Method and apparatus for controlling the risetime of a digital magnetic recording waveform

Claim 2

In a magnetic recording system wherein digital signals represented as binary electric recording current are applied to a magnetic transducer which produces a corresponding magnetic field for recording saturated binary magnetization patterns on a magnetic medium, said recording current including: a first half-cycle having a first polarity, a shallow leading edge and a relatively steep trailing edge; and a second half-cycle immediately following the first half-cycle, having a polarity opposite the first polarity, a shallow leading edge and a relatively steep trailing edge.

Claim 3

The system of claim 1 wherein the transducer and medium are in relative motion at a velocity v, the magnetization patterns have a dimension d, and the risetime of the leading edges is on the order of d/2/v.

Claim 4

Means for generating a current to a transducer for recording digital information signals as saturated magnetic indicia on a magnetic medium, comprising: a source of binary recording current; first control means, connected to said source, for varYing the current with respect to time as a function of information signals to assume the shape of alternating positive and negative going periodic pulses lying between two levels on each side of a zero axis; and second control means, connected to said source and to said first control means, for causing the leading edge of each pulse to change from the zero axis to one of the levels during a period which is a substantial portion of the period of that pulse.

Claim 5

Means for generating a current to a transducer for recording digital information signals as saturated magnetic indicia on a magnetic medium, comprising: a source of binary recording current; first control means, connected to said source, for varYing the current with respect to time as a function of information signals to assume the shape of alternating positive and negative going periodic pulses lying between two levels on each side of a zero axis; and second control means, connected to said source and to said first control means, for causing the leading edge of each pulse to change from the zero axis to one of the levels during a period which is a substantial portion of the period of that pulse.

Claim 6

The means of claim 3 wherein the transducer and medium are in relative motion and the leading edge period is substantially a function of the dimension of the magnetic indicia and the relative velocity of the transducer and medium.

Claim 7

A circuit for supplying a recording current to a magnetic head utilized to record as saturated magnetic indicia on a magnetic medium digital information represented by the recording current during relative head-medium motion, including: an information signal source for supplying digital binary information signal pulses having a fixed duration with steeply rising leading and trailing edges; a controllable time constant device, connected to the source, for converting steeply rising information signal pulses to a pulse having the same duration as the signal pulse and a controlled time constant leading edge; a current source for supplying an electric current quantity; and a current gate, connected to the current source and to the time constant device for varying the current between two levels on each side of an intermediate value, the change of current from the intermediate value to each level occurring during a period which is a substantial portion of the pulse duration.

Claim 8

A circuit for supplying a recording current to a magnetic head utilized to record as saturated magnetic indicia on a magnetic medium digital information represented by the recording current during relative head-medium motion, including: an information signal source for supplying digital binary information signal pulses having a fixed duration with steeply rising leading and trailing edges; a controllable time constant device, connected to the source, for converting steeply rising information signal pulses to a pulse having the same duration as the signal pulse and a controlled time constant leading edge; a current source for supplying an electric current quantity; and a current gate, connected to the current source and to the time constant device for varying the current between two levels on each side of an intermediate value, the change of current from the intermediate value to each level occurring during a period which is a substantial portion of the pulse duration.

Claim 9

The circuit of claim 5 wherein the period during which the current changes from the intermediate value to a level is a function of the indicia dimension and the head-medium velocity.

Claim 12

A circuit for generating from digital input signals controlled risetime write currents for saturated recording of magnetic indicia on a medium, comprising: two input driver transistors, connected to complementary input signal sources supplying uncontrolled leading edge risetime signals as a function of the input signals; two RC time constant control devices, each connected to one of the input driver transistors, for providing a controlled risetime signal for each uncontrolled risetime signal from the connected driver transistor; two discharge transistors each connected at the output of a different one of the RC devices and to the signal sources, for providing a rapidly falling trailing edge discharge time signal which is substantially the same as the uncontrolled trailing edge of the input signal; a plurality of current driver transistors connected to the RC time constant control device and the discharge transistors for providing two outputs complementary current signals with controlled risetime lead edges and rapidly falling trailing edges; and a transducer winding having two leads connected to the current driver transistor outputs for generating magnetic fields as a function of the currents from the transistors which record indicia on the medium.

Claim 13

A circuit for generating from digital input signals controlled risetime write currents for saturated recording of magnetic indicia on a medium, comprising: two input driver transistors, connected to complementary input signal sources supplying uncontrolled leading edge risetime signals as a function of the input signals; two RC time constant control devices, each connected to one of the input driver transistors, for providing a controlled risetime signal for each uncontrolled risetime signal from the connected driver transistor; two discharge transistors each connected at the output of a different one of the RC devices and to the signal sources, for providing a rapidly falling trailing edge discharge time signal which is substantially the same as the uncontrolled trailing edge of the input signal; a plurality of current driver transistors connected to the RC time constant control device and the discharge transistors for providing two outputs complementary current signals with controlled risetime lead edges and rapidly falling trailing edges; and a transducer winding having two leads connected to the current driver transistor outputs for generating magnetic fields as a function of the currents from the transistors which record indicia on the medium.

Claim 14

In a magnetic recording system wherein digital signals represented as binary electric recording current are applied to a magnetic transducer which produces a corresponding magnetic field for recording saturated binary magnetization patterns on a magnetic medium, said recording current including: a first half-cycle having a first polarity and a shallow leading edge and a trailing edge; and a second half-cycle immediately following the first half-cycle, having a polarity opposite the first polarity, a shallow leading edge and a trailing edge.

Claim 15

In a magnetic recording system wherein digital signals represented as binary electric recording current are applied to a magnetic transducer which produces a corresponding magnetic field for recording saturated binary magnetization patterns on a magnetic medium, said recording current including: a first half-cycle having a first polarity and a shallow leading edge and a trailing edge; and a second half-cycle immediately following the first half-cycle, having a polarity opposite the first polarity, a shallow leading edge and a trailing edge.

Claim 16

The system of claim 9 wherein the transducer and medium are in relative motion at a velocity v, the magnetization patterns have a dimension d, and the risetime of the leading edges is on the order of d/2/v.

Claim 21

In combination: a magnetic medium having a surface and magnetic transducer adjacent said surface in relative motion at a fixed average velocity; a source of write current, connected to said transducer, for providing a change of current causing the transducer to produce a magnetic field transition which magnetically orients semi-circular portions of the medium adjacent thereto; and a circuit, connected to said source, for controlling the rate of said write current change to produce a plurality of successive magnetically oriented portions on the medium all having common points in a line parallel to the medium surface.

Claim 22

In combination: a magnetic medium having a surface and magnetic transducer adjacent said surface in relative motion at a fixed average velocity; a source of write current, connected to said transducer, for providing a change of current causing the transducer to produce a magnetic field transition which magnetically orients semi-circular portions of the medium adjacent thereto; and a circuit, connected to said source, for controlling the rate of said write current change to produce a plurality of successive magnetically oriented portions on the medium all having common points in a line parallel to the medium surface.