JPS6266454A - Tracking control circuit - Google Patents

Abstract

PURPOSE:To attain excellent tracking control by providing a filter circuit excluding a part or all of undesired signals having a frequency mixed in a tracking control signal supplied from a tracking control signal generating means. CONSTITUTION:The tracking control signal generating circuit consists of a low pass filter 4, a mixing circuit 6, a pilot signal generator 7, band pass filters 9, 10, detectors 11, 12, a differential amplifier 13 and a polarity switch 14. Since a 4-frequency pilot signal is changed over, a fundamental frequency fL of a pilot signal switching circulating frequency is expressed as fL=60(Hz)/4=15Hz. Thus, an undesired signal comprising the fundamental frequency of the pilot signal switching circulation frequency and its harmonics n fL(n=1.2...) is mixed in a tracking control signal from the mixing circuit 6 and the polarity switch 14. Thus, a filter circuit 15 eliminating a part or all of the undesired signal is connected to the post-stage of the tracking control signal generating circuit. Thus, the adverse effect due to the undesired signal such as reduction in the tracking control capability or the time axis fluctuation of a reproduced information signal is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a tracking control circuit, and in particular to a tracking control circuit, in which a HI'! The present invention relates to a trunking control circuit that controls the position of a read head using a tracking control signal obtained by reproducing a recording medium.

2. Description of the Related Art Conventionally, there has been a method of performing racking control by controlling the traveling speed of the recording medium or the position of the reading head so that the reading head accurately scans the recording track traces on the recording medium. be.

As an example of such a method, there is known a method for controlling the position of a reading head disclosed in Japanese Patent Application Laid-Open No. 53-116120. In this method, pilot signals of n different frequencies are first distributed in m consecutive 1-racks (m ≥ 4) in a circular order, and appropriate frequency conversion is performed during playback, resulting in a predetermined scanning range. The difference in frequency between one track and its two adjacent tracks generates two scale signals that always correspond to the same set of frequencies. Next, the direction of the tracking deviation is detected from the level difference and frequency of these two types of signals, and a racking control signal is generated, which controls the scanning position of the read head to a predetermined i-rack. Accurately followed 1! Ru.

Problems to be Solved by the Invention However, in the conventional I-control method, firstly, the two pilot signals recorded on each track are different, so when reproducing them, the two pilot signals must be recorded separately. The crosstalk characteristics at this frequency become distorted. Secondly, since various characteristics such as the frequency characteristic f1 of the recording medium and the head are responsible for each recording medium and the head, it is important to note that the level of the playback signal for track deviation varies at each frequency. Variation 4 will occur. As a result, the tracking til control signal generated based on the level difference between the reproduction pilot I signal inevitably contains unnecessary signals consisting of the signal cut H circulation frequency and harmonics of integral multiples thereof. Therefore, when tracking control is performed using the above 1-racking control signal, the unnecessary signal may cause the reproduction information signal to fluctuate on the time axis, or the tracking control may become unstable, causing the playback screen to become unstable. Various negative effects occur, such as a decline in self-confidence. Also, the above unnecessary signals are tracked from the regenerated pilot signal! ,
It is also likely to occur from the circuit that generates the II II+ signal.
In order to prevent this, there were problems such as enough (7 spirit plagues were required, resulting in a] l-up).

Therefore, the present invention provides a tracking control circuit that solves the 2F distribution problem by providing a filter circuit that removes part or all of the l-distribution unnecessary signal at the subsequent stage of the tracking control signal 1 generation circuit to be described later. The purpose is to

Means for Solving the Problems The tracking control circuit according to the present invention simultaneously reproduces two types of pilot signals recorded on two adjacent tracks, and combines these pilot signals with the Byron I signal of the track to be scanned. The position of the track to be scanned is determined based on the difference in frequency between the two signals. one of the unnecessary signals of frequency n·fL ((IIL, "1 is a natural number)" mixed in the switching control signal; It consists of a filter circuit that removes some or all of the

Effectively, the tracking control signal is applied to the filter circuit, which adversely affects the tracking control] - Opening wave number n -
Since unnecessary signals of f1- are removed, good tracking control is possible.

Embodiment FIG. 1 shows a block diagram of an embodiment of a tracking control circuit according to the present invention. In the figure, information signals and pilot signals are multiplex recorded on the same track 10 on a recording medium (not shown) from which information signals and the like are read by a read head 1, as described above. Well, here - as an example, four consecutive tracks have different frequencies f, , f2.
．． f3.

The following explanation will be given by taking as an example the case where the signals are distributed in a circular order and the present invention is applied to a home VTR.

Here, the read head 1 simultaneously reproduces the information signal and pilot signal from the track being scanned, and two types of pilot signals from two adjacent 1-racks using the RI[1 stalk. do.

