Dynamic magnetic information storage or retrieval – General recording or reproducing – Signal switching
Patent
1997-12-11
2000-07-25
Kim, W. Chris
Dynamic magnetic information storage or retrieval
General recording or reproducing
Signal switching
360 7715, G11B 1514, G11B 558
Patent
active
06094319&
DESCRIPTION:
BRIEF SUMMARY
The invention is based on a helical track recording and replay apparatus for data.
It is known in the case of digital helical track recording and replay apparatuses for audio, video and general data to be recorded for pilot tones to be interleaved in the data tracks, for tracking. The interleaving can be carried out simultaneously with the data by frequency decoupling (a) or by superimposition (b).
The entire track length is advantageously available for evaluation in such cases. In case (a), the necessary limitation of the data channel bandwidth and the precise maintenance of the pilot carrier amplitudes in order to avoid interference from harmonics are disadvantageous. In case (b), the small amplitude is disadvantageous since use is made of a method of digital sum variation in time with the pilot carrier frequency, which allows only a low level of pilot carrier energy. The interleaving of the pilot tones can be carried out using time-division multiplex (burst ATF). Since no data are transmitted at the same time, the energy in the pilot frequencies is very high. The time duration for pilot tone keying, which time duration is reduced to the necessary settling time of the evaluation filters, is disadvantageous.
The systems according to (a) and (b) are prior art and are sufficiently known. Solutions using separate ICs for Digital Audio Tape DAT are known in the case of burst ATF combined with a digital servo system on a microcontroller basis. The pilot carrier signal is filtered and rectified in these ICs, and a track error signal is produced from the crosstalk signals. This is added as a phase correction signal to the control signal, which is provided by the servo system, for the tape feed. Such a solution is expensive and extremely inflexible if, for example, various tape feed operating modes are desired which are all intended to be carried out on a phase-synchronized basis using various rules.
The invention is based on the object of providing a helical track recording and replay system which carries out tracking in a simple manner. This object is achieved by the features of the invention specified in claim 1. Advantageous developments are specified by the subclaims.
In the case of the solution according to the invention, the processing of the ATF information (including the burst ATF) for the DVC (Digital Video Cassette) format is included in a microcontroller system, so that all the correction signals are processed by this system and the corresponding motor control signals are provided as a function of the operating modes. The area of the embedded ATF is in this case used for tracking in normal replay operation, while the burst ATF area is used during overwriting operation and during search replay of recorded data in order to find predetermined track elements, for example MPEG data.
According to the invention, the ATF signal is obtained in a filter module, which also carries out the rectification of the filtered-out pilot tones. The two DC voltage levels are interrogated and processed in the servo microcontroller, with A/D converters. Coupled to the rotation of the head drum, pulses are produced by the servo system which switch the ATF conditioning over between direct operation and tracking operation, so that evaluation is achieved by the microcontroller during the fast ATF burst phase.
According to the invention, the digital magnetic tape recording apparatus for tracking signals, some of which have a short duration, is fitted with a head drum, a tape drive mechanism, a head amplifier, a servo control system and tracking signal processing having filter stages and rectifiers.
The tracking signal processing will retain the previous value for the duration of a track pulse emitted by the servo control system, during time intervals which are dependent on the operating mode. The track pulse is derived from the head drum rotation. The tracking state is used to mask out interference and to evaluate signals of short time duration with respect to the overall evaluation duration.
The position and length of the track
REFERENCES:
patent: 4237500 (1980-12-01), Sanderson
patent: 4890173 (1989-12-01), Yokozawa
patent: 4943873 (1990-07-01), Kawasaki
Rijckaert, et al., "An Experimental Digital Consumer HDTV Recorder Using MC-DCT Video Compression", Nov. 1993, pp. 711-721.
Braeuer Dietmar
Kaaden Juergen
Reiner Gerhard
Davenport Francis A.
Deutsche Thomson-Brandt GmbH
Kim W. Chris
Laks Josep J.
Tripoli Joseph S.
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