JPS62219806A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To attain the proper waveform equalizing processing to an input signal of a broad band over low and high frequency regions by providing a low/high frequency level characteristic correction circuit and a phase shift circuit correcting the phase characteristic and correcting separately the level and phase of the input signal. CONSTITUTION:After an unnecessary high frequency noise component such as an operating clock component mixed in a filter 9 is attenuated or rejected from a reproducing signal inputted to a reproducing input terminal 7, the result is inputted to a correction circuit 11 and the level at a high frequency region near a frequency 1/T attenuated by the recording/reproduction is subjected to emphasis correction by the correction circuit 11. Then the reproducing signal is inputted to a correction circuit 14 and the level of the low frequency region of nearly frequency 1/9T attenuated by the differentiation characteristic of magnetic recording/reproduction is subjected to emphasis correction by a correction circuit 14. Further, the reproducing signal is inputted to a phase shift circuit 15 via a transistor Q3 and a capacitor C4 and the time constant of the phase shift circuit 15 is set to nearly 150nsec and only the phase of frequency 1/4T-1/T component shifted by 90 deg. based on the magnetic recording/reproducing characteristic is subjected to 90 deg. phase shift and corrected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides an input signal whose level in the lower and higher frequency ranges is attenuated and whose phase is shifted from that of the original signal, for example, obtained by reproducing a magnetic regeneration system. The present invention relates to a waveform equalizer that performs waveform equalization processing on a signal.

[Conventional technology]

Conventionally, in order to record and reproduce audio signals with high quality and high density, it has been considered to digitally record and reproduce audio signals.For example, "Nikkei Electronics" published May 20, 1985 (Nikkei McGraw-Hill) 148-150
On the page, there is an 8mm video tape recorder (hereinafter referred to as 8mm! JV).
It has been described that audio signals are digitally recorded and reproduced using a digital audio signal (hereinafter referred to as "TR").

In addition, conventional helical scan methods for home use (VH8,
An EIAJ format PCM processor has also been devised, which digitally records and reproduces audio signals using a video tape recorder of the β format).

Furthermore, with a new format, a fixed head and rotating head type digital audio tape recorder (hereinafter referred to as D) records and plays digital audio signals on magnetic tape.
(referred to as AT) has also been proposed. 2. The detailed structure of DAT has not been invented.

By the way, analog 2 and digital signals.

When transmitting via a transmission system such as the various magnetic recording and reproducing systems mentioned above, the level and phase characteristics of the signal passing through the transmission system generally change compared to the signal before transmission. When transmitting via a system, based on the magnetic recording and reproducing characteristics,
The levels of the low and high frequency ranges are attenuated, and the phase of the entire frequency range is shifted.

Therefore, it is necessary to perform waveform equivalent processing on the signal obtained via the transmission system and to correct the level and phase.

And 8mi! When recording and reproducing audio signals digitally using a JVTR, the PCM data (NRZ data) of the audio signal is inverted at the boundaries of each bit of the PCM data by bi-phase modulation using a two-phase clock, and the logic It is modulated into bi-phase modulation data that changes at the center of the l bits and recorded on the magnetic tape, and if the period of the unit bit of the modulation data is T (1/MH2), then the data inversion of the recorded modulation data The period becomes T or 2T.

On the other hand, based on the magnetic recording and reproducing characteristics, the reproduction signal of the magnetic head obtained by reproducing the magnetic tape has the levels in the low and high frequency ranges attenuated and the overall phase shifts with respect to the recording signal of the magnetic tape. do.

By the way, as mentioned above, since the data inversion period of the modulated data is of two types, T and 2T, the frequency band of approximately 2T to T in the reproduced signal, that is, the middle frequency.

It can be a relatively narrowband component spanning a high frequency band or a component of modulated data.

Therefore, it is necessary to perform waveform equivalent processing on the high frequency components of the audio signal using an 8mm VTR.
403 Service Guide J (published in 1985) describes that waveform equivalent processing of a reproduced signal is performed using the elegant waveform configuration shown in the block indicated by the dashed line in FIG.

