JPS6143918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an equalization device suitable for a transmission system that handles a signal containing a plurality of frequency components whose amplitudes are predetermined.

[Conventional technology]

In general, color video signals are composed of a carrier wave signal modulated by luminance information and a subcarrier signal modulated by color information, etc. When recording and reproducing these signals, the frequency response is naturally changed by the recording and reproducing means. Some properties may deteriorate. Therefore, it has become necessary to compensate for this frequency response characteristic in the reproducing system and to equalize the frequency characteristic for the reproduced signal.

In particular, when a disk-shaped record carrier such as a magnetic disk is used, as shown in the frequency characteristics shown in FIG.
The highest frequency that can be effectively recorded and reproduced is determined.
That is, when a disk-shaped record carrier is used, the recording/reproducing head scans in a spiral pattern from the periphery to the center, so that the frequency characteristic of characteristic 1 in Fig. 1 can be obtained at the outer periphery of the disk-shaped record carrier. In the inner periphery, only the frequency characteristic of characteristic 2 in the figure is obtained, and the effective maximum frequency in the inner periphery is considerably reduced. Therefore, it is clear that unless some kind of equalization of the frequency characteristics is performed, the image quality of the reproduced signal will deteriorate, making it impossible to put it into practical use. However, since the disk-shaped record carrier is scanned in a spiral manner, the characteristics shown in FIG. An automatic equalization device is required that performs predetermined equalization according to the characteristics of the reproduced signal.

In response to such requests, the Unexamined Patent Application Publication No. 1986-
A technique as shown in Publication No. 120210 has been proposed. In this method, in addition to the carrier signal, a reference signal of constant amplitude is set at a separate frequency (lower frequency side of the carrier signal).
The frequency characteristics are compensated by comparing the amplitudes between the two signals.

[Problem that the invention seeks to solve]

However, in the conventional method as described above, it is necessary to simultaneously record a reference signal of a constant amplitude in advance. However, in general, it is sufficient to use a frequency-modulated audio signal or a pilot signal for hue variation compensation as a reference signal, but if such a signal is not included, it is necessary to prepare a reference signal with a constant amplitude and simultaneously It has to be recorded, which is very troublesome.

In other words, when only a carrier wave signal frequency-modulated by luminance information and an amplitude-modulated color signal converted to a lower frequency thereof are recorded simultaneously,
Alternatively, in the case where only a carrier wave signal is frequency-modulated by a composite signal of a composite color video signal and an audio signal, simultaneous recording of a reference signal is required separately, which is not preferable.

Furthermore, in the above-mentioned method, compensation is not performed for frequencies higher than the carrier wave frequency-modulated by luminance information, and the characteristic deterioration starting point shown in FIG.
That is, if the number of carrier frequencies is provided in the vicinity of the cutoff frequency 3, there is a drawback that compensation for frequencies higher than this is completely impossible.

The present invention has been made in view of these points,
It can automatically equalize and compensate the amplitude characteristics within the required band, including the higher frequencies than the carrier signal (main signal).
The purpose of this invention is to provide an equalization device that can perform reproduction, transmission, etc. with high fidelity.

[Means for solving problems]

The equalizer according to the present invention includes a variable control equalizer that controls the amplitude of a transmitted signal with an equalization characteristic according to a control input, and a variable control equalizer that controls the amplitude of a transmitted signal using an equalization characteristic that corresponds to a control input. An extraction circuit located on the high-frequency side and low-frequency side of the carrier signal and extracting a high-frequency subcarrier signal and a low-frequency subcarrier signal modulated by information, respectively, and the above-mentioned high-frequency subcarrier signal output from the extraction circuit. A comparison circuit is provided which compares the amplitudes of the carrier signal and the low frequency subcarrier signal and sends a control signal to the control variable equalizer according to the comparison result.

[Effect]

In this invention, a high frequency subcarrier signal and a low frequency subcarrier signal included in a transmission signal are individually extracted, and the amplitudes of these extracted signals are compared so that the amplitude ratio is equal to that on the transmission side. .

