JPS61150479A - Nonlinear signal processor - Google Patents

Abstract

PURPOSE:To obtain a nonlinear emphasis device and a nonlinear de-emphasis device which are quite different from each other just by changing the coefficient of a converting circuit and then to share other parts just with the replacement of a ROM when said both devices are applied to a VTR and the switching is carried out between NTSC and PAL systems. CONSTITUTION:A differential circuit 10 extracts the variation component per unit time of signals, and a delay circuit 14 delays the signal by a single unit time. The coefficient R is set for compression of the signal through a converting circuit 11. Then two nonlinear emphasis devices of different characteristics are obtained just by changing only the coefficient R of the circuit 11. Thus other component parts can be used in common. The circuit 11 is actually formed with a ROM. Then it is possible to obtain a nonlinear emphasis device coping with the NTSC and PAL systems just by using ROMs of different contents with other circuits used as conventional.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a nonlinear signal processing device applied to video tape recorders (abbreviated as VTR) and the like.

Prior art The inventors of the present invention previously filed a patent application in 1983 as a nonlinear signal processing device.
-191018 is proposed.

Figure 3 shows a block diagram of the nonlinear signal processing device proposed earlier. 1 is an input terminal, and 2 is a differential circuit that extracts the change per predetermined time in the signal obtained from input terminal 1. . 3 is a conversion circuit that nonlinearly compresses the amplitude of a signal according to its amplitude; 4 is a delay circuit that delays the output of conversion circuit 3 by a predetermined time; and 6 is a conversion circuit that adds the output of difference circuit 2 and the output of delay circuit 4. a first addition circuit leading to circuit 3;
6 is a multiplication circuit that multiplies the output of the conversion circuit 3 by a predetermined value, 7 is a second addition circuit that adds the output of the multiplication circuit 6 to the signal obtained from the input terminal 1, and 8 is an output terminal.

The nonlinear signal processing device configured as described above is generally called a nonlinear emphasis device, and hereinafter referred to as a nonlinear emphasis device.

The operation will be explained below using a Z transformation formula representing a discrete time system.

First, it is assumed that the difference circuit 2 extracts the amount of change in the signal per unit time, and the delay circuit 4 delays the signal by one unit time. Let F be the coefficient by which the signal is compressed by the conversion circuit 3, and A be the multiplier by which the signal is multiplied by the multiplication circuit 6. However, the coefficient F of the conversion circuit 3 is constant if the amplitude of the signal input to the conversion circuit 3 is smaller than a certain reference value, but if a signal with an amplitude larger than the reference value is input, the coefficient F becomes smaller. In other words, the coefficient F is set so that nonlinear compression can be performed such that the larger the amplitude of the input signal, the larger the compression ratio.

From the above, for the conventional nonlinear emphasis device shown in FIG. 3, the transfer function H(z) can be determined using a two-conversion formula in which one unit time delay is represented by Z''', as shown in the following formula.

Here, since the second term on the right side of equation (1) becomes a high-pass filter, H(z) works as an emphasis device that emphasizes only the high frequency range. Further, at this time, the time constant is determined by F, but the amount of emphasis is determined by A and F. Now, regarding the differential circuit 2, it is itself a high-pass filter, but since it is unrelated to the signal level of the input signal,
The signal level is transmitted to the conversion circuit 3 as is. Therefore, even if signals have the same frequency components, if the signal level is higher than a certain standard, the coefficient F of the conversion circuit 3 will compress the signal at a higher compression rate. In other words, the nonlinear emphasis device shown in Figure 3 responds to input signals in the low frequency range regardless of the signal level, but for input signals in the high frequency range, the greater the signal level, the greater the amount of emphasis. It shows a nonlinear emphasis characteristic with a small response.

Next, the coefficient F of the conversion circuit 3 and the multiplier A of the multiplication circuit 6 will be explained.

Emphasis characteristics that emphasize only the high frequency range can be expressed by the following equation using two conversion equations.