By the way, at 2 in FIG. 5, (l) is the reproduction input terminal into which the reproduction signal of the magnetic head is input, (21 is the input terminal i1
1 is a preamplifier connected to 1, (3) is a resonant circuit for correcting high-frequency level characteristics connected to the amplifier +21, (41 is a band-limiting filter for removing unnecessary high-frequency noise connected to the resonant circuit (3) , (6) is a differential circuit for phase correction connected to the filter (4), and (6) is a waveform equivalent output terminal connected to the differential circuit (6).

2. Filter (4) consists of operational amplifier (AI) 2, resistor (R1), (R2), capacitor (Ct), (
C2) is a positive feedback type second-order low-pass active filter.

In addition, the differentiating circuit (5) includes a capacitor (Ca) and a resistor (
It is formed by an R, C differentiator consisting of:

The reproduction signal of the magnetic head is input to the input terminal il+.

When input to the resonant circuit +31 via the amplifier 121,
Since the resonance characteristic of the resonance circuit (3) is set to approximately the high frequency of the data inversion period T when Ru.

In addition, the reproduced signal via the resonance circuit (3) is transmitted through the filter (4).
), and at this time, the characteristics of the filter (41) are set to attenuate frequency components higher than frequency 1, such as the operating clock component of a tape recorder, so the filter (4) or the reproduced signal Unnecessary high frequency noise components such as mixed operation clock components are removed, and the carrier power/noise (C/N'') is improved by the filter (4).

Furthermore, the reproduced signal that has passed through the filter (4) is transferred to the differentiating circuit (
61, and at this time, the characteristics of the differentiating circuit (5) are 1
The seal is set to a characteristic that corrects only the phase for components in the frequency range from frequency 7 to 〒, and the differentiating circuit (5)
Phase correction of the reproduced signal is performed.

Then, the frequency-level characteristics 1 frequency-phase characteristics of the waveform equalizer formed by the resonant circuit (31 or the differential circuit (61) are lifted and the frequency At the same time, the phase shift based on the differential characteristics of the magnetic sickle is corrected. A signal obtained by waveform-equivalent processing of components in a wide frequency band fa-fb is obtained.

In other words, when digitally recording and reproducing an audio signal using an 8mm video tape recorder, the data inversion period of the modulated data is of two types, T and 2T, and the frequency domain of the modulated data in the reproduced signal, that is, the waveform equivalent. The frequency band to be used is approximately between 7 and 〒.

Since the band is relatively narrow across the high frequency range, level correction in the high frequency range by the resonant circuit (31) and differentiation circuit (6
), appropriate waveform equivalent processing of the reproduced signal is performed.

[Problem that the invention seeks to solve]

By the way, the above-mentioned rotating head type DAT (hereinafter referred to as R-DA)
When recording and reproducing an audio signal digitally using a recording medium (referred to as T), the audio signal is converted into 8-bit PCM data, and the 8-bit PCM signal is converted into 10-bit modulation data and recorded on a magnetic tape. In this case, the data inversion period of the modulated data is
Based on the PCM data, the cycle is one of four types: T, 2T, 3T, and 4T.

In addition, in R-DAT, it is considered that recording and playback tracking is controlled by tracking control using a so-called pilot signal method, and for this reason, along with the above-mentioned lθ bit modulation data, 6T, 9
It has been proposed to record sync data for tracking control having a data inversion period of T.

However, in the case of R-DAT, magnetic tape 8mm 1
The band extends to a lower frequency range than the recording band when using JVTR.

When audio signals are digitally recorded and played back using l(,-DAT, the level of the low and high frequency ranges of the playback signal is attenuated and the phase of the playback signal is shifted due to the magnetic recording and playback characteristics of the recorded signal. In order to obtain recorded modulation data and sync data, it is necessary to perform waveform equalization processing on the reproduced signal. In this case, the frequency band to be subjected to waveform equalization processing is approximately the low frequency range of - line or the high frequency range of approximately 〒. The frequency range becomes wide.

