Fujitsu Corporation

Ricoh Company, Ltd.

Ryoji Okita

Takashi Kaku

Noboru Kawada

Takeshi Asahina

Toyomi Obikawa

Hideo Miyazawa

Masayoshi Inoue

Tohru Ogawa

Shozo Kudo

Michiko Kawada

A method used in equalization processing is provided, in which a reference signal is received and a change point of transmission line characteristics is detected. A basic frequency signal of fluctuation period of the transmission line characteristics is extracted, and vectorized. The vector is adjusted such that vectors corresponding to two change points become symmetrical with respect to X axis. Then, fluctuation interval of transmission line characteristics is judged by comparing X component of the vector with a reference value. As a result, equalization processing is performed in accordance with the fluctuation.

Equalization processing method and the apparatus for periodic fluctuation of transmission line characteristic

A data processing apparatus includes a decision section that determines a predetermined plurality of channels of original data and a predetermined channel of correction data based on data of received signals; an exclusive OR circuit that calculates an exclusive OR upon the channels of the decided data; a signal quality decision section that detects signal quality of received data on each channel; and a correction section that replaces a channel of data whose channel has a worst detection result as detected by the signal quality detection section with the result of the exclusive OR calculation when the result of the calculation is other than '0'. The signal quality detection section calculates a mean signal quality and an instantaneous signal quality that are used by the correction section to determine the worst channel.

Data processing apparatus and data processing method

A canceling method and apparatus can achieve a fast communication by improving an S/N value by adaptively canceling a noise with respect to a frequency or band having a large noise by selecting noise canceling band in accordance with a condition of noise being generated. A reception signal contains a specific signal having a specified time position, amplitude and phase. A noise distribution of the specific signal is recognized so as to predict a noise by extracting a frequency band having a larger noise component from a pair of frequencies generated by the insertion of the specific signal. An original transmission signal is reproduced by canceling the predicted noise from the reception signal.

Noise canceling method and apparatus

The present invention is concerned with an error correction device and method for correcting errors in data items sent on a plurality of channels. An identification unit calculates an exclusive OR value for data items sent on the plurality of channels, and adopts the calculated value as data sent on a separate error correction channel. A signal quality detection unit detects the signal qualities concerning the plurality of channels. If the exclusive OR value is not equal zero, an identifying and processing unit replaces data on a channel whose signal quality is detected to be worst with an exclusive OR value for data items sent on channels other than the channel whose signal quality is worst.

Error correction device and error correction method

Disclosed is a PLL control method of controlling a phase of a PLL for taking synchronism of a receiving signal in a data receiving apparatus. The phase of the PLL is synchronized with a phase when training irrespective of a line characteristic. The PLL control method comprises a step of training a timing phase of PLL in accordance with a training signal, a step of obtaining, immediately after training, a right-side reference value from a sum of tap coefficients of taps on the right side of a center tap of the auto equalization unit, and obtaining a left-side reference value from a sum of tap coefficients of taps on the left side of the center tap of said auto equalization unit, a step of calculating a sum of the tap coefficients of the taps on the right side of the center tap of the auto equalization unit, thereafter obtaining a first difference between the above sum and a right-side reference value, calculating a sum of the tap coefficients of the taps on the left side of the center tap of the auto equalization unit, and thereafter obtaining a second difference between the above sum and a left-side reference value, and a step of obtaining a PLL control signal by obtaining a difference between the first and second differences.

PLL control method in data receiving apparatus

A transmission system for transmitting a data signal with an analog passband signal through a analog transmission line. The data signal is transformed to a signal representing a descrete data signal point in a vector signal space. The analog passband signal is transformed to a base band signal, and the base band signal is superimposed on the signal representing a descrete data signal point. A signal representing the superimposed data signal point is modulated and transmitted through the analog transmission line. In a receiver, the data signal point is decided from the signal representing the superimposed data signal point, and the superimposed bass band signal is extracted by subtracting the decided result from the signal representing the superimposed data signal point. The base band signal is transformed to the analog passband signal. A portion of information carried by the analog passband signal may be converted to a digital signal, and the digital signal is multiplexed with the data signal. Further, a portion of information of each of a plurality of analog passband signals may be converted to a digital signal, and the digital signal is multiplexed with each other, and the other portion of the information is transformed to a base band signal, and the base band signal is superimposed on a signal representing a data signal point generated from a signal generated by the multiplexing.

Multiplex transmission system wherein analog signal is transformed to base band, random-transformed and superimposed on dispersed signal points in vector signal space

A frequency modulation method and modem unit for a frequency modulation using a common filter which uses a large number of carrier frequencies include a frequency-shifting unit for subjecting an input data to a frequency shift corresponding to a binary data value, a filter for limiting an output obtained by the frequency-shifting unit to a common band, and a modulation unit for frequency-modulating an output obtained by the filter, by a carrier frequency having an intermediate value of the frequencies respectively corresponding to the binary data values.

