Dynamic magnetic information storage or retrieval – General processing of a digital signal – Head amplifier circuit
Reexamination Certificate
2001-03-26
2004-04-06
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Head amplifier circuit
C360S061000, C360S062000, C360S064000, C360S067000, C360S068000, C360S077020
Reexamination Certificate
active
06717761
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus capable of controlling with high precision the recording and reproduction of signals by plural heads, and more particularly to a recording/reproducing apparatus in which a recording/regenerative integrated circuit with plural magneto resistive heads (hereinafter abbreviated to MR heads) connected thereto can be controlled with high precision. The invention further relates to an apparatus for reproducing digital information signals or the like with MR heads, and more particularly to a rotary magnetic head type apparatus in which bias currents to MR heads mounted on a rotary drum can be appropriately controlled.
An MR head, which can detect magnetic information signals entered from a recording medium, such as a magnetic tape or a magnetic disk, by variations in resistance, requires the supply of a detecting current (sense current). Furthermore, as such variations in resistance have a nonlinear characteristic with respect to the input magnetic field, an MR head also needs a bias current for keeping the operating point in a more linear region. Recently developed MR heads are designed to utilize these currents (hereinafter to be together referred to as bias currents).
Where MR heads are to be used in a rotary head type magnetic recording/reproducing apparatus, a bias current circuit and a preamplifier circuit are mounted on the rotary drum. Therefore, power to drive these circuits needs to be supplied to the rotary drum side, and it is usually transmitted via a rotary transformer or a slip ring (contact). Also, MR head bias current control signals are transmitted to the rotary drum side via the rotary transformer after being converted into A.C. signals, and further rectified on the rotary drum side to be converted into D.C. voltage signals for controlling the MR heads.
A technique to mount MR heads on a rotary drum and control bias currents to determine the operating points of the MR heads is described, e.g. in J-P-A No. 177924/1998. Further, J-P-A No. 105909/1998 discloses a bias current regulating apparatus capable of flowing optimal bias currents to individual MR heads. J-P-A No. 201005/1995 reveals a method by which optimal bias currents are applied to active MR heads at the time of executing each head switching command.
SUMMARY OF THE INVENTION
For high density recording/reproducing apparatuses using a magnetic tape, the prevailing trend is to increase the number of magnetic heads (MR heads) mounted on the rotary drum in order to expand the capacity and enhance the transfer rate. Since each MR head differs in sensitivity and optimal operating point according to its element length from the sliding surface of the tape (MR height), it is preferable to individually optimize the bias current where plural MR heads are to be used. However, if it is necessary to provide the rotary transformer for controlling the MR bias currents with as many channels as the MR heads, it will become difficult to increase the number of MR heads to be mounted on the rotary drum. Furthermore, where control information is to be transmitted in analog signals, there will be another problem of difficulty to achieve high enough precision.
An object of the present invention, therefore, is to provide a rotary magnetic head type apparatus permitting independent and precise regulation of bias currents supplied to plural MR heads mounted on a rotary drum in a simple structure.
In order to achieve the object, a rotary magnetic head type apparatus according to the invention is provided on a stationary drum side with a control signal generator for generating control signals for controlling the operating amperages of magneto resistive heads and on the rotary drum side with a decoder circuit for discriminating data of the control signals and a current supply circuit for supplying operating currents to the magneto resistive heads in response to the output signals of the decoder circuit. The control signals are transmitted over a single channel of a rotary transformer and set the operating currents of the magneto resistive heads. Further, the control signals may include control information regarding a regenerative amplifier for reproduced outputs of the magneto resistive heads and recording current setting for recording heads.
Another aspect relates to a regenerative integrated circuit comprising a current supply circuit and a regenerative amplifier, which is mounted on the rotary drum to switch over among the plurality of MR heads for operation in turn. Usually a regenerative integrated circuit for MR heads is controlled with digital data on three lines including Data, Clock and Chip Select (CS) lines. For this reason, a control signal generator for generating control signals for controlling the regenerative integrated circuit is provided on the stationary drum side, and a decoder circuit for discriminating data of the control signals is provided on the rotary drum side. The three-line signals for controlling the regenerative integrated circuit are supplied from the decoder circuit. This structure requires only one control line for transmission from the stationary side to the rotary side, even if the number of MR heads is increased. Moreover, since the transmitted signals are digital signals, highly precise transmission is made possible.
However, since additional functions in such a regenerative integrated circuit would entail a substantial increase in the quantity of data bits required for their control, if data required for all the controls are transmitted on every occasion of head switching, it will take too long a time. In the worst case, head switching may fail to be done at the desired timing, inviting a loss of some head-reproduced signals. If the number of MR heads is increased and the number of regenerative integrated circuits mounted on the rotary drum also increases, a similar problem will arise because the data for the increased integrated circuits that are used are transmitted by time-division multiplexing. This is also true of controlling the plurality of recording heads in each recording integrated circuit. It is essential to perform head switching at the desired timing in a recording/reproducing apparatus provided with plural heads not only of the MR type but also of any type.
Another object of the present invention is to provide a recording/reproducing apparatus permitting switching over among plural heads with high precision, in particular a rotary magnetic head type apparatus permitting switching over plural MR heads and recording heads mounted on a rotary drum at high speed.
In order to achieve the object, a recording/reproducing apparatus according to the present invention is provided with a recording/reproducing unit for recording/reproducing signals onto/from a recording medium with plural heads, a generating unit for generating control data for controlling the recording/reproducing unit, and a transmitting unit for transmitting control data generated by the generating unit to the recording/reproducing unit, wherein data for controlling the switching over among the plurality of heads are transmitted with priority over other control data.
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Masuda Kemmei
Tsuchiya Toshio
Yamazaki Shigeru
Figueroa Natalia
Hitachi , Ltd.
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