JPH0271631A - Noise volume detection circuit - Google Patents

Abstract

PURPOSE:To always identify an input signal with the optimum threshold voltage by extracting noise components in the neighborhood of the threshold voltages of high level and low level in the input signal, finding difference between both components after averaging them, and utilizing the difference. CONSTITUTION:Signal components in the neighborhood of the threshold voltages VH, VM, and VL (where, it is assumed as VH>VM>VL) and the noise components V1, V2, and V3 are outputted by amplifying the input signal by an identification part having the threshold voltages VH, VM, and VL in an identification means 2. Next, the noise component V4 in the neighborhood of the voltage VM and the noise component V5 in the neighborhood of the voltage VL can be obtained by eliminating the signal component in the components V1 and V3 by a noise cemponent extraction means 3 by utilizing the component V2. An averaged noise component V6 in the neighborhood of the voltage VH and an averaged noise component V7 in the neighborhood of the voltage VL can be obtained by averaging those two noise components by an averaging means 4. Then, since a DC voltage corresponding to noise difference in the neighborhood of the H level and the L level of the input signal can be obtained by taking the difference between the components V6 and V7, it is possible to identify the input signal with the optimum thrashold voltage by utilizing the DC voltage.

Description

[Detailed Description of the Invention] [Summary] For example, regarding a noise amount detection circuit used in an identification circuit for identifying an input signal, even if noise is superimposed on the input signal, it is possible to always perform identification with an optimal threshold voltage. For the purpose of
Discrimination means for amplifying nearby noise components and signal components;
noise component extracting means for extracting noise components near the threshold voltages VM and VL using the noise components and signal components near the threshold voltage v8 output from the identification means; The apparatus is configured to have averaging means for averaging the outputs of the extraction means, taking a difference, and outputting the difference.

[Industrial application field]

The present invention relates to, for example, a noise amount detection circuit used in an identification circuit for identifying input signals.

Generally, an input signal that has attenuated and deteriorated through a transmission path is amplified to the extent that it is possible to determine the presence or absence of the signal. The identification result of 0 is output.

At this time, even if noise is superimposed on the human signal.

It is desirable to be able to discriminate with an optimal threshold voltage.

[Conventional technology]

FIG. 4 shows an example of a block diagram of a conventional identification circuit.

As shown in the figure, an input signal containing noise is applied to a + terminal of a comparator 11 after the noise is removed by a low-pass filter 12. On the other hand, a fixed threshold voltage VLk generated by dividing the voltage V by resistors R, , R2 is applied to one terminal. Therefore, the level of the input signal is compared with the threshold voltage VLk.

The comparison result will be output.

[Problem to be solved by the invention]

Here, as shown in FIG. 5, the amount of noise superimposed on the H level side and the L level side of the input signal is rarely equal to each other, and is larger on the H level side, for example.

Therefore, if the optimal threshold voltage of the comparator when no noise is superimposed on the input signal is V, then the optimal threshold voltage when noise is superimposed is VLh! is lower than Vthl. Also, since the amount of noise changes with time and temperature, the optimum threshold voltage also changes.

On the other hand, the low-pass filter 12 shown in FIG. 4 is for attenuating noise components above the cutoff frequency.

The amount of noise is not detected.

Therefore, there is a problem in that it is difficult to always set the threshold voltage to an optimal value in response to the varying amount of noise as described above.

SUMMARY OF THE INVENTION An object of the present invention is to always enable identification using an optimal threshold voltage even when noise is superimposed on an input signal.

[Means to solve ¥5B] FIG. 1 shows a block diagram of the principle of the present invention.

In the figure, 2 is a predetermined threshold voltage VH, VM +
A discrimination section to which VL is applied is a discrimination means for amplifying the noise component and signal component in the vicinity of the threshold voltage VH+νM +VL in the input signal, and 3 is the threshold voltage VM output from the discrimination means. This is a noise component extracting means for extracting noise components near the threshold voltages v, l and VL by using nearby noise components and signal components.

Further, reference numeral 4 denotes an averaging means for averaging the outputs of the noise component extracting means, taking the difference, and outputting the difference.

[Effect]

The present invention amplifies an input signal having an H level and an L level by a discrimination part having a threshold voltage VH+VM+VL in the discrimination means 2, and amplifies the signal component near the threshold voltage VH and the noise component v0. Signal component and noise component near threshold voltage VM v2. Signal component and noise component VM near threshold VL
Output. Note that the threshold voltages VH, VM, and VL are set near the H level, near the center, and near the L level of the input signal.

