JPS6075136A - Automatic selection system of fixed equalizer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an amplitude equalizer for a modem, and in particular, to an amplitude equalizer for a modem, in particular, the correction amount of a fixed equalizer is sequentially switched in order to automatically compensate for the frequency of a line. This relates to a fixed equalizer automatic selection method.

[Prior art and problems]

For example, when transmitting and receiving a digital signal having signal points as shown in Figure 1 via a line (dedicated line #) with a modem installed, the receiving side uses amplitude equalization of the modem to correct the frequency characteristics of the line. It is necessary to adjust the instrument (ABQL). In this case, as shown in FIG. 2, an amplifier 1 equipped with an amplitude equalizer 1-1 is provided on the receiving station side to amplify the received signal and correct its frequency characteristics, and then the demodulator 2 demodulates the received signal. The x and y components are extracted to determine which signal point the received signal corresponds to.

In this case, as mentioned above, it is necessary to change the frequency characteristics of the 9 lines by adjusting the frequency characteristics of the modem and the equalizer 1-1.

In this case, if tap mark] is connected, the correction tL will be zero, if tap CI) is connected, the correction plate will be small, if tap [2J is connected, the correction amount will be medium, if tap C] is connected, the correction plate will be thick. and connect one of the taps.

When adjusting the amplitude equalizer, it is a manual process that involves observing the receiving eye pattern and checking the received signal quality while changing the amplitude equalizer's correction amount and finding the setting that provides the best convergence of the eye pattern. The disadvantage is that it requires adjustment work and a measuring instrument such as an oscilloscope, and moreover, it takes a long time to make this adjustment.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixed equalization amount automatic selection method that automatically corrects a fixed amplitude equalizer in order to overcome such drawbacks.

[Structure of the invention]

In order to achieve this object, in the fixed equalizer automatic selection method of the present invention, a received signal of received data is Received signal quality detection means for detecting quality status.

It is equipped with CD detection means for detecting a carrier signal, and retraining control means for requesting +11 training signal transmission, and after detecting the carrier signal, checks the convergence state of the modem based on the output of the received signal quality detection means, and performs spreading. If it is in the state, the correction amount of the amplitude equalizer is changed and the retraining control means is operated to request the transmitting side to perform writing training.

[Embodiments of the invention]

An embodiment of the present invention will be described based on FIGS. 6 and 4 and with reference to other figures.

FIG. 6 is a configuration diagram of an embodiment of the present invention, and FIG. 4 is an explanatory diagram of a training signal.

In FIG. 6, 10 is a signal amplifying section and includes an amplitude equalizer 10-1, and this amplitude equalizer 10-1 is f4s
It has a switching section that corresponds to the tap LOJ-(3) shown in FIG. Reference numeral 11 denotes a demodulating section which demodulates the received signal to extract the X-axis component and the X-axis component, and also includes a received signal quality determination circuit 11-1.

This received signal quality determination circuit 11-1 determines whether or not the received signal converges on one signal point shown in FIG. 1, and if it converges on each signal point, the SQD O
N and outputs SQD OFF if it is in a non-convergent state such as intersecting adjacent signal points.

12 is a sequencer, and when a training signal as shown in FIG. 4 comes, the signal state is "A".

This detects the boundary between the B area and the DJ area area C.

13 is a CD detection section, in which the sequencer 12 detects [c,
After receiving the scramble 2 detection signal outputted when the DJ area changes to the scramble Z area, an rCDJ (carrier zoract) signal outputted after a certain period of time is detected. Since data is output after this "CD" signal, the terminal device operates when this "CD" signal is detected.

Reference numeral 14 denotes a timer which is started upon detection of the "CD" signal and operates the determination circuit 15 after a certain period of time.

15 is a judgment circuit; the received signal quality judgment circuit 11;
-1 determines whether the output is 5QDON or 8QD Oi'F, and if it is SQD OFF"'C, the amplitude equalizer 10-
The switching unit is controlled to increase the equalization amount of 1 by one step, and the retraining control circuit 16 is controlled to
1 training transmission request signal is output.

