JPH0778966B2 - Equalization control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an equalization control device for receiving and reproducing a digital signal in a system such as a digital magnetic recording / reproducing device in which distortion in the amplitude direction is the main fluctuation. .

2. Description of the Related Art In recent years, various algorithms have been proposed for automatic equalization in an equalization control device, and among them, there is one in which a peak distortion is used as an evaluation criterion. However, in either case, the correlation between the equalized signal and the quantized or discriminated signal amplitude is set for each tap of the transversal filter.

As a conventional equalization control device, for example, Japanese Patent Application Laid-Open No. 1-253874
It is disclosed in the publication.

The conventional equalization control device will be described below.

FIG. 8 is a block diagram showing a conventional equalization control device.
FIG. 9 is a frequency spectrum diagram showing the high-frequency and low-frequency signal comparison bands of the equalization controller 25 of FIG. In the figure,
The diagonally left hatched portion indicates the low-frequency signal comparison band of the equalization controller, and the diagonally right hatched portion indicates the high-frequency signal comparison band of the equalization controller.

In FIG. 8, 1 is a recording medium for recording data, 3 is a reproducing head for reproducing data from the recording medium 1, 5 is a reproducing amplifier for amplifying a minute reproduced signal, and 6 is an integral for compensating the characteristics of the recording / reproducing system. 9 is an equalizer for compensating for intersymbol interference of reproduced signals generated by the recording / reproducing system, 14 is a low-pass filter (hereinafter abbreviated as LPF) for band limiting the signal, 1
5 is a quantizer for quantizing the reproduction signal, 25 is an equalization controller for obtaining the optimum equalization amount from the reproduction signal and the quantized data at the input / output point of the quantizer 15 and supplying it to the equalization unit 9, Reference numeral 17 is a clock recovery PLL circuit that recovers a clock from the quantized data, and 16 is a discriminator that latches the quantized data at the cycle of the clock recovered by the clock recovery PLL circuit 17.

The operation of the equalization control device configured as described above will be described below. The data recorded on the recording medium 1 is reproduced by the reproducing head 3, amplified by the reproducing amplifier 5, compensated for the differential characteristic of the recording / reproducing system by the integrator 6, and then supplied to the equalizer 9. The equalization unit 9 performs optimum equalization under the control of the equalization controller 25, thereby compensating for intersymbol interference of the reproduction signal caused by the influence of the recording / reproduction system. Optimal equalization is to maximize the eye aperture ratio of the eye pattern of the reproduction signal. The equalization controller 25 puts the reproduced signal after equalization in the equalizer 9 and the quantized data obtained by quantizing the reproduced signal in the quantizer 15 into each signal band shown by hatching in FIG. The signal energies are separated and compared, and the equalizer 9 is controlled so that the equalization is optimized. Optimized equalization, band limited by LPF14, quantized quantized data is clock recovery PL
After being supplied to the L circuit 17 and the discriminator 16 for identification, they are supplied to a decoding circuit (not shown) in the subsequent stage.

However, in the above-described conventional configuration, the operation of the equalization controller 25 becomes unstable when a signal in which the signal spectrum of the reproduction signal is concentrated at one point is reproduced, and the equalization unit 9 is operated. On the other hand, there was a problem that wrong control was performed. This means that, for example, when the shortest recording period is fm / 4, if the period is reproduced for a long period of time in the shortest recording period, as shown in FIG. Since the signal spectrum only exists in the signal comparison band, it becomes impossible to compare it with the target value that the equalization controller 25 has in advance for equalization control, and the equalization controller 25 lacks the low range of the reproduced signal. If so, a control signal is applied to the equalizer 9 so as to increase the gain in the low frequency range, so that the feedback loop eventually falls into an oscillating state.

The present invention solves the above-mentioned conventional problems, and equalization control provided with a control means capable of performing stable equalization even if the signal spectrum of the reproduced signal is biased in the signal band on the reproducing side. The purpose is to provide a device.

Means for Solving the Problem In order to achieve this object, an equalization control device of the present invention comprises a gain varying means for controlling the amplification degree of a reproduction signal by a control signal, and a gain of a filter according to the control signal. The frequency characteristic varying means for varying the frequency characteristic with respect to the reproduction signal, the relative velocity detecting means for detecting the relative velocity of the recording medium and the reproducing pickup, and the gain varying means and the frequency characteristic according to the detected relative velocity. And a control signal generating means for generating a control signal applied to the variable means.

With the above-described structure, the present invention controls the gain varying means and the frequency characteristic varying means according to the relative speed from the relative speed signal detected by the relative speed detecting means by calculating the control signal generating means, and thus the reproduction is performed. It is possible to perform stable equalization control without being affected by the signal spectrum.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an equalization control device in one embodiment of the present invention. FIG. 4 is a reproduction signal spectrum diagram for the relative speed in the portion A of FIG. FIG. 5 is a reproduction signal spectrum diagram for the relative speed in the portion B of FIG.
FIG. 6 is a characteristic diagram showing the calculation output with respect to the relative speed in the relative speed calculator 12 of FIG. FIG. 7 is a diagram showing the characteristics of the control signal applied to the equalizer 9 by the equalization controller 13 of FIG. 1 with respect to the relative speed.

