JPH0477125A - Emphasis/de-emphasis device - Google Patents

Abstract

PURPOSE:To supply a sufficient amount of emphasis without worrying about the generation of signal distortion by returning the output signal of a non-linear circuit added while positioned after the emphasis circuit successively through corresponding other reverse non-linear and de-emphasis circuits. CONSTITUTION:The recovery output signal of a transmission side post de- emphasis device is returned to the input edge of a P circuit 7 in the emphasis device, and an input signal in the past on this kind of emphasis circuit is formed based on the recovery output signal including the waveform distortion. In the reception side emphasis device, the correction processing, corresponding to the performance of the de-emphasis processing to the amplitude recovery output signal including the waveform distortion generated by the non-linear/reverse non-linear processing, is performed to the input signal before the emphasis processing in the emphasis device on the transmission side, and the waveform distortion generated in the recovery output signal caused by the non-linear/ reverse non-linear processing is offset and eliminated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention performs signal processing to improve the SN ratio during transmission of image signals, etc., and also uses nonlinear processing to reduce the signal amplitude increased by the signal processing within the dynamic range. Regarding an emphasis/de-emphasis device that suppresses the transmission signal to noise, in particular, it is possible to significantly increase the effect of improving the signal-to-noise ratio of a transmitted signal by applying a sufficient amount of emphasis without having to fear the occurrence of signal waveform distortion due to nonlinear processing. This is what I did.

(Summary of the Invention) The present invention selectively increases the relative amplitude of a signal component in a band where the S/N ratio is likely to deteriorate due to transmission line noise, restores the signal component after transmission, and In an emphasis/de-emphasis device that performs nonlinear/inverse nonlinear processing on the transmitted signal to suppress the signal amplitude within a predetermined dynamic range and restore it after transmission, the transfer function of the emphasis circuit exhibits minimum phase filter characteristics, and the When the transfer function of the emphasis circuit becomes the inverse transfer function, by placing a de-emphasis device having the same configuration as the receiving side after the transmitting-side emphasis device and feeding back the de-emphasis output signal to the emphasis device. , the signal distortion that occurs in the restored output signal is compensated in advance by nonlinear/inverse nonlinear signal processing, and a sufficient amount of emphasis is applied without fear of signal distortion, making the effect of improving the transmission signal S/N ratio better than before. It is designed so that it can be significantly increased compared to the previous model.

(Prior Art) Conventionally, in the above-mentioned type of emphasis/de-emphasis device, a nonlinear circuit is generally provided in order to suppress the signal amplitude of the large amplitude portion that occurs in the transmission signal due to emphasis within a predetermined dynamic range. In that case, an inverse nonlinear circuit exhibiting mutually opposite nonlinear characteristics for both transmission and reception is provided on the receiving side to prevent waveform distortion from occurring in the restored output signal.

(Problems to be Solved by the Invention) As described above, in the conventional emphasis/deemphasis device of this type, a nonlinear circuit and an inverse nonlinear circuit having opposite nonlinear characteristics are used in both transmission and reception. By using this, waveform distortion generally does not occur in the restored output signal. However, Fig. 5(a) shows the nonlinear characteristics on the transmitting side, Fig. 5(b) shows the inverse nonlinear characteristics on the receiving side, and Fig. 5(C) shows the overall amplitude characteristics of the transmitting and receiving side. In other words, if the nonlinear circuit on the transmitting side has a nonlinear characteristic that suppresses the amplitude of the large amplitude part of the signal, and the inverse nonlinear circuit on the receiving side has an inverse nonlinear characteristic that expands the signal amplitude of the suppressed part on the transmitting side, In the side inverse nonlinear circuit,
This increases the noise superimposed on the large amplitude portion of the transmission signal. Therefore, in order to suppress the signal amplitude of the transmission signal within a predetermined dynamic range and to avoid an increase in the noise superimposed on the large amplitude part, the amplitude characteristics of the transmitting side are shown in Fig. 6(a), and Figure 6(b) shows the amplitude characteristics of the receiving side, and Figure 6(c) shows the overall amplitude characteristics of the transmitting and receiving side.
One effective method is to have the receiving side have the opposite characteristics except for the clip area. However, when such amplitude characteristics are used, the transmission and reception cannot have complementary characteristics that are opposite to each other, so waveform distortion occurs in the input signal of the de-emphasis circuit on the receiving side, and the signal with the waveform distortion Since de-emphasis is applied to the signal, the waveform distortion is spatially spread, resulting in even greater deterioration of signal quality. Furthermore, even if the nonlinear circuit on the transmitting side is not made to have clipping characteristics, quantization errors will occur when the signal processing is digitized and the nonlinear circuit is constructed using digital circuits. In various types of emphasis de-emphasis devices, it has been difficult to sufficiently improve the signal-to-noise ratio without deteriorating signal quality.