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, signals transmitted in the transmission system of this embodiment will be explained. Figure 2 is a diagram showing the spectral distribution of the transmission signal, showing a signal E 1 (main signal) with frequency F ₁ frequency-modulated by luminance information and a signal E ₁ (main signal) with frequency F 1 frequency-modulated by luminance information, and a signal E 1 (main signal) with a lower frequency than the main signal E ₁ . Frequency F ₂ that is amplitude modulated by small color information
This shows the spectral distribution when the signal E ₂ (low-frequency sub-signal) is frequency-multiplexed, converted into two-level information by a limiter, and recorded on a disk-shaped record carrier.

It is well known that when two frequency components are nonlinearly transmitted in this way, harmonics and cross-modulation components of each signal component are generated, and the component frequencies are
It is given by mF ₁ ±nF ₂ (m, n are integers). Especially when performing a vertically symmetrical limit operation,
Only odd components (m+n) occur, and the main components are F ₁ , F ₂ and 2F ₁ −F ₂ (System Coding Parameters, Mechanic and
Electromechanics of the Reflective Videodisc
Player: SMPTE Journal, February 1977,
(See Volume 86, pages 74-79). Of these (2F ₁
−F ₂ ) is the signal with frequency F ₃ shown in Figure 2.
E ₃ (high-frequency sub-signal), and this high-frequency sub-signal E ₃ is inevitably generated by performing the above-mentioned limiting, and as is well-known, this high-frequency sub-signal E ₃
is a cross-modulation line segment with equal amplitude and sub-modulation.

FIG. 3 shows a basic block configuration diagram of an equalizer according to an embodiment of the present invention, and the input (IN) is a transmission signal with a spectral distribution as shown in FIG.
In other words, a signal containing a main signal E ₁ and high-frequency and low-frequency sub-signals E ₂ and E ₃ with a mutual amplitude-subsignal ratio of 1 is transmitted through a transmission system having frequency characteristics as shown in Fig. 1, for example. Given. 6 is a control variable equalizer (CEQ) provided between the input (IN) and the output (OUT), which controls the amplitude of the transmission signal with equalization characteristics that change according to control from the comparison circuit 5, which will be described later. As the control variable equalizer 6, a resonant circuit having a predetermined resonant frequency is used, and a variable impedance element such as a diode is connected in parallel with this for damping, and the control variable equalizer 6 is connected to a resonant circuit having a predetermined resonant frequency. It is sufficient to provide the output of a comparison circuit 5, which will be described later, and as the output of the comparison circuit 5 increases, the impedance of the diode increases, the resonance characteristics of the resonant circuit become remarkable, and the deterioration of the high frequency characteristics is compensated for. However, if a transistor or the like is used as the variable impedance element, the inverting amplifier can be omitted, and it is also possible to optionally use it in combination with various equalization circuits such as T-type and L-type.

4 is an extraction circuit provided on the output side of the control variable equalizer 6, and in this extraction circuit 4, 41 is a low frequency sub-signal E ₂ of the transmission signal output from the control variable equalizer 6. A filter (FIL ₁ ) that extracts
42 is a filter (FIL ₂ ) that extracts the high frequency sub-signal E ₃ ;
43 and 44 are detectors (DET ₁ ) and (DET ₂ ) for detecting the amplitudes of the low-frequency sub-signal E ₂ and the high-frequency sub-signal E ₃ , respectively. The filter 42 and the detector 44 constitute a low-frequency sub-signal extracting circuit, and a high-frequency sub-signal extracting circuit.

Here, the filters 41 and 42 will be explained in more detail. In the case of this embodiment, since the components of the main signal E ₁ and the components of the low-frequency sub-signal E ₂ do not overlap,
The pass characteristics of the filter 41 may be made to match the frequency band of the low-frequency sub-signal _E2 . In addition, the high frequency sub-signal E ₃
As mentioned above, the frequency band of _F3 is the sum of twice the band of the main signal _E1 and the band of the low-frequency sub-signal _E2 , as shown by ( _2F1 - _F2 ). ,
There is a possibility that the bands of the main signal _E1 and the high-frequency sub-signal _E3 overlap as shown in FIG. Therefore, as for the filter 42, it is necessary to use a filter with relatively high-quality pass characteristics so that mainly the components of the high-frequency sub-signal _E3 can be extracted.

