JPH0778848B2 - Magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a magnetic recording / reproducing apparatus having a reproducing waveform equalizing circuit suitable for a rotary head type digital audio tape recorder.

(Prior Art) Regarding the waveform equalization circuit of the conventional magnetic recording / reproducing apparatus,
A transversal filter using a delay line is often used as described in Japanese Patent Laid-Open No. 54-3603. The waveform equalization circuit described in this publication is configured by minimizing the number of delay lines used in a transversal filter and the delay time of the delay lines, and thus it is possible to reduce the circuit scale and the cost of the circuit. Very good in terms.

Further, in this example, the relationship between the frequency and the phase of the recording medium and the head (hereinafter referred to as the phase frequency characteristic) is represented by ε-jωτ and is linear, and only the amplitude enhancement is performed without changing the phase of the reproduced waveform. This is the most suitable circuit configuration when you want to perform. Here, the angular frequency ω ₀ at which the maximum gain is obtained is ω ₀ = π / τ, where τ is the delay time of the delay line. However, no consideration was given to the case where the phase frequency characteristics of the recording medium and the head are non-linear.

Next, a case where the phase frequency characteristic is non-linear and the reproduced waveform has phase distortion is described in JP-A-58-3117. This known example is intended to improve only the rising portion of the reproduction pulse, and no consideration has been given to the case where the reproduction pulse has a wide skirt at the rising and rising edges.

(Problems to be Solved by the Invention) Generally, in an apparatus that handles a high frequency reproduction signal such as a rotary head type magnetic recording apparatus, resonance occurs in the reproduction frequency characteristic due to the inductance of the rotary head and the input capacitance of the reproduction preamplifier. The phase frequency characteristic becomes non-linear. Therefore, the reproduced waveform obtained has phase distortion.
According to the waveform equalizing circuit disclosed in Japanese Patent Laid-Open No. 54-3603, the amplitude frequency characteristic of the reproduced waveform is improved, but the phase distortion cannot be improved at all.

Further, the device described in JP-A-58-3117,
When the reproduced waveform of the magnetic recording / reproducing apparatus has a phase distortion, it is intended to improve only the rising portion thereof, and there is a problem that it does not correct both the rising and falling of the reproduced waveform. Further, this conventional device does not take into consideration the case where the magnetic recording device has two reading speeds of a recording signal and two central angular frequencies at which the amplitude of the waveform equalization circuit should be emphasized are not considered. However, there is a problem in that it cannot be applied to a magnetic recording device in which the value is variable.

An object of the present invention is to correct both the rising and falling edges of the reproduction waveform of the magnetic recording / reproducing apparatus, completely correct the phase distortion, and to be compatible with the magnetic recording apparatus having two or more reading speeds. Especially.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides the speeds V1 and V2 (where V1 <
V2) has at least two speeds, and is connected via an input terminal impedance matching resistor as a waveform equalizing means for compensating that the amplitude of the signal recorded on the recording medium decreases as the frequency increases. And a delay circuit using an LC low-pass filter having a delay time of τ seconds, in which a reflectance adjusting resistor for setting the reflectance to a value of 1 or less is connected between the output terminal and the common potential, and an input signal of the delay circuit. And an attenuator circuit for adjusting the amplitude of a signal obtained by adding a signal delayed by 2τ seconds from the input signal, and a subtractor circuit for subtracting the signal delayed by τ seconds from the input signal by the delay circuit and the signal obtained from the attenuator circuit. In a magnetic recording / reproducing apparatus having a reflection type waveform equalization circuit, the LC low-pass filter is composed of a plurality of capacitors and a capacitance switching circuit of the plurality of capacitors, and the waveform etc. The central angular frequency ω0 performing amplitude emphasizing means at the time of the reading speed V1 .omega.01, reading speed V2
At the time of ω2, by controlling the switching circuit and changing the value of the capacitor, the delay time τ is τ1 = π / ω01 and τ depending on the read speeds V1 and V2, respectively.
The delay time switching means for switching the delay time so that 2 = π / ω02, and the impedance matching resistance and the reflectance adjusting resistance are interlocked with the operation of the switching circuit of the delay time switching means. It is characterized in that it has a control means for switching and selecting.

