JPH0536041A - Tracking error detector - Google Patents

Abstract

PURPOSE:To improve a detection S/N without executing the narrow band of a BPF, in a tracking error detector which detects a tracking error by comparing the output levels of reproducing pilots. CONSTITUTION:Two signals whose frequencies are the same with the frequency of the pilot, and whose phases are different from the phase of the pilot by 90 degrees, are generated by a frequency-dividing means 6, a regenerative signal and the signals are respectively multiplied by multiplying means 8 and 9, useless components are removed by two LPF 12 and 13. Then, the two outputs from the two LPF 12 and 13, and the outputs of inverting means 16 and 17, are synthesized into one waveform by a four signal switch means 21. The detection of an envelope is operated by an error detecting means 23 by using the output of the four signal switch means 21, the tracking error is detected regardless of the reproduced phase of the reproducing pilot, and the narrow band of the LPF 12 and 13 is executed, so that the detection S/N can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention records and reproduces a tracking error detecting pilot signal on a magnetic recording medium together with a main signal.
The present invention relates to a tracking error detection device for detecting a tracking error by comparing reproduction output levels of pilot signals reproduced as crosstalk signals from both adjacent tracks during reproduction.

[0002]

2. Description of the Related Art Conventionally, in a tracking error detecting device used for 8 mm video, four low frequency pilot signals having different frequencies are set, and one low frequency pilot signal for each video track is used as a video signal. Record in multiplex.

During reproduction, as crosstalk from adjacent video tracks, two low-frequency pilot signals recorded on both adjacent video tracks are detected by an envelope detection method,
Tracking error is detected by comparing the reproduction output levels of two low-frequency pilot signals (for example, Akira Hirota, 8 mm video (1), Television Society Technical Report, VR61-1). .

In addition, V which records recent digital signals is used.
In TR, a block for performing digital modulation in a form suitable for magnetic recording / reproduction, the digital integrated value (hereinafter, referred to as DSV) is changed according to the frequency of the low frequency pilot signal, and the low frequency pilot is changed to 2 of the digital signal. A method of inserting a low-frequency pilot on a value pattern is performed (for example, author: SMC Borge).
rs et al., Annexperimental digital
l VCR with 40mm drumsingl
e actuator and dct-based
bit-rate reduction, IEEE T
transaction on Consumer El
electronics, Vol. 34, No. 3, Aug
ust, 1988).

[0005]

FIG. 5 shows an example of the structure of a conventional tracking error detection apparatus using the conventional envelope detection method.
Shown in.

The magnetic recording medium 1 shown in FIG.
Track 1 is recorded in the recording format shown in
The tracking pilot f1 is recorded on the track 2, the tracking pilot f2 is recorded on the track 2, and the tracking pilot f3 is recorded on the track 3 (provided that f1 ≠ f2 ≠ f3 and track 1 and track 3 are the same). In azimuth, track 2 is a reverse azimuth record.)

The signals recorded on the magnetic recording medium 1 are digital signals, and the pilots f1, f2 and f3 are used.
Shall be inserted by changing the DSV during digital modulation.

Further, for the sake of explanation, as a reproducing state, it is assumed that the track 2 is reproduced by the magnetic head 2 as shown in FIG. 2 for the sake of convenience.

Next, returning to FIG. 5, the signal reproduced from the magnetic head 2 is a signal containing pilots from both adjacent tracks, and the pilot f is generated in the BPFs 52 and 53.
Extract 1 and f3 respectively.

Next, in the envelope detection means 54 and 55, 2
Envelope detection such as multiplicative detection or full-wave detection is performed to detect the amplitude level of the signals output from the band pass filters (hereinafter referred to as BPF) 52 and 53, and the low pass filter (hereinafter referred to as LPF). The tracking error signal is detected by removing unnecessary components by 56 and 57 and obtaining the output difference of the LPFs 56 and 57 by the power difference means 58.

However, when the tracking error detecting device shown in FIG. 5 is intended to support a narrower track format, it is necessary to further improve the accuracy of tracking error detection.

Therefore, in order to improve the detection accuracy, the BP
If the band of F52 and F53 is set to a band of about 200 Hz to narrow the band, a tank circuit having a circuit Q of about 80 to 200 is used, which makes it difficult to harden the BPF.

