JPS61242125A - Phase error absorber - Google Patents

Abstract

PURPOSE:To improve the probability of data transmission by discriminating a phase error based on the form of an eye pattern showing the equalizing state of demodulating device and controlling a phase changing means in the direction where the phase error is eliminated. CONSTITUTION:A phase error discriminating circuit 6 supplies an eye pattern signal EP to convert it into the digital data by A/D conversion and detects a waveform to discriminate the delay or advance of the phase for production of a phase error signal PE. This signal PE is delivered to a control signal generating circuit 7. The circuit 7 delivers the phase control signals PC1 and PC2 produced in response to the signal PE together with the amplitude control signal AC to D/A converters 8-10. Thus the cut-off points of filters 2 and 3 are set at the frequencies corresponding to the signals PC1 and PC2 respectively. At the same time, the gain of a variable gain amplifier 4 is controlled. Then the phase characteristics of an analog transmission circuit L are improved with variation. In such a way, the reliability of the data transmission is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a phase error absorbing device that absorbs phase errors in analog transmission lines.

[Prior Art] Generally, when transmitting data using an analog transmission line such as a public telephone network, it is necessary to modulate the data to be transmitted using a modulation method that corresponds to the characteristics of the analog transmission line.

A modulation method for this purpose has been recommended by CCITT (International Telegraph and Telephone Consultative Committee). For example, a four-phase differential phase modulation method (1
200 baud) to Recommendation V, 26A, data rate 4
800bps 8-phase differential phase modulation method (1600bau
d) Recommendation V, 27ter, data rate 9600b
The PS 16-level orthogonal amplitude modulation method (2400 baud) is defined in Recommendations V and 29, respectively. Also, Recommendation V
, 27ter has 240 as a backward channel.
0 bps (V, 26A L: same), but Recommendation V,
29ni is 7200 bps as a backward channel
(8-level quadrature amplitude modulation method; 2400 baud) and 4
800 bps (4-level quadrature amplitude modulation method; 2400 bau
d) are determined respectively.

By the way, the line condition in an analog transmission line network is not always constant, and may change within a certain range depending on the line condition between the transmitting device and the receiving device, for example, the relay condition between stations, the line condition, the environmental condition, etc. Therefore, the phase characteristics of one line also change.

When the phase characteristics of a single line change in this way, the phase relationship of the transmitted signal changes in data transmission using phase modulation or quadrature amplitude modulation, which is a mixed modulation method of phase modulation and amplitude modulation, as described above. Therefore, the data reception probability changes.

For this reason, especially in modulation systems for high-speed data transmission, a backward channel is set as described above, and when the error rate of data transmission at the highest speed is large, switching to data transmission at a lower speed is performed. That's what I do.

For this reason, in the past, even if a high-speed modulation/demodulation device was provided, data transmission at the maximum speed could not always be realized, and data transmission efficiency sometimes deteriorated.

[Objective] The present invention has been made in order to eliminate the above-mentioned disadvantages of the prior art, and it is an object of the present invention to provide a phase error absorbing device that can improve the probability of data transmission by absorbing phase errors in analog transmission lines. purpose.

[Configuration] The present invention provides a phase change means between an analog transmission line and a demodulator, determines a phase error based on the shape of an eye pattern representing an equalization state of the demodulator, and removes the phase error. The above objective is achieved by controlling the phase changing means.

FIG. 1 shows a phase error absorbing device according to an embodiment of the present invention.

In the figure, a network control device 1 is for connecting this device to an analog transmission network, and its output terminal is composed of an operational amplifier 2a, resistors 2b, 2c, a capacitor 2d, and an FET 2e, and has a power output of -6dB10ct. filter 2, operational amplifier 3a, resistors 3b, 3c, capacitor 3d and FE
A filter 3 and an operational amplifier 4 are composed of T3e and have an amplitude-frequency characteristic of 6 dB10 ct (see Fig. 3).
a, resistors 4b, 4c, and a FET 4d. These filters 2. By setting (adjusting) the characteristics of the filter 3 and variable gain amplifier 4, the phase characteristics can be changed arbitrarily.

The demodulator 5 demodulates the transmission signal applied from the variable gain amplifier 4 using a predetermined method, and outputs the demodulated signal D0 to the next stage signal processing device (II not shown). Also.

This demodulation s5 is equipped with an adaptive automatic equalizer, and in order to comprehensively evaluate the equalization amplification system, the output waveform of the equalization amplifier, which is one element of the adaptive automatic equalizer, is synchronized with the data clock frequency. 111m in condition! It outputs an eye pattern signal EP for

This eye pattern signal EP has a waveform as shown in FIG. This waveform changes depending on the state of the transmission signal applied to the demodulator 5, and is usually made available for observation because it is observed when adjusting the equalization amplification system.

The phase error discriminating circuit 6 receives the eye pattern signal BP, converts it into digital data through analog/digital conversion, and stores it in a pattern memory to detect the waveform, and detects the waveform when the phase characteristic is good. Compare by pattern matching processing, etc. Then, based on the comparison results such as the difference in the degree of opening between the top and bottom of the eye pattern, the delay or advance of the phase and its degree are determined to form a corresponding phase error signal PR, and this phase error signal PR is used to generate a control signal. Output to circuit 7.

The control signal generation circuit 7 has an RO circuit that stores phase control signals PCI, PC2 and an amplitude control signal AC for eliminating the phase error, corresponding to the input phase error signal PR.
It consists of M (read-only memory), etc.
Phase control signals Pct, PC2 and amplitude control signal AC generated in response to input phase error signal PR are output to digital/analog converters 8, 9.10, respectively.

The output signal of the digital/analog converter 8, 9.10 is
It is output to FET 2a of filter 2, FET 3a of filter 3, and FET 4a of variable gain amplifier 4, and the resistance value of each of these FETs 2a, 3a, and 4a changes accordingly.

As a result, the cutoff points fl and f2 of filters 2 and 3 (see FIGS. 2 and 3) are adjusted to the phase control signal P.
ct, is set to a frequency corresponding to PC2, and
The gain of variable gain amplifier 4 is controlled. Therefore, the filters 2 and 3 and the variable gain amplifier 4 change the phase characteristics of the analog transmission line to improve them, and as a result, the phase characteristics of the transmission signal input to the demodulator 5 become better.

Furthermore, since the 1-phase characteristic tends to some extent depending on the region, the control signal generation circuit 7 uses the input phase error signal PH.
It is equipped with a plurality of ROMs (for example, a ROM for Hokkaido, a ROM for Honshu, a ROM for Shikoku, a ROM for use, etc.) that store phase control signals PCI, PC2 and amplitude control signals AC corresponding to each region. One of them is selected by the select data SD output from the selector 11 consisting of a ditch switch or the like. This selector 11 is operated in advance in accordance with the region where this device is used.

In this way, phase errors in the analog transmission line are absorbed, so that a proper transmission signal is always input to the demodulator 5, and as a result, demodulation processing is performed satisfactorily. This reduces data errors in data transmission, so data transmission can always be performed under the same conditions regardless of the state of the analog transmission line, and the reliability of data transmission can be improved.

In addition, in the embodiment described above, the phase changing means is
A filter with amplitude-frequency characteristics of dB10ct.

Although it is constituted by a filter having an amplitude-frequency characteristic of 6 dB10 ct and a variable gain amplifier, the configuration of the single phase changing means is not limited to this, and may also be constituted by a digital filter or the like.

Furthermore, the configuration of the 1-phase error discrimination circuit 6 is not limited to that described above.

[Effects] As explained above, according to the present invention, - phase changing means is provided between the analog transmission line and the demodulator.

This is because the phase error is determined based on the shape of the eye pattern representing the equalization state of the demodulator, and the phase changing means is controlled in a direction to remove the phase error.

The advantage is that the probability of data transmission can be improved by absorbing phase errors in analog transmission lines.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a phase error absorbing device according to an embodiment of the present invention, FIG. 2 is a graph showing the characteristics of filter 2, and FIG. 3 is a graph showing the characteristics of filter 3. FIG. 4 is a graph diagram showing an example of an eye pattern. 2.3... Filter, 4... Variable gain amplifier, 5...
...Modulator, 6...Phase error discrimination circuit, 7...Control signal generation circuit, 8,9.10...Digital/analog converter, 11...Selector. Part 1, Fig. 2, Fig. 3, Fig. 4, Procedures... Author (self-motivated) June 25, 1985 1. Display of the incident 1985 Patent Application No. 82655 2. Name of the invention Phase error absorption Device 3, Relationship with the person making the amendment Patent applicant address 1-3-6 Nakamagome, Ota-ku, Tokyo Name (674)
) Ricoh Co., Ltd. Representative Hama 1) Hiro 4, Agent 105 Address 1-18-11 Nishi-Shinbashi, Minato-ku, Tokyo "
"Detailed Description of the Invention", 1 Brief Drawing 6, Contents of Amendment (1) Delete "Also..." from lines 8 to 13 on page 5 of the specification of the present application. do. (2) In lines 14 to 18 of the same page of the same book, "This eye pattern signal EP is..." is changed to [
Further, the demodulator 5 outputs an eye pattern signal EP that changes depending on the state of the transmission signal applied to the demodulator 5 and is detected when determining the receiving state of the demodulator 5. ” is corrected. (3) In the same book, page 6, line 5, change the ``vertical opening degree'' to ``
Correct it to ``the opening degree of the top, bottom, left, and right.'' (4) In the same book, page 9, lines 7 to 9, "Figure 3 is a graph showing the characteristics of the filter 3, and Figure 4 is a graph showing an example of an eye pattern." 3 is a graph showing the characteristics of filter 3.'' (5) Figure 4 of the drawings will be deleted. that's all

Claims (1)

[Claims] a phase characteristic changing means interposed between an analog transmission line and a demodulator to change the phase characteristic of the analog transmission line;
an eye pattern detection means for detecting an eye pattern representing the equalization status of the demodulator; a phase error determination means for determining a phase error by comparing the output of the eye pattern detection means with a predetermined pattern; A phase error absorbing device characterized by comprising a control signal output means for outputting a control signal to the phase characteristic changing means based on an output of the means, and absorbing a phase error of an analog transmission line.