16 is a retraining control circuit, which controls the reception (i side co
In order to retrain the modem, a retraining transmission request signal is output to the transmitting side for sending and receiving a training signal.By the way, the recommendation V29 of the Consultative Committee on Telegraph and Telephone International (CCITT) specifies 9600 BI.
This is done for the modulation method of the t/s modem, and it is specified that retraining is to be performed when divergence occurs on the receiving side.

Reference numeral 17 denotes a transmitter that outputs a signal to be transmitted to one line.

20 is a transmitting station.

Next, the present invention will be explained in detail.

(1) First, the equalization amount of the amplitude equalizer 10-1 of the signal amplifying section 10 is set to the minimum (zero). Then, the training signal shown in FIG. 4 is transmitted from the transmitting station 20.

The sequencer 12 receives "A" from this training signal.

B'' area and [c, DJ area area boundaries are detected. In the training signal, the IcDJ signal is
.

Since it is specified that the boundary detection signal is output after a certain number of symbols after the "B" area, when the boundary detection signal is output from the sequencer 12, the CD detection section 16 counts the number of symbols after that. And when it reaches the specified value,
A CD detection signal obtained by detecting the l'' CDJ signal is sent to the timer 14 to start it.

This timer 14 is activated after a certain period of time (0 to several seconds).
When the signal goes out, an output signal is sent to the determination circuit 15. Thereby, the determination circuit 15 checks the output state of the received signal quality determination circuit 11-1. At this time, the modem is not in a converged state but is diverging, as described above (SQD (J
Since the FF is being output, the equalization amount of the amplitude equalizer 10-1 is increased by one step and the switching section corresponding to the tap θ is turned on.

It also reports SQD OFF to the retraining control circuit 16. As a result, the retraining control circuit 16 outputs an old training transmission request signal, which is transmitted to the transmission section 17.
The signal is sent to the transmitting station 20 via.

The transmitting station 20 thereby retransmits the training signal shown in FIG. 4.

(2) When this training signal is sent.

Control similar to the above (1) is performed. and timer 14
When the output is sent to the judgment circuit 15 from 9 judgment circuit 1
5 determines the output of the received signal quality determination circuit 11-1.

And even though the equalization amount was increased, S
If QD OFF is output.

Perform output control. This happens when the modem converges and
It is repeated until QDON is obtained, and the amplitude equalizer 10-
The amount of correction for 1 increases.

(3) If the modem converges, the output of the received signal quality determination circuit 11-1 becomes SQD ON.

When the determination circuit 15 determines this, no further correction is performed, and the equalization selection sequence for the fixed equalization amount ends.

In addition, if the configuration of the received signal quality judgment circuit is configured so that it can output not only the judgment of modem convergence or non-convergence, but also the judgment of single convergence state where the modem is in a convergence state and the amount of non-convergence is small, the third This single convergence state signal shown by the dotted line in the figure is received by the AND circuit A also shown by the dotted line, and this is turned off, and the correction amount of the amplitude equalizer 10-1 is increased by one stage. According to Yokogi's invention, even in a fixed equalizer, the correction amount can be adjusted to the 1111th order according to the convergence state of the modem to control the modem to be in the convergence state. In this way, it is possible to improve the troublesomeness caused by hand verbs.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of signal points, Fig. 2 is an explanatory diagram of the adjustment state of a conventional fixed equalizer, Fig. 6 is a configuration diagram of an embodiment of the present invention, and Fig. 4 is an explanatory diagram of a training signal. . In the figure, 10 is a signal amplification section, and 10-1 is an amplitude equalizer. 11 is a demodulator, and 11-1 is a received signal quality determination circuit. 12 is a sequencer, 16 is a CD detection section, 14 is a timer,
15 is a determination circuit, 16 is a retraining control circuit, 17
indicates a transmitting unit, and 20 indicates a transmitting station. Patent applicant Fujitsu Ltd. Representative Patent Attorney Akira Yamatani

Claims (1)

[Claims] In a modem having an amplitude equalizer provided with a plurality of correction amount adjusting units each selecting a different correction amount, a received signal quality detection means for detecting a received signal quality state of received data and a CD detection means for detecting a carrier signal. and retraining control means for requesting retraining signal transmission, selectively switching the correction amount of the amplitude equalizer according to the output of the received signal quality detecting means after carrier signal detection, and controlling the retraining. An automatic fixed equalizer selection method, characterized in that a transmission side is requested to perform retraining by operating a means.