Even if the LPF 56, 57 limits the frequency band to several tens of Hz, the envelope detection method is used by the envelope detection 54, 55, so that the frequency in the BPF band is converted to near DC. , The narrowing band of the LPF cannot improve the SN ratio of the tracking error detecting pilot so much.

Further, when a tracking pilot signal is generated during recording and modulation by using a digital signal as a main signal and recording / reproducing is performed, since the digital signal has a signal component up to a low frequency, the BPF is further narrowed. Need to

The present invention has been made in view of the above points, and has a characteristic equal to or higher than that of narrowing the bandwidth of the BPF without using the narrow band BPF, and a tracking error detecting device that is easy to implement in hardware. The purpose is to provide.

[0016]

In order to achieve the above-mentioned object, the present invention mainly applies to a magnetic recording medium by inserting a tracking error detecting pilot into a digital signal of a main signal by changing DSV during recording modulation. A reproduction clock generating means for generating a reproduction clock from a digital signal of the reproduced main signal, which is recorded together with the signal and reproduced, and an output of the reproduction clock generating means are frequency-divided to have a phase of 90 at the same frequency as the pilot frequency. Frequency dividing means for generating two signals having different degrees, two multiplying means for respectively multiplying the digital signal containing the pilot reproduced from the magnetic recording medium and the two signals having different phases by 90 degrees, and Two LPFs for extracting only low frequency components from the outputs from the two multiplication means and two outputs from the two LPFs are respectively assigned. Two inverting means for inverting the 2
4 signal switch means for switching a total of 4 output signals of the output of one LPF and the output of the two inverting means according to the output signal of the oscillating means for oscillating a single frequency to generate one waveform; And an error detection means for detecting a tracking error from the output of the signal switch means.

[0017]

According to the present invention, the BPF has a narrow band, instead of the BPF having a narrow band, by multiplying the reproduction signal by a signal having the same frequency as the pilot frequency.
Even if there is no PF, it is possible to realize a characteristic equivalent to narrowing the band of the BPF, realize hardware reasonably, and narrow the band.

The phase of the tracking error detecting pilot recorded / reproduced on the adjacent track is not constant due to an error in the head mounting height position.

Therefore, even if the same signal as the pilot frequency is multiplied, the level of the signal output from the LPF varies due to the phase error.

Therefore, two signals (sin wave and cos) having the same frequency as the pilot frequency but different in phase by 90 degrees are used.
Wave) and a reproduction signal containing a pilot reproduced as adjacent crosstalk from the magnetic recording medium,
Unnecessary high frequency components are removed by inputting the multiplication outputs to the two LPFs, respectively, and the amplitude value of the pilot is output from the two LPFs in the form of vector decomposition into the sin axis and the cos axis. ing.

Therefore, as described above, by outputting in the form of vector decomposition, the amplitude value of the pilot is accurately detected even if a phase error occurs, and the level fluctuation does not occur.

Also, with the 4-signal switch means, two LPs are used.
The amplitude of the pilot reproduced as the adjacent crosstalk is obtained by sequentially switching and outputting the output of F and the output of the two inverting means, which are the phases of the outputs of the two LPFs, according to the single frequency which is the output of the oscillating means. A waveform having the same value, having a frequency of 1/4 of that of the oscillating means, and having the high frequency noise component removed is output.

Therefore, if the output of the 4-signal switch means is detected by using the envelope detection method having the same structure as that of the conventional tracking error detection device, the tracking error signal determined in the two LPF bands can be detected. .

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a main part of a tracking error detecting apparatus according to the first embodiment of the present invention.

The magnetic recording medium 1 shown in FIG.
Track 1 is recorded in the recording format shown in
The tracking pilot f1 is recorded on the track 2, the tracking pilot f2 is recorded on the track 2, and the tracking pilot f3 is recorded on the track 3 (provided that f1 ≠ f2 ≠ f3 and track 1 and track 3 are the same). In azimuth, track 2 is a reverse azimuth record.)

The signals recorded on the magnetic recording medium 1 are digital signals, and the pilots f1, f2, f
It is assumed that 3 is inserted by changing the DSV during digital modulation.

For convenience of explanation, it is assumed that the reproducing state is such that the track 2 is reproduced by the magnetic head 2 as shown in FIG.

Now, returning to FIG. 1, the present invention will be described.
The signal reproduced from the magnetic head 2 is a digital signal containing the pilots f1 and f3 reproduced as adjacent crosstalk.

