Abstract: A recording and reproducing apparatus includes a rotatable rotating assembly and a fixed assembly disposed opposite thereto. The apparatus also includes a plurality of recording and reproducing heads and an erasing head mounted on the rotating assembly and first and second rotary transformers, having primary windings mounted on the rotating assembly and secondary windings mounted on the fixed assembly. A control signal generator is mounted on the rotating assembly and receives signals via the primary winding of the second rotary transformer. A first signal processor is mounted on the rotating assembly and connects the plural recording and reproducing heads to the primary winding of the first rotary transformer and a switch connects the erasing head with primary winding of the second rotary transformer. A recording and reproducing processor is connected the secondary winding of the first rotary transformer while a modulation signal generator is connected to the second winding of the second rotary transformer.

Abstract: Apparatus and method of even harmonic distortion compensation are provided for digital data detection in a disk file. The disk file includes a magneto-resistive (MR) head or other magnetic transducer head and an analog-to-digital converter (ADC) for providing a sampled readback signal. An even harmonic filter is coupled to the ADC for providing a filtered readback signal having only even harmonic components. An adder subtracts the filtered readback signal from the sampled readback signal for providing a compensated output signal. The compensated output signal is applied to a digital channel of the disk file.

Abstract: A method and apparatus for identifying and synchronizing to two different fields in a disk drive employs different synchronization or "sync" patterns to reduce the chances of mis-identifying and false-identifying a field. Two very distinct synchronization patterns have been found that satisfy the d=1, k=7 run-length constraints of a data code used in the disk drive. During operation, one sync pattern is searched for to identify and synchronize to its associated field, then the field itself is read. This procedure is then repeated for the other sync pattern and its associated field. Also, the phase of a preamble preceding each sync character is established, so that the number of comparisons needed to find either sync character is reduced. A sync detector operates on cell pairs, and has a selector that selects which sync pattern to search for. The sync detector also has special features that enable it to find preamble and DC Erase fields in the disk cell stream.

Abstract: In a magnetic recording/reproducing apparatus data is recorded in the trailing portion of an area erased by an erase magnetic head, thereby surely extracting a regenerative clock at the reproducing time so that the operation of a regenerative clock system can be stabilized.

Abstract: A method for measuring the error rate of a magnetic recording device, such as a hard disk storing a set of data. The device has a partial response maximum likelihood data detecting channel (PRML channel) which differs from a conventional PRML channel by including a margin separator (58) which is connected between the output of A/D converter (54) and the input of a sequence detector (60). The system may contain a error counter (70) and data recovery units (66 and 68). The method consists mainly of changing the noise level in the samples received from the output of the A/D converter (54) and then counting the errors, and determining a dependence of a number of errors on a preselected criterion which characterizes a signal-to-noise ratio of the PRML channel. The above dependence can be extrapolated for an actual error rate of the channel being tested.

Abstract: A magnetic recording correction circuit for a video tape recorder comprises a first multiplier supplied with a first signal to output a signal having a frequency which is twice as high as that of the first signal; a second multiplier supplied with a second signal and a first multiplier output signal outputted from the first multiplier to output a correction signal having a component of a sum frequency of the second signal and the first multiplier output signal and a component of a difference frequency therebetween; an adding circuit for adding the first and second signals and the correction signal; and a phase shifter provided on the output side of the second multiplier to exert a phase characteristic on the correction signal with respect to the first and second signals.

Abstract: Apparatus and method are provided for servo signal demodulation using a servo processor and a partial-response maximum-likelihood (PRML) data channel in a disk file. A servo burst timing window is identified. Then a plurality of digital samples are detected with the PRML data channel responsive to identifying the servo burst timing window. Sequential sets of the detected digital samples are accumulated by the PRML data channel and transmitted to the servo processor. The digital samples are processed by the servo processor for providing servo phase information that is used to provide servo position information.

Abstract: A magnetic transducer has its opposite coil extremities connected to a direct current power supply via a pair of inductance elements, respectively. The transducer coil is excited not only from the power supply but from the inductance elements as a write control circuit applies a binary write control signal, representative of digital information to be recorded, to a pair of semiconductor switches thereby causing the same to be alternately turned on and off. Being typically in the form of metal oxide semiconductor field effect transistors, the semiconductor switches permit the flow therethrough of a current of varying magnitudes when open. A pair of reverse blocking diodes are therefore connected in series with the respective semiconductor switches in order to make constant the current flowing through the transducer.

Abstract: A reference signal is recorded in different locations on a record medium with a controllable recording current level that is changed when the reference signal is recorded in such different locations. Location signals representing those different locations at which the reference signal is recorded also are generated and they too are recorded. Thereafter, the reference and location signals are reproduced from the different locations and stored. The stored reference signal whose signal level is the largest is detected and the location signal representing the particular record medium location at which that reference signal was recorded is identified. The recording current level which was used to record the reference signal at that particular location is determined. This determined recording current level may be used subsequently to record a signal, such as a video signal, with optimum characteristics.

Abstract: A method and apparatus are provided for biasing a non-center tapped magneto-resistive head at a constant voltage using two separate biasing stages to provide independent control over the voltage at each of the two terminals of the head. A first control device detects the voltage at a first head terminal and directs changes to the output of a current source, interconnected with a first terminal of the head, to maintain the voltage at the first terminal at a first predetermined voltage. A second control device detects the voltage at second terminal of the head and directs changes to the input of a current sink, interconnected with the second terminal, to maintain the voltage at the second terminal at a second predetermined voltage. Each control device is interconnected to a separate reference voltage source; by appropriate selection of the voltages of the reference voltage sources, the voltages at the two head terminals and the potential across the head can be established and maintained.

Abstract: A driver circuit for providing drive current to a coil for positioning a read/write head of a memory disk system and method are presented. The driver circuit includes a pair of high side driver transistors having current paths connected between respective terminals of the coil and a voltage source, a first pair of low side driver transistors having current paths connected between respective terminals of the coil and a first voltage sense node, and a second pair of low side driver transistors having current paths connected between respective terminals of the coil and a second voltage sense node. A first sense resistor is connected between the first and second voltage sense nodes, and a second sense resistor is connected between the second sense node and a reference potential.