JPH01223655A - Rotary head system audio recording and reproducing device - Google Patents

Abstract

PURPOSE:To faithfully detect an automatic track finding (ATF) pilot signal by detecting a zero crossing point of a reproducing RF signal and setting its section as an ATF pilot signal area, when the time between the zero crossing points has satisfied a prescribed condition. CONSTITUTION:From a reproducing RF signal from an input terminal 10, a time interval Tn of a rise/fall edge is measured, based on a measuring clock from a terminal 14 by an inter-edge time measuring instrument 13. Subsequently, by a condition deciding circuit 17, a latch signal L is outputted only in case when Tn is within a prescribed range, and a difference of a measured value is below a prescribed value. In such a way, when the signal L has continued by a prescribed number of times through registers 231-23n and an averaging circuit 24, it is regarded as an ATF signal, and a discrete value of its period is outputted. Accordingly, even if a relative speed of a head and a tape is varied, an ATF pilot signal can be detected faithfully.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a rotary head type audio system which improves the portion of a rotary head type digital audio recorder that detects the relative speed between the head and the tape. The present invention relates to a recording/reproducing device.

(Prior Art) In a rotary head type digital audio table recorder, the relative speed between the head and the tape during playback has a large effect on accurate data playback. It is important to maintain

The method for detecting the relative speed in a digital audio recorder is to
F (Automatic Track Finding) There is a method of detection by measuring the reproduction frequency of the pilot signal.

FIG. 3 shows the position (ATF) of the ATF ballot signal recorded on tape 1. Further, FIG. 4 shows a reproduced RF signal and a partially enlarged signal thereof. In this way, ten waves are allocated to one ATF pilot signal area. This frequency is 9.4 during normal playback.
08 MHz/72 (-about 130 KHz). However, if the relative speed between the head and the tape changes, it goes without saying that the reproduction frequency of the ATF pilot signal changes in proportion to this.

Further, the ATF pilot signal has the lowest frequency among the recorded signals, and has a frequency that is 1/4 of the ATF synchronization signal, which has the next lowest frequency.

In order to detect the frequency of the above ATF pilot signal, it is first necessary to extract the ATF pilot signal from the reproduced RF signal. To this end, there are methods of extracting through a low-pass filter or extracting only the ATF pilot signal area using a window signal.

(Problem to be Solved by the Invention) According to the conventional ATF pilot signal detection method described above, for example, when the relative velocity between the tape and the head changes in the range of 1/2 to 2 times that of normal playback, The reproduction frequency of the ATF pilot signal is approximately 65KHz ~ 260KH
Changes to z. On the other hand, the ATF synchronization signal with adjacent frequencies changes from 28QKHz to 1080KHz. Therefore, in order to extract the ATF pilot signal using a low-pass filter, this low-pass filter must have a frequency of 280 KHz.
A very steep attenuation characteristic with a cutoff frequency is required.

On the other hand, in order to extract the ATF pilot signal using the window signal, it is very difficult to match the window signal accurately to the ATF pilot signal area when the rotational speed of the drum to which the head is attached changes.

Therefore, the present invention has been developed to detect the ATF pilot signal faithfully without being affected by noise, even if the relative speed between the head and the tape changes by about 1/2 to 2 times that during normal playback. An object of the present invention is to provide a rotary head type audio recording and reproducing device having a means for recording and reproducing audio.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, zero cross points of a reproduced RF signal are detected, and the time between these zero cross points is measured. The time between one zero cross point is Tn, and this Tn is Twln <Tn <T
max (condition A), this Tn is Tm
(m-1, 2, 3, -) and l Tw+ -T(m-
1) When N consecutive T-s satisfy l < ΔT (condition B), that section is determined to be the ATF pilot signal area, and To+, Ta1l.

Tm+2. . . . etc. as effective measurement values.

(effect) Twin in condition A by the above means.

If Twax is set to a value corresponding to 65 KHz and 260 KHz, the actual range is 65 KHz to 260 KH.
It is possible to form a steep bandpass filter that passes z,
It is possible to faithfully select components in the frequency band (relative speed, 1/2 to 2 times that of normal reproduction) that the ATF pilot signal can take.