(Operation) In the present invention, the non-matching side terminal of the delay line is terminated with a resistor and the reflectance is set to 1 or less. Therefore, the amplitude of the signal fed back to the matching side terminal which is the input side of the delay line is adjusted. A signal having a delay amount τ from a signal obtained by adding a signal having no delay on the input side of the delay line and a signal having the delay amount 2τ which has been adjusted and fed back, which can be adjusted to a value corresponding to the reflectance. By subtracting, it is possible to improve not only the amplitude frequency characteristic of the reproduced waveform but also the phase frequency characteristic.

Further, by selecting a delay circuit having two or more delay amounts according to the reading speed, the waveform equalizing circuit having the above characteristics is applied to a magnetic recording / reproducing apparatus having two or more reading speeds. can do.

(Example) Below, this invention is demonstrated with an Example. FIG. 1 is a circuit configuration diagram showing the principle of the present invention.

In the figure, 1 is a reproduction signal obtained from a recording medium, 2 is a delay line for delaying the reproduction signal 1 by τ seconds, and 3 is an impedance matching resistance equal to the characteristic impedance Zo of the delay line 2. Reference numeral 4 is a reflectance adjusting resistor for adjusting the reflectance at the non-matching terminal of the delay line, and its resistance value is set to about 3 to 5 times the characteristic impedance Zo. Further, 6 is an attenuator for adjusting the amplitude of the signal obtained from the matching side of the delay line, and 5 is a subtraction circuit for subtracting the signals obtained from the two terminals on the matching side and the non-matching side of the delay line.

FIG. 2 shows waveforms on the time axis in each part of the circuit of FIG. 1, and the same conditions as the symbols showing the waveforms in FIG. 1 are given. The time interval T seconds in FIG. 2 is the pulse transmission interval in the magnetic recording apparatus, and the delay time τ seconds of the delay line 2 is set to be substantially equal to the pulse transmission interval T seconds.

Next, the detailed operation of the circuit of FIG. 1 will be described. The reproduced signal 1 obtained from the recording medium is input to the delay line through the matching resistor 3 to obtain a waveform 2c shown in FIG. At this time, the characteristic impedance of the delay line 2 is Zo, the resistance value of the reflectance adjustment resistor 4 is R, and the ratio of the voltage of the signal transmitted from the matching terminal by the delay line 2 to the reflectance adjustment resistor 4 is shown. Transmittance mt It is represented by. Therefore, the amplitude of the signal appearing on the non-matching terminal side in FIG. 2b is mt times larger than that in FIG. 2c.

Furthermore, letting mr be the reflectance indicating the rate at which the reproduced waveform that reaches the non-matching terminal of the delay line 2 returns to the matching side again, It is reflected at a rate that satisfies the above condition, is transmitted through the delay line 2 again, and returns to the matching terminal to obtain a waveform obtained by delaying the reproduced waveform by 2τ seconds. At this time, the value of the matching resistor 3 is significantly different from the characteristic impedance Zo of the delay line 2, so that mτ in equation (2)
Becomes 0, and a signal is generated at the matching terminal and reflected to the non-matching terminal again.

FIGS. 2d and 2e show the waveform generated at the matching terminal and delayed by 2τ seconds from the reproduced waveform, where e is the reflectance mr of, for example, 0.
It is about 6 and d shows the case where the reflectance adjusting resistor 4 is opened and mr = 1.

Of the three signals shown in FIG. 2, b, c, and e obtained as described above, c and e are added at the matching terminal of the delay line 2 and then the amplitude is adjusted by the attenuator 6. Further, the subtraction circuit 5 subtracts from FIG. 2B to obtain a sharp pulse with a short rise and fall time as shown in FIG. 2F.

