JPH0428043A - Tracking error detector for multivalue recording - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy of a tracking error by detecting the tracking error from ratio of cycles or that of phases of two recovery carriers recovered with two multimagnetic heads having azimuths opposite to each other. CONSTITUTION:Band-pass filters 22, 23 are provided which perform the recording/reproduction of a signal in which a multivalue digital signal is added on a pilot signal by the multimagnetic heads 19, 20 with the azimuths opposite to each other, and detect the pilot signal from a reproduced signal. Also, PLL circuits 24, 25 which generate the recovery carrier from the pilot signal, a cycle measuring instrument 26 which measures the cycle of the recovery carrier by using the output of the circuits, a subtraction circuit 29 which calculates the tracking error by subtracting a reference value from the output of the instrument, and an integration circuit 32 which accumulates the output of the circuit 29 are provided. Therefore, the tracking error including the linearity of a video track can be detected. In such a way, it is possible to improve the detecting accuracy of the tracking error and to prevent the multivalue digital signal disturbed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-value recording tracking error detection device for detecting tracking errors in a magnetic recording/reproducing device for recording and reproducing multi-value digital signals.

Conventional technology Trunking error detection devices conventionally used in home VTRs use pulses indicating the rotational phase of the head drum as control signals to control the longitudinal direction of the magnetic tape, in addition to the video track for recording and reproducing video signals. Tracks are provided for recording, and during reproduction, tracking errors are detected by comparing the phase of the reproduced control signal and the phase of the rotation pulse of the head drum. (For example, supervised by Ryo Takahashi, VTR technology (Japan Broadcasting Corporation)).

On the other hand, in a tracking error detection device used for 8 mm video, four low frequency pilots with different frequencies are set, and one low frequency pilot is frequency-multiplexed onto a video signal for each video track and recorded. During playback, two low frequency pilots recorded on both adjacent video tracks are detected as crosstalk from adjacent video tracks, and the tracking error is detected by comparing the power difference between the two low frequency pilots. are doing.

Problems to be Solved by the Invention However, with the above conventional method using a control track, the video track linearity cannot be detected, and it is extremely difficult to improve the accuracy of detecting tracking and tracking errors.

In addition, the tracking error detection device used for 8mm video can detect the video track linearity, but frequency multiplexing of the low frequency 7 inch plot is difficult due to the magnetic field between it and the multilevel digital signal. There were problems such as crosstalk occurring during the recording process, resulting in interference waves.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a tracking error detection device that detects the linearity of a video track, improves tracking error detection accuracy, and does not interfere with multilevel digital signals. The purpose is

Means for Solving the Problems In order to achieve the above object, the multi-level recording tracking error detection device of the present invention (claim 1) converts a signal obtained by adding a multi-level digital signal and a pilot signal into multiple signals having mutually opposite azimuths. Two band-pass filters detect two pilot signals from signals reproduced from the two multi-magnetic heads, and two band-pass filters generate reproduced carrier waves from the pilot signals. a PLL circuit, a period measuring device that measures the period of a reproduced carrier wave using the outputs of the two PLL circuits, a subtraction circuit that calculates a tracking error by subtracting a reference value from the output of the period measuring device, and the subtraction circuit. It consists of an integrating circuit that accumulates the output of the circuit.

According to the above-described structure, the present invention utilizes the characteristic that the phases of the two reproduced carrier waves change in opposite directions when the two multi-magnetic heads deviate from the video track during reproduction, to change the period of the reproduced carrier wave or the carrier wave. The tracking error is detected by measuring the period of the signal obtained by dividing the frequency of the signal. Therefore, it is possible to detect tracking errors including video tracking and track linearity, and it is possible to improve tracking error detection accuracy. Furthermore, since pilots and the like are not frequency multiplexed on low frequencies, there is no interference with the multilevel digital signal.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of main parts of a multilevel recording tracking error detection device according to a first embodiment of the present invention.

First, a digital signal is input from terminal 1 on the recording side. Next, multi-value conversion circuits 2 to 5 perform multi-value conversion in the amplitude direction, and low-pass filters (hereinafter referred to as LPFs) 6 to 9 output only multi-value digital signals. Next, the outputs of the LPFs 8 to 9 and the carrier wave output from the frequency conversion circuit 13 are multiplied by two quadrature two-phase modulation circuits 10 and 11 to obtain a two-channel quadrature two-phase modulated multilevel digital signal. Occur. Here, the frequency conversion circuit 13 has a block configuration shown in FIG.
The clock input from the terminal 12 in FIG. 1 is input to the N divider circuit 61 through the terminal 60, and the clock input from the terminal 60 is divided by N. Next, in the M multiplier circuit 62, N
A carrier wave is generated by multiplying the output of the frequency dividing circuit 61 by M, and a band pass filter (hereinafter referred to as BPF) 63
After removing unnecessary components, the carrier wave is output from the terminal 64.

