JPH03252954A - Phase servo error signal generating circuit - Google Patents

Abstract

PURPOSE:To reduce deviation between track heights by switching a delay amount to delay the rotary position signal of a head at the time of recording and reproducing. CONSTITUTION:A detecting means 3 is provided to detect the rotary position signal of the head, and a delay means 6 is provided to delay the position signal. Then, a switching means 10 is provided to switch the delay amount at the time of recording and reproducing. The delay time of the delay circuit 6 is set at the time of reproducing by a variable resistor 8 and a capacitor 13 and at the time of recoding by the variable resistor 8 and the capacitor 13 respectively. In such a way, the delay amount of the position signal is switched at the time of recoding and reproducing respectively synchronously with the rotation of the head. Thus, at the time of recording or reproducing, the optimum track width can be always obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application]
The present invention relates to a phase servo error signal generating circuit that generates a phase servo error signal corresponding to the rotational phase of a head in a recording/reproducing apparatus represented by T.

[Prior art] In R-DAT, normal track (track pitch 1
3.591 μm) and wide track (track pitch 2
0.41 μm) using the same head, the head width is made almost the same as the wide track width.

Also, in R-DAT, A (+azimuth) track and B
(-Azimuth) The two heads that reproduce each track are switched by a head switch to obtain a reproduction output. The switching timing (head switching position) by this head switch (not shown) is determined by the position signal P G (g
It is adjusted and set by changing the amount of signal delay.

Furthermore, during playback, the pyroi 143 recorded on the tape
Since ATF (tracking) servo control is performed by the number, the center of the head and the center of the track are aligned.

[Problem to be Solved by the Invention] However, as shown in FIG. 4, when recording with a normal track width, the recording track (indicated by a broken line in the figure) is different from the reproduction track (indicated by a solid line in the figure). The tape 2 will shift in the short and long directions. Misalignment in the longitudinal direction of the tape 2 is not a problem because the ATF servo is used during playback, but misalignment in the transverse direction of the tape 2, that is, in the track height, is caused by the head switching position shown by the dashed line in the figure. This results in a timing lag between when each signal on the track is reproduced, and necessary signals may be missing.

In particular, when performing after-recording (rewriting) using head 1 on a portion of a track on tape 2 that has been previously recorded, data in areas that are not originally to be rewritten may be erased because the height of the track will shift due to rewriting. It ends up.

The R-DAT standard provides a margin to avoid the effects of such track height deviations, but
It is preferable that the deviation in track height is small.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the deviation in track height.

[Means for Solving the Problem] In order to achieve this object, the phase servo error signal generation circuit of the present invention performs recording and reproduction by rotating a head whose head width is wider than the track width to be recorded. In a phase servo error signal generation circuit corresponding to the rotational phase of a head of a recording/reproducing device, a detection means for detecting a position signal indicating the rotational position of the head, a delay means for delaying the position signal, and a delay amount of the delay means are recorded. The device is configured to have a switching means for switching between the time and the time of reproduction.

[Operation] In the phase servo error signal generation circuit with the above configuration,
By switching the delay amount of the delay means that delays the position signal obtained from the drum that rotates the head, for example, during recording and playback, it is possible to obtain the optimal track height both during recording and playback. I have to.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a phase servo error signal generation circuit according to the present invention.

In FIG. 1, a PG flaw signal (see FIG. 2(a)) outputted from a PG head 3 (detection means) is amplified by an amplifier 4 and supplied to a waveform shaping circuit 5 (detection means). In the waveform shaping circuit 5, the PG (g) is converted into a square waveform, and the second
The signal is supplied to the delay circuit 6 (delay means) as the DPG signal shown in FIG. 6(b).

The delay circuit 6 is a delay circuit whose delay amount can be controlled by adjusting a time constant, and the time constant is set by variable resistors 8 and 9 and a capacitor 13 connected in series.

The variable resistor 9 is shunted by an analog switch 10 (switching means), which is turned off during recording and turned on during playback. Therefore, the time constant is set by the variable resistor 8 and capacitor 13 during reproduction, and by the variable resistors 8 and 9 and capacitor 13 during recording.

