Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Kazuhiro Nojima

Hirofumi Yoshida

Hiroshi Katayama

Tomoaki Ohira

Akifumi Miyano

Kei Murayama

Seiho Kitaji

Naomi Ohashi

A positioning receiver in which the circuit configuration of the receiving system corresponding to a plurality of positioning systems can be simplified and the current consumption and circuit size of which can be reduced. A positioning receiver () comprises first low-pass filters () which limit outputs of a first signal mixer () and a second signal mixer () to a first bandwidth, and second low-pass filters () which are provided on the output side of the first low-pass filters () and limit the outputs of the first low-pass filters () to a second bandwidth narrower than the first bandwidth and sets the filter bandwidth of the first low-pass filters () greater than that of the second low-pass filters ().

Positioning receiver

An object of this invention is to provide a modulator, an optical transmitter and an optical transfer device which can modulate a channel signal while suppressing residual AM signals regardless of the frequency of a channel signal and suppressing deterioration of the channel signal due to impossibility of giving a sufficient FM demodulation amplitude. A modulatoraccording to this invention is a modulatorfor modulating an input signal, comprising: a branching circuitfor producing an inverted signal with an inverted phase of the phase of a first input signal transferred within a first frequency bandwidth; a first semiconductor laserfor FM-modulating the first input signal to produce a first FM-modulated light beam; a second semiconductor laserfor FM-modulating the inverted signal to produce a second FM-modulated light beam; an optical phase-modulating unitfor changing the phase of one of the first FM-modulated light beam and the second FM-modulated light beam on the basis of a second input signal transferred within a second frequency bandwidth, thereby producing a phase-modulated light beam; an optical merging unitfor merging the other of the first FM-modulated light beam and the second FM-modulated light beam and the phase-modulated light beam thereby to produce a modulated light beam; and a photoelectric converting unitfor converting the modulated light beam in a modulated signal through optical heterodyne detection.

Modulator, optical transmitter and optical transmission apparatus

In a multi-channel video optical transmission system comprising an optical transmitter and an optical receiver, a frequency modulation function incorporated pilot signal generating unit is provided in the optical transmitter to generate a pilot signal frequency-modulated. This frequency-modulated pilot signal is superimposed on a multi-channel video signal inputted thereto and is converted into a frequency-modulated signal in a frequency modulator, and is transmitted through an optical fiber to an optical receiver in a state converted into an optical signal in a semiconductor laser device. In the optical receiver, the optical signal is again converted into an electric frequency-modulated signal in a light-receiving device and, after amplified in an amplifier, is demodulated in a frequency demodulator, thereby regenerating the multi-channel video signal before the input to the frequency modulator. In this configuration, the pilot signal is frequency-modulated to modulate the frequency of a distortion occurring at frequencies corresponding to the sum of or difference between the frequencies of the pilot signal and the multi-channel video signal, thus making fringe patterns on a TV monitor disappear.

Multi-channel video optical transmission system, optical transmitter and optical receiver

In a signal transmission system made up of a transmission section, a receive section and an optical fiber installed between the transmission section and the receive section, a harmonic producing circuit and a harmonic phase shifting circuit are provided on the downstream side of an FM modulator. The harmonic producing circuit superimposes a harmonic of an FM signal on the FM signal, and the harmonic phase shifting circuit shifts the phase of the harmonic. This arrangement compensates a group delay deviation occurring in system components when an AM signal or QAM signal is modulated into an FM signal or PM signal in a modulator and then transmitted to be demodulated in a demodulator, thereby improving transmission quantity.

Signal transmission system and signal transmission apparatus

In an automatic gain control circuit comprising a variable gain amplifying circuit for amplifying an input signal through the use of variable gain control to send out an output signal and a gain control circuit for amplitude-controlling the input signal fed into the variable gain amplifying circuit, a peak detecting circuit of the variable gain amplifying circuit detects a peak voltage value of the output signal, and the gain control circuit generates an amplitude control signal corresponding to an amplitude value of the output signal. The generated amplitude control signal is fed back to the variable gain amplifying circuit for controlling the amplitude of the output signal to a constant value with respect to amplitude variations of the input signal. With this arrangement, even if a largely amplitude-varying input signal appears, the gain control circuit can control the amplitude of the output signal readily to a constant value.

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Yokohama, Japan

Kazuhiro Nojima