However, N and M are integers, N≧M, and the frequency relationship is such that the phase of the clock can be detected simultaneously with the phase of the carrier wave. Next, the adder circuits 14 and 15 shown in FIG. 1 add the carrier waves outputted from the frequency conversion circuit 13 on the time axis as burst-like pilot signals of a constant period according to the timing waveform diagram shown in FIG. Next, return to Figure 1,
The adder circuit 16.17 frequency-multiplexes the bias signal output from the oscillation circuit 18 and the signal output from the adder circuit 14.15, and connects the two multi-magnetic heads 19.20.
Bias recording is performed on the magnetic tape 21 via the magnetic tape 21.

Next, on the reproduction side, the signal on the magnetic tape 21 is reproduced through two multi-magnetic heads 19 and 20.

Next, the BPF 22.23 detects a burst pilot signal and outputs it to a PLL (phase loop) circuit 24.25. The PLL circuits 24 and 25 generate two channels of regenerated carrier waves and output them to the period measuring device 26. Here, if the tracking of the signal reproduced by two multi-magnetic heads 19 and 20 having opposite azimuths as shown in FIG. 5(a) is shifted in the direction of the arrow, then TI) rack regenerated carrier wave, (
The T2 track reproduced carrier waves in c) each have a characteristic in which the phase is shifted in the opposite direction shown by the dotted line in principle. Therefore, the first
Returning to the figure, the carrier waves reproduced from the PLL circuits 24 and 25 differ in phase by the amount of tracking deviation. Therefore, the period measuring device 26 is composed of a frequency dividing circuit 27 and a period counter circuit 28. The frequency dividing circuit 27 divides the frequency of the carrier wave reproduced by the PLL circuit 24. Next, in the period counter circuit 28, the output of the frequency dividing circuit 27 is transferred to the PLL circuit 25.
The period is counted using the carrier wave which is the output of , and is output to the subtraction circuit 29 . Next, the subtraction circuit 29 detects a tracking error by subtracting the reference value, which is the output of the reference value circuit 30, from the output of the period measuring device 26.

Next, the integrating circuit 32 measures the amount of tracking deviation from a certain point by accumulating the output of the subtracting circuit 29. Next, in order to detect the amount of tracking error from the optimum tracking position, the maximum value position of the pilot signal output from the BPF 22 is detected by the maximum value detection circuit 31.
Detect with. Next, the maximum value detection circuit 31 resets the integration circuit 32 in accordance with the signal from which the maximum value position has been detected, thereby detecting a tracking error from the optimum tracking position.

Next, FIG. 2 is a block diagram of main parts of a multilevel recording tracking error detection apparatus according to a second embodiment of the present invention. The main block diagram shown in FIG. 2 shows only the reproduction side, and the recording side has the same block configuration as shown in FIG. The signals recorded on the magnetic tape 21 are transferred to two multi-magnetic heads 19.
20 and output to BPF41.42. B
The PF41.42 detects the carrier pilot signal and outputs it to the PLL circuit 44.45. Next, PLL circuits 44 and 45 generate regenerated carrier waves using the pilot signals. Next, in the frequency dividing circuits 47 and 48, the PLL circuit 4
The frequency of the reproduced carrier wave which is the output of 4.45 is divided and outputted to the phase comparator circuit 49. Here, similar to the principle of the first embodiment, the carrier waves frequency-divided by the frequency dividing circuits 47 and 48 have different phases depending on the amount of tracking deviation. Therefore, by comparing the phases of the outputs of the frequency dividing circuits 47 and 48 with the phase comparator 49, a tracking error can be detected.

However, the frequency-divided carrier waves output from the frequency divider circuits 47 and 48 have an increased degree of freedom in the phase to be taken according to the frequency division ratio of the frequency divider circuits 47 and 48. Therefore, BPF41.4
The constant insertion period of the pilot signal output from 2 is
Detected by synchronization detection circuits 43 and 46, and frequency dividing circuit 47
．． The phase of each frequency-divided carrier wave outputted from 48 is uniquely determined, and the influence of the degree of freedom of the frequency division ratio described above is eliminated.

Next, the tracking error signal output from the phase comparison circuit 49 is input to a subtraction circuit 50 and a hold circuit 51. Here, the tracking error signal output from the phase comparator circuit 49 indicates only the amount of tracking error from a certain tracking position.

Therefore, in order to detect the tracking error amount from the optimum tracking position, the maximum amplitude position of the pilot signal which is the output of the BPF 42 is detected by the maximum value detection circuit 52, and the phase comparison circuit 49 is detected at the maximum value position of the pilot signal. The tracking error amount is held in a hold circuit 51. Next, the subtraction circuit 50 subtracts the value held in the hold circuit 51 from the output value of the phase comparison circuit 49 to detect and output the amount of tracking error from the optimum tracking position.

Effects of the Invention As described above, the first advantage of the present invention is as follows. According to the second embodiment, tracking errors including video track linearity can be detected by measuring the period of the reproduced carrier waves or by comparing the phases of the reproduced carrier waves. can be improved.