Further, 5 compares the amplitudes of the outputs of the extraction circuits 43 and 44, that is, the low-frequency and high-frequency sub-signals E ₂ and E ₃ , and outputs the output according to the level difference or level ratio to the control variable equalizer 6. This is a comparison circuit that supplies the control input, and is composed of a comparator (CPR), etc.

In addition, in the description of the filter 42 above, the main signal
The reason why the bands of E ₁ and high frequency sub-signal E ₃ overlap is as follows.

The center frequency of the main signal E ₁ is F ₁₀ and the signal band is ±Δ
F ₁ , the center frequency of the low-frequency sub-signal E ₂ is F ₂₀ , the signal band is ±ΔF ₂ , the center frequency of the high-frequency sub-signal E ₃ is F ₃₀ , and the signal band is ±ΔF ₃ .

The main signal E ₁ and the low-frequency sub signal E ₂ are independent signals, and if we assume that the instantaneous frequency at a certain point is the main signal
It is assumed that _{F 1 =} F ₁₀ -ΔF ₁ for E 1 and F ₂ =F ₂₀ +ΔF ₂ for low-frequency sub-signal E ₂ . The frequency F ₃ of the high frequency sub-signal E ₃ in this case is given by the following equation, as is clear from the previous explanation.

F ₃ = 2F ₁ − F ₂ = 2 (F ₁₀ − ΔF ₁ ) − (F ₂₀ + ΔF ₂ ) = (2F ₁₀ − F ₂₀ ) − (2 ΔF ₁ + ΔF ₂ ) Also, the instantaneous frequency at another point in time is , main signal
Assuming that _{F 1 =} F ₁₀ + ΔF ₁ for E 1 and F ₂ = F ₂₀ − ΔF ₂ for the low-frequency sub-signal E ₂ , the frequency F ₃ of the high-frequency sub-signal E ₃ in this case can be calculated using the following formula. is given by

F ₃ = 2F ₁ −F ₂ = 2 (F ₁₀ + ΔF ₁ ) − (F ₂₀ − ΔF ₂ ) = (2F ₁₀ − F ₂₀ ) + (2ΔF ₁ + ΔF ₂ ) Main signal E ₁ and low-frequency sub signal E ₂ is modulated using the frequencies in the above two cases as upper and lower limits, so
The high frequency sub-signal E ₃ has a signal band of ±(2ΔF ₁ +ΔF ₂ )=±ΔF ₃ with F ₃₀ =2F ₁₀ −F ₂₀ as the center frequency.

This situation is illustrated in FIG. 4, where it can be seen that the band of the main signal E ₁ and the band of the high-frequency sub-signal E ₃ overlap.

Next, the effects will be explained.

Input IN has main signal E ₁ and low frequency and high frequency sub signals.
A transmission signal including E ₂ and E ₃ is given via a predetermined transmission system. At this time, if the predetermined transmission system has frequency characteristics as shown in FIG. 1, for example, the high-frequency side level of the transmission signal will drop considerably. When such a transmission signal is input to the control variable equalizer 6, the signal is outputted with its amplitude controlled using the previously controlled equalization characteristics. This output signal is then input to the extraction circuit 4, where the filters 41 and 42 extract the low-frequency sub-signal E ₂ and the high-frequency sub-signal E ₃ .
3 and 44, the amplitudes of the respective signals E ₂ and E ₃ are detected.

Next, the output of this extraction circuit 4 is a comparator (CPR)
Here, the amplitudes of both sub-signals E ₂ and E ₃ are compared, and an output corresponding to the level difference or level ratio between them is obtained as the output of the comparison circuit 5. That is, in the case of this embodiment, the amplitudes of both sub-signals E ₂ and E ₃ on the transmitting side are equal as described above, and the amplitude ratio is 1.
If the transmission system has frequency characteristics as shown in Figure 1, the level of the high-frequency sub-signal will be lower than that of the low-frequency sub-signal, and the amplitude ratio of both sub-signals E ₂ and E ₃ will be 1. It disappears. Therefore, this is detected by the comparator circuit 5, and an output corresponding to the amplitude difference or amplitude ratio between the two is obtained.

