JPH03211920A - Line equalizer - Google Patents

Abstract

PURPOSE:To keep a convergence time almost constant and to attain stabilized convergence decision by independently executing peak value control by a flat gain variable circuit, and inter-code interference control by a variable equalizer. CONSTITUTION:The output of a flat gain variable circuit 2 is inputted to a peak value detector 4 and the gain of the flat gain variable circuit 2 is controlled by a direct current amplifier 5. A variable equalizer 3 is set in the rear step of the flat gain variable circuit 2, the output is inputted to an inter-code interference detector 6 and the inter-code interference detector 6 controls the gain of the variable equalizer 3. Thus, since the inter-code interference detector 6 controls the gain after the flat gain variable circuit 2 is convergent, inter-code interference can be made zero without changing a peak value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a line equalizer that compensates for line loss in digital transmission.

(Prior Art) FIG. 2 is a block diagram showing a line equalizer using a conventional variable equalization method disclosed in Japanese Patent Publication No. 64-8936, for example. In the figure, (1) is an input terminal; 2) is a flat gain variable circuit in which the frequency characteristic of the amount of gain change is flat, (
3) is a variable equalizer whose frequency characteristics have the same slope as the loss characteristics of the line, (4) is a peak value detector that detects the peak value of the output signal of the variable equalizer (3), and (5) is the peak value detector (4
) is a DC amplifier that controls the gain of the variable equalizer (3) by comparing the peak value detected by the reference value with the reference value so that the peak value and the reference value match. ), an intersymbol interference detector that detects intersymbol interference in adjacent time slots of the output signal and outputs a corresponding signal to control the gain of the flat gain variable circuit (2), (7) is an output terminal. .

Next, the operation will be explained with reference to the waveform diagram shown in FIG. A received signal input from an input terminal (1) passes through a variable flat gain circuit (2) and a variable equalizer (3) and is output from an output terminal (7). At this time, the peak value detector (4) detects the peak value of the output signal of the variable equalizer (3), and the DC amplifier (5) detects the peak value of the output signal of the variable equalizer (3) so that the peak value becomes equal to the reference value. (3) Control the gain. Here, the frequency characteristics of the variable equalizer (3) completely correspond to the line loss, so if the amplification and time width of the transmitted pulse waveform are normal, when the peak value and the reference value match, Intersymbol interference becomes 0 (3rd
(See waveform A in the figure). However, for example, if the amplification of the transmitted pulse waveform is larger than the normal value, the variable equalizer (3
) and the line loss no longer correspond to each other, so if the gain of the variable equalizer (3) is controlled to match the peak value and the reference value, intersymbol interference will occur (waveform B in Figure 3). reference). Then, the output of the intersymbol interference detector (6) lowers the gain of the variable flat gain circuit (2), and the output of the variable equalizer (3) lowers the gain of the variable flat gain circuit (2).
) becomes small, so the peak value detection circuit (4)
The gain of the variable equalizer (3) is increased by the DC amplifier (5). By repeating this series of operations, the combination of gains of the flat gain variable circuit (2) and variable equalizer (3) is finally determined, with zero intersymbol interference and the peak value and reference value. be done. Similar results can also be obtained when the amplitude of the transmitted pulse waveform is small (see waveform C in FIG. 3).

[Problem to be solved by the invention]

Since the conventional line equalizer is configured as above,
There are problems in that the peak value and intersymbol interference must be controlled simultaneously, the convergence time is not constant, and it is difficult to determine convergence.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a line equalizer that performs peak value control and intersymbol interference control independently and converges more stably.