A reproduction signal consisting of these information signals and three types of pilot signals is passed through a reproduction amplifier 2 to a high-pass filter (+-I
PF) 3 and a low-pass filter (+-PF) 4, respectively.

The blocking wavenumbers of the high-pass filter 3 and the low-pass filter 4 are both about 200 kHz, for example, and the high-pass filter 3 outputs one wave of information signal with a frequency of 200 k)-1z or more from the incoming reproduction signal. output to terminal 5, while low-pass filter 4 outputs the upper ka below frequency 200k l-I
One wave of the fifi type pilot signal is supplied to the mixing circuit 6.

On the other hand, the pilot signal generator 7 is connected to the 60
Pylon 1-1 is supplied with the HZ track switching control signal and is recorded on the scanning track accordingly.
38r+, I'2. It is cyclically switched for each track and output to the mixing circuit 6 so that the same pie as f3 and ``4'' is outputted.

The mixing circuit 6 receives the three types of PI[1] signals W1 that enter through the low-pass filter 4 and the PI[1] signal generator 7.
Two types of signals with one-digit frequencies fa and th are obtained by subtracting the frequency from Pi [ ] 1 to Shinzuki supplied from the ! ? It is output to a bandpass filter (BPF) 9.10.

Here, to explain in more detail the function of this mixing circuit 60, the pi 1-1 I signal f1. f2. f3. An example of fn is shown in the table below.

Now, assuming that the reading head 1 is scanning the second track in which a pilot signal of frequency f2 is recorded, the mixing circuit 6 receives the three types of pilot signals of frequencies f, , f2 . A pilot signal of frequency f is received, while a pilot signal of frequency f2 is supplied from the pilot signal generator 7. Since this mixing circuit 6 takes the difference in frequency of each incoming signal as shown in -, the difference in frequency with the track before connection is f2- f + = 15 k
Frequency difference between HZ and next track f3 f2=4
A signal of 5 kHz is generated respectively. As shown in the table above, the pilot signal frequency is determined so that the difference in the frequency of the pilot signal between the previous track and the next track is 45kllZ and 15kHz, which are generated alternately. When the passing frequencies fa and fb of are set to 15kHz and 45kHz7, the previous 1
~ The signal of the difference in frequency with the track and the next track is the husband/
The signal is converted into a fiF wave and supplied to the detectors 11 and 12.

The detectors 11 and 12 perform envelope detection on the incoming signals of frequencies fa and fb, and output DC voltages corresponding to the levels of these signals to the inverting input terminal and non-inverting input terminal of the differential amplifier 130, respectively.

The differential amplifier 13 generates a signal of the difference between the incoming currents IF (
The signal is then output to the polarity switch 14. Here, the frequency difference fa or fh indicating a tracking deviation of 1 to 1 with the track immediately before scanning (power 1 to rack), and the frequency difference rb or fa indicating a tracking deviation with the track immediately after the previous R
i! As shown in the table, the tracks are replaced every track. Therefore, the polarity switch 14 is supplied via the terminal 8] - The polarity of the input signal should be inverted for each track according to the rack switching control signal, and the input signal should be played back. A tracking control signal is generated and output with a polarity such that the deviation between the position of the read head 1 and the position of the read head 1 is reduced.

By means of this tracking control signal, the reading head 1 is displaced by known means in such a way that the scanning position of the reading head 1 is minimized.

The above-mentioned low-pass filter 4, mixing circuit 6, pylon 1 to signal generator 7, bandpass filters 9 and 10, detectors 11 and 12, differential amplifier 13 and polarity switch 14 are used for tracking l!
Configure the l++m signal generation circuit.

Here, in this embodiment, since the rack switching control signal frequency is (')OH7 and the 4-frequency pilot signal is switched, the fundamental frequency fL of the pi[1]-signal switching circulation frequency is f+ --60(Hz)/4=15Hz.

Therefore, in the mixing circuit 6 and the polarity switch 14, the unnecessary signal consisting of the fundamental frequency of the upper two pilot signal switching circulation frequencies and its harmonics n−f+− (where n=1°2, . . . ) is tracked. It will be mixed in the control signal.

The present invention is characterized in that a filter circuit 15 capable of removing part or all of the unnecessary signals listed in -L is connected to the subsequent stage of the tracking control signal generation circuit.

FIG. 2 shows a circuit diagram of a first embodiment of the filter circuit 15. The circuit shown in FIG. 2 shows an example in which a low-pass filter is used as the filter circuit 15, and this includes a differential amplifier A+,
It is a so-called active filter that utilizes A2, A3, resistors R, and capacitors C1 to C61.It generally has excellent cutoff characteristics, and its resonant frequency can be arbitrarily determined by the resistors and η. Here, for example, resistance R = 470 Ω, capacitor ηG + = 47XIO
3PF, C2=56X102PF, Ca-39X103
PF, C4=56X102PF.

