Sharp Kabushiki Kaisha Corporation

Hiroshi Ii

Kengo Sudoh

Syuhei Yasuda

Yukihiko Haikawa

Taizo Sasada

Hiroyuki Matsuoka

Katsubumi Koyanagi

A magnetic recording and reproducing apparatus for recording digital signals of a plurality of channels on tracks on magnetic recording medium and reproducing the same includes an A/D converter for converting analog video signals to digital signals, a signal dividing circuit for dividing the digital signals into first and second digital signals having first and second bit numbers for each channel, a signal permuting circuit for permuting the first and second digital signals of the same channel so as to be recorded on different tracks separately, a magnetic head for recording the permuted first and second digital signals on the different tracks and separately reproducing the same, a signal generating circuit for generating digital signals having a predetermined bit number based on the reproduced first and second digital signals, and a D/A converter for converting generated digital signals into analog signals. The externally applied digital signals are divided into signals of a higher and lower bit groups by the signal dividing circuit. The divided higher and lower bit group signals are permuted and recorded on the separate tracks. The recorded higher and lower bit group signals are separately reproduced. The separately reproduced higher and lower bit group signals are selected by the signal generating circuit, permuted once again and outputted as the original digital signals. The digital signals are converted into analog signals and supplied to other video equipments.

Magnetic recorder/reproducer for recording digital signal on a plurality

Two magnetic heads having different azimuth angles are mounted spaced from each other on a cylindrical rotary drum. Data is recorded on a magnetic tape using of the magnetic heads. On the magnetic tape, one track is formed by one of the magnetic heads and another (second) track is formed by another magnetic head. The two tracks form one frame on the tape. The data is recorded in the unit of one frame. When reproducing, the data recorded in one track is read out by one magnetic head, and the data recorded in the other track is read out by the other magnetic head. When reproducing in the normal direction, the data in one frame is first read out on one track and then on the other track. When reproducing in the reverse direction, first the data of the other track is read out, and the data is fed into a delay circuit composed of memory. The delay circuit, after the data of one track is read out and output, outputs the data of the other track. Also in reproduction in the reverse direction, the data composing one frame is output in the same sequence as in reproduction in the normal direction.

Method and apparatus for reproduction of magnetic tape by using rotary

An azimuth recording system has been adopted in order to heighten the recording intensity in a DAT (digital audio tape) recorder of rotary head type. For this reason, the width of a track is made more narrow than that of the magnetic head, and tracking control is conducted on the basis of the reproduction signals from the tracks at both sides during reproducing. In such a DAT recorder, in the case of rewriting data, the magnetic head is changed over to the recording mode at a point of time when reproduction operation is terminated for a corresponding track so that rewriting begins at a track which is disposed at least one thereafter the track to be rewritten, and new data is recorded, thereby causing a desired track which must be maintained to be prevented from being recorded over by a new track. In addition, a distinguisher information is recorded in each of tracks. In the case the same distinguisher information is detected when a distinguisher information is read out and compared, data which has been previously read out is not outputted, thereby ensuring that data which must be originally deleted, be prevented from being erroneously outputted. Therefore, a rewriting operation can be easily conducted without the need of any complicated control circuits.

Recording and reproducing apparatus for rewriting data onto a previously

A digital phase locked loop system uses a clock signal from an oscillator which is frequency-divided by a frequency divider, thereby causing a phase locked loop clock signal locked to the input signal being produced. At this time, the phase difference between the input signal and the phase locked loop clock signal is computed by a counter. Then, by setting a frequency dividing ratio on the basis of the computed figure, the phase locked loop clock signal from the frequency divider is locked to the input signal. Furthermore, to correspond to fluctuation when the input signal is digitally pulse-width modulated, the pulse width of the input signal is computed by counter on the basis of the clock pulse. The computed figures are converted to the values which match the minimum repeatable frequency of the input signal. After the frequency dividing ration correspolnding to the phase difference is set for the frequency divider, such a frequency dividing ratio can coincide the phase of the input signal and the phase of the phase locked loop clock signal in accordance with the converted figures corresponding to the frequency of the input signal. Namely, such a digital phase locked loop system as described above can be of a simplified construction and can produce the phase locked loop clock signal locked to the input signal with good characteristics, even with a wide range of fluctuations in the input signal.

Digital phase locked loop system

A digital phase-locked loop system having an oscillator which generates a clock signal of a stationary frequency, a frequency divider which frequency-divides the clock signal to produce a phase-locked loop clock signal, a phase difference detector which detects a phase difference between an input signal and the phase-locked loop clock signal and outputs a phase difference detection signal, and a frequency dividing rate setting device to set a frequency dividing rate corresponding to the phase difference in response to the phase difference detection signal and apply the rate to the frequency divider. The phase difference detector includes a first counter to detect a phase difference at a leading edge of the clock signal from the oscillator and a second counter to detect it at a trailing edge of the clock signal. The frequency dividing rate setting device includes an adder to add the phase differences detected by the first and second counters, a latch to hold an addition result produced by the adder, and a decoder to decode the frequency dividing rate corresponding to the addition result held by the latch. The frequency divider frequency-divides the clock signal according to the frequency dividing rate decoded by the decoder and newly generates a phase-locked loop clock signal.

Digital phase-locked loop system

An apparatus for recording and reproducing a digital data signal carrying digital information at each periodically appearing reference 'P1' phase includes a detector for detecting and producing a phase data signal at each sampling point. Two subsequently sampled phase data are stored in latches for use of the digital data signal by three signal comparators. The first comparator compares the first sampled phase data signal and the second sampled phase data signal. The second comparator compares the first sampled phase data signal with a predetermined value, and the third comparator compares the second sampled phase data signal with the same predetermined value. Utilizing the outputs of the three comparators, a phase condition detector detects whether or not a reference phase is contained between two subsequent sampling points. A detection pulse generator is provided which generates a data detection pulse when the phase condition detector detects the reference phase.

Apparatus for recording and reproducing digital signals on magnetic tape

An apparatus for recording and reproducing digital signals includes a detector for detecting and producing a phase data signal of a sampled point of the digital signal, a first comparator for comparing a first phase data signal at one sampling point and a second phase data signal at one previous sampling point, a second comparator for comparing a predetermined value with a phase difference between the second phase data and newly detected phase data, a condition detecting means, utilizing the results of the first and second comparators, for detecting whether two adjacent sampling points are within a reference phase period, and sampling pulse generating means for generating one sampling pulse when the two sampling points are separated by a distance equal to the reference phase period, two sampling pulses when the distance is greater than the reference phase period; and no sampling pulse when the distance is less than the reference phase period.

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Hiroshima, Japan

Hiroshi Ii