Fujitsu Corporation

Hideyuki Matsuura

Ken Atsumi

Yoshito Koyama

Yoshifumi Nakajima

Akira Kikuchi

Minoru Sakai

Takeshi Hoshida

Osamu Takeuchi

Koji Nakamuta

Hironobu Hongou

Daijiro Tanaka

An optical receiver including: a digital filter that performs spectral shaping on a signal; an analyzer that analyzes a spectrum waveform of the signal; a determiner that determines, based on an analysis result by the analyzer, whether the spectrum waveform of the signal is a Nyquist waveform on the basis of a Nyquist first reference; and a controller that stops the spectral shaping of the signal to be performed by the digital filter when the spectrum waveform of the signal is not the Nyquist waveform as a result of the determination by the determiner, and controls a filter coefficient of the digital filter based on the spectrum waveform of the signal when the spectrum waveform of the signal is the Nyquist waveform as the result of the determination by the determiner.

Optical receiver and signal processing method

A data receiver includes a writing unit that receives transmission data including live data and excessive data for adjusting a signal length to store the live data in a storage unit, an AND circuit that generates a first signal indicating the positions of the live data and the excessive data in the signal length of the transmission data, a signal converting unit that generates a second signal indicating positions at which positions of the excessive data in the first signal are rearranged at certain intervals in the signal length, a digital phase locked loop (DPLL) unit that smoothes the positions of the live data in the second signal to generate a third signal indicating the timing to read the live data in the signal length, and a reading unit that reads the live data stored in the storage unit by using the third signal.

Data receiver, clock generation device, and method for controlling data receiver

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.

Growing community of inventors

Sapporo, Japan

Hideyuki Matsuura