Here, assuming that time 0 in FIG. 2 is the center of the reproduced pulse, if the reproduced waveform has phase distortion as shown in FIG. 2b and the amplitude at time T is smaller than the amplitude at time −T, The reflectance mr is set to 1 or less as shown in FIG.
As a result, the amplitude of the reproduced signal delayed by 2τ seconds in FIG. 2e can be made smaller than the amplitude of the reproduced signal not delayed in FIG. 2c. Therefore, the amount of subtraction of the amplitude at time T can be set smaller than the amount of subtraction of the amplitude at time -T, so the waveform 2f shown in FIG. 2f output from the subtraction circuit 5 becomes bilaterally symmetrical on the time axis and may include phase distortion. Absent.

Generally, the reproduction signal obtained from the recording medium has a wide pulse tail with respect to the pulse transmission interval T seconds as shown in FIG. Therefore, the pulses interfere with each other. In order to eliminate this interference, it is necessary to emphasize the reproduced signal in the high frequency range and sharpen the rising and falling edges of the pulse. However, according to the waveform equalization circuit of the present embodiment, it is possible to obtain a pulse whose amplitude is zero at the adjacent pulse transmission times as shown in FIG.

Further, in order to detect the data transmitted from the pulse shaped as shown in FIG. 2f without error, it is necessary to be symmetrical with respect to the center of the pulse on the time axis.
However, the reproduced waveform obtained from the recording medium often has phase distortion as shown in FIG. 2A, and the pulse is asymmetric. According to the principle, not only the pulse having the phase distortion as shown in FIG. 2a is emphasized in the high frequency range, but also the asymmetry of the pulse can be improved at the same time.

Next, a case where the present principle is applied to a rotary head type digital audio tape recorder (hereinafter, R-DAT) will be described with reference to FIG. FIG. 3 is a block diagram of the entire R-DAT.

First, when the R-DAT is in the recording state, the audio signal input from the audio input terminal 7 is converted into digital data by the A / DT converter 8. Next, the digital data is converted into recording data according to the recording format by the recording signal processing circuit 9, amplified by the recording amplifier 10, and recorded on the magnetic tape by the rotary head 11.

Next, when the R-DAT is in the reproducing state, the rotary head 1
1 scans the magnetic tape and reads the recorded data. After the read data is amplified by the reproduction amplifier 12,
The waveform equalization circuit 13 eliminates interference between pulses. Further, the data identifying circuit 14 extracts the clock from the read data, and determines whether the data is "0" or "1". Further, this read data is input to the reproduction signal processing circuit 15 to detect and correct an error, and then becomes the audio signal again by the D / A converter 16.

The feature of this application example resides in the waveform equalizing circuit 13 in FIG. The waveform equalizing circuit 13 is a means for compensating various losses generally occurring in the magnetic recording / reproducing process, and its frequency-amplitude characteristic rises in the high range of the reproducing signal band. Further, in the case of a velocity proportional head such as a coil head, it is necessary for the waveform equalization circuit 13 to have an integral characteristic in order to cancel the differential characteristic generated in the magnetic recording / reproducing process. Further, in a system such as R-DAT which handles a reproduction signal of a relatively high frequency, the rotary head 11 and the reproduction amplifier 12 easily cause peaking characteristics, and the reproduction signal contains phase distortion at the high frequency. Therefore, it is necessary to give the waveform equalizing circuit 13 a frequency-to-phase characteristic opposite to the peaking characteristic to cancel the phase distortion.

Further, when the magnetic recording device has two read speeds, the pulse transmission interval T seconds changes according to the read speed, so that data detection is reliably performed even if the signal read speed of the magnetic recording device changes. It is necessary to be able to.

FIG. 4 is a circuit diagram showing an embodiment of the waveform equalization circuit in FIG. In the figure, 18 is a magnetic tape, 19 is a rotary head, 20 is a rotary transformer, 21 is a reproducing amplifier, 22 is an integrating circuit, 30a and 30b are matching resistors, 31a, 31b, 31c, 31d and 31e are magnetic recording devices. A switching transistor that is short-circuited when the signal reading speed is V1, 32 is a delay line of delay time τ1 and τ2 using an LC low pass filter, 33 is an attenuator, 34 and 35 are reflectance adjusting resistors, 36 is a differential amplifier, 37
Is an output terminal of the waveform equalization circuit, and 46 is a control signal input terminal of the switching transistors 31a to 31e. In addition, in FIG. 4, the same reference numerals as those of the waveform of FIG. 2 are attached to the portions where the waveform corresponding to the waveform of FIG. 2 is obtained.