Here, P and Q are values determined by the time constant of the emphasis characteristic and the amount of emphasis. In the nonlinear emphasis characteristic, not only Q, which determines the amount of emphasis, but also the time constant P, change nonlinearly with respect to the signal level of the input signal. Therefore, equation (2) is approximated by a configuration using one nonlinear coefficient F, as in equation (1). In other words, (2).

From formula (1), P and Q are P≧F ・・・・・・・・・
(3) Q≧A@F ・・・・・・
... Since it is expressed as (4), as an approximate expression, A
With Q≧AψP as a constant, Q≧AψP ・・・・・・・・・
・(5) becomes.

As described above, the sub-emphasis, which is a non-linear emphasis device used in a VTR, has achieved the connection characteristics between the sub-emphasis and the main emphasis with the non-linear emphasis device shown in FIG.

Still, the transfer function H-1(z) of the nonlinear de-emphasis device, which exhibits the inverse characteristics of the nonlinear emphasis device, is given by equation (1), so in the configuration shown in FIG. It is replaced with a subtraction circuit that subtracts the signal obtained from the multiplication circuit 6 from the signal obtained by the conversion circuit 3.
By selecting the coefficient F' of , and the multiplier A' of the multiplier circuit 6, the nonlinear emphasis device shown in FIG. 3 also operates as a nonlinear deemphasis device.

Problems to be Solved by the Invention However, in the above configuration, if it is desired to change the characteristics of the nonlinear emphasis device to a different characteristic, not only the coefficient F of the conversion circuit 3 but also the multiplier circuit A must be replaced. . This is used when switching the VTR's emphasis characteristics between NTSC and PAL systems.
In the configuration shown in FIG. 2, when switching between only the main emphasis and the case where the sub-emphasis and main emphasis are connected, it is necessary to prepare two types of conversion circuits 3 and two types of multiplication circuits 6 and switch between them.

For example, the main emphasis only characteristic Emo(z)
The characteristic Em1(Z) of the connection between the sub-emphasis and the main emphasis is expressed as the following two equations from equation (2) above.

These two equations are described above (using equation 11, the coefficient F and the multiplier A are
F for main emphasis only characteristics. and Ao,
If Fl and A are the characteristics of the connection between the sub-emphasis and the main emphasis, then F, although they have the same configuration. , Fl Still A. .

Means for solving the problem that A1 cannot be shared and the circuit scale cannot be reduced.The present invention provides a differential circuit that extracts changes in an input signal per predetermined time. , a conversion circuit that compresses the amplitude of the signal by the amplitude and outputs the compressed signal, and a first circuit that multiplies the signal by a constant by a predetermined value.
a multiplication circuit, a first addition circuit that adds the output of the first multiplication circuit and the output of the conversion circuit, a delay circuit that delays the output of the first addition circuit for a predetermined time, and the difference circuit. a second adder circuit which adds the output of this delay circuit to the output of the converter circuit and guides it to the converter circuit and the first multiplier circuit; a second multiplier circuit which multiplies the output of the converter circuit by a constant by a predetermined value; The nonlinear signal processing device includes an arithmetic operation circuit that performs arithmetic operations on the output of the second multiplication circuit and the signal input to the difference circuit and outputs the result.

Effect The present invention uses the above-described configuration to feed back a signal obtained by adding a signal multiplied by a nonlinear coefficient and a signal multiplied by a certain number through a delay circuit, thereby allowing only the nonlinear coefficient to be processed while the other configurations remain unchanged. Just by switching, you can obtain two different nonlinear emphasis characteristics and two different nonlinear deemphasis characteristics, so V
If you use it when switching between NTSC and PAL systems in a TR, or switching between main emphasis only characteristics and main emphasis and sub-emphasis connection characteristics, you can use a nonlinear signal processing device with many common parts and a small circuit size. realizable.

