JPH0583164A - Reception circuit for transmission signal - Google Patents

Abstract

PURPOSE:To improve the signal transmission quality by implementing optimum amplitude equalization. CONSTITUTION:Pre-filters 2, 10 in a digital line circuit 1 and a terminal equipment 9 connected by a transmission line eliminate a noise component from a received transmission signal (setting equalization characteristic) and outputs the result as a 1st signal. Automatic gain control circuits 3, 11 output information representing a gain to make the amplitude of the 1st signal constant and a 2nd signal whose amplitude is made constant. Equalizer circuits 4, 12 equalize a frequency characteristic of the 2nd signal according to a setting signal (a) and outputs the result as a 3rd signal. Waveform comparator circuits 6, 14 calculate a difference between the 3rd signal and a reference value at which a data error to be identified by data identification circuits 5, 13 is minimized and outputs the result as difference information. Equalizer control circuits 7, 15 output the setting signal (a) according to the gain information and the difference information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission signal receiving circuit, and more particularly to a transmission signal receiving circuit for transmitting between a digital line circuit and terminals.

[0002]

2. Description of the Related Art In a conventional transmission signal receiving circuit, as shown in FIG. 2, a terminal 9a of a digital line circuit 1a includes a pre-filter circuit 2 and a pre-filter circuit 2 for removing noise components from a received transmission signal. The automatic gain control circuits 3 and 11 that make the amplitude of the signal output from the signal 10 constant, the equalizer circuits 4 and 12 that correct the frequency characteristics of the signal output from the automatic gain control circuits 3 and 11, and the equalizer circuits 4 and 12 Has data identification circuits 5 and 13 for identifying the data of the signal output by the output circuit 8 and output circuits 8 and 16. The equalizer circuits 4 and 12 have automatic gain control among several preset equalization characteristics. The equalization characteristic corresponding to the gain of the circuits 3 and 11 was selected.

[0003]

In the conventional receiving circuit for a transmission signal, the equalizer characteristic is selected according to the gain of the automatic gain control circuit from among several preset equalizer characteristics of the equalizer circuit. Therefore, there is a problem that the quality of the transmission signal is deteriorated when the equalization characteristic prepared in advance cannot correct the frequency characteristic of the transmission line.

[0004]

A transmission signal receiving circuit according to the present invention has a filter for removing a noise component from a reception transmission signal and outputting the first signal as a first signal, and a constant amplitude of the first signal. An automatic gain control circuit that outputs gain information and a second signal having a constant amplitude; an equalizer circuit that equalizes the frequency characteristic of the second signal according to a setting signal and outputs the equalized third signal; A data discriminating circuit for discriminating the data of the third signal; a waveform comparing circuit for calculating a difference between the third signal and a reference value that minimizes an error in the discriminating data; And an equalizer control circuit that outputs the setting signal according to gain information and the difference information.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 3 is a format diagram of a transmission signal for setting the equalization characteristic of the present embodiment.

Digital line circuit 1 connected by a transmission line
Further, in the terminal 9, the pre-filters 2 and 10 remove noise components from the reception transmission signal (which sets the equalization characteristic) shown in FIG. 3 and output it as the first signal. The automatic gain control circuits 3 and 11 output gain information for making the amplitude of the first signal constant and a second signal having a constant amplitude. The equalizer circuits 4 and 12 equalize the frequency characteristic of the second signal according to the setting signal a and output it as a third signal. The waveform comparison circuits 6 and 14 calculate the difference between the third signal and the reference value that minimizes the error of the data identified by the data identification circuits 5 and 13, and outputs it as difference information. The equalizer control circuits 7 and 15 set the setting signal a according to the gain information and the difference information.
Is output.

Next, the operation of this embodiment will be described. The digital line circuit 1 and the terminal 9 perform initial setting for each circuit of the digital line circuit 1 and the terminal 9 when the power is turned on or reset. Next, the output circuit 8 of the digital line circuit 1 and the output circuit 16 of the terminal 9 output the flag for synchronization shown in FIG. 3 and the transmission signal of a predetermined fixed pattern. The digital line circuit 1 and the terminal 9 remove noise components from the received signals by the prefilters 2 and 10, respectively, and correct the amplitude to a constant level by the automatic gain control circuits 3 and 11, and then the automatic gain control circuits 3 and 11 are used. Data equalizer circuit 5, which is equalized by the equalizer circuits 4 and 12 in which an appropriate equalizer specification is selected by
13 identifies 0.1 of the received signal, and the detection of the synchronization flag establishes the synchronization between the digital line circuit 1 and the terminal 9.

Next, in the received signals output from the equalizer circuits 4 and 12, data of a predetermined fixed pattern and the data identification circuits 5 and 13 discriminate between the data and the preset reference value which minimizes the data error. The waveform comparison circuits 6 and 14 calculate the difference between and, and the equalizer control circuits 7 and 15 control the equalizer characteristics of the equalizer circuits 4 and 12 in accordance with the calculated values so that the data error is minimized when performing data identification. Change the equalizer characteristics. Next, the digital line circuit 1 and the terminal 9 perform normal data transmission / reception.

[0009]

As described above, according to the present invention, the amplitude equalization characteristic of the receiving circuit is set by comparing it with a preset reference value at which the data error is the smallest, so that the type of transmission line and the transmission The optimum amplitude equalization characteristic can be set regardless of the transmission characteristics such as the path connection method, so that the transmission quality can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of an example of a conventional receiving circuit for a transmission signal.

FIG. 3 is a format diagram of a transmission signal for setting the equalization characteristic of the present embodiment.

[Explanation of symbols]

 1 Digital Line Circuit 2 Pre-filter 3,11 Automatic Gain Control Circuit 4,12 Equalizer Circuit 5,13 Data Discrimination Circuit 6,14 Waveform Comparison Circuit 7,15 Equalizer Control Circuit 8,16 Output Circuit 9 Terminal

Claims (1)

[Claims] 1. A filter for removing a noise component from a received transmission signal and outputting the first signal as a first signal, gain information for keeping the amplitude of the first signal constant, and a second for making the amplitude constant.
, An equalizer circuit for equalizing the frequency characteristics of the second signal according to a setting signal and outputting the third signal, and a data identification for identifying the data of the third signal. A circuit, a waveform comparison circuit that calculates a difference between the third signal and a reference value that minimizes an error in the identifying data, and outputs the difference as difference information, and the setting signal according to the gain information and the difference information. And an equalizer control circuit for outputting the signal.