(Means for Solving the Problems) An object of the present invention is to solve the above-mentioned conventional problems, and to suppress the signal amplitude of the large amplitude part increased by emphasis within a predetermined dynamic range. An emphasis/de-emphasis device that suppresses waveform distortion and applies a sufficient amount of emphasis without fear of signal distortion, greatly improving the S/N ratio of the transmitted signal compared to conventional methods. It is about providing.

In other words, the emphasis/deemphasis device of the present invention has a transfer function H38 that satisfies the minimum phase condition, where 0kn<1 and N is a positive integer, and a transfer function H (
In an emphasis/de-emphasis device in which a non-linear circuit and an inverse non-linear circuit corresponding to the non-linear circuit are added to an emphasis circuit and a de-emphasis circuit each exhibiting a filter characteristic of the inverse transfer function H' (g) for the transfer function H' (g), The output signal of the nonlinear circuit added after the emphasis circuit is sent to the emphasis circuit through another inverse nonlinear circuit and another deemphasis circuit corresponding to the inverse nonlinear circuit and the deemphasis circuit, respectively. It is characterized by the fact that it is designed to return home.

(Function) Therefore, in the emphasis/de-emphasis device of the present invention, there is no need to worry about the occurrence of signal distortion due to nonlinear processing for suppressing the signal amplitude of the large amplitude portion caused by emphasis within a predetermined dynamic range. By applying the amount of emphasis, it is possible to significantly increase the effect of improving the transmission signal-to-noise ratio compared to the conventional method.

(Example) The present invention will be described in detail below with reference to the drawings.

As mentioned above, the emphasis/de-emphasis device of the present invention is originally an emphasis circuit that exhibits a filter characteristic of a transfer function that satisfies the minimum phase condition where 0kn<1 and N is a positive integer, and its inverse. This is based on the assumption that de-emphasis circuits exhibiting filter characteristics with a transfer function that exhibits filter characteristics are used on the transmitting and receiving sides, respectively. Regarding the emphasis circuit, Japanese Patent Laid-Open No. 1-103.08 proposed by the present inventor
This is detailed in Publication No. 4. This type of emphasis circuit consists of the difference between the current input signal and the weighted addition of past input signals that have been sequentially delayed through unit delay elements, each multiplied by an appropriate coefficient. Emphasis processing is performed by multiplying the high-frequency signal component by a total coefficient related to each of the above-mentioned coefficients, and this type of de-emphasis circuit multiplies the above-mentioned total coefficient on the transmission signal that has undergone such emphasis processing. De-emphasis processing is performed by calculating the sum of a product multiplied by a coefficient opposite to the coefficient and a product obtained by sequentially delaying and weighting addition as described above.

Such a transfer function H(2) and the inverse transfer function H−′iZ
A conventionally well-known emphasis/de-emphasis device in which a non-linear circuit for suppressing the signal amplitude within a dynamic range and a non-linear circuit for its inverse purpose are added to an emphasis circuit and a de-emphasis circuit each having 1, respectively, satisfy the above conditional expression (1). .

In (2), for example, when kl·a and kg·b are used, the emphasis device and de-emphasis device are shown in FIGS. 3(a) and 3(b), respectively.

That is, in the emphasis device shown in FIG. 3(a), coefficients a are applied to sequentially delayed signals by unit delay elements (D) 8.10 and 12 by coefficient multipliers 9.11 and 13.
, b and -ab are added together by an adder 14, and the delay/weighted addition circuit (P
), and this circuit P forms the core of this type of emphasis/de-emphasis device. That is, in the conventional emphasis/deemphasis device of this kind shown in FIGS. 3(a) and 3(b), each coefficient unit, a nonlinear circuit, and an inverse nonlinear circuit are assembled in this sequential delay/weighted addition circuit P. The signal waveforms of each part are sequentially shown in FIGS. 4(a) and 4(b), with the same symbols attached to each part. Note that the signal waveforms of each part shown in FIG. 4(a) are the same as those of FIG. 5(a) in the nonlinear/inverse nonlinear circuit.