Embodiment FIG. 1 shows a block diagram of a nonlinear signal processing apparatus in a first embodiment of the present invention. In Figure 1,
Reference numeral 9 represents an input terminal, and 1o represents a differential circuit which extracts a change in the signal obtained from the input terminal 9 per predetermined time. 1
1 is a conversion circuit that compresses the amplitude of a signal by the amplitude and outputs it; 12 is a first multiplication circuit that multiplies the signal by a predetermined value; and 13 is the output of the first multiplication circuit 12 and the conversion circuit 1.
a first adder circuit which adds the output of the first adder;
16 is a second multiplication circuit that multiplies the output of the conversion circuit 11 by a constant by a predetermined value;
17 is a third addition circuit that adds the output of the second multiplication circuit 16 to the signal obtained from the input terminal 9; 18 is an output terminal.

The nonlinear signal processing device of this embodiment configured as described above is generally called a nonlinear emphasis device, and its operation will be described below as the nonlinear emphasis device.

First, it is assumed that the difference circuit 10 extracts a change in the signal per unit time, and the delay circuit 14 delays the signal by one unit time. Let R be the coefficient by which the signal is compressed by the conversion circuit 11, B be the multiplier multiplied by the first multiplication circuit 12, and C be the multiplier multiplied by the second multiplication circuit 16.
shall be. Here, the transfer function G(z) of the nonlinear emphasis device in FIG.
When expressed in the Z transformation formula using , it becomes as follows.

Since the second term on the right side of equation (9) is a high-pass filter, G(z) exhibits an emphasis characteristic that emphasizes only the high frequency range, and its time constant is B+R and the amount of emphasis is C-H. Determined by Further, although the differential circuit 10 itself is a high-pass filter, it is unrelated to the signal level of the input signal, so it is thought that the signal level of the input signal is directly guided to the conversion circuit 11, so the frequency is the same. Even if a signal has a component, if the signal level is thicker than a certain standard, the coefficient H of the conversion circuit 11 compresses the signal at a higher compression rate. That is, the embodiment shown in FIG. 1 exhibits nonlinear emphasis characteristics equivalent to the conventional nonlinear emphasis device shown in FIG. 3 described above.

The emphasis characteristic that emphasizes only the high frequency range is expressed by the above-mentioned equation (2), and P and Q, which determine the time constant and the amount of emphasis, are
Using the three formulas R, B, and C, P main B + R...
・・・・・・ aa QmiC@R・・・・・・・・・ αQ Therefore, as an approximate formula, with B and C as constants, Q-principal CP = BC・Rule・・・・ α・becomes. From the above, the nonlinear characteristics are approximated by the coefficient R, but the coefficient R
is not a nonlinear coefficient that changes depending on the signal level, but
If the value is always constant, it is clear that the nonlinear emphasis device shown in FIG. 1 works as a so-called linear emphasis device that emphasizes only the high frequency range regardless of the signal level of the input signal.

Next, consider a case where the nonlinear emphasis characteristic in the embodiment shown in FIG. 1 is replaced with a different characteristic.

Now, let us consider the transfer functions that exhibit two different characteristics as described above (9
), Kmo(z), Eml(z)) of the 00 formula are used. (9) of the coefficient R9 multiplier B and C of the embodiment of FIG.
The values for the equations are Ro, Bo, C0, respectively, and the values for the 00 equation are R,, B1 . If it is C1, then by the approximation formula of α0 formula (1 is also Po?Bo+Ro from formula 69...
・αηQo みCO・Ro ・・・・
...... (To) P1 Mi B1 + R1...
・It can be approximated as α9Q1miC1・R1, , , , , , . However, from formula 00, Bo, C0°B1. C1
is a constant, and R8 and R1 are nonlinear coefficients.

Next, in formula αη~(1), let Ro and R1 be Bo, C0 and B1. C1 is obtained from αη~(a) formula, and as a result, the following two formulas are obtained.

Bo=B1 ・・・・・・・・・
■Co=C1... (2) From the above results, in the configuration of the nonlinear emphasis device of the embodiment shown in FIG. This can be realized by changing only the coefficient R of , and the other configurations can be shared. Especially for VTRs, the television signal is NTSC or P.
There are AL systems, etc., in which a nonlinear emphasis device is used in the signal processing section. If the embodiment of the present invention shown in FIG. 1 is used for the nonlinear emphasis characteristic, the conversion circuit 11
can actually be realized using a ROM (IJ-only memory), so by simply using a ROM with different contents and leaving the other circuits as they are, a nonlinear emphasis device compatible with NTSC and PAL can be configured. can.

