A digital information receiver having a tapped delay line equalizer for reducing intersymbol interference caused by a linear time dispersive transmission channel. The tapped delay line equalizer includes a plurality of amplifiers the gains of which are adjusted such that the combined response of the equalizer and channel approximates a multi-element coded digital signal which has the same number of levels as the signals to be transmitted, has the same number of elements as the channel response signal, and wherein the mean squared error between the combined channel and equalizer response signal and the channel response signal is a minimum. The output of the equalizer is connected to a decoder via a quantizer for decoding the transformed signal.
In this pcm digital-to-analog converter, a probability value (soft decision), rather than the conventional one/zero value (hard decision), is given each sampled input of signal-plus-noise as a function of signal-to-noise ratio, thereby reducing the mean squared error in the output analog signal.
If a time domain equalizer with capacitive-resistive voltage dividers for adjusting the level of the individual time-delayed partial signals as commonly employed for high frequencies is to be used to equalize broad communication bands, the noise requirements for the lower communication band cannot be satisfied because of the frequency response of the voltage dividers. This effect is reduced by adding to the signal to be corrected, besides the signals delayed by n..tau., at least one signal delayed by .tau./m.
Techniques are disclosed for converting a multibit digital data word into a corresponding analog signal. The converter of the present invention utilizes information in a received signal plus noise associated with the information in such a manner as to reduce the mean squared error in the generated analog signal. The actual voltage associated with each bit position in the digital word is measured. In addition, a measurement of the signal-to-noise ratio is made. From these two measurements a processing device is adapted to generate a value corresponding to the statistical probability that the detected voltage level for each bit is a logical one. The probability values are used as scaling factors to modify the weights to be given each bit during the normal digital to analog conversion process.
A signal detection system comprising detecting means for detecting the differential between a first and a second sampled value of an electrical signal subjected to sampling, comparing means for comparing the output of the detecting means with a predetermined first threshold value, discriminating means for discriminating the polarity of the output of the detecting means, adding means controlled by the output of the discriminating means for adding a predetermined second threshold value to the first sampled value, and means controlled by the output of the comparing means for deriving the result of addition from the adding means. The signal detection system serves for reducing or removing noises involved in or superposed on an electrical signal and more particularly a bioelectrical signal such as one recorded on an electroencephalogram or electrocardiogram.
A signal processing apparatus for use in data communications systems where the transmitted signal is subject to the effects of short duration interference, such as impulse noise, or for use in data recording systems where recorded data is subject to the effects of imperfections in the recording media, wherein a coded transformation is performed on an input signal to the apparatus in accordance with a selected time distribution and selected multi-level, integer related weighting functions to produce a coded signal. A decoder can be used to reversibly transform such signal so as to substantially reproduce the input signal in a manner such that the effects of such noise and recording imperfections are minimized.
