摘要:
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.
摘要:
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.
摘要:
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.
摘要:
A transfer process in which, an original vector signal is precoded to an intermediately-precoded vector signal, and the extended modulo operation is performed when the intermediately-precoded vector signal is located outside a predetermined extended-modulo limit area, and the precoded vector signal is transferred through a system having a predetermined filtering characteristic. From the transferred vector signal, the original vector signal is detected, based on a relationship between the vector components of the original vector signal and the transferred vector signal.
摘要:
The present invention discloses a timing phase control apparatus which is particularly suitable for use in a modem used for very high speed data transmission employing a metallic line. The timing phase control apparatus includes a timing phase extracting portion to extract timing phase information from an input signal, a timing phase control filter portion to make a timing phase control to the input signal depending upon the timing phase information from the timing phase extracting portion through filter processing using a coefficient operation having a preset impulse response characteristic, and a filter processing coefficient determining portion to determine a coefficient used for the filter processing in the timing phase control filter portion depending upon the timing phase information and information about an approximate expression of the impulse response characteristic. An accuracy of a tap coefficient can be improved while reducing an amount of information about the tap coefficient, which should be stored.
摘要:
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.
摘要:
The invention provides a phase jitter extraction circuit and a phase jitter cancellation circuit for use with a reception section of a communication apparatus such as a modem used to transmit data using a telephone line or a private line, which are improved in that noise of a signal is prevented from increasing to suppress phase jitters with a high degree of accuracy and high noise components can be suppressed irrespective of the power of the input signal. The phase jitter extraction circuit includes a phase jitter detection section for detecting phase jitters from input/output information of a signal discriminator, a phase jitter forecasting section for forecasting phase jitters which will be produced later from the phase jitters detected by the phase jitter detection section, a selector for selectively outputting the phase jitters detected by the phase jitter detection section or the forecast phase jitters obtained by the phase jitter forecasting section, and a selector control section for discriminating a region of signal points received by the communication apparatus by way of a transmission line and controlling the selector in accordance with a result of the discrimination.
摘要:
A modulator and demodulator apparatus for use with a network is provided. The modulator and demodulator apparatus comprises a modulation section which includes a timing phase discrimination section for receiving, as an input signal thereto, a demodulation vector signal sampled into a digital value and discriminating to which one of a plurality of regions of a discrimination plane the phase of the input signal belongs. The timing phase discrimination section supplies, as an input to a next processing stage, a rotation vector obtained by rotating an input vector, moves the rotation vector to a quadrant which includes a reference discrimination region of the discrimination plane and performs, when the vector after the movement is not in the reference discrimination region, a predetermined calculation. When the vector after the movement comes to the reference discrimination region, another calculation is performed. This discriminates a timing phase of the input vector from the result of the calculation.
摘要:
In a timing extraction device coupled to a demodulator which derives a real signal component and an imaginary signal component from a signal received via a transmission line, a band-pass filter extracts a 1/2-Nyquist frequency from either the real signal component or the imaginary signal component. The 1/2-Nyquist frequency includes two symmetrical frequency components. A vector conversion unit processes the 1/2-Nyquist frequency so that a vector signal corresponding to one of the two symmetrical frequency components of the 1/2-Nyquist frequency is output from the vector conversion unit. A square multiplier squares the vector signal received from the vector conversion unit and thereby generates a phase error signal indicating timing information concerning the analog signal. The phase error signal has an angle which is double an angle of the vector signal.
摘要:
A method for transmitting a signal with a signal transmission rate selected from a plurality of signal transmission rates applicable to a facsimile transmission system. The distortion amount of a distortion measurement signal transmitted from a transmitting equipment is measured at a receiving equipment on the basis of the variation in the received distortion measurement signal. The distortion allowance range to which the measured distortion amount belongs is decided on the basis of the result of the measurement of the distortion amount. The transmission of the working signals is carried out with a transmission rate corresponding to the result of the decision of the distortion allowance range.