Fujitsu Corporation

Ken Atsumi

Hideyuki Matsuura

Yoshito Koyama

Yoshifumi Nakajima

Akira Kikuchi

Minoru Sakai

Koji Nakamuta

A phase locked loop circuit including: a loop filter having a high cutoff characteristic and a low cutoff characteristic that are switchable, and a switching circuit configured to: detect a timing when an irregular gap of no signal, included in a input signal, does not occur, and switch, in the detected timing, a cut off characteristic of the loop filter from the high cutoff characteristic during entrainment of phase locking of a output signal with the input signal to the low cut off characteristic after the phase locking.

Phase locked loop circuit and phase locked loop method

A digitally controlled oscillator that generates an output frequency according to input data includes a determination unit that determines whether the input data has a value that causes deterioration in a phase noise characteristic of the digitally controlled oscillator, an offset unit that offsets the input data when the input data is determined to have the value that causes deterioration in the phase noise characteristic, and a generating unit that generates the output frequency using the input data after being offset.

Digitally controlled oscillator and output frequency control method

A method used by a phase difference detection circuit for detecting a phase difference between two signals includes shifting a detected phase difference between the two signals by an offset value, outputting the detected phase difference, and controlling the offset value such that the outputted detected phase difference falls within a phase difference range between a lower limit and an upper limit.

Phase difference detection method, phase difference detection circuit, and wireless power transmission device

There is provided a phase locked loop circuit which includes a frequency divider, a phase comparator, a filter, and an output signal oscillator. The frequency divides a feedback signal by a specific ratio and the feedback signal is used for synchronizing a phase of a reference signal and a phase of an output signal. The phase comparator compares the phases of the reference signal, the output signal, and the feedback signal and adjusts a gain of an analog signal used for generating the output signal in accordance with increase or decrease of the ratio. The filter filters the analog signal to pass signals in a specific frequency band, the gain of the analog signal having been adjusted by the phase comparator and the output signal oscillator outputs the output signal on the basis of the analog signal.

Phase locked loop circuit and communication device

A phase comparator includes an edge detecting unit to which a reference signal is input and to which a referred signal based on the reference signal is input as a feedback signal. The edge detecting unit detects an edge of the reference signal and an edge of the referred signal. The phase comparator also includes a phase-difference detecting unit that detects a phase difference between the edge of the reference signal and the edge of the referred signal. The phase comparator also includes a phase-difference-signal output unit that outputs a phase-difference signal for current control based on the phase difference. The phase comparator also includes an input-break detecting unit that detects an input break of the reference signal when an edge of the referred signal is again detected after an edge of the referred signal is detected and before an edge of the reference signal is detected.

Phase comparator, phase synchronizing circuit, and phase-comparison control method

The present invention relates to a static magnetic field applying structure for use in an atomic oscillator in which plural sets of magnetic field generating means are provided with spacing interposed among them, and a resonance cell is disposed in a space between the magnetic field generating means. The object of the present invention is to realize the static magnetic field applying structure which can be small-sized and produced at a low cost.

Static magnetic field applying structure for use in atomic oscillator

A compact atomic oscillator with improved frequency stability. A voltage-controlled oscillator generates an oscillation signal based on a given control voltage, and a modulator modulates it with a low-frequency signal. A phase-locked loop (PLL) upconverts the modulated oscillation signal directly to a first frequency in atomic resonance frequency band. The first frequency is an integer multiple of the oscillation signal. A frequency synthesizer produces a second frequency specified by a frequency setting unit, and a mixer combines the first and second frequencies to produce an RF signal for driving an atomic resonator. The amount of discharge lamp light passing through the atomic resonator depends on the difference between RF signal frequency and atomic resonance frequency. This quantity is measured as a resonance detection signal, and a frequency controller applies it to synchronous detection to produce a control voltage for the voltage-control oscillator.

Atomic oscillator

In an atomic oscillator of an optical pumping system, a slot line resonator, as a microwave resonator, is arranged in a portion where atoms are excited. The slot line resonator forms a microstrip line inputting microwaves so as to be orthogonal to a slot line with a dielectric substrate being sandwiched therebetween. A container in which the atoms are enclosed is mounted on the slot line resonator, and the slot line resonator and the container are covered with a metallic case having a pumping light passage hole and a photo element.

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 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.

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Sapporo, Japan

Ken Atsumi