Furthermore, even if there is a single signal that satisfies Twin < Tn < Tmax due to noise etc., the condition B that there are N consecutive TIs satisfying I Tm - T (m-1) 1 < 8 T is added. Therefore, the desired signal frequency can be detected extremely accurately without using a window signal.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a reproduced RF signal is supplied to an input terminal 10, and is supplied to one input section of a comparator 12 as periodic waveform detection means. A reference potential is applied to the other input of the comparator 12, and a binary signal is obtained at its output. This binary signal is supplied to the edge-to-edge time measuring device 13. Edge time measuring device 1
3 is a frequency that is sufficiently higher than the frequency of the ATF pilot signal, and the measurement clock applied from the terminal 14 is used to measure the time interval between rising edges or falling edges. The n bits Tn representing the time between edges are supplied to a comparator 15.16.

The comparator 15 determines whether Tn is smaller than a predetermined T max and sends the result to the condition determination circuit 17.
supply to. The comparator 16 has Tn determined in advance.
It is determined whether or not it is smaller than iln, and the result is supplied to the condition determination circuit 17.

Furthermore, the register 18 and the subtracter 19 store T of the previous sample.
n-1 and the current Tn, and supplies the value to the absolute value circuit 20. The absolute value from the absolute value circuit 20 and the predetermined value ΔT are compared by the comparator 21, and a determination output as to whether or not lTn −Tn−11<8T is satisfied is supplied to the condition determination circuit 17. Ru.

The condition determination circuit 17 determines that Twin < Tn < Tmax (Condition A) IT
Only when n-Tn-11<8T (condition B) is satisfied, a latch signal is output and supplied to the registers 231 to 23N. The registers 231 to 23N sequentially latch Tn from the delay circuit 22, for example, cyclically, each time conditions A and B are satisfied.

If the latching operations of the registers 231 to 23N occur N times in succession, the contents of the registers 231 to 23N are averaged by the averaging circuit 24, and the result is output as the final detected value. This final detected value indicates the relative speed between the tape and the head, and the servo circuit (not shown) adjusts the tape speed, head rotation speed, or data extraction clock so that the detected value becomes the target value. It will control the frequency.

In other words, the above circuit measures the times Tl, T2, T3, -T'n (see Figure 2) between zero crosses of the reproduced RF signal, and determines that Tn is within a predetermined range (condition A).
, and Tn that satisfies this condition A is T1°Tm+1.
...and... Then, it is determined that the difference between the two TIl and Ti-1 is less than or equal to a predetermined value ΔT (condition B). Further, when the condition B is met a predetermined number of times or more consecutively in a predetermined period, the reproduced signal is regarded as an ATF pilot signal, and the measured value TI for that period is output.

In this embodiment, since the measured value Ts+ is output when the condition B is continuously met a predetermined number of times or more, it is possible to detect the ATF pilot signal with higher accuracy.

[Effects of the Invention] As explained above, the present invention allows for faithful playback without being affected by noise, even if the relative speed between the head and the tape changes by about 1/2 to 2 times that during normal playback. ATF pilot signals can be detected.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of this invention, Fig. 2 is a signal waveform diagram shown to explain the basic idea of this invention, and Fig. 3 shows the recording format of a digital audio tape recorder. Explanatory diagram, FIG. 4 is an explanatory diagram of the ATF pilot signal. 12...Comparator, 13...Edge-to-edge time measuring device, 1
5. 16, 18, 231-23N middle register, 17...
- Condition determination circuit, 19... Subtractor, 20... Absolute value circuit, 21... Comparator, 24... Averaging circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 2 4"t#v!-r (1) Figure 3 4121

Claims (2)

[Claims] (1) In a rotary head type digital recording/reproducing device, a periodic waveform detecting means for obtaining a periodic waveform corresponding to the repetition period or inversion period of the reproduced signal waveform, and each period of the periodic waveform from the periodic waveform detecting means are provided. a measuring means for sequentially measuring and obtaining measured values T_n (n: integer); and a measuring means for obtaining measured values T_n (n: integer);
a first condition determining means for identifying the condition A); and a first condition determining means for identifying the T_n(hereinafter referred to as condition A);
Hereinafter, when T_m (m=1, 2, 3, . . . ) is identified, a second condition that identifies that the difference between two measured values T_m is less than or equal to a predetermined value (hereinafter referred to as condition B). and condition determination means, and when the establishment of condition B is counted a predetermined number of times or more in a predetermined period, the regenerated signal is regarded as an ATF pilot signal, and the measured value T_n for that period is output. A rotating head type audio recording and reproducing device. (2) If the difference between the above two T_m is due to the continuous T_n, and the above condition B is met continuously for a predetermined number of times or more, the regenerated signal is used as the ATF pilot signal. 2. The rotary head type audio recording and reproducing apparatus according to claim 1, wherein the rotating head type audio recording and reproducing apparatus outputs a measured value for that period.