Next, the reproduction clock generating means 3 generates a reproduction clock from the digital signal which is the main signal reproduced from the magnetic head 2.

Next, the BPFs 4 and 5 respectively extract the pilots f1 and f3 and their vicinity using tank circuits having a small Q, and output them to the multiplications 8, 9, 10, and 11. on the other hand,
The frequency dividing means 6 and 7 divide the clock output from the reproduced clock generating means 3 to generate a total of 4 signals of sin wave and cos wave having a single frequency of the pilots f1 and f3 and having phases different by 90 degrees. And multiplying means 8, 9, 10, 1
Output to 1.

Here, the reason why the pilot frequency can be generated by dividing the reproduced clock is that the pilot is inserted by changing the DSV when performing digital modulation, so that it is set to an integer fraction of the reproduced clock. This is because, as described above, if the pilot is generated using the reproduction clock, it is possible to generate the signal of the pilot frequency including the fluctuation of the time axis during the reproduction.

Next, in the multiplication means 8, 9, 10, and 11,
The amplitude components of the pilots f1 and f3 are sin by multiplying the outputs of the BPFs 4 and 5 and the outputs of the frequency dividing means 6 and 7, respectively.
Vector decomposition into axes and cos axes.

Here, the reason why the vector decomposition is performed is as follows.
Reproduction pilots f1, f3 output from BPFs 4, 5
Of the frequency division means 6, 7 due to an error in the mounting height position of the magnetic head, an error in the 180 degree indexing mounting position of the magnetic head, and the width of the magnetic head stepping on the adjacent track. This is because, although the frequency matches the signal output from, the final phase cannot be uniquely determined and the amplitude values of the reproduction pilots f1 and f3 cannot be accurately detected. Even if the phases are different, the amplitude component can be accurately vector-divided and detected.

Further, since the amplitude components of the pilot are detected by the coherent detection method by using the multiplication means 8, 9, 10, 11, the unnecessary noise component is in the vicinity of DC, that is, as compared with the envelope detection method. , The detection band is not converted to the detection band, and the detection band is determined by the LPFs 12, 13, 14, and 15 in the next stage, so that it is not necessary to make the BPFs 4 and 5 extremely narrow.

Next, in the LPFs 12, 13, 14, and 15, as described above, only the amplitude components of the pilots f1 and f3 are extracted from the outputs of the multiplication means 8, 9, 10, and 11.

Next, the inverting means 16, 17, 18, and 19 invert the phases of the outputs of the LPFs 12, 13, 14, and 15.

Therefore, the amplitude value of the pilot f1 is set to 2A, and the sine wave output from the frequency dividing means 6 and the pilot f
If the phase is different from θ by θ, LPF12,1
3 and the outputs of the inverting means 16 and 17 are respectively Asin
It can be expressed as θ, Acos θ, −A sin θ, −A cos θ.

Further, for the pilot f3, if the same definition as the above-mentioned pilot f1 is made, the LPFs 14, 1
5 and the outputs of the inverting means 18 and 19 are similarly Acos
It can be expressed as θ, Asin θ, −A cos θ, −A sin θ.

Here, θ = π / 2T * t1 (T> t1
Then, T and t1 are arbitrary constants. ), If the data is sequentially switched at every cycle T, the waveform shown in FIG. 3B is obtained.

Therefore, if the BPF having the waveform of FIG. 3B as the center frequency (1 / 4T) (Q of the circuit may be a tank circuit that does not have a realization range), the amplitude shown in FIG. 3A is obtained. It becomes a sine wave of A (cycle 4T).

In this case, the waveform of FIG. 3A shows the amplitude component of the reproduction pilot, and the noise band is shown in FIG.
It is determined in the bands of LPFs 12, 13, 14, and 15 shown in FIG.

Next, returning to FIG. 1, the four-signal switch means 2
1, 22 are output from the oscillation means 20.

In accordance with a single frequency signal (cycle T), the above Asin θ, Acos θ, -Asin θ, -Acos θ
4 data are switched to generate the waveform of FIG. 3B described above and output to the error detector 23.

Next, in the error detecting means 23, the BPF2
4A, 25, detection means 26, 27, LPFs 28, 29, and power difference means 30. The BPFs 24, 25 band-limit the waveforms output from the 4-signal switch means 21, 22 to obtain the waveform shown in FIG. The waveform shown in is output.

Next, in the detecting means 27, 28, the BPF2
Envelope detection is performed on the outputs of 3 and 24, the amplitude value of the reproduction pilot is detected, and the detected value is input to the power difference means 30.

