Dynamic magnetic information storage or retrieval – General recording or reproducing – Signal switching
Reexamination Certificate
1998-05-27
2001-02-20
Faber, Alan T. (Department: 2753)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Signal switching
C360S281000, C360S272000
Reexamination Certificate
active
06191907
ABSTRACT:
The present invention relates to a head drum for magnetic tape apparatuses. In the following text, a magnetic tape apparatus should be understood as meaning any apparatus in which signals, data or information in analogue and/or digital form are recorded on a magnetic tape and/or read from the latter. Independently of this, these apparatuses may also have other functions, e.g. they may be combined with an electronic camera. The invention additionally relates to a method for writing and/or reading signals or data to or from a magnetic tape. Finally, the invention relates to a magnetic tape apparatus which is equipped with a head drum.
The prior art discloses a video recorder in which the amplifier for the head is arranged inside the head drum. This arrangement means that the path of the head signal read is shorter in comparison to those video recorders in which the amplifiers are located outside the head drum, with the result that interference, caused by electromagnetic fields, in the read signal is reduced. In apparatuses sold nowadays, the bandwidth of the recorded data can be managed well with such system.
In digital video systems, which have a higher recording density and therefore require a larger bandwidth, the passive systems described in the digital video systems, the recording density can be increased, on the one hand, by reducing the width of the tracks on the magnetic tape, and, on the other hand, by increasing the bit density inside the tracks. It is frequently not desirable to reduce the track widths, however, because, on the one hand, the mechanical complexity greatly increases with reducing tracks widths, and, on the other hand, the track widths have to be kept constant on account of the compatibility of different systems. If the bit density is increased, the write/read heads have to be designed for better signal-to-noise ratios at higher frequencies. Such a system is disclosed in the prior art. In the video recorder disclosed in that article, the head amplifiers rotate together with the heads, with the result that the signal path from the read head to the head amplifier is as short as possible, in order to reduce interference in the head signal, as a result of electromagnetic fields, even more. The greatest interference is produced by stray fields originating from the transformer which is used to transmit the signals and transfer the electrical power for the head amplifiers between the stationary lower cylinder and the rotating upper cylinder of the head drum. The head amplifiers typically require a few hundred milliwatts of power, whereas the unamplified head signal is about 200 &mgr;V, with the result that the stray fields lead to interference that cannot be ignored, particularly in the case of low to medium frequencies. In the context of the present invention, for example, frequencies up to 1 MHz are termed low frequencies, frequencies between 1 MHz and 3 MHz are termed medium frequencies, and frequencies between 4 MHz and 21 MHz are termed high frequencies.
Similar difficulties occur with all apparatuses which have been covered by the term “magnetic tape apparatuses” in the introduction.
On this basis, it is the object of the invention to reduce the influences of interference on the head signal further.
This object is achieved by a head drum which is characterised in that, on the rotating upper cylinder, storage means for electrical energy are arranged which are capable of supplying electrical power to all the electronic components rotating together with the upper cylinder, at least at times.
The storage means enable the head amplifiers to be supplied with power from the storage means during the time period in which the signal is being read by the at least one head. The power supply, which is switched off during the reading and/or writing of data, results in electromagnetic interference fields in the signal path of the heads being largely avoided.
In an advantageous embodiment of the invention, two write/read heads are arranged at different azimuth angles in the rotating upper cylinder of the head drum. This arrangement of the write/read heads allows the video tracks to be recorded next to one another on the magnetic tape without a guard band, whilst ensuring good crosstalk attenuation. A pair of amplifiers may be allocated to each write/read head, in each case one of the amplifiers amplifying the data which are read and the other amplifier amplifying the data which are written.
the head drum rotates, for example, at about 9000 revolutions/minute, so that the storage means are charged and discharged very frequently. Capacitors can therefore expediently, be provided as storage means. In addition, means for stabilizing the output voltage can also be provided on the rotating upper cylinder of the head drum in order to ensure that all the rotating electronic components operate correctly.
In one advantageous exemplary embodiment of the invention, a controller is arranged on the rotating upper cylinder, monitors the charge state of the storage capacitors and controls the energy transfer as a function of this. This ensures that only as much energy is transferred as is actually required by the rotating electronic components.
In order to make sure that the head drum runs with as few mechanical problems as possible, it is advantageous to arrange the components rotating together with the rotating upper cylinder such that their centre of gravity coincides essentially with the centre of the axis of rotation of the rotating upper cylinder.
A further object of the invention is to specify a method for writing and/or reading information on a magnetic tape, in which the influences of interference is a result of electromagnetic stray fields are largely avoided.
This object is achieved by a method according to Claim
8
. One advantage of this method is that the reading and writing of information signals and the transfer of electrical power between the bottom and the upper cylinder of the head drum occur successively in time, with the result that the influences of interference, from electromagnetic stray fields, on the signals from the write/read heads are largely avoided. The time periods can be chosen such that, together, they correspond approximately to the rotation time of the rotating upper cylinder of the head drum. The time periods can also be subdivided into a number of time intervals which are separated from one another in time. For example, during each half-revolution of the head drum, power can be transferred and data can be transmitted. This has the advantage that the method according to the invention can also be applied to head drums having more than one pair of heads. Finally, the method can also be performed in such a way that the first and the second time period in each case take place during various revolutions of the head drum.
Advantageously, the second time period can be regulated such that just as much energy is transferred into the storage means as is actually required by the electronic components rotating with the rotating upper cylinder of the head drum. This method has the advantage that particularly low energy consumption is achieved, which is very important for battery-operated apparatuses.
Changing over between energy transfer and data transmission can advantageously be achieved by means of a changeover signal and a selection signal, which are transmitted together with the energy signal.
According to one refinement of the invention, a data word can initially be produced for this purpose from the changeover signal and the selection signal as well, and the said data word is transmitted, in order to perform the necessary control functions, to a control circuit which rotates with the rotating cylinder of the head drum.
A final object of the invention is to provide a magnetic tape apparatus which has an improved signal-to-noise ratio. The magnetic tape apparatus can be an apparatus from the field of consumer electronics or from professional electronics, such as video recorders, camcorders or data storage devices. In particular, such data storage devices ca
Kaaden Jurgen
Oldermann Klaus
Wursthorn Edgar
Deutsche Thomson-Brandt GmbH
Faber Alan T.
Kolodka Joseph J.
Tripoli Joseph S.
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