Nec Corporation

Takenori Ogata

Masaru Yamaguchi

Masanobu Arai

Shin'ichi Koike

In a baude rate sampling type receiving circuit for use in a system for transmitting digital data signal at a transmission baude rate, in order to control the sampling phase at the optimum phase, desired elements of an autocorrelation function of a series of baud rate sampled signals are calculated and are linearly summed by a calculating circuit to provide a linear summation as a power of the series of sampled signals. The sampling phase at the baud rate sampling is controlled by a control circuit by use of the linear summation so that the power is maximized, whereby the sampling phase is maintained at the optimum sampling phase.

Digital signal receiving circuit with means for controlling a baud rate

The whole or part of a waveform is cancelled by a circuit comprising a nonrecursive filter and a recursive filter. The nonrecursive filter has a plurality of first multipliers having first tap weights for modifying symbols successively shifted along a shift register. The recursive filter is connected in a series circuit to the shift register and has a second tap weight for recursively modifying the output of the shift register. The recursively modified symbol is modified by a second multiplier having a third tap weight and combined in an adder with the symbols modified by the first tap weights to produce a replica of an undesired waveform. The replica is destructively combined in a subtractor with an incoming symbol having an undesired waveform. The output of subtractor is utilized to derive the tap weights to adaptively control the inputs to the adder.

Circuit for cancelling whole or part of a waveform using nonrecursive

In a receiver comprising a filter section for filtering a transmitted digital signal into a filtered digital signal and an equalizer section for equalizing the filtered digital signal into an equalized digital signal as a reproduced digital signal in response to controllable tap gains supplied from a control arrangement, the equalizer section comprises a first arrangement for filtering the filtered digital signal in response to predetermined ones of the controllable tap gains to produce an intermediate digital signal and a second arrangement for equalizing the intermediate digital signal into the equalized digital signal in response to remaining ones of the controllable tap gains except for the predetermined controllable tap gains to produce the reproduced digital signal. The control arrangement controls the predetermined tap gains so as to minimize noise power of a noise signal accompanying the filtered digital signal and the remaining controllable tap gains and to equalize the intermediate digital signal into the equalized digital signal.

Receiver capable of improving signal-to-noise ratio in reproducing

A digital automatic line equalizer for compensating distortion of a digital signal transmitted through a transmission line comprises a transversal filter having a set of tap gains for producing an equalized signal as a filter output from the digital signal incoming thereto. A first multiplier squares a current one of the filter output to produce a squared signal and other multipliers multiply the current and the previous ones of the filter outputs to produce product signals. In a calculator, the product signals are weighted and are, thereafter, summed together with the squared signal to produce summed signals which are averaged for a predetermined time duration into a mean value. A controller has a plurality of sets of values for the set of tap gains, compares the mean value with a reference value to produce an error signal and determines one set of the plurality of sets of values in response to the error signal to make the set of tap gains equal to the set of values thereby to maintain the mean value to the reference value so that the transversal filter produces the equalized signal.

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Miyagi, Japan

Takenori Ogata