that the third light is maximally absorbed in the cavity resonator. In the oscillator, by properly changing a wavelength of the third light in the wavelength shift part, stability of the first microwave signal may be increased.

Rubidium atomic oscillator with laser diode wavelength adjustment

A rubidium atom oscillator has an increased allowable temperature range in which a frequency fluctuation due to change in the ambient temperature is suppressed. The frequency is stabilized in an increased temperature range as compared to the conventional rubidium atom oscillator. The rubidium atom oscillator oscillates a microwave having a predetermined stable frequency by using an optical pumping effect of rubidium gas. A rubidium lamp radiates a resonance light. A cavity resonator accommodates a gas cell containing rubidium gas and a photodetector detecting an amount of the resonance light passing through the gas cell. It is determined whether or not an ambient temperature of the cavity resonator is within a predetermined temperature range between a lower-limit temperature and an upper-limit temperature. A temperature correction signal is generated based on the determination. A current determined by the temperature correction signal is supplied to a coil surrounding the cavity resonator. The coil generates a magnetic field in the cavity resonator so as to change a resonance frequency of the cavity resonator.

Rubidium atom oscillator with temperature stabilized frequency output

Wavelength stabilized light source

A cesium oscillator includes a cesium beam tube, and an oscillator circuit which generates an oscillation signal of a frequency to be supplied to the cesium beam tube. A frequency control circuit including a sweep circuit and a feedback loop circuit continuously varies the frequency of the oscillation signal. The frequency of the oscillation signal is continuously varied two times when the frequency of the oscillation signal is to be adjusted. A hold circuit holds the highest signal level of the resonance signal supplied from the cesium beam tube when the frequency control circuit continuously varies the frequency of the oscillation signal first. A control circuit controls the frequency control circuit so as to stop continuously varying the frequency when a signal level of the resonance signal obtained by continuously varying the frequency of the oscillation signal by the frequency control circuit for the second time becomes equal to the highest signal level held by the hold circuit.

Growing community of inventors

Kawasaki, Japan

Yoshifumi Nakajima