Next, in the power difference means 30, the LPF2
The difference between the outputs from 8 and 29 is detected and output as a tracking error detection signal.

Here, the configuration of the error detecting means 23 is shown in FIG.
Although it has the same configuration as the conventional envelope detection method shown in, as described above, the amplitude component of the reproduction pilot is vector-decomposed, and the LPFs 12, 13, 14, and 15 perform band limitation,
Since the tracking error is detected from the signal whose frequency has been converted to the high frequency range by the four-signal switch means 21 and 22, the noise band is determined by the LPFs 12, 13, 14, and 15, and B
Q of the circuits of PF4, 5 and BPF24, 25 is
It can be achieved without making it too big.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram of essential parts in the second embodiment of the present invention, and the same blocks as those in the first embodiment are designated by the same reference numerals.

Further, in the signal processing of the tracking pilots f1 and f3 reproduced as crosstalk from both adjacent tracks, the processing of the pilots f1 and f3 has the same configuration except that the frequencies are different.
1, the description of the pilot f3 is omitted.

The signal recorded on the magnetic recording medium 1 is also the same as that of the first embodiment and is a digital signal in which a tracking pilot is inserted.

Next, the signal reproduced from the magnetic head 2 is output to the reproduction clock generating means 3 and the BPF 4, and the reproduction clock generating means 3 generates the reproduction clock as in FIG.

Also in the BPF 4, as in FIG. 1, the pilot f1 is extracted in a tank circuit configuration having a small Q of the circuit,
It outputs to n multiplication means 32-33.

Next, the n-phase dividing means 31 divides the reproduction clock which is the output of the reproduction clock generating means 3 and outputs n outputs having the same pilot frequency but different phases by n phases. It outputs to the multiplication means 32 to 33.

Next, in the n multiplying means 32 to 33, B
The output from the PF 4 and the output from the n-phase frequency dividing means 31 are respectively multiplied, synchronous detection is performed, and output to the n signal detecting means 34 to 35.

The reason for the synchronous detection is that the noise band is determined by the n LPFs 36 to 37 as in the first embodiment, and the amplitude component is detected by decomposing into a polyphase vector. Therefore, the amplitude can be accurately detected regardless of the phase of the reproduction pilot.

Next, n signal detecting means 34 to 35 are provided.
Are composed of an LPF 36 and an inverting means 38, respectively, remove unnecessary components, and extract the amplitude component 2 of the reproduced pilot.
One polar signal is output, and a total of 2n signals are output.

Next, the 2n signal switch means 40 sequentially switches the input 2n signals in accordance with the output of the oscillation means 20 to generate a waveform having the same amplitude value as the amplitude value of the reproduction pilot.

However, the sequential switch is composed of n LPFs 3
6 to 37 are sequentially output, and then n inversion means 3
8 to 39 are sequentially output.

That is, A * sin (π / n * N + θ) (where N is a positive integer from 1 to 2n) are sequentially switched.

Here, the difference between the first embodiment and the second embodiment is that 4 signals are switched to generate a waveform showing the same amplitude value as the reproduction pilot, or 2n signals are switched to reproduce. Whether to generate a waveform having the same amplitude value as the pilot.

Therefore, in the case of the second embodiment, assuming that the oscillation cycle of the oscillation means 20 is T, the 2n signal switch means 4 is used.
The basic period of the waveform output from 0 is 2nT, the frequency interval is wider than in the first embodiment, and the phase error of the sequential switches is π / n, the difference between the signals sequentially switched is small, Harmonic power is reduced.

Therefore, the error detecting means 23 having the same configuration as that of the first embodiment can easily remove the harmonic and the component of the period T generated at the time of switching, and the BP forming the error detecting means 23.
Realization of F becomes easier.

Finally, the error detecting means 23 has the same configuration as that of the first embodiment, and detects the tracking error signal from the output from the 2n signal switch means 40 and outputs it as in the first embodiment. .

Therefore, in the second embodiment, as in the first embodiment, the noise band is determined by the band of the n LPFs 36 to 37, so that the BPF which constitutes the second embodiment.
The band does not have to be very narrow,
The BPF forming the error detecting means 23 has a smaller number of harmonic components, and thus can be realized in a wider band than that of the first embodiment.