Cs = 12 x 10' PF and C6-18
When set to x103PF, the cutoff wave number fc of this filter circuit 15 is 7H7. As a result, the unnecessary signal of the frequency n·'L is removed.

FIG. 3 shows a block diagram of a second embodiment of the filter circuit 15. This is an example in which a comb filter is used as the filter circuit 15. Here, the input signal is directly supplied to the demultiplexer 16, while the input signal is supplied to the demultiplexer 16 via the delay element 17.
The signal is supplied to the post-processor 16, which is delayed by 111S. The sieve 16 attenuates the input signal from the input signal delayed by 66+ns and outputs it.

Therefore, unnecessary signal components of frequency 151-1z and their harmonics are removed from the input signal.

Note that the filter circuit 15 has the fundamental frequency of the pilot signal switching circulation frequency and its harmonics n-f1-
Any circuit may be used as long as it has a filter function of being able to remove part or all of the unnecessary signals caused by the noise, and in addition to the circuits shown in FIGS. 2 and 3, there are, for example, the circuits listed above.

■ Frequency fL (7) Bandpass filter for removing the fundamental wave and some of its harmonics.

■ A trap circuit that attenuates harmonic n-f1- and its combination.

(2) A circuit that combines the above (2) and (2), as well as the low-pass filter shown in FIG. 2 and the comb filter shown in FIG.

Note that the configuration of the tracking control signal generation circuit is the first one.
The configuration is not limited to that shown in the figure, and any circuit for generating a tracking control signal may be used.

Further, in this embodiment, only the case where four-frequency pilot signals are recorded and reproduced has been described, but the present invention
By cyclically switching and recording the signal for 1-Run-1: with the information signal, and re-swiping this, the 1-Run 1:
It goes without saying that the present invention can be applied to all of Haku's recording and reproducing apparatuses that perform filling and till operations.

Therefore, the present invention is also effective when applied to, for example, capacitive or optical data recording/reproducing devices and magnetic recording/reproducing devices other than VTRs.

Furthermore, although this embodiment has been described only during playback, it is also effective to apply pilot 1J-BO during recording.

Effects of the Invention As described above, according to the present invention, a filter circuit for removing part or all of unnecessary signals consisting of the fundamental frequency of the pilot signal switching circulation frequency and its harmonics nf is provided at the subsequent stage of the tracking control signal generation circuit. As a result, it has a number of features as follows.

(2) It is possible to prevent the occurrence of adverse effects caused by the unnecessary signals described in 1-, such as a decrease in tracking control ability and a change in the time axis of the reproduced information signal IJ+.

(2) Conventionally, in order to reduce the adverse effects of the above-mentioned unnecessary signals, the adverse effects can be alleviated by lowering the control ability of the tracking control signal, but this required sacrificing the tracking control ability. However, as described above, the present invention makes it possible to eliminate the adverse effects of unnecessary signals without sacrificing the tracking control ability.

(2) Conventionally, in order to reduce unnecessary signals generated in a tracking control signal generation circuit, it has been necessary to improve the operational accuracy of this circuit. However, by using the present invention, there is no need to require the above-mentioned circuit to have high accuracy, so costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing one embodiment of the 1-racking control circuit according to the present invention, FIG. 2 is a circuit diagram showing a first embodiment of the filter circuit in the block system shown in FIG.
The figure is a block system diagram showing a second embodiment of the filter circuit. 1...Reading head, 2...Playback amplifier, 3...
High-pass filter (HPF), 4...Low-pass filter (1,
r')F), 5...information signal output terminal, 6...
Mixing circuit, 7... Pilot signal generator, 8... Track switching control signal input terminal, 9.10... Bandpass filter (BPF), 11.12... Detector, 13...
Differential amplifier, 14... Polarity switch, 15... Filter circuit, 16... Elementor, 17... Delay element, 1
8...[-Racking control signal output terminal, A1-A3
... Performance amplifier.

Claims (1)

[Claims] A recording medium in which m types of pilot signals of different frequencies are sequentially multiplexed and recorded on m tracks (m is a natural number of 4 or more) with an information signal in a cyclic order at a cyclic frequency f_L for each track is reproduced. In a tracking control circuit that controls the position of the read head based on the obtained pilot signals, two types of pilot signals recorded on two adjacent tracks are simultaneously reproduced, and these pilot signals and the pilot of the track to be scanned are used. means for generating a tracking control signal having a polarity such that the deviation between the position of the track to be scanned and the position of the read head is reduced based on the two signals having a frequency difference between the signals; and the tracking control signal generating means. Frequency n・f_L mixed in the tracking control signal supplied by (however, n is a natural number)
A tracking control circuit comprising a filter circuit that removes part or all of unnecessary signals.