US 4,544,963 AGranted

Read signal detection in ternary 3PM magnetic recording

AssigneeSperry Corporation

InventorsGeorge V. Jacoby, Allan A. Schwartz

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Abstract

Circuitry for distinguishing each value in a read signal magnetically recorded in ternary-3 position modulation in which the values 1, 2 and 0 are detected and equalized into a singlet, a doublet and absence of magnetic flux change. The circuitry first determines the position locations of each singlet peak and doublet crossover point to establish proper timing of the output signals and then identifies the particular type of signal appearing at the timing points in the read signal sequence. Singlets are identified by the much greater amplitudes in the integrated read signal. Doublets are identified as waveforms having slopes at zero crossovers that correspond in polarity to that of the previous singlet. A novel detector circuit is provided that can correctly identify doublets in a code sequence, irrespective of the presence of a previous singlet, when a recording rule is followed that includes the insertion of a number of consecutive ternary 0 symbols into the recorded signal.

Claims19

Dependent claims

Circuitry responsive to a detected analog read signal for identifying each symbol in a sequence of recorded signals coded in a ternary-3-position modulation in which a ternary 1 symbol is recorded as a single flux reversal at the center of a timing detent and is read as a singlet analog signal, a ternary 2 symbol recorded as two flux reversals within the boundaries of a detent is read as a sinusoidal shaped doublet analog signal, and a ternary 0 symbol is recorded and read as the absence of flux change in a detent, said circuitry including:

receiving means for detecting the read signals of the recorded ternary code and for producing therefrom equalized analog signals containing ternary-3-position modulation symbols;
doublet and singlet position locator circuitry coupled to said receiving means and responsive to said equalized analog signals for detecting the location of the center of each detent identified with a doublet and singlet and for producing a doublet position locator signal and a singlet position locator signal indicative thereof;
singlet identifier circuitry coupled to said receiving means and to said singlet position locator circuitry for identifying each singlet by its amplitude, for correctly timing each identified singlet with said singlet position locator signal, and for generating output signals indicative of said timed singlet and its positive and negative sign;
and
doublet identifier circuitry coupled to said receiving means, said doublet position locator circuitry, and to said singlet identifier circuitry, said doublet identifier circuitry including control signal producing means responsive to positive and negative sign signals from said singlet identifier for producing a control signal of first and second signs, said doublet identifier circuitry further including gating circuitry responsive to positive and negative excursions of said equalized analog signals and to said control signal for producing timed output pulses indicative of those doublets in said equalized analog signal that have a slope at the center of their respective detent that corresponds in sign to the sign of the previous singlet.

2 more elements

The method for identifying each symbol in a sequence of binary signals recorded in ternary-3-position modulation and read by a transducer as distorted analog wave shapes representing the recorded signals, said ternary-3-position modulator having a ternary 1 symbol recorded as a single flux reversal at the center of a timing detent and being read as a singlet analog signal, a ternary 2 symbol being recorded as two flux reversals within the boundaries of a detent being read as a sinusoidal shaped doublet analog signal and a ternary 0 symbol being recorded and read as the absence of flux changes in a detent, said method comprising the steps of:

equalizing the output signal of the read transducer to reform distortions in said output signal into a sequence of equalized analog read signals;
determining from said equalized read signals the center location in each detent containing singlets and doublets and generating singlet and doublet position locator signals, respectively, identifying said central detent locations;
comparing the amplitudes of signals representing each singlet and each doublet in said equalized read signal sequence and generating singlet identifier signals representing the presence and positive and negative polarity sign of each singlet;
triggering the combined positive and negative polarity sign singlets with said generated singlet position locator signals to generate timed singlet output signals;
separating said equalized analog signals into a first channel and a second channel respectively conducting positive and negative polarity sign portions of said equalized analog signals;
gating each of said positive and negative polarity sign portions with a control signal having a polarity sign determined by the sign of the previously detected singlet to thereby identify those doublets having half wave portions with signs that correspond to the polarity sign of the previously detected singlet;
and
triggering said identified doublets with said generated doublet position locator signals to generate timed doublet output signals.

5 more elements

Dependencies are inferred from the claim text.