JPS63156456A - Method for measuring s/n of data communication line - Google Patents

Abstract

PURPOSE:To measure an S/N automatically by using a MODEM incurporated in a data communication equipment, by converting an error signal which represents a difference between a single tone reception signal and a reference signal to a scalar quantity, outputting an integration value corresponding to the scalar quantity, and obtaining the S/N of a data communication circuit based on the integration value. CONSTITUTION:An S/N information generating part 19 subtracts the reference signals REFAR and REFAI equivalent to signals respectively from the reception signals SR and SI consisting of real number parts and imaginary number parts at two sets of adders 21 and 22, obtaining the error signals IER ald IEI, and obtaining the absolute values of those values at absolute value calculators 23 and 24 as the scalar quantity. And those values are added at a second adder 25, and are integrated at an integrator 26, and the signal corresponding to the S/N is outputted. The S/N of the data communication line is outputted from a table stored in a read only memory ROM20 by an integrated value. Therefore, it is possible to measure the S/N of the data communication line without using a level meter separately and by using the MODEM of the data communication equipment.

Description

[Detailed Description of the Invention] [Summary] In order to measure the S/N ratio of a data communication line without using a level meter, an error signal indicating the difference between a received tun tone signal and a reference signal is generated as a scalar signal. It converts into a quantity, outputs an integral value, and based on this integral value S
The modem of the data communication device can automatically measure the S/N ratio of the data communication line by obtaining the S/N ratio.

[Industrial application field]

The present invention relates to a method for measuring the S/N ratio of a data communication line, and in particular to a method for measuring the S/N ratio of a data communication line without using a level meter equipped with a dedicated notch filter or the like. This invention relates to a method for measuring the S/N ratio of a line.

[Conventional technology]

Conventionally, the S/N ratio of a data communication line has been measured by an operator connecting a level meter to the terminal of the line to be measured and measuring the signal level and noise level.

This level meter is equipped with a notch filter and a bandpass filter, and is a relatively large-scale device, and the cost of the device is also high.

[Problem that the invention attempts to solve]

By the way, when supporting NMS (Network Management Service), etc., it is desired to automatically and easily measure the S/N ratio of data communication lines, but the above-mentioned conventional S/N ratio of data communication lines In the N ratio measurement method, a level meter is required to measure the S/N ratio, and the measurement must be performed by an operator, which is cumbersome and cannot be done automatically. could not.

(Means for solving the problems) Means for solving the above problems in the present invention are as follows:
As shown in Figure 1, an error signal indicating the difference between a single-tone received signal and a reference signal is generated (l), this error signal is converted into a scalar gate (2), and then an error signal corresponding to this scalar quantity is 3) To output the integral value and obtain the S/N ratio of the data communication circuit based on this integral value.

[Effect]

According to the present invention, an error signal indicating the difference between a single tone received signal and a reference signal is converted into a scalar quantity.

Next, we output an integral value according to this scalar value and obtain the S/N ratio of the data communication circuit based on this integral value, so these processes can be performed using the modem built into the data communication device. It can be easily done automatically.

(Example) Next, an example of the method for measuring the S/N ratio of a data communication line according to the present invention will be described with reference to the drawings.

FIGS. 2 to 4 show S/S of the data communication line according to the present invention.
0 In this embodiment, the method for measuring the S/N ratio of a data communication line is performed by the modem M (modem) of the data communication device connected to the terminal of the data communication line. That's what I do.

FIG. 2 shows a modem 10 for carrying out an embodiment of the S/N ratio measurement method for a data communication line according to the present invention. In this embodiment, the modem 10 converts an analog signal in a data communication line into a digital signal. Analog/digital converter A/Dll to convert, and this analog/digital converter A/
an automatic gain control device AGcl 2 that automatically adjusts the level of the signal from the Dll; a demodulator DEM 1 3 that demodulates the digital signal; a carrier generator CRR 14 that generates a carrier signal for the demodulator DEM13; a roll-off filter ROF 15 that transmits a predetermined part of the demodulated signal; an equalizer AEQ 16 that equalizes the phase and amplitude of the signal that has passed through the roll-off filter ROF 15;
Frequency offset circuit CAPCl to remove phase jitter
7, and a determination circuit DE that determines the frequency and phase of the signal.
It is composed of C18. In this embodiment, one frequency offset circuit CAPCl 7 and a determination circuit D
EC18 has an S/N that generates information corresponding to the S/N ratio.
An information generating section SND l 9 is provided, and this S/N information generating section SND l 9 is provided with an S/N information generating section SND l 9.
As shown in FIG. The reference signals REFAR and REFAI are subtracted from the received signals SR and SI consisting of the sum 4121°22 to obtain an error signal, and the absolute value calculation bag M23 is calculated to calculate the absolute value of these values to be a scalar. 24 and
It consists of an addition a25 that adds these absolute values together, and an integration device 26 that integrates this added value. The integrating device 26 is provided with a multiplier and an adder for multiplying, combining, or adding various coefficients, and a feedback gain circuit T to perform integration.