Next, the general operation of the circuit of FIG. 4 will be described.
It is assumed that the switching transistors 31a to 31d are in an open state and the delay time of the delay line 32 is τ seconds. First, the signal recorded on the magnetic tape 18 is read from the rotary head 19 by the rotary transformer 20 and the reproduction amplifier 21.
The reproduction waveform output from the reproduction amplifier 21 is input to the integration circuit 22, and the differential characteristic generated during the magnetic recording / reproduction process is canceled. Next, the reproduced waveform is delayed by the delay line 32 through the matching resistor 30a.
2, a waveform c that does not delay the input signal as shown in FIG. 2, a waveform b that delays the input signal by τ seconds, and a waveform e that delays the input signal by 2τ seconds are obtained.

At this time, in the circuit of FIG. 4, unlike the circuit of FIG.
Since the integrating circuit 22 is connected in front of the matching resistor 30a (corresponding to the matching resistor 3 in FIG. 1), the reproduced waveform is slightly different from that in FIG. 2, but it has been described with reference to FIG. High-frequency emphasis is performed in exactly the same way as in the process, so the description will be given with reference to FIG.

A waveform obtained by adding the waveform c which does not delay the input and the waveform e which is delayed by 2τ seconds and whose amplitude is adjusted by the reflection adjusting resistor 34 is taken out from the matching terminal of the delay line 32 as shown in FIG. The amplitudes of the waveforms c and e are adjusted by 33 and input to the positive phase input terminal of the differential amplifier 36. On the other hand, the signal b obtained by delaying the input signal by τ seconds is input from the non-matching terminal of the delay line 32 to the negative phase input terminal of the differential amplifier 36. The differential amplifier 36
Is differentially amplified by the difference between the added signal of the waveforms c and e and the signal b, and is output from the output terminal 37. The output terminal 37
The signal output from is a waveform with high-frequency emphasis and phase distortion removed, as shown in FIG.

Next, the operation of this embodiment when the magnetic recording apparatus is used by switching between the relatively slow read speed V1 and the fast read speed V2 will be described. Here, the recording interval of the recording signal pulse on the magnetic tape is constant, the pulse transmission time interval at the reading speed V ₁ is a relatively long time T ₁ , and the pulse transmission time interval at the reading speed V ₂ is Is a short time T ₂ . In the overall configuration of the circuit of FIG. 4, the delay time of one delay line 32 can be changed to τ ₁ and τ ₂ in order to correspond to two different pulse transmission time intervals. For this reason, the transistor switches 31b, 31c, 31d form a switching circuit, and the characteristic impedance change caused by switching the delay time is also switched by the transistor switches 31a, 31e between the matching resistor and the reflectance adjusting resistor. There is.

Next, the detailed operation of this circuit will be described. First, when the signal reading speed of the magnetic recording device is V _{2 which} is relatively fast,
The reproduction signal obtained by the reproduction amplifier 21 is input to the integration circuit 22. Next, the output of the integrating circuit is input to the delay line 32 via the matching resistor 30a. Here, the switching transistors 31a, 31b, 31c, 31d and 31e are all in an open state, and the resistance value of the matching resistor with respect to the delay time τ ₂ of the delay line 32 is determined only by 30a. Similarly, the resistance value of the reflectance adjusting resistor with respect to the delay time τ ₂ is determined only by 34. Further, the delay line 32 is composed of an LC7 low pass filter, and each built-in capacitor can change its capacitance into two types.