By the way, as mentioned above, the detailed structure of R-DAT has not yet been invented, and the waveform equivalent base of the DAT has not yet been invented.

That is, of course, a waveform equalizer that performs waveform equalization processing on a wideband signal including a low frequency range 2 and a high frequency range has not yet been invented.

On the other hand, it is possible to form an R-DAT waveform equalizer by adding a router in the middle and high frequency range to the waveform equalizer shown in Fig. 5, but in this case, a differentiating circuit ( 6) causes the problem that the level of the low frequency range to be emphasized is attenuated, making it impossible to perform appropriate waveform equalization processing.

[Means for solving problems]

This invention was made with the above points in mind,
The waveform equalizer processes the input signal whose phase has been shifted while attenuating the levels of the low and high frequencies, and consists of a lag lead type low-pass filter, etc., and emphasizes the level of the low frequency range of the input signal. a low-frequency level characteristic correction circuit for correcting, a high-frequency level characteristic correction circuit for emphasizing and correcting the level of a high frequency region of the input signal, which includes a resonance circuit, and a phase shift circuit for correcting the phase characteristic of the input signal; and separately corrects the level and phase of the input signal T
This is a waveform equalizer characterized by:

[Effect]

Since the level correction 2 and phase correction of the low and high frequency ranges of the input signal are performed independently by the low and high frequency level characteristic correction circuit 2 and the phase shift circuit, a wide range of low frequency range or high frequency range is achieved. Waveform equivalent processing of input signals can be performed.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 to 4 showing embodiments thereof.

Figure 1 shows the case where it is applied to R-DAT. In the same figure, (7) is the reproduction input terminal into which the reproduction signal of the magnetic head is input, and (8) is connected to the input terminal (7). The preamplifier (9) is a band-limiting filter for removing unnecessary high-frequency noise connected to the amplifier (8), and one end is connected to the amplifier (8).
) connected to filter resistor (Rt), resistor (R,
A filter coil (Ll) and a capacitor (C1) provided in series between the other end of t) and the ground terminal αO
2, a filter coil (R2), and a resistor (R2), which are connected in series between the connection point of the coil (Ll) and capacitor (CI) and the ground terminal αO. ing.

(11) is a high-frequency level characteristic correction circuit connected to the filter (9), whose base is a coil (R2) and a resistor (R2).
2) is connected to the connection point of the NPN type resonant transistor (Ql) and the coil (R) forming the LCR parallel resonant circuit.
3) Level emphasis in high frequency range, consisting of a capacitor (C2), a level adjustment variable resistor (V, R1) E, and an NPN buffer transistor (C2) connected to the base or collector of the transistor (C2). The collector of the transistor (Ql) is connected to the positive power supply terminal via the collector resistor (Ra)E and the LCR parallel resonant circuit, and the emitter of the transistor (Ql') or the emitter resistor (R4)
The collector of the transistor (C2) is connected to the negative voltage 0 terminal (I3) via the positive power supply terminal Q21, and the emitter of the transistor (C2) is connected to the ground terminal αO via the emitter resistor (R5). It is connected.

(Ura is a low-frequency level characteristic correction circuit connected to the correction circuit (1■), and connected to the level adjustment variable resistor (VB2) 2 connected to the emitter of the transistor (C2) and the variable resistor (VB2) Capacitor for filter (
C3) and a lag lead type low-pass filter consisting of a resistor (R6). (C3) is an NPN buffer transistor whose base is connected to the contact point between the variable resistor (VB2) and the capacitor (C3), whose collector is connected to the positive power supply terminal UZ, and whose emitter is connected to the emitter resistor (R7). ) is connected to the ground terminal αO. (C4) is a coupling capacitor whose one end is connected to the emitter of the transistor (C3).

ao is a phase shift circuit connected to the other end of the capacitor (C4), with positive and negative power terminals +121, (131 positive,
It consists of a first-order phase shifter using a differential amplifier (AI) driven by a negative power supply, and the inverting input terminal (
-), non-inverting input terminal (or filter resistance (Rg))
, the other end of the capacitor (C4) via the variable capacitor (VCI), and the amplifier (At
) inversion.