(b) and (C) are provided with nonlinear characteristics showing examples of transmitting side, receiving side, and overall characteristics, respectively, and the signal waveforms of each part shown in FIG. 4(b) are )
, (b) and (C) are provided with clipping characteristics showing examples of the transmitting side, receiving side, and overall characteristics, respectively.

Therefore, in the emphasis device shown in FIG. 3(a), the input signal of waveform A is supplied to the subtracter 1, and is also sequentially supplied to the same subtractor l via the delay/weighted addition circuit (P) 7. to form the difference between the two, and supply the difference signal having waveform B to the coefficient unit 2 to calculate the coefficient 1/(1-a)(1
-b) to form an emphasis circuit. Next, the emphasis output signal of waveform C is supplied to the nonlinear circuit 3 to extract the waveform output transmission signal. therefore,
In the emphasis device shown in FIG. 3(a), the input signal is subjected to emphasis processing by taking the difference between the current input signal and the past input signal via the circuit P.

On the other hand, in the de-emphasis device shown in FIG. 3(b), a transmission signal having a waveform is supplied to an inverse nonlinear circuit 15 to restore the amplitude characteristic, and an amplitude characteristic restored output signal having a waveform I is sent to a coefficient multiplier 16. The coefficient multiplier 2 on the transmitting side multiplies the coefficients (1-a) and (1-b) opposite to each other, and sends the multiplied output signal having a waveform J to the adder 7, which is sequentially delayed and has the same configuration as the transmitting side.・A de-emphasis circuit is configured by supplying the output signal to the weighted addition circuit (P) 18 and supplying the waveform output signal to the adder 7 and adding it to the original coefficient multiplication output signal, and de-emphasis output according to the waveform. The signal is taken out as a restored output signal of the emphasis/deemphasis device.

In this type of conventional emphasis/de-emphasis device having such a configuration, as shown in the sequential waveforms in FIG. This will cause significant signal quality deterioration. In order to prevent such signal waveform distortion from spreading, it is preferable that the input signal be subjected to signal processing in advance in the transmitting side emphasis device to compensate for and cancel out the waveform distortion occurring in the de-emphasis output signal.

Therefore, the configuration of the conventional emphasis/de-emphasis device of this type shown in FIGS. 3(a) and 3(b) is shown in FIG. 7(a) in a simplified manner. On the other hand, as shown in FIG. 7(b), there is a de-emphasis device having exactly the same configuration as the receiving-side de-emphasis device, that is, an inverse nonlinear circuit I9, a coefficient multiplier 20, an adder 21, and a sequential delay/weighted addition circuit (P ) 22 is provided after the transmitting-side emphasis device. The de-emphasis output signal having the waveform L(M) of the de-emphasis circuit in such a post-de-emphasis device has the same waveform as the restored output signal having the waveform of the receiving de-emphasis device, and is non-linear.
If there is no remaining waveform distortion due to inverse nonlinear signal processing, the input signal of waveform A will have the same waveform, but if there is distortion in the signal waveform, the waveform distortion will propagate one after another.

Therefore, in order to pre-compensate the input signal for the waveform distortion by applying emphasis processing to the next input signal based on the restored output signal containing such waveform distortion, the method shown in FIG. 7(C) is shown in FIG. As shown, the restored output signal of the post-de-emphasis device on the transmitting side is fed back to the input terminal of the P circuit 7 in the emphasis device, and the past input signal described above for this type of emphasis circuit is converted into a signal containing waveform distortion. It is configured to be formed based on the restored output signal.

In a configuration with such a feedback connection, if no waveform distortion occurs due to nonlinear/inverse nonlinear signal processing, the seventh
The circuit operation is exactly the same as that of the conventional configuration of this type of emphasis/de-emphasis device shown in Figure (a), but when waveform distortion occurs, the past input signal containing the waveform distortion is used. Emphasis processing will be applied to the current input signal. In other words, compensation processing corresponding to de-emphasis processing being performed on the amplitude characteristic restoration output signal containing waveform distortion caused by nonlinear/inverse nonlinear processing in the receiving-side de-emphasis device is performed before the emphasis processing in the transmitting-side emphasis device. As a result, the waveform distortion occurring in the restored output signal is canceled out by the nonlinear and inverse nonlinear processing.

Therefore, in the configuration of FIG. 7(C), the output signal waveform H of the P circuit 7 in the emphasis device and the output signal waveform of the P circuit 22 in the post-de-emphasis device are the same waveform, so both P circuits have the same waveform. Circuits 7 and 22 can be combined into a single sequential delay and weighted addition circuit (P),
The final circuit configuration is as shown in FIGS. 1(a) and 1(b).