The DPG signal delayed by this delay circuit 6 is supplied to a phase comparator 7. The phase comparator 7 compares the DPG signal delayed by the delay circuit 6 with the reference (REF) (g) which is the output of the reference signal generator 11, and calculates the phase difference between the two as a phase servo error of the drum 12. (Output to the outside as g.

Next, the operation of one embodiment of the phase servo error signal generation circuit according to the present invention will be explained using FIGS. 2 and 3.

FIG. 3 explains a method of calculating the delay amount (correction amount) of the delay circuit 6. That is, if the amount of delay to be corrected is △T, the amount by which the head 1 deviates between recording and playback is (20,4-13,59)/2=3.4am, so x=3.4Xcosθ △T =(X/2613)X7500=9.7 μs.

Here, θ is the inclination angle of the track (6°72'59°5"
), x is the track height to be corrected. Further, calculations are made on the assumption that the effective recording width of each track is 2613 mm, the drum diameter is 30 φ, and the head tracing time is 7500 us according to the standard. In FIG. 3, recorded tracks are shown by broken lines, and reproduced tracks are shown by solid lines. Furthermore, the timing of switching by the head switch is indicated by a dashed line as a head switching position.

From this calculation, it can be seen that during recording, the height of the head switch position, which is the starting point of head tracing, can be increased by delaying the drum phase by 9°7 μs compared to during reproduction.

As described above, the delay time of the delay circuit 6 is set by the variable resistor 8 and the capacitor 13 during reproduction, and by the variable resistors 8 and 9 and the capacitor 13 during recording.

If the delay amount of the delay circuit 6 at the time of reproduction (analog switch 10 is on) is expressed as ADJ1, the DPG' signal delayed by the delay circuit 6 at the time of reproduction is as shown in FIG. 2(C). PG (This is a signal that is delayed by ADJ 1 from the DPG signal with the same timing as No. 3 (Fig. 2 (b)). Also, the delay amount of the delay circuit 6 at the time of recording (analog switch 10 is off) is ADJ. When expressed as 1 + ADJ2,
The DPG' signal delayed by the delay circuit 6 during recording is
As shown in FIG. 2(d), the DPG signal (FIG. 2(b)) is delayed by ADJ 1 +ADJ2. Adjust the variable resistors 8 and 9 so that the difference between the delay amount ADJ1 and ADJ1+ADJ2 is equal to the above-mentioned ΔT,
When recording, the analog switch 10 is turned off and the delay circuit 6
By increasing the amount of delay, the deviation in track height can be reduced.

[Effects of the Invention] As described above, according to the phase servo error signal generation circuit of the present invention, by switching the delay amount of the position signal synchronized with the rotation of the head between recording and reproduction, It becomes possible to obtain the optimum track height at any time of reproduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the phase servo error signal generation circuit according to the present invention, FIG. 2 is a timing chart explaining the operation of the embodiment of FIG. 1, and FIG. FIG. 4 is a conceptual diagram illustrating the operation of the phase servo error signal generation circuit according to the invention. FIG. 4 is a conceptual diagram illustrating the operation of an example of the conventional phase servo error signal generation circuit. DESCRIPTION OF SYMBOLS 1... Head, 2... Tape, 3... PG head, 4... Amplifier, 5... Waveform shaping circuit, 6... Delay circuit, 7... Phase comparator, 8, 9...variable resistance,
10... Analog switch, 11... Reference signal generator, 12... Drum, 13... Capacitor.

Claims (1)

[Claims] A position indicating the rotational position of the head in a phase servo error signal generation circuit corresponding to the rotational phase of the head of a recording and reproducing apparatus that performs recording and reproduction by rotating a head having a wider head width than the track width to be recorded. A phase servo error signal generation circuit comprising a detection means for detecting a signal, a delay means for delaying the position signal, and a switching means for switching the delay amount of the delay means between recording and reproduction.