JP2907587B2 - Eye pattern monitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eye pattern monitor for phase modulation and quadrature amplitude modulation.

[0002]

2. Description of the Related Art With the recent development of information and communication technology, higher-speed data transmission has been realized. As a method of this high-speed data transmission, CCITT Recommendation V. 27ter
And V. 29 or V.I. For example, there are a phase modulation system (PSK) and a quadrature amplitude modulation system (QAM) which are standardized as 33. The core of data transmission using such a modulation method is a modem (modem).

In a transmission system having this modem, an eye pattern has conventionally been used as a means for observing the performance of the modem itself and the effects of noise, distortion, and the like due to the transmission path. 4 and 5 show examples of this eye pattern. FIG. 960 specified in 29
0 bps eye pattern, and FIG.
33 shows an example of an eye pattern of 14400 bps specified by 33.

[0004] The PSK signal and the QAM signal are given by the following equations. s (t) = a ₁ (t) sin (wct) + a ₂ (t) cos (wct)… (1) s (t): Modulated signal at time t wc: Carrier (carrier) frequency a ₁ (t): Amplitude of the in-phase component at time t a ₂ (t): Amplitude of the quadrature component at time t The eye pattern is the amplitude a ₁ (t) of the in-phase component in equation (1). The amplitude of the orthogonal component is plotted on the horizontal axis on the horizontal axis.

As can be seen from the figure, the number of points in the eye pattern is determined by the V.V. 29 is 16 points, and V.29 shown in FIG. 33 are 128 points, and the number of points increases exponentially as the transmission speed increases. The eye pattern is used to observe an output signal of an equalizer that compensates for distortion on a transmission line corresponding to the heart of a modem receiving unit. FIG. 6 shows the configuration of the eye pattern generation unit after the modem equalizer.

Normally, the inside of a modem is a DSP (Digital Signal).
If the transmission path is an analog transmission path, digital-to-analog (D / A) conversion is performed at the exit of the modem transmission section, and analog-digital (A / D) conversion is performed at the entrance of the modem reception section. Is done. FIG. 6 assumes this case. In FