Victor Company of Japan, Limited

Keiichi Kaneko

Katsumi Takaoka

Kazunari Matsui

Takaaki Saiki

Yutaka Osada

Ken Miyazaki

Katsumi Ohno

Masakatsu Moriyama

An orthogonal frequency division multiplexed signal transmitting apparatus executes a time-division multiplexing process that inserts a reference signal at a predetermined interval based on reference signal position information into an information signal to be transmitted. The transmitting apparatus generates an orthogonal frequency division multiplexed signal by digital-modulating the time-division multiplexed signal to radiate into a spatial transmission line. An orthogonal frequency division multiplexed signal receiving apparatus receives the signal from the transmitting apparatus to get the reference signal by demodulating the signal.

Orthogonal frequency division multiplexed signal transmitting apparatus, orthogonal frequency division multiplexed signal receiving apparatus, and orthogonal frequency division multiplexed signal transmitting/receiving system

Non-compensation signal points are determined in a two-dimensional plane without considering a signal error caused by digital quadrature modulation. The two-dimensional plane is defined by a real axis and an imaginary axis. The real axis corresponds to real-part signal components. The imaginary axis corresponds to imaginary-part signal components. Compensation signal points are determined in the two-dimensional plane in response to a signal error caused by digital quadrature modulation if the non-compensation signal points are used. The non-compensation signal points and the compensation signal points are point-symmetry. Digital information signal pieces are sequentially assigned to one of the compensation signal points in response to contents of the digital information signal pieces. The digital information pieces are subjected to a modulation process including digital quadrature modulation in response to the above-mentioned assignment to generate a radio-frequency transmission signal.

Method and apparatus for generating transmission signal by processing which includes digital quadrature modulation

Data pieces representative of in-phase components and quadrature components of a digital-modulation-resultant signal are assigned to frequencies for inverse fast Fourier transform. The inverse fast Fourier transform is executed at a predetermined sampling frequency Fs to convert the data pieces into a real-part signal and an imaginary-part signal. Phases of the real-part signal and the imaginary-part signal are shifted. Each of the phase-shifted real-part signal and the phase-shifted imaginary-part signal is divided into a sequence of even-numbered samples and a sequence of odd-numbered samples. A digital quadrature-modulation-resultant signal is generated from further manipulation of the even-numbered and odd-numbered samples.

Method and apparatus for modulation and demodulation related to orthogonal frequency division multiplexing

An apparatus for transmitting an orthogonal-multi-carrier signal includes a first device for subjecting an information signal to first inverse discrete Fourier transform to convert the information signal into an orthogonal-multi-carrier signal. The ortogonal-multi-carrier signal generated by the first device is outputted to a transmission line. The orthogonal-multi-carrier signal is received from the transmission line. The received orthogonal-multi-carrier signal is subjected to discrete Fourier transform to recover the information signal from the received orthogonal-multi-carrier signal. A second device contained in the first device operates for subjecting the information signal to M-point inverse discrete Fourier transform and thereby implementing a first stage of the first inverse discrete Fourier transform, and for generating a transform result signal representative of results of the M-point inverse discrete Fourier transform, where M denotes a predetermined natural number greater than 2. A third device contained in the first device operates for subjecting the transform result signal generated by the second device to N-point inverse discrete Fourier transform and thereby implementing a second stage of the first inverse discrete Fourier transform to generate the orthogonal-multi-carrier signal, wherein N denotes a predetermined natural number greater than twice M. The second stage follows the first stage.

Method and apparatus for transmitting orthogonal-multi-carrier signal

A first orthogonal-multi-carrier signal is generated through N-point inverse discrete Fourier transform. The first orthogonal-multi-carrier signal has &ldquo;N&rdquo; or less orthogonal multiple carriers, where &ldquo;N&rdquo; denotes a predetermined natural number equal to or greater than 2. Every 1-unit time segment of the first orthogonal-multi-carrier signal is repeated &ldquo;M&rdquo; times to generate every 1-symbol time segment of a second orthogonal-multi-carrier signal. The second orthogonal-multi-carrier signal has a thinned set of &ldquo;N&rdquo; or less orthogonal multiple carriers spaced at M-carrier intervals, where &ldquo;M&rdquo; denotes a predetermined natural number equal to or greater than 2.