Next, a case will be described in which this modem is used to measure the S/N ratio of a data line. In this case, the destination data communication device first performs transmission using a tun-tone, for example, 1004 Hz. The data communication device on the receiving side then receives the above-mentioned modem lO lever signal.

At this time, the modem 10 is adjusted as follows, unlike the normal reception state.

(1) Either the automatic equalizer AEQl 6 is bypassed 27 and no signal is allowed to pass therethrough, or the automatic equalizer AEQ is kept in a fixed state. To keep the automatic equalizer in a fixed state, the feedback signal within the automatic equalizer AEQ is multiplied by O.

(2) Match the carrier signal input to the demodulation circuit DEM13 with the transmission frequency of the transmitter. That is, in this example, it is 1004 hertz.

(3) The dynamic range of the SQD circuit of the automatic equalizer AEQ16 is widened to the extent that the S/N ratio can be measured.

(4) Set the decision point of the decision circuit DEC18 to one point in accordance with the width-tone being sent out.

Therefore, according to this embodiment, the S/N of the data communication line is
To measure the ratio, configure the modem of the receiving data communication device as shown in L to transmit a single tone signal from the transmitting data communication device.

Then, in the data communication device on the receiving side, the signal is converted into a digital signal by an analog-to-digital converter A/D l l. Then, the automatic gain control device AGC12 amplifies the signal to a constant level. The signal demodulated by the demodulator DEM13 passes through a roll-off filter ROF15 and is output to an automatic equalizer AEQ16. However, in this example, the automatic equalizer AEQl 6 is bypassed 27 or left in a fixed state, so that no processing is performed on the signal [).

Next, this signal is input to the frequency offset circuit CAPC17, where phase jitter is removed and the first judgment base DEC
1B, the frequency and phase are determined, and this result is input to the S/N information generating section SND19. In this state, the signal is determined to be located on the actual plane, as shown in FIG. If there is no noise at all, all points will be located at the origin O, or, as shown in Figure 4, normally the signal S will be deviated from the origin due to the addition of line noise (SR + S I ). Therefore, if we measure the deviation from this origin O and compare it with the signal, we can determine the S/N of the data communication line.
It is possible to measure the ratio. On the other hand, in this embodiment, since the signal value is always kept constant by the automatic gain adjustment device 1AGcl2, the S/N ratio can be automatically determined if the noise level is determined.

In this embodiment, as shown in FIG. 3, the S/N information generating section uses two adders to generate a reference signal REFAR corresponding to the signal from the received signals SR and St consisting of a real number part and a real number part.
, REFAI are respectively subtracted to obtain error signals IER and IEI, and an absolute value calculation device obtains the absolute values of these values as scalar quantities.The second adder 25 adds them together to calculate this value. Then, an integrator integrates the signal and outputs a signal corresponding to the S/N ratio. Based on this integrated value, the S/N ratio of the data communication line is output from a table stored in the read-only memory ROM 20.

Therefore, according to this embodiment, the S/N of the data communication line can be adjusted without using a level meter equipped with a filter or the like.
It is possible to measure the ratio. The measurement can be performed using a modem built into the data communication device.

(Effects of the Invention) As described above, according to the present invention, the S/N ratio of a data communication line is measured by converting an error signal indicating the difference between a width-tone received signal and a reference signal into a scalar quantity. The S/N of the data communication circuit is determined based on this integrated value.
Since the S/N ratio of the data communication line can be measured using the modem of the data communication device without using a special level meter, the S/N ratio of the data communication line can be measured.
This has the effect that ratio measurement can be easily automated.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of the S/N ratio measurement method of a data communication line according to the present invention, and Fig. 2 is a diagram showing this modem manufactured by Data Communication which implements the S/N ratio measurement method of a data communication line according to the present invention. FIG. 3 is a diagram showing an equivalent circuit of the S/N information generating section of the modem shown in FIG. 2, and No. 4U'A is a diagram showing signal states.

Claims (1)

[Claims] Generates an error signal indicating the difference between the received signal of a single tone and a reference signal, converts this error signal into a scalar quantity, then outputs an integral value according to this scalar quantity, and based on this integral value A method for measuring an S/N ratio of a data communication line, the method comprising obtaining the S/N ratio of the data communication circuit.