Now, when the relatively short delay time τ ₂ is selected, the switching transistors 31b, 31c and 31d are in the open state, so that the capacitance of the capacitor in the delay line 32 is reduced and the delay time is shortened. The three signals obtained from the delay line 32, the signal that does not delay the reproduction signal, the signal that is delayed by τ seconds, and the signal that is delayed by 2τ seconds are input to the differential amplifier 36 and output to the waveform equalization circuit 37 at the pulse transmission time interval T ₂ In contrast, a sharp pulse with a short rise and fall time is obtained.

Next, when the read speed of the magnetic recording device is V _{1 which} is relatively slow, the switching transistors 31a, 31b, 31c, 31d and 3
All of 0e are short-circuited, and the resistance value of the matching resistor for the delay time τ ₁ of the delay line 32 is determined by the parallel combined value of 30a and 30b. Similarly, the resistance value of the reflectance resistor is determined by the parallel combined value of 34 and 35. Also, the capacitance value of the capacitor in the delay line 32 depends on the switching transistors 31b, 31c and 31d.
Is relatively short-circuited and the delay time is relatively long.
It will be ₁ second. Therefore, it is possible to obtain a sharp pulse having a short rise time and a short fall time with respect to the pulse transmission interval T ₁ second at the output terminal 37 of the waveform equalization circuit.

Generally, the delay line is very expensive and has a large outer shape, but by adopting this embodiment, it is possible to deal with a magnetic recording device having two different read speeds by using only one delay line. Therefore, cost reduction and space saving of the circuit can be achieved.

(Effect of the Invention) According to the present invention, by adjusting the reflectance of the delay line using one resistor, it is possible to eliminate the phase distortion of the reproduced signal that is easily generated in the rotary head type magnetic recording device or the like. Therefore, it is not necessary to provide a phase removing circuit, and the cost of the device can be reduced. Further, as compared with the case where the same operation is performed in a 3-tap type transversal filter using a delay line that does not use reflection, the adjustment can be remarkably simplified, so that the number of manufacturing steps of the device can be reduced and the reliability can be improved. Can be planned.

Furthermore, since the read speeds of the two magnetic recording devices can be supported with the smallest number of delay lines and differential amplifiers, it is possible to reduce the circuit cost and improve the reliability of the circuit.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing the principle of the present invention, and FIG.
FIG. 3 is a diagram showing a time axis waveform of a signal of a main part of the figure, FIG. 3 is a block diagram of a rotary head type digital audio tape recorder to which the circuit of the above principle is applied, and FIG. 4 is a circuit showing an embodiment of the present invention. It is a figure. 1 ... Playback signal, 2 ... Delay line, 3 ... Matching resistor, 4
...... Reflectance adjustment resistance, 5 …… Subtraction circuit, 6 …… Attenuator,
32 ... Delay line, 31a to 31e ... Switching transistor for switching delay time

Claims (1)

[Claims] 1. When reading a recording signal from a recording medium, the recording signal has at least two velocities V1 and V2 (where V1 <V2), and the amplitude of the signal recorded on the recording medium increases with an increase in frequency. As a waveform equalizing means for compensating for this decrease, a reflectance adjusting resistor that connects the input terminal through an impedance matching resistor and sets the reflectance between the output terminal and the common potential to a value of 1 or less is used. A delay circuit using an LC low-pass filter having a connected delay time of τ seconds, an attenuation circuit for adjusting the amplitude of a signal obtained by adding an input signal of the delay circuit and a signal delayed by 2τ seconds from the input signal, and the delay circuit In a magnetic recording / reproducing apparatus having a reflection type waveform equalization circuit configured by a subtraction circuit for subtracting a signal delayed by τ seconds from an input signal and a signal obtained by the attenuation circuit, the LC low pass fill The center angular frequency ω0 for emphasizing the amplitude of the waveform equalizing means is ω01 at the read speed V1 and ω02 at the read speed V2. In this case, by controlling the switching circuit to change the value of the capacitor, the delay time is switched so that the delay time τ becomes τ1 = π / ω01 and τ2 = π / ω02 according to the read speeds V1 and V2, respectively. And a control means for switching and selecting the impedance matching resistance and the reflectance adjusting resistance in association with the operation of the switching circuit of the delay time switching means. And a magnetic recording and reproducing device.