In FIG. 1, 1 is a recording medium for recording data, 2 is a rotating drum rotating at high speed, 3 is a reproducing head for reproducing data from the recording medium 1, and 4 is a control signal recorded on the recording medium 1. Control head, 5
Is a reproduction amplifier that amplifies a minute reproduction signal, 6 is an integrator that compensates the characteristics of the recording / reproduction system, 7 is an amplitude variable device that controls the amplitude of the reproduction signal with a control signal, and 8 is the gain of the filter according to the control signal , A frequency characteristic varying device for varying the frequency characteristic, 9 is an equalizing unit composed of an amplitude varying device 7 and a frequency characteristic varying device 8 for compensating the intersymbol interference of the reproduced signal generated by the recording / reproducing system, Reference numeral 1 is a drum rotation speed detector for detecting the rotation speed of the rotating drum 2, 11 is an amplifier for amplifying a reproduction control signal from the control head 4, 12 is a drum rotation speed detector 10 and reproduction control signal and the recording medium 1 and reproduction. A relative speed calculator that calculates the relative speed of the head 3, and 13 is an equalizer that performs control for optimum equalization on the amplitude variable device 7 and the frequency characteristic variable device 8 based on the calculation result of the relative speed calculator 12. A controller, 14 is a low-pass filter that limits the band of the signal, 15 is a quantizer that quantizes the reproduced signal, 17 is a clock recovery PLL circuit that recovers a clock from the quantized data, 16 is a clock recovery PLL circuit 17 This is a discriminator that latches the quantized data at the cycle of the clock regenerated by.

The operation of the equalization control device of the present embodiment configured as described above will be described below with reference to FIGS. 4 to 7. The data recorded on the recording medium 1 is reproduced by the reproducing head 3, amplified by the reproducing amplifier 5, compensated for the differential characteristic of the recording / reproducing system by the integrator 6, and then supplied to the equalizing unit 9. The equalization unit 9 performs optimal equalization under the control of the equalization controller 13 to compensate for intersymbol interference of the reproduction signal caused by the influence of the recording / reproduction system. Here, when the relative speed between the recording medium 1 and the reproducing head 3 changes, the reproduction signal spectrum from the reproducing head 3 changes as shown in FIG. In order to perform optimum equalization by following the change in relative speed, the relative speed calculator 12 calculates from the control signal reproduced by the drum speed detector 10 and the control head 4, and the relative speed signal shown in FIG. 6 is obtained. Supply to the equalization controller 13. Equalization controller
At 13, the relative speed signal from the relative speed calculator 12 causes the amplitude varying device of the equalizer 9 to have the respective control signal characteristics shown in FIG.
7. The frequency characteristic changer 8 is controlled to perform optimum equalization as shown in FIG. The optimum equalized reproduction signal is band-limited by the LPF 14 and then supplied to the quantizer 15. The quantized data quantized by the quantizer 15 is supplied to the clock recovery PLL circuit 17 and the discriminator 16 for discrimination, and then supplied to a decoding circuit (not shown) in the subsequent stage.

As described above, according to the present embodiment, the relative speed is calculated from the drum rotation speed and the control signal, and the equalization control according to the calculation output signal is performed, so that the reproduction signal spectrum is not affected and stable at all times. Equalization can be performed.

FIG. 2 is a block diagram showing a first embodiment of the equalization controller 13 of FIG. In the figure, 18 is a first operational amplifier, R1 and R2 are resistors for determining the amplification degree together with the first operational amplifier 18, and VR1 is a variable resistor for adjusting the offset of the output of the first operational amplifier 18. , 19 is the second operational amplifier,
R3 and R4 are resistors that determine the degree of amplification together with the second operational amplifier 18, and VR2 is a variable resistor that adjusts the offset of the output of the second operational amplifier 19.

The operation of the equalization controller configured as described above will be described below. When the relative speed signal having the characteristic shown in FIG. 6 is supplied to the first operational amplifier 18 and the second operational amplifier 19, the output of the first operational amplifier 18 is changed by the resistors R1 and R2 and the variable resistor VR1. The characteristics shown by the solid line in FIG. 7 are obtained, and the amplitude varying device 7 is controlled. The output of the second operational amplifier 19 has the characteristic of the one-dot chain line in FIG. 7 by the resistors R3 and R4 and the variable resistor VR2, and controls the frequency characteristic variable device 8.

As described above, according to this embodiment, the optimum equalization control characteristic can be easily realized by using the operational amplifier, and the circuit scale can be small.