Then, by applying the output of this comparison circuit 5 to the control input of the control variable equalizer 6 and controlling its equalization characteristics so that the amplitudes of both sub-signals E ₂ and E ₃ are equal,
At the output (OUT), a signal with equal amplitudes of both sub-signals E ₂ and E ₃ and equalized frequency characteristics is obtained. Therefore, sufficient equalization is performed on the main signal E ₁ between these, and the deterioration of the high frequency characteristics shown in FIG. 1 is reduced to the high frequency sub signal E ₃ shown in FIG. 2.
The frequency is compensated up to _F3 .

FIG. 5 shows another embodiment of the present invention, which is designed to simplify the characteristics of the filter for extracting the high frequency sub-signal _E3 .

That _is , while the embodiment shown in _FIG . 47, and the detection of both the above-mentioned sub-signals E ₂ and E ₃ is performed at arbitrary time intervals. For example, if the transmission signal is a video signal, sampling is performed by turning on the gate 47 using an output from a synchronization signal detection circuit (not shown) or the like during the burst period of the video signal. Then, during this burst period, the brightness information is at the pedestal level, so the carrier wave of the main signal _E1 is in an unmodulated state, that is, the frequency shown in Figure 2.
Since it is a single frequency of F ₁ , there is no band overlap between the main signal E ₁ and the high-frequency sub-signal E ₃ in the output signal of the gate 47 (in Fig. 4, ΔF ₁ is 0).
state). Therefore, as the filter 42',
It is not necessary to use a high-quality one as in the embodiment shown in FIG. 3, and it is possible to simply use one with simple characteristics that match the frequency band of the high-frequency sub-signal _E3 .

This applies not only to video signals, but also generally speaking, even if the bands of the main signal E ₁ and high-frequency sub-signal E ₃ overlap, if both signals are viewed at a certain timing, both signal frequencies will change. may not overlap (this cannot always be said). Therefore, in such a case, if a signal is extracted in a certain time width at this specific timing, the main signal _E1 and both sub-signals contained in the transmission signal extracted at that time can be extracted.
There is no band overlap between E ₂ and E ₃ , and both sub-signals E ₂ and E ₃ can be detected with a simple configuration.

Here, when detecting both the sub-signals E ₂ and E ₃ at predetermined time intervals as in this embodiment, the output of each of the detectors 43 and 44 is intermittent, so each of the detectors 43 and 44 , 44 through smoothing low-pass filters 45, 46 with a time constant sufficiently longer than the sampling period.
(LPF ₁ , LPF ₂ ) etc.
As a result, the comparator circuit 5 outputs both sub-signals E ₂ and E ₃
A control signal corresponding to the level difference between them or the level ratio is applied to the control input of the control variable equalizer 6.

As described above, in addition to the same effects as in the above-mentioned embodiments, the device of this embodiment is extremely effective in countering band overlap between the main signal E ₁ and the high-frequency sub-signal E ₃ .

In the above embodiment, a case was explained in which the amplitudes of both sub-signals E ₂ and E ₃ were equal at each instant, but a certain amplitude difference or amplitude ratio between the two may be established in advance, or it may be predicted. In some cases, it is sufficient to use a comparator circuit 5 that generates an output according to a level difference between inputs or a deviation of a level ratio from a constant value, thereby further expanding the scope of application of the present invention.

Furthermore, the equalization device according to the present invention can be applied to various signals such as those described below.