Generation and decoding of multi-carrier signal

Each of a plurality of carrier waves is modulated with one of information signals for each symbol, one of two types of reference signals known on a receiving side is alternately inserted into a pair of particular carrier waves of which frequencies are symmetric to each other with respect to a frequency of a central carrier wave for each symbol while changing the frequencies of the pair of particular carrier waves at two symbol intervals to insert the reference signal into all carrier waves every prescribed symbols, a symbol number is inserted into one carrier wave to specify the pair of particular carrier waves, and an orthogonal frequency division multiplex (OFDM) signal composed of the modulated carrier waves are transmitted from transmitting apparatus to a receiving apparatus through a spatial transmission path. In the receiving apparatus, the OFDM signal is demodulated, two types of reproduced reference signals are obtained, a characteristic of a transmission path including the spatial transmission path and transmission characteristics of the transmitting and receiving apparatuses is detected by comparing the reproduced reference signals and the reference signals, a correcting equation is calculated, and each modulated information signal is reproduced according to the correcting equation. Accordingly, the reproduced information signals can be obtained with a high accuracy without complicating the configuration of the transmitting and receiving apparatuses.

Method for transmitting an orthogonal frequency division multiplex

An IDFT section has a set of input terminals subjected to components of an information signal respectively. The IDFT section subjects the information signal to inverse discrete Fourier transform to convert the information signal into a pair of a first in-phase signal and a first quadrature signal while assignment of the components of the information signal to the input terminals is in a first state. A first power-related value of one of the first in-phase signal and the first quadrature signal is calculated. The first in-phase signal and the first quadrature signal are written into an output buffer memory when the calculated first power-related value does not exceed a predetermined reference value. The assignment of the components of the information signal to the input terminals is changed from the first state to a second state when the calculated first power-related value exceeds the predetermined reference value. The IDFT section subjects the information signal to inverse discrete Fourier transform to convert the information signal into a pair of a second in-phase signal and a second quadrature signal while the assignment of the components of the information signal to the input terminals is in the second state. A second power-related value of one of the second in-phase signal and the second quadrature signal is calculated. The second in-phase signal and the second quadrature signal are written into the output buffer memory when the calculated second power-related value does not exceed the predetermined reference value.

Frequency division multiplexed signal generating apparatus and related

Disc recorder for recording information is comprised of a plurality of disc faces and correspondingly provided heads for recording information on the disc faces, the heads are connected to corresponding recording/reproducing circuits controlled by a control device, the disc faces, the heads and the recording/reproducing circuits constitute recording/reproducing channels. The disc recorder performs recording and/or reproducing operations by utilizing 2 or more of the recording/reproducing channels concurrently where an information unit to be processed in the recording/reproducing channels and recorded on every sector on the disc faces, is adopted to be a logical block unit having a control signal region and a data region. Further feature of the invention is that the control device has an output signal line connected to a host system.

Disc recorder for recording information

A position control system for a read/write device for fast positioning the read/write device at a particular track of a disk having a tracking pattern in the recording medium. The system having a transportation unit for transporting the read/write device to a target track and a control loop containing a BAF (multi-peak band-pass filter), includes a position control unit for controlling the position of the read/write device so as for the read/write device to track the target track, and a storage unit for storing the internal variables of the BAF filter. When the operation by the transportation unit is switched to the operation of the position control unit, the operation of the BAF filter is performed in accordance with the internal values or initial values stored beforehand, a particular one of the variables stored beforehand is used for the operation by the position control unit, or a reference value of the speed control is adjusted in accordance with a particular one of the variables stored beforehand.

Position control system for read/write device

A high density signal recording and reproducing apparatus comprises a disc drive comprising for recording and reproducing with an existing recording format a digital signal on and from a disc rotating at a rotational speed which is 1/N times a standard rotational speed, a circuit for generating N index pulses in one revolution time period of the disc, a selecting circuit for generating a selecting instruction which selects and designates an arbitrary track part on and from which the digital signal is to be recorded and reproduced out of N track parts of one track, a circuit responsive to the selecting instruction for generating a switching signal and an operation stop signal for stopping a recording or reproducing operation of the disc drive during a scanning period in which the remaining N-1 track parts excluding the arbitrary track part are scanned, and for passing out of the N index pulses in one revolution time period of the disc only one index pulse corresponding to the arbitrary track part, and a circuit responsive to the switching signal for selectively passing and supplying the reproduced digital signal to the selecting circuit only during a time period in which the digital signal is reproduced from the arbitrary track part.

High density signal recording and reproducing apparatus

A disk drive apparatus includes apparatus for elimination of off-track errors of a read/write head by deriving and storing correction data for all of the tracks on a disk on the basis of the signal level resulting from read-out of the contents of gap portions of the format data in two specific tracks. If, as indicated by a read error indication signal from a host computer, read errors subsequently occur in spite of position correction based on a stored correction value, then the off-track error for the track concerned is detected and an updated correction value is derived and stored. Accurate position control is thereby attained without a need for servo data tracks or regions to be recorded on each disk.

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Atsugi, Japan

Keiichi Kaneko