[Means to solve the problem]

A line equalizer according to the present invention includes a flat gain variable circuit whose frequency characteristic of gain change is flat, a peak value detector that detects the peak value of an output signal of the flat gain variable circuit, and a DC amplifier that compares the peak value detected by the peak value detector with a reference value and controls the gain of the variable flat gain circuit so that the peak value and the reference value match; and an output signal of the variable flat gain circuit. A variable equalizer whose frequency characteristic of gain change has the same slope as the loss characteristic of the line, and intersymbol interference in adjacent time slots of the output signal of this variable equalizer are detected, and the intersymbol interference is detected manually. and an intersymbol interference detector that controls the gain of the variable equalizer so as to make it zero.

[Effect]

The line equalizer in the present invention inputs the output of the variable flat gain circuit to a peak value detector, controls the gain of the variable flat gain circuit with a DC amplifier, and has a variable equalizer installed after the variable flat gain circuit. By manually inputting the output to the intersymbol interference detector, the intersymbol interference detector controls the gain of the variable equalizer. Therefore, after the flat gain variable circuit converges, it is controlled by the intersymbol interference detector to reduce the intersymbol interference to zero without changing the peak value.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) is an input terminal, (2) is a flat gain variable circuit whose frequency characteristic of gain change is flat, and (3) is a variable equalizer whose frequency characteristic has the same slope as the loss characteristic of the line. (4) is a peak value detector that detects the peak value of the output signal of the flat gain variable circuit (2), and (5) is a peak value detector (4).
A DC amplifier (6) is a variable equalizer (3) that controls the gain of the flat gain variable circuit (2) by comparing the detected peak value with a reference value so that the peak value and the reference value match. An intersymbol interference detector (7) is an output terminal for detecting intersymbol interference in adjacent time slots of the output signal of and detecting a signal corresponding to the intersymbol interference to control the gain of the variable equalizer (3).

Next, the operation will be explained. A received signal input manually from the input terminal (1) is input to the flat gain variable circuit (2). The output of the flat gain variable circuit (2) is the peak value detector (4)
The DC amplifier (5) controls the gain of the flat gain variable circuit (2) so that the peak value is equal to the reference value.

The output signal of the flat gain variable circuit (2) whose peak value coincides with the reference value is input to the variable equalizer (3). Variable equalizer (
The output signal of 3) is input to the intersymbol interference detector (5),
The gain of the variable equalizer (3) is controlled so that intersymbol interference becomes zero. At this time, the gain of the variable equalization amount (3) corresponds only to the slope portion of the line loss, and is set so that even if the gain is changed, only the intersymbol interference value changes and the peak value does not change.

With this configuration, the flat gain variable circuit (2)
to match the peak value with the reference value, and then a variable equalizer (3
) can reduce intersymbol interference to 0.

In the above embodiment, the gain of the variable flat gain circuit (2) is controlled by an analog signal using the DC amplifier (5), but the gain may be controlled by a digital signal.

(Effects of the Invention) As described above, according to the present invention, since the peak value control by the variable flat gain circuit and the intersymbol interference control by the variable equalizer are performed independently, the convergence time is also approximately constant. This has the effect of making a more stable convergence determination possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the amount of line equalization according to a partial embodiment of the present invention, FIG. 2 is a block diagram of a conventional line equalizer,
FIG. 3 is an equalized waveform diagram. (1) is the input terminal, (2) is the flat gain variable circuit, (3
) is a variable equalizer, (4) is a peak value detector, (5) is a DC amplifier, (6) is an intersymbol interference detector, and (7) is an output terminal. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A flat gain variable circuit whose frequency characteristic of gain change is flat, a peak value detector that detects the peak value of the output signal of this flat gain variable circuit, and a peak value detected by this peak value detector. a DC amplifier that controls the gain of the flat gain variable circuit so as to match the peak value and the reference value by comparing the peak value and the reference value;
A variable equalizer which receives the output signal of the above flat gain variable circuit as input and whose frequency characteristic of gain change has the same slope as the loss characteristic of the line, and intersymbol interference between adjacent time slots of the output signal of this variable equalizer. and an intersymbol interference detector that controls the gain of the variable equalizer so as to reduce intersymbol interference to zero.