That is, the same effect can be achieved even if a carrier wave modulated by audio information or a pilot signal for hue variation compensation is used as both sub-signals E ₂ and E ₃ . However, even in these cases, the high-frequency sub-signal of the extraction circuit 4
It is necessary to use a filter that separates E ₃ with a pass characteristic that suppresses unnecessary components, and the above-mentioned sampling method (the embodiment shown in FIG. 5) is suitable for this purpose. Furthermore, the same effect can be obtained by using a carrier wave frequency-modulated by a composite color video signal as the main signal E ₁ and using carrier waves modulated by audio information as both sub-signals E ₂ and E ₃ .

Furthermore, in the above embodiment, two or more signals based on the main signal E ₁ and the low-frequency sub-signal E ₂ are multiplexed as different frequencies, and a mirror image generated signal, that is, a high-frequency sub-signal E ₃ is generated by passing through a limiter. Although the equalization is performed using the above, it is also possible to use the upper and lower side wave components generated when the carrier wave is modulated by a predetermined signal.

For example, if the carrier wave is frequency modulated by a composite color video signal, the carrier wave will have a single frequency when the luminance information is at the pedestal level, so
This is used as the above-mentioned main signal E ₁ , and the first lower side wave component of the burst signal is used as the low frequency sub signal E ₂ , and the first upper side wave component of the burst signal is used as the high frequency sub signal E ₃ . It can be used in exactly the same way if it is sampled appropriately during the burst period.

In addition, the present invention is applicable to other transmission systems, such as VTR,
It is suitable for recording and reproducing devices such as data recorders, various signal transmission lines using high-frequency cables, and other devices that handle broadband signals, and of course can be modified and combined in various ways depending on the application conditions.

〔Effect of the invention〕

As described above, according to the present invention, a carrier wave signal modulated by information and a high frequency band having a predetermined amplitude-to-substance ratio on the transmission side and having a higher frequency and a lower frequency than the carrier signal, respectively, and which are modulated by information. In an equalizer that equalizes a transmission signal having a subcarrier signal and a low frequency subcarrier signal, a control variable equalizer controls the amplitude of the transmission signal according to a predetermined equalization characteristic, and the output of the equalizer , extract each subcarrier signal from which a high frequency subcarrier signal and a low frequency subcarrier signal are respectively extracted, and compare the amplitudes of the extracted subsignals so that the amplitude ratio is equal to that on the sending side. Since the equalization characteristics of the variable control equalizer described above are controlled, the equalization compensation of the amplitude characteristics is automatically performed, and the characteristics within the required band can be kept flat, allowing playback, transmission, etc. This has the effect of being able to perform it with high fidelity.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the frequency characteristics of the outer circumference and inner circumference of a disk-shaped record carrier, Fig. 2 is a spectral distribution diagram showing an example of a signal applied to the present invention, and Fig. 3 is an embodiment of the present invention. Block diagram showing 4th
This figure is a diagram showing the frequency distribution of signals for explaining the operation of the apparatus shown in FIG. 3, and FIG. 5 is a block diagram showing another embodiment of the present invention. 4...Extraction circuit, 41, 42, 42'...Filter,
43, 44...Detector, 45, 46...Low pass filter,
47...gate, 5...comparison circuit, CPR...comparator,
6...Control variable equalizer, IN...input, OUT...output.

Claims (1)

[Claims] 1 A carrier signal modulated by information and a high frequency subcarrier signal and a low frequency subcarrier signal having a predetermined amplitude ratio on the transmission side and having a higher frequency and a lower frequency than the above carrier signal and modulated by information, respectively. An equalizer that equalizes a transmission signal,
a control variable equalizer into which the transmission signal is input and which controls the amplitude of the transmission signal by an equalization characteristic controlled in accordance with a control signal to be described later; and a high-bandwidth carrier wave signal output from the control variable equalizer. , a high-frequency subcarrier signal extraction circuit and a low-frequency subcarrier extraction circuit that extract the low-frequency subcarrier signals and detect the amplitude of each signal, and compare the outputs of the respective extraction circuits to detect the high-frequency subcarrier signal and the low-frequency subcarrier signal. An equalizer comprising: a comparison circuit that sends a control signal to the control variable equalizer so that the amplitude ratio of the subcarrier signal is equal to that on the sending side.