[0066]

As described above, according to the present invention, by multiplying the signal having the same frequency as that of the pilot and passing it through the narrow band LPF, a characteristic equivalent to that of narrowing the BPF can be obtained. You can get it, you can easily harden it,
The SN ratio of tracking error detection can be improved.

In addition, the tracking error component is vector-decomposed by multiplying two signals having the same frequency as the pilot and different in phase by 90 degrees, and after passing through the LPF, they are combined into one waveform by the four-signal switch and tracking is performed. Since the error is detected, the tracking error can be detected regardless of the phase of the recorded pilot.

Further, since the four-signal switch forms one waveform to detect the tracking error, the blocks after the four-signal switch can have the same structure as the conventional structure, and the conventional circuit can be diverted.

Further, as in the second embodiment, if n-phase signals are used for multiplication and one waveform is generated by the 2n signal switch means, the harmonic component to be removed by the BPF can be reduced. , A broadband BPF can be used.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part showing a configuration of a tracking error detection device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a tape format showing a recording arrangement of tracking error detection pilots when recording a digital signal.

FIG. 3 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 4 is a principal block diagram showing the configuration of a tracking error detection device according to a second embodiment of the present invention.

FIG. 5 is a principal block diagram showing the configuration of a conventional tracking error detection device.

[Explanation of symbols]

1 Magnetic recording medium 2 magnetic head 3 Regenerated clock generation means 4,5,24,25 BPF 6,7 frequency divider 8-11, 32, 33 Multiplier means 12-15, 28, 29, 36, 37 LPF 16-19,38,39 Inversion means 20 oscillation means 21,22 4 signal switch means 23 Error detection means 26,27 Detection means 30 power difference means 31 n-phase dividing means 34, 35 signal detection means 40 2n signal switch means

Claims (3)

[Claims] 1. A tracking error detecting pilot is generated by changing a digital integrated value when recording and modulating a digital signal of a main signal, and is recorded together with the main signal on a magnetic recording medium, and at the time of reproduction, cross from both adjacent tracks. A tracking error detecting device for detecting a tracking error by comparing reproduction output levels of the pilot reproduced as a talk signal, wherein reproduction clock generating means for generating a reproduction clock from the digital signal of the reproduced main signal, Frequency dividing means for dividing the output of the reproduction clock generation to generate two signals having the same frequency as the pilot frequency but a phase difference of 90 degrees; a digital signal containing the pilot reproduced from the magnetic recording medium; Two multiplying means for respectively multiplying two signals having different phases by 90 degrees; Two low-pass filters that extract only low-frequency components from the outputs from one multiplication means, two inverting means that respectively phase-invert two outputs from the two low-pass filters, and the two low-pass filters. 4 signal switch means for switching a total of 4 output signals of the output of the filter and the output of the two inverting means in accordance with the output signal of the oscillating means for oscillating a single frequency to generate one waveform; And a tracking error detecting device for detecting a tracking error from the output of the switch means. 2. The error detecting means includes a band pass filter for extracting and filtering only the vicinity of the frequency of the oscillating means for oscillating a single frequency, a detecting means for extracting amplitude information from the output of the band pass filter, and the detecting means. 2. The tracking error detecting device according to claim 1, further comprising: a power difference means for extracting a tracking error from the output of FIG. 3. A tracking error detection pilot is generated by changing a digital integrated value when recording and modulating a digital signal of a main signal, and is recorded together with the main signal on a magnetic recording medium, and at the time of reproduction, a cross from both adjacent tracks. A tracking error detecting device for detecting a tracking error by comparing reproduction output levels of the pilot reproduced as a talk signal, wherein reproduction clock generating means for generating a reproduction clock from the digital signal of the reproduced main signal, Frequency division means for dividing the output of the reproduction clock generation means to generate n signals having the same frequency as the pilot frequency but different in phase by 2π / n degrees; and the pilot reproduced from the magnetic recording medium. N multiplication means for multiplying the digital signal and the n signals whose phases are different from each other by 2π / n degrees And n low pass filters for extracting only low frequency components from the outputs of the n multipliers, and n inverting means for respectively phase inverting the outputs from the n low pass filters, A total of 2n output signals of the output of the n low-pass filters and the output of the n inverting means are switched according to the output signal of the oscillating means that oscillates a single frequency.
A tracking error detection device comprising: a 2n signal switch means for generating two waveforms; and an error detection means for detecting a tracking error from the output of the 2n signal switch means.