On the other hand, the noise superimposed on the input signal is H
It is superimposed on the level side and the L level side, and is at its minimum near the center between the H level and L level.

The output v2 of the discriminator is a signal component with a minimum noise component. Therefore, the noise component extraction means 3 uses the above v2 to remove the signal components in vl and v3.

Noise component v4 near threshold voltage VM. threshold voltage V
A noise component v5 near t is obtained.

When these two noise components are averaged by the averaging means 4, an averaged noise component VM near the threshold voltage VM and an averaged noise component v7 near the threshold voltage VL are obtained.

Therefore, if we take the difference between VM and VM, we get the difference between the noise components near the threshold voltage V□ and near the threshold VL, that is, the H of the input signal.
Since a DC voltage corresponding to the noise difference between the level and the L level is obtained, input signals can be identified using the optimum threshold voltage using this.

〔Example〕

FIG. 2 shows an example of a block diagram of an identification circuit to which the present invention is applied, and FIG. 3 shows an operation explanatory diagram of FIG. 2.

Here, the symbols on the left side of FIG. 3 indicate the waveforms of the portions with the same symbols in FIG. Further, the diagonal line downward to the right in FIG. 3 indicates noise on the H level side, and the noise downward to the left indicates noise on the L level side. Note that the comparators 21 to 23 are the constituent parts of the identification means 2, and the OR
31 and 32 are the constituent parts of the noise component extraction means 3, and the resistors R31 and R41 and the capacitor C are the constituent parts of the averaging means 4.The operation of FIG. 2 will be explained below with reference to FIG.

First, +Vll +VM +VL is a threshold voltage, which is applied from the reference voltage generator 5 to the comparator 21 . 22. Apply to one terminal of 23.

Next, the input signal shown in FIG.
23, the comparator 21 amplifies the vH neighborhood component of the input signal, the comparator 22 amplifies the VW neighborhood component of the input signal, and the comparator 23 amplifies the VM neighborhood component of the input signal.
Outputs as shown in Figures ■ to ■ can be obtained. Furthermore, the comparator 22
A part of the output of the comparator 23 becomes an inverted output.

Then, the OR gate 31 selects the output of the comparator 21 and the output of the comparator 2.
2 and the inverted output of comparator 23, and the OR gate 32 calculates the sum of the output of comparator 22 and the inverted output of comparator 23.
The signal components are canceled out by the outputs of gates 31 and 32, making it near +VH.

Only the noise component near Vt remains (see Figure 3 - ■, ■)
.

This is because, as mentioned above, the output of the comparator 22 is almost only a signal component due to the changing point of the input signal, and the operating points of the comparators 21 to 23 are set so that the levels of the amplified signal components are the same. This is because it is being done.

-OR game) 31.32 output is resistor R3+ R4+
The noise components near VM + near VL are averaged by an integrating circuit made up of capacitor C, and the difference is taken by a differential amplifier.

That is, a DC potential difference that does not correspond to the difference between the noise components on the H level side and the L level side of the input signal is applied to the reference voltage generator 5 (see (1) and (2) in FIG. 3).

Therefore, the reference voltage generator 5 shifts the three threshold voltages by an amount corresponding to the input DC potential difference so that this DC potential difference becomes 0.
R gate, integration circuit, differential amplifier 6, reference voltage generator 5
This is because they form a negative feedback loop. still,
The identified result is output from the comparator 22 (Fig. 3-
(See 〇).

That is, even if noise is superimposed on the input signal, it can always be identified using the optimal threshold voltage.

〔Effect of the invention〕

As described in detail above, the present invention has the effect that even if noise is superimposed on the input signal, it can always be identified using the optimum threshold voltage.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the principle of the present invention, Figure 2 is a block diagram of an identification circuit to which the present invention is applied, and Figure 3 is a block diagram of the identification circuit to which the present invention is applied.
The figure is an explanatory diagram of the operation of Fig. 2, and Fig. 4 is an example of a block diagram of a conventional identification circuit. Figure 1 Figure 2

Claims (1)

[Claims] At the identification portion to which predetermined threshold voltages V_H, V_M, and V_L are applied, the threshold voltage V in the input signal is
Near _H, V_M, V_L (H level of input signal > V_
H>V_M>V_L>L level of input signal)), a discriminating means (2) for amplifying the noise component and signal component of the input signal; The threshold voltages V_H and V
Noise component extraction means (3) for extracting noise components near _L
and averaging means (4) for averaging the outputs of the noise component extraction means and outputting the difference.