FIG. 1(a) shows a configuration example of the transmitting side emphasis device in the emphasis/deemphasis device of the present invention made through the above process, and FIG. 1(b) shows a configuration example of the receiving side deemphasis device. Examples of the signal waveforms of each part are sequentially shown in FIG. 2 with the same symbols assigned to each part.

As mentioned above, in the emphasis device shown in FIG. 1(a), the P circuit 22 in the circuit configuration shown in FIG. 7(c) also serves as the P circuit 7, and the inverse nonlinear circuit 19 is replaced by , the coefficient unit 20 is set to 5, and the adder 21 is set to 6.
They are each expressed as follows.

Note that the waveform distortion remaining in the restored output signal of the emphasis/de-emphasis device of the present invention shown in FIGS. 1(a) and (b) is increased to a large amplitude by the emphasis processing, as can be seen from the signal waveform shown in FIG. The waveform distortion does not spread spatially, and the remaining waveform distortion appears in the large amplitude part, so it is difficult to perceive, and it actually impairs the quality of the restored output signal. It doesn't reach.

(Effects of the Invention) As is clear from the above explanation, in this type of emphasis/de-emphasis device, conventionally, nonlinear processing is performed to suppress the signal amplitude of the large amplitude part generated by emphasis processing within a predetermined dynamic range. However, when nonlinear processing is performed using clipping characteristics to avoid deterioration of the S/N ratio in large amplitude parts, the nonlinear and inverse nonlinear processing do not complement each other, resulting in waveform distortion. In contrast, in this type of emphasis/de-emphasis device according to the present invention, waveform distortion caused by nonlinear processing is prevented from spreading spatially, and waveform distortion remains only in large amplitude parts. In this way, a special effect can be obtained in that the quality of the reconstructed output signal is not substantially degraded due to such waveform distortion.

[Brief explanation of the drawing]

1(a) and (b) are block diagrams showing configuration examples of an emphasis device and a de-emphasis device according to the present invention, respectively, and FIG. 2 is a waveform diagram sequentially showing examples of signal waveforms of each part in the same configuration example. , FIGS. 3(a) and (b) are block diagrams showing the configurations of a conventional emphasis device and a de-emphasis device, respectively, and FIGS. 4(a) and (b) similarly show signal waveforms of each part in the conventional configuration. Waveform diagrams are shown sequentially for cases in which signal processing is performed using nonlinear characteristics and clipping characteristics. Figures 5 (a), (b), and (c) show examples of characteristics of nonlinear circuits on the transmitting side, receiving side, and overall transmitting and receiving side. Figures 6(a), (b) and (c) are characteristic curve diagrams respectively showing other characteristic examples of nonlinear circuits for the transmitting side, receiving side, and overall transmission/reception; Figure 7(a) ), (b) and (c) are block diagrams sequentially showing the process of sequentially adding circuits to the conventional device shown in FIG. 3 to arrive at the device of the present invention shown in FIG. 1. ■...Subtractor 2, 5.9.11.13.16.20...Coefficient unit 3.
...Nonlinear circuit 4, 15.19...Inverse nonlinear circuit 6, 14.17.21...Adder 7, 18.22...Sequential delay/weighted addition circuit (P) 8
, 10.12... Unit delay element. C Yu (1, L; Figure 3 Conventional ESO 77/Z TIF 77/λMl's 11 stroke (b)-rE Soft?/S device-1 and Figure 7 Circulation 3 illustrated conventional v1. &iA1 country Hokuhonsuke eB separation to Jbuki^'s change! (l) - M3Xhocn (11 days ay!

Claims (1)

[Claims] If 1, 0kn<1 and N is a positive integer, there are ▲ mathematical formulas, chemical formulas, tables, etc. ) is an emphasis/de-emphasis system in which a non-linear circuit and an inverse non-linear circuit corresponding to the non-linear circuit are added to an emphasis circuit and a de-emphasis circuit each exhibiting filter characteristics of an inverse transfer function H^-^1_(_2_) for the non-linear circuit. In the apparatus, the output signal of the nonlinear circuit added after the emphasis circuit is sequentially passed through another inverse nonlinear circuit and another deemphasis circuit corresponding to the inverse nonlinear circuit and the deemphasis circuit, respectively. An emphasis/de-emphasis device characterized by feeding back to an emphasis circuit.