An adaptive equalizer includes a recording density detector for calculating a recording density reference value by obtaining the track radius using input track information, a reference tap coefficient storage portion for storing the reference tap coefficient obtained according to the channel impulse response at the lowest density position, a tap coefficient controller for obtaining a tap coefficient according to the recording density using the recording density reference value on the basis of the reference tap coefficient stored in the reference tap coefficient storage portion, and a waveform equalizer for eliminating the interference of the signal adjacent to the input reproducing digital signal using the tap coefficient obtained from the tap coefficient controller, to output the reproducing information signal. Therefore, the recording density is assumed by the track information of the reproduced data and the reproduction signal is adaptively waveform-equalized, so that high-speed real-time processing is possible and the circuit construction can be simplified.
Signal processing methods for addressing intersymbol interference in page-access optical memories such as holographic or two photon systems are disclosed. The invention takes advantage of the cartesian arrangement of data in page-access optical memories. A detector using the Viterbi algorithm is used to decode data row by row. Decision feedback is used in the direction perpendicular to the Viterbi direction. The use of data from previously decoded rows allows a reduction in the complexity of the Viterbi detector.
A novel and useful apparatus for and method of interference reduction in a communications receiver. The invention first finds the channel estimate and the noise vector from the receive signal. An interference detector is then used to choose an appropriate compensation filter and select between adaptive and deterministic moving average models for noise prediction. After compensation filtering, a new channel estimate and noise vector is calculated. The new noise vector is used to determine noise whitening coefficients if the adaptive model is used. In the deterministic model case, the coefficients do not need to be calculated since they are already known, having been calculated a priori. The noise whitening coefficients are then used in an equalizer such as a Viterbi algorithm based equalizer.
The equalizer is capable of generating an equalized output that is compensated in the non-linearity of the signal reproduced by an MR head and a reliable high-density magnetically recorded-signal reproducer. The equalizer of an FIR-type filter structure includes a plurality of delay elements for delaying an input signal by a certain period, a plurality of coefficient processing units provided to input or output taps of the delay elements, and an adder for obtaining the sum of the outputs of the coefficient processing units. The distortion of the reproduced waveform can be corrected by a relatively simple circuit structure by comparing the signal value inputted to the coefficient processing unit from each tap with a predetermined threshold level and changing the signal value and a coefficient value to be multiplied in accordance with the comparison result. Therefore, any one of various existing signal processing systems can be applied to the decoding of reproduced signals of an MR head having the non-linear characteristic.
An information reproducing apparatus for reproducing information of information marks by scanning information marks recorded on tracks inside a predetermined information recording region by an optical spot, the apparatus includes a driving device, an optical head, a head driving device, a laser driving device, an automatic gain control circuit, a non-linear equalization circuit, a phase locked loop circuit, a data demodulation circuit, and a control circuit.
A method for laying out an adaptive zone of a hard disk drive adopting a partial response signalling and maximum likelihood (PRML) detection comprises the steps of obtaining a pulse width by reading an isolated pulse written on a disk as a recording medium, obtaining a channel bit period by calculating the ratio between the channel density according to PRML and the pulse width, and selecting the optimum zone data rate from a zone table to record it on a memory.