Filter resistors (TL9) and (RIO) are provided between the non-inverting input terminal ←)l+) and the ground terminal αG. (161 is a waveform equivalent output terminal connected to the output terminal of the amplifier (AI).

The reproduction signal of the magnetic head is input to an input terminal (7).

The reproduced signal is inputted to the filter (9) via the amplifier (8), and at this time, the level of the low and high frequency ranges is attenuated and the phase is shifted based on the magnetic recording and reproducing characteristics.

Modulation data 2 and sync data are present, and it is necessary to perform waveform equalization processing on the components of the frequency band 9, which is a little wider than .

The filter (9) is set to have a third-order Butterworth characteristic with a cutoff frequency slightly higher than the highest frequency fd to be subjected to waveform equalization processing, and, like the filter (41 in FIG. Unnecessary high frequency noise components such as operating clock components are attenuated and removed, and the level of components below the highest frequency fd.

The phase is hardly affected by the filter (9).

Furthermore, whether the reproduced signal via the filter (9) or the correction circuit (
11) and is attenuated by recording and playback, the level of the high frequency region around the peak frequency is input to the correction circuit (111).
At this time, the Q of the correction circuit (11) is
The value is set low so as not to affect the phase characteristics, and the correction circuit fi11 only corrects the level characteristics in the high frequency range of the reproduced signal. What? , correction circuit (I
The level correction amount of ll is variably adjusted by a variable resistor (VRI).

In addition, the reproduced signal via the correction circuit (IIIi) is input to the correction circuit α4, and the level of the low frequency range approximately in the frequency range attenuated by the differential characteristics of magnetic recording and reproducing is input to the correction circuit II.
The emphasis is corrected by 4.

8. The resistance values of variable resistor (VB2) and resistor (R6) are r
a.

rb, and when the capacitance of the capacitor (C3) is C, the time constant τ1. which determines the characteristics of the correction circuit iI4+. τ2 is, for example, C・(ra+rb)=2.5μsec, cr−r
b = 1.4μsec each, and the correction circuit (
The 14+ correction is set so as not to affect components in the middle and high frequency ranges.

In addition, the level correction amount of the correction circuit 1141 is determined by a variable resistor (
■Adjusted by 2).

Then, the reproduced signal via the correction circuit (141) is inputted to the phase shift circuit surface via the transistor (C3) and the capacitor (C4), and at this time, the time constant of the phase shift circuit (151) is set to about 150 nsec. The frequency shifted by almost 90 degrees based on the magnetic sickle characteristics...~ Only the phase of the component is corrected by shifting the phase by 90 degrees. 2. Phase shift circuit (1
5) The amount of phase shift is variably adjusted by a variable capacitor (VC).

Therefore, the signal obtained at the output terminal Q61 has its levels in the low and high frequency ranges corrected separately by the correction circuits 141 and +I11, and also by the phase shift circuit Q51.
At this time, the elegant frequency-level characteristic 1 frequency-phase characteristic such as the waveform formed by the filter (9) or the phase shift circuit (151) is as shown in FIG. 2(a) and (bl, respectively). As shown in , the level of the high frequency region of approximately frequency 〒 is again emphasized and corrected, and the phase of the necessary band is corrected so as to have linearity.

In other words, in the case of the waveform equalizer shown in FIG.
l+, 1141g, and a phase shift circuit Q51, and performs level correction 2 and phase correction in the low and high frequency ranges separately, so fc-fd, that is, approximately frequency
It is possible to perform waveform equalization processing on a wide band signal spanning from a low frequency range to a high frequency range, that is, a reproduced signal of R-DAT.

In addition, the correction circuit Ill corrects to 141! By providing a variable resistor (Vftl) for adjustment (■2) and a variable capacitor (VC) for adjusting the correction amount in the phase shift circuit Oω, it is possible to set the level correction amount in the low and high frequency ranges. 2, the amount of phase correction can be set variably, and, for example, the correction characteristics can be adjusted to the optimum characteristics according to the variations in the magnetic forest reproduction characteristics, thereby absorbing the above-mentioned variations.