FIG. 3 is a block diagram showing a second embodiment of the equalization controller 13 of FIG. In the figure, 20 is an analog / digital converter (hereinafter abbreviated as ADC) that converts an input signal into n-bit digital data, and 21 is a digital value control data corresponding to the input n-bit digital data. 1 is a read only memory (hereinafter abbreviated as ROM), 22 is a first for converting digital data to analog
Digital-to-analog converter (hereinafter abbreviated as DAC), 2
Reference numeral 3 is a second ROM that outputs digital value control data corresponding to input n-bit digital data, and 24 is a second DAC that converts the digital data to analog.

The operation of the equalization controller configured as described above will be described below. The relative speed signal having the characteristics shown in FIG. 6 is converted into n-bit digital data by ADC21,
It is supplied to the first ROM 21 and the second ROM 23. Digital value control data is stored in advance in the first ROM 21 so as to have the characteristics shown by the solid line in FIG. 7, and the digital value control data corresponding to the input digital data is supplied to the first DAC 22. The control signal converted into analog by the first DAC 22 is supplied to and controlled by the amplitude varying device 7. The second ROM23 is the seventh
Digital value control data is stored in advance so as to have the characteristic indicated by the alternate long and short dash line in the figure, and digital value control data corresponding to the input digital data is supplied to the second DAC 24. The control signal converted into analog by the second DAC 24 is supplied to the frequency characteristic varying device 8 for control.

As described above, according to this embodiment, the control characteristic data for the relative speed is stored in the ROM, and the relative speed signal is converted to the ADC.
By reading with digital data, even if the optimum equalization characteristic with respect to the relative speed is a complex characteristic that is not linear, the digital value control data of the ROM can be stored so as to match the optimum equalization characteristic. simply,
Moreover, fine equalization control can be performed.

EFFECTS OF THE INVENTION As described above, according to the present invention, the gain varying means (amplitude varying device 7) whose amplification degree with respect to the reproduction signal is controlled by the control signal.
And a frequency characteristic varying means (frequency characteristic varying device 8) for varying the frequency characteristic with respect to the reproduced signal by changing the gain of the filter according to the control signal, and the recording medium (1) and the reproducing pickup (reproducing head 3) relative to each other. Relative speed detecting means (relative speed calculator 12) for detecting speed, and control signal generating means (equalization controller 13) for generating control signals to be added to the gain varying means and the frequency characteristic varying means according to the detected relative speed. ) And are not affected by the playback signal spectrum, and when the playback signal is interrupted by head switching such as VTR, special playback, high-speed playback, the playback signal is lost due to crossing the track. Even if occurs, the gain varying means and the frequency characteristic varying means can always be controlled to the optimum state, so that the clock recovery PLL circuit in the subsequent stage, The discriminator can be stably operated, the erroneous discrimination rate can be reduced, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an equalization control device in an embodiment of the present invention, and FIG. 2 is a block diagram showing the internal configuration of the equalization controller 13 in the first embodiment of FIG. FIG. 3 is a block diagram showing the internal construction of the second embodiment of the equalization controller 13 of FIG. 1, FIG. 4 is a reproduction signal spectrum diagram for the relative speed in the portion A of FIG. 1, and FIG. FIG. 1 is a spectrum diagram of a reproduced signal with respect to the relative speed in the portion B, FIG. 6 is a characteristic diagram showing an arithmetic output with respect to the relative speed in the relative speed calculator 12 of FIG. 1, and FIG. 7 is equalization of FIG. FIG. 8 is a characteristic diagram showing the characteristic of the control signal applied to the equalizer 9 by the controller 13 with respect to the relative speed, FIG. 8 is a block diagram showing the configuration of a conventional equalization control device, and FIG. 9 is the equalization of FIG. FIG. 6 is a frequency spectrum diagram showing a high-frequency and low-frequency signal comparison band of a controller 25. 1 ... Recording medium, 3 ... Playback head, 4 ... Control head, 7 ... Amplitude variable device, 8 ... Frequency characteristic variable device, 9 ... Equalization unit, 10 ... Drum rotation speed detector, 12 ... Relative speed calculator, 13
…… Equalization control device.

Claims (3)

[Claims] 1. A gain varying means for controlling an amplification degree for a reproduced signal by a control signal, a frequency characteristic varying means for varying a frequency characteristic for the reproduced signal by changing a gain of a filter according to the control signal, And a relative speed detecting means for detecting a relative speed of the medium and the reproducing pickup, and a control signal generating means for generating a control signal to be applied to the gain varying means and the frequency characteristic varying means according to the detected relative speed. Control device. 2. The equalization control apparatus according to claim 1, wherein the control signal generating means is constituted by an analog calculating means for calculating a relative speed signal to generate a control signal. 3. An analog / digital conversion means for converting a relative speed signal into a digital signal, and a digital value control for making an equalization characteristic according to the relative speed from the digitalized relative speed signal. 2. The equalization control device according to claim 1, comprising digital value control signal converting means for converting into a signal and digital / analog converting means for converting the digital value control signal into an analog value control signal.