Frequency modulation method and modem unit employing such method

A transmission system for transmitting a data signal with an analog passband signal through a analog transmission line. The data signal is transformed to a signal representing a descrete data signal point in a vector signal space. The analog passband signal is transformed to a base band signal, and the base band signal is superimposed on the signal representing a descrete data signal point. A signal representing the superimposed data signal point is modulated and transmitted through the analog transmission line. In a receiver, the data signal point is decided from the signal representing the superimposed data signal point, and the superimposed base band signal is extracted by subtracting the decided result from the signal representing the superimposed data signal point. The base band signal is transformed to the analog passband signal. A portion of information carried by the analog passband signal may be converted to a digital signal, and the digital signal is multiplexed with the data signal. Further, a portion of information of each of a plurality of analog passband signals may be converted to a digital signal, and the digital signal is multiplexed with each other, and the other portion of the information is transformed to a base band signal, and the base band signal is superimposed on a signal representing a data signal point generated from a signal generated by the multiplexing.

Multiple transmission system wherein analog signal is transformed to base band, random-transformed and superimposed on dispersed signal points in vector signal space

A transmitter has a power calculation unit for calculating the power of a signal. A maximum value detection circuit determines a maximum value of an output of the power calculation unit, and a floating point transformation circuit changes an output of the maximum value detection circuit into a floating point representation. A significant bit extracting circuit extracts significant bits from an output of the floating point transformation circuit and outputs the significant bits as the transmitting signal.

A transmission apparatus applied as a modem connected to a private branch exchange discriminates coordinates of an analog signal inputted thereto on a two-dimensional coordinate plane and transmits the signal, whose coordinates have been discriminated, as a digital signal. The transmission apparatus includes a frequency shifting section for performing frequency shifting for the inputted analog signal so that a tone signal of a single frequency may be a dc signal, and a coordinate discrimination section for discriminating coordinates on the two-dimensional coordinate plane of the analog signal for which the frequency shifting by the frequency shifting section has been performed. By the transmission apparatus, a single tone signal is transmitted without suffering from deterioration of the S/N ratio and so forth.

Transmission apparatus, reception apparatus and communication apparatus

In a modem signal transmitting/receiving system which includes a modem signal transmitter and a modem signal receiver connected to each other via a transmission line, a modem signal transmitter is suitable to transmit by multiplexing an analog signal such as audio and a modem carrier with digital data. Analog signals and digital data can be multiplex-transmitted at a high rate by effectively using an analog signal line. The modem signal transmitter includes a modem transmitting unit, an analog/digital converting unit which converts an analog signal into a digital signal, a demodulating unit which demodulates the digital signal with a predetermined carrier frequency signal, a decimation processing filter which decimates the demodulated signal and a deciding unit which decides a coordinate on a two-dimensional plane for the output from the decimation processing filter and then inputs the decision result to the modem transmitting unit. The signal received from the transmission line is subjected to an interpolation process, modulated with a predetermined carrier frequency, converted to an analog signal and outputted to the analog signal line.

Modem signal transmitter, modem signal transmitting method, modem signal

A transmission apparatus such as a modem has a receiving unit which receives information and a clock-supplying unit which supplies a clock signal to the receiving unit. It further has an instantaneous dropout detection unit which detects the occurrence of an instantaneous dropout on the receiving circuit and a clock supply control unit which stops the supply of a clock to the receiving unit for a prescribed amount of time when the instantaneous dropout detection unit detects an instantaneous dropout, the stopping of the clock supply causing holding of receiving parameters and the restarting of clock supply causing restarting of the receiving operation.

Transmission apparatus and control method therefor

A transmission apparatus, connected via a hybrid circuit to a line, such as a modulator-demodulator which can perform stable echo cancellation, whether the level of the far-end echo is high or not, provided with a transmission unit which generates a transmission signal to be transmitted to the line via the hybrid circuit, a reception unit which receives the reception signal supplied from the line via the hybrid circuit, and a superimposing means for superimposing the reception signal applied to the hybrid circuit onto the transmission signal. The transmission signal onto which the reception signal is superimposed by the superimposing means is transmitted to the line via the hybrid circuit.

Transmission apparatus having echo cancellation facility

An apparatus for recovering a timing signal from a received signal in a transmission apparatus includes an equalizer equalizing a processed signal which is provided by processing the received signal with a first signal and adjusting tap coefficients so as to eliminate distortion in the processed signal. A tap-power distribution detector detects a distribution of the tap coefficients adjusted in the equalizer. A phase control part controls a phase of the first signal according to the distribution of the tap coefficients detected in the tap-power distribution detector. In the apparatus, the phase of the first signal is controlled so as to be synchronized with a timing signal component in the received signal.

Apparatus and method of recovering a timing signal in a transmission

A transmission system includes a transmitter and a receiver and transmits a data signal with an analog passband signal through an analog transmission line. The data signal is transformed to a signal representing a descrete data signal point in a vector signal space. The transmitter includes a data signal point generation unit and a vector signal superimposing unit. The analog passband signal is transformed to a base band signal, and the base band signal is superimposed on the signal representing a descrete data signal point. A signal representing the superimposed data signal point is modulated and transmitted through the analog transmission line. The receiver includes a demodulator unit and a decision unit, wherein the data signal point is decided from the signal representing the superimposed data signal point, and the superimposed base band signal is extracted in a subtracter unit by subtracting the decided result from the signal representing the superimposed data signal point. The base band signal is transformed to the analog passband signal. A portion of information carried by the analog passband signal may be converted to a digital signal, and the digital signal is multiplexed in a multiplexer unit with the data signal. The base band signal is superimposed on a signal representing a data signal point generated from a signal generated by the multiplexing.

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Kawasaki, Japan

Ryoji Okita