Next, consider the nonlinear de-emphasis device.

Since the characteristics of nonlinear de-emphasis are the inverse characteristics of the nonlinear emphasis characteristics, the transfer function G''''(z) showing the inverse characteristics to the transfer function G(z) of the nonlinear emphasis device in FIG.・・・・・・・・・ It becomes a kan. In addition to the nonlinear de-emphasis replacement indicated by the characteristics of this Kan type, the coefficient R' of the conversion circuit 11 and the second multiplier circuit 1
This can be realized by setting the multiplier C' of 6 to be C'. At this time, the multiplier B of the multiplier circuit 12 is equal for the nonlinear emphasis device and the nonlinear deemphasis device.

Although the embodiment of FIG. 1 has been described above, the coefficients, multipliers, etc. described above may be negative numbers.

At this time, the conversion circuit 11 is relatively easy to implement because it is implemented using a ROM, but it may be necessary to add a circuit to the multiplication circuit. Therefore, even when operating as a nonlinear emphasis device, the third adder circuit 1
It is quite conceivable and easy to replace 7 with a subtraction circuit. The same can be said of nonlinear de-emphasis devices.

FIG. 2 is a block diagram showing the configuration of a conversion circuit of a nonlinear signal processing device according to a second embodiment of the present invention. A configuration in which 11 is replaced with the conversion circuit shown in FIG. 2 constitutes the second embodiment. In FIG. 2, 19 is an input terminal of the conversion circuit, 2o is a nonlinear circuit that nonlinearly compresses the signal obtained from the input terminal 19 according to its amplitude, and 21 is a constant for the signal obtained from the input terminal 19 at a predetermined value. A multiplication circuit 22 is a nonlinear circuit 20 and a multiplication circuit 2.
1 is a switch for selecting one of the two outputs, and 23 is an output terminal of this conversion circuit.

In the above configuration, when the switch 22 is set to the nonlinear circuit 20 side, the characteristic shows a nonlinear emphasis characteristic,
When applied to the multiplier circuit 21 side, the characteristic exhibits a linear emphasis characteristic. This is used for the main emphasis and sub-emphasis of the VTR.

First, coefficients and multipliers are set using the QB-(to) formula so that the characteristics when the switch 22 is on the nonlinear circuit 20 side and on the ξ path 21 side match the characteristics of only the main emphasis. As a result, VTR' emphasis%
tl: Switching between the combined characteristics of the main emphasis and sub-emphasis and the characteristics of only the main emphasis can be performed only by switching the switch 22.

Moreover, according to the configuration in which the conversion circuit 11 in FIG. 1 is replaced with the conversion circuit in FIG. 2, and the third addition circuit 17 in FIG. A switch that exhibits the inverse characteristics of the nonlinear emphasis device using the conversion circuit shown in FIG. 2 by setting the multiplier of the circuit 21 and the coefficient of the second multiplication circuit 16 of FIG. A nonlinear de-emphasis device can be constructed that can switch between the combined characteristics of emphasis and sub-emphasis and the characteristics of only main emphasis.

By configuring the conversion circuit shown in Fig. 2 above, it is very effective because the connection characteristics of the main emphasis characteristic domain emphasis and sub-emphasis, and the linear characteristics of the main domain can be switched with a smaller circuit scale.
By replacing the multiplier circuit 21 with a nonlinear circuit having different characteristics from the nonlinear circuit 20 in the conversion circuit shown in FIG.
It is also easy to configure the nonlinear emphasis device and nonlinear de-emphasis device corresponding to L to be switched by a switch.

Furthermore, in the case where the coefficients of the nonlinear circuit 20 and the multipliers of other multiplication circuits are negative numbers, as explained in the embodiment of FIG. The circuit 17 may be replaced by a subtraction circuit, and vice versa if the embodiment operates as a non-linear de-emphasis device.