In addition, since pilots and the like are not frequency-multiplexed on low frequencies, tracking errors can be detected without interfering with the quadrature two-phase modulated multilevel digital signal, which is very easy to do.

Furthermore, since the tracking error is detected on the reproduction side using the pilot signal that serves as a phase reference between the carrier wave and the clock, there is no need to insert a new pilot signal for tracking error detection.

In addition, in both the first and second embodiments, the tracking error is detected from the period ratio and phase ratio of two reproduced carrier waves reproduced by two multi-magnetic heads having mutually opposite azimuths. Therefore, the influence of jitter is canceled out, and tracking errors can be detected with higher accuracy without being influenced by jitter.

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts of a multilevel recording tracking error detection device showing a first embodiment of the present invention, and FIG. 2 is a main part of a multilevel recording tracking error detection device showing a second embodiment of the present invention. FIG. 3 is a block diagram of the first part of the present invention. A block diagram of the main part of the frequency conversion circuit constituting the second embodiment, FIG. 4 is a timing diagram when inserting a pilot signal, and FIG. 5(a)
is a tracking state diagram showing the direction of tracking deviation, the fifth
Figures (b) and (c) are waveform diagrams showing a phase shift of a reproduced carrier wave due to tracking shift. 2, 3. 4. 5...Multi-value circuit, E3.
7. 8゜9...LPFl 10,11...Right angle two-phase modulation circuit, 13...Frequency conversion circuit, 14.
15...Addition circuit, 19.20...Multi magnetic head, 21...Magnetic tape, 22. 23.
83...BPF, 24°25...PLL
Circuit, 26... Period measuring device, 27°47.48.
...Frequency divider circuit, 28...Period counter circuit,
29.50... Subtraction circuit, 30... Reference value circuit, 31.52... Maximum value detection circuit, 32...
・Integrator circuit, 41.42...BPFl 43,
DESCRIPTION OF SYMBOLS 1...Synchronization detection circuit, 44.45...PLL circuit, 49...Phase comparison circuit, 51...Hold circuit, 61...N frequency division circuit, 62...M multiplication circuit. Name of agent: Patent attorney Shigetaka Awano (1 person) Fig. ■ Regular synchronization (a)

Claims (4)

[Claims] (1) Multilevel the input digital signal in the amplitude direction, perform quadrature two-phase modulation on the multilevel digital signal, and generate the quadrature two-phase modulated signal, the carrier wave for the quadrature two-phase modulation, and the quadrature two-phase modulated signal. A multi-value digital signal recording device that adds a clock of a multi-value digital signal and a pilot signal that simultaneously indicates the signal and records the resultant signal on a magnetic tape with a bias bias, the signal obtained by adding the multi-value digital signal and the pilot signal to each other is inverted. Two bandpass filters detect two pilot signals from the signals reproduced from the two multi-magnetic heads for recording and reproducing with two multi-magnetic heads having a multi-configuration having an azimuth; and detecting a reproduced carrier wave from the pilot signals. Two Ps that occur
a LL circuit; a period measuring device that measures the period of a reproduced carrier wave using the outputs of the two PLL circuits; a subtraction circuit that calculates a tracking error by subtracting a reference value from the output of the period measuring device; A multi-level recording tracking error detection device comprising an integrating circuit that accumulates the output of the circuit. (2) The multilevel recording tracking error detection device according to claim 1, wherein the integrating circuit resets the cumulative value by a timing pulse of a maximum value detection circuit that detects the maximum amplitude value position of the pilot signal. (3) Multi-value the input digital signal in the amplitude direction, perform quadrature two-phase modulation on the multi-valued multi-value digital signal, and generate the quadrature two-phase modulated signal, the carrier wave for the quadrature two-phase modulation, and the quadrature two-phase modulated signal. A multi-value digital signal recording device that adds a clock of a multi-value digital signal and a pilot signal that simultaneously indicates the signal and records the multi-value digital signal in a bias manner on a magnetic tape, the signal obtained by adding the multi-value digital signal and the pilot signal to each other in opposite azimuths. two bandpass filters for recording and reproducing with two multi-magnetic heads having a multi-configuration and detecting two pilot signals from signals reproduced from the two multi-magnetic heads; and generating a reproduced carrier wave from the pilot signals. The two P's to
A multilevel recording tracking error detection device comprising: an LL circuit; two frequency divider circuits that frequency divide the reproduced carrier waves; and a phase comparison circuit that compares the phases of the two frequency divider circuits to detect a tracking error. . (4) a maximum value detection circuit that detects the maximum amplitude value position of the pilot signal; a hold circuit that holds the tracking error according to the output of the maximum value detection circuit; and a hold circuit that holds the tracking error from the output of the phase comparison circuit. 4. A subtraction circuit for subtracting the held value, and a multi-level recording tracking error detection device according to claim 3.