JPH04129053A - Tracking control circuit for rotary head type digital audio tape recorder - Google Patents

Abstract

PURPOSE:To stabilize tracking and to increase the leading-in speed by performing the switching between plural tracking error signals, which are obtained from a reproduced signal of larger one of reproduced outputs of first and second tracings, and the average value at an arbitrary timing to perform tracking control. CONSTITUTION:Sampling pulses SP1 and SP2 and sampling pulses SP2a and SP2c are outputted from a first gate circuit 13 by two first tracings, where the reproduced output is sufficiently obtained, out of four continuous tracings at the time of double scanning. When a certain time elapses after generation of a third sampling pulse (c), the gate signal of a second gate circuit 18 is switched to the high level. As the result, an operator 17a of a changeover switch 17 is switched to the side of a contact (b), and an average voltage generated by an average value calculating circuit 15 is supplied to a capstan motor driving circuit only for a certain time till generation of the first sampling pulse (d) of next four continuous trackings. Thus, tracking control effective for unstability of tracking is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a tracking control circuit for a rotary head type digital audio tape recorder (hereinafter referred to as DAT).

(B) Prior Art Conventionally, in addition to the standard mode, DAT has an optional mode in which recording and reproduction are performed at half the tape speed and cylinder rotation speed of the standard mode.

The tape recorded in this optional mode is played back at half the tape speed of the standard mode and at the same cylinder rotation speed as the standard mode, a so-called double scan method. Regeneration methods are known. Tapes recorded in option mode,
By playing back using this double scan method,
The frequency band played is the same as the standard mode, so
There is no need to separately provide a regeneration circuit for the option mode, and there is an advantage that the circuit configuration is simplified.

This double-scan tracking method is described in Japanese Patent Application Laid-Open No. 1-137456 (GlI B 15
/467). This prior art will be explained with reference to FIGS. 3 and 4.

FIG. 3 shows a block diagram of the tracking control circuit in the DAT, in which (1) is the playback input terminal;
2) is a regenerative amplifier, (3) is a low-pass filter for pilot signal extraction, (4) is an envelope detection circuit, and (5) is a low-pass filter for pilot signal extraction.
) is the first sample hold circuit that samples the input signal using the sampling pulse SPI, and (6) is the first sample hold circuit that samples the input signal using the sampling pulse SPI.
A subtracter (7) calculates the level difference between the sample and hold signal and the output signal of the detection circuit (4), and a second subtracter (7) samples the input signal using the sampling pulse SP2.
The output of the sample and hold circuit becomes a tracking error signal and is outputted from an output terminal (8) to a capstan motor drive circuit (not shown). (9) is a reproduction equalizer circuit for waveform equalization, and (10) is a comparison 5. for digital conversion that binarizes the output signal. (11) is a control circuit that outputs sampling pulses, and (13) is a first circuit that selectively supplies sampling pulses to the first and second sampling and hold circuits (5) and (7) during playback using the double scan method. It is a gate circuit.

The tracking operation by the tracking control circuit having such a configuration will be explained using FIGS. 4(a) to 4(c). FIG. 4(a) is a diagram showing the timing of the sampling pulses output from the control circuit (11). Tracking control is performed using all the sampling pulses during hand-to-hand playback, but during playback using the double scan method, tracking control is performed using all sampling pulses. As shown in FIG. 4(c), the gate circuit (13) generates sampling pulses (a) (b) of the first trace.
) and the sampling pulse (C) of the second trace are supplied to the second sample and hold circuit (7), and tracking is performed by generating a tracking error signal at the timing of the three sampling pulses (a), (b), and (c). It controls.

(c) Problems to be Solved by the Invention However, according to the double-scan tracking control method according to the prior art described above, the tracking error signal obtained at the timing of the sampling pulse of the second trace of the series of 64 races is is held for more than two traces (T period), so the influence of the error signal is quite large. For example, in tracking control of a tape with a high level of unerased signal during override recording,
The gain of the tracking servo increases and an offset state occurs, causing instability of the tracking servo.

(d) Means for Solving the Problems The present invention is intended to solve the above problems, and provides tracking at the trace start and end of each track of a tape that is helically scanned by a rotating head. A recording area is formed, and tracking control is performed using the tracking control signal recorded in the tracking area during playback, and the tape is recorded at half the tape speed and cylinder rotation speed of the standard recording/playback mode. When playing back, set the tape speed to 1 of the standard recording/playback speed.
/2, and the rotational speed of the cylinder is the same as in the standard recording/playback mode, and each recorded track is traced twice in a rotary head digital audio tape recorder configured to trace each recorded track twice. A rotation characterized in that tracking control is performed by switching at an arbitrary timing a plurality of tracking error signals obtained from a reproduced signal from a trace having a larger reproduction output and an average value of these plurality of tracking error signals. A tracking control circuit for a head-type digital audio tape recorder is proposed.