Furthermore, since G'% does not require special parts such as delay elements, it can be formed easily and at low cost.

By the way, in the above embodiment, the filter (9) and the phase shift circuit Q
5i 'e, an LC low-pass filter, and a first-order phase shifter using an amplifier (AI), respectively, but the filter (9) may be formed by an operational amplifier (
A2) may be formed by a positive feedback type second-order low-pass filter, or the phase shift circuit Q51 may be formed by a first-order phase shift filter using an operational amplifier (83) as shown in FIG. It may also be formed by a container.

2. In Figure 3, (Rt) and (TL2) are the two filter resistors connected in series to the input terminal of the amplifier (A2), and (C5) is the connection between the input terminal of the amplifier (A2) and the ground. A filter capacitor provided between (C6
) is the connection point of the resistor (Rth), (R12) and the amplifier (A2
) is a filter capacitor provided between the output terminal of the

2 in Fig. 4, (Rla) is a filter resistor connected to the inverting input terminal (←) of the amplifier (A3), (V
C2) is a variable capacitor connected to the non-inverting input terminal (+) of the amplifier (A3), and (R14) is a filter capacitor connected between the non-inverting input terminal (+) of the amplifier (A3) and ground. The resistor (R16) is a filter resistor provided between the inverting input terminal (←) and the output terminal of the amplifier (A8).

Furthermore, the correction circuit (11) may be formed by an active filter, the correction circuit +ll+ may be formed by a resonant circuit, and the phase shift circuit 051 may be formed by a second-order or higher-order phase shifter. Good too.

Also, filter (9), correction circuit fllll, IJ4
The connection order of 1:8 and the phase shift circuit Q51 may be different from the example, and the connection order of the filter (9) 2 and the transistor (Qa)
, the buffer circuit such as the capacitor (C4,) can be omitted.

It goes without saying that the present invention can be applied not only to the R-DAT waveform equalizer, but also to waveform equalizers for various magnetic recording and reproducing devices that perform analog 8 and digital magnetic recording and reproducing, and signal transmission devices.

〔Effect of the invention〕

As described above, according to the waveform equivalence basis of the present invention, the low and high frequency level characteristic correction circuits +141 and +Ill2 that emphasize and correct the levels in the low and high frequency ranges, and the phase shift circuit α-th that corrects the phase characteristics. By separately correcting the level and phase of the input signal, it is possible to perform appropriate waveform equalization processing on a wide band input signal spanning a low frequency range to a high frequency range.

[Brief explanation of drawings]

Figure 1 is a wiring diagram of one embodiment of the waveform equalizer of the present invention, Figure 2 (a), (bl is the frequency-level of Figure 1. Frequency-phase characteristic diagram, Figures 3 and 4). are connection diagrams of other examples of the band-limiting filter and phase shift circuit shown in Fig. 1, Fig. 5 is a connection diagram of a conventional waveform equalizer, Fig. 6(a), (
bl is a frequency-level and frequency-phase characteristic diagram of FIG. (111...High frequency level characteristic correction circuit, (I41...
-Low level characteristic correction circuit, I51...phase shift circuit. Agent: Patent Attorney Fuji 1) Ryutabu procedural amendment (white side, April 25, 1986)

Claims (1)

[Claims] 1. A waveform equalizer that performs waveform equalization processing on an input signal in which the levels in the low and high frequency ranges are attenuated and the phase is shifted, which is comprised of a lag lead type low-pass filter, etc., and emphasizes and corrects the level in the low frequency range of the input signal. a low-frequency level characteristic correction circuit that includes a resonant circuit, and emphatically corrects the level of a high frequency region of the input signal; and a phase shift circuit that corrects the phase characteristic of the input signal. A waveform equalizer comprising: a waveform equalizer that separately corrects the level and phase of the input signal.