Finally, in the configuration of FIG. 1 of the present invention, the difference circuit 10 extracts the change per unit time of the signal and the delay circuit 14 is set to delay the signal by 1 unit time, but these changes are calculated as the change per 2 unit time. Even if the differential circuit 10 takes out the minute, the delay circuit 14 delays 2 unit times, and even if these extend over a time longer than 2 units, the coefficients of the conversion circuit and the multiplication circuit are adjusted so that the transfer function shows the characteristics to be approximated. By setting the multiplier, a nonlinear signal processing device can be realized with exactly the same configuration. Furthermore, even if an extra delay circuit is inserted into the configuration of the embodiment of the present invention in terms of the calculation speed of the actual circuit with respect to the conversion circuit, multiplication circuit, and other circuits, the transfer function of the device will eventually change. If G(z) of the α4 formula and G-1 of the fourth formula (→), it is clear that the nonlinear signal processing device has the same configuration as the present invention in terms of digital signal processing technology. be.

As described in detail, according to the present invention, two completely different nonlinear emphasis characteristics can be realized by simply changing the coefficients of the conversion circuit, and a nonlinear de-emphasis characteristic, which is the opposite characteristic of these two characteristics, can be realized. Since the present invention can also be realized in a VTR, when switching between the NTSC and PALO systems, all that is required is to replace the ROM mounted as a conversion circuit, and the other parts become common, which has a great practical effect. Furthermore, by configuring the conversion circuit to switch between a nonlinear coefficient and a constant multiplier and multiply the signal, it is possible to realize two circuits for a VTR's main emphasis and sub-emphasis with the configuration of the present invention. Two circuits, switch emphasis and sub-emphasis, can also be realized with the same configuration. As a result, when the device is integrated into an IC, the circuit can be shared, and the circuit scale can be significantly reduced, which has a very large practical effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a nonlinear signal processing device according to one embodiment of the present invention, FIG. 2 is a block diagram of a conversion circuit used in a nonlinear signal processing device according to another embodiment of the present invention, and FIG. 3 is a block diagram of a nonlinear signal processing device according to another embodiment of the present invention. FIG. 2 is a block diagram of the proposed nonlinear signal processing device. 10...Differential circuit, 11...Conversion circuit, 12゜16.21...Multiplication circuit, 13,15
．． 17...Addition circuit, 14...Delay circuit, 20...Nonlinear circuit, 22...Switch.

Claims (4)

[Claims] (1) A difference circuit that extracts the change in the input signal per predetermined time, a conversion circuit that nonlinearly compresses the amplitude of the signal according to the amplitude and outputs it, and a first multiplication that multiplies the signal by a constant by a predetermined value. a first addition circuit that adds the output of the conversion circuit and the output of the first multiplication circuit; a delay circuit that delays the output of the first addition circuit for a predetermined time; a second addition circuit that leads the output of the difference circuit to the conversion circuit and the first multiplication circuit; a second multiplication circuit that multiplies the output of the conversion circuit by a constant by a predetermined value;
A nonlinear signal processing device comprising: an arithmetic operation circuit that performs an arithmetic operation on the output of the second multiplication circuit and the input signal input to the difference circuit and outputs the result. (2) The nonlinear signal processing according to claim 1, wherein the arithmetic operation circuit is constituted by an addition circuit that adds the output of the second multiplication circuit to the input signal input to the difference circuit and outputs the result. Device. (3) The nonlinear signal processing according to claim 1, wherein the arithmetic operation circuit is constituted by a subtraction circuit that subtracts the output of the second multiplication circuit from the input signal input to the difference circuit and outputs the result. Device. (4) The conversion circuit includes a nonlinear circuit that nonlinearly compresses the signal input to the conversion circuit according to its amplitude and outputs it, a multiplication circuit that multiplies the signal input to the conversion circuit by a constant by a predetermined value, and this nonlinear circuit. Claims 1, 2, or 3, characterized in that the converter is comprised of a switch that selects one of the output of the circuit and the output of the multiplier circuit and outputs the output of the conversion circuit. Nonlinear signal processing device.