(e) Effect: According to the above means, tracking is performed using an error voltage according to the actual tracking state, thereby stabilizing tracking and increasing the speed of pull-in.

(F) Embodiment Hereinafter, one embodiment of the tracking control circuit according to the present invention will be described with reference to FIGS. 1 and 2. Note that the same parts as in the prior art are given the same drawing numbers, and the explanation thereof will be omitted.

(14a), (14b), and (14c) sample and hold the tracking error signal output from the subtracter (6) using sampling pulses 5P2a, 5P2b, and 5P2c generated by the first gate circuit based on the sampling pulse SP2. This is a sample and hold circuit.

(15) are sample hold circuits (14a) (14b)
(14c) is an average value calculation circuit that calculates the average value of the output, and is composed of a plurality of voltage dividing resistors R and an operational amplifier (16). (17) is the second sample hold circuit (7)
This is a changeover switch that selectively switches between the tracking error signal output from the second gate circuit (15) and the average value output from the average value calculation circuit (15), and is controlled by the gate signal of the second gate circuit (18).

The trunking operation during double scan in the trunking control circuit having the above configuration will be explained based on FIG. 2.

Figure 2 (a) shows the reproduction signal, (b) shows the head switching signal, (c), (d), (e), (f), (g) shows the sampling pulse, and (h) shows the gate signal. This shows a tracking error signal.

First, among the four consecutive traces, in the first two traces where sufficient reproduction power can be obtained, as shown in FIGS. 2(c) and (d), the sampling pulse SPI output from the first gate circuit (13) , SP2 performs tracking control, and at the same time, the sample and hold circuit (14a)
(14b) For (14c), Fig. 2(e)(f)
As shown in (g), each sampling pulse 5P2a,
Output 5P2b and 5P2c. A certain period of time after the third sampling pulse C (for example, cylinder 1
/2 rotations), the gate signal of the second gate circuit (18) is switched to high as shown in FIG. 2(h). As a result, the actuator (17a) of the changeover switch (17) is (
A certain time t from switching to the b) side until the first sampling pulse (d) of the next four consecutive traces occurs.
The average voltage generated by the average value calculation circuit (15) by x is supplied to the capstan motor drive circuit (not shown). After that, as mentioned above, the gate signal of the second gate circuit (18) becomes low, the actuator (17a) of the changeover switch (17) switches to the (a) side, and the second sample and hold circuit (7) generates Tracking control is performed using the tracking error signal.

Note that the above control may be performed using a microcomputer. Alternatively, the resistance values of the plurality of voltage dividing resistors R may be appropriately selected and weighted when calculating the average value.

(G) Effects of the Invention According to the present invention, in tracking control during double scanning, the tracking error signal using the third sampling pulse of two traces is held for a long time so that a sufficient reproduction output can be obtained. Since the offset track can be reduced and the apparent gain can be suppressed, effective tracking control can be performed against tracking instability caused by unerased components due to overriding.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a tracking control circuit according to the present invention, FIGS. 2(a) to (1) are diagrams showing various signals for explaining the operation of the four tracking control circuits according to the present invention, and FIG. 3 is a block diagram showing a tracking control circuit according to the present invention. A block diagram showing a conventional tracking control circuit,
FIGS. 4(a) to 4(c) are diagrams for explaining the operation of a conventional tracking control circuit. (13)...first gate circuit, (15)...average value calculation circuit, (17)...changeover switch, (18)
...Second gate circuit.

Claims (1)

[Claims] (1) A tracking area is formed at the beginning and end of each trace of each track of the tape that is helically scanned by a rotating head, and tracking control is performed using the tracking control signal recorded in the tracking area during playback. At the same time, when playing back a tape recorded at 1/2 the tape speed and cylinder rotation speed of the standard recording/playback mode, the tape speed is 1/2 of the standard recording/playback speed and the cylinder rotation speed is In a rotary head digital audio tape recorder configured to trace each recorded track twice, assuming that the mode is the same as the standard recording/playback mode, the one with the greater playback output of each of the two traces Tracking of a rotary head type digital audio tape recorder characterized in that tracking control is performed by switching at arbitrary timing a plurality of tracking error signals obtained from a reproduced signal by tracing and an average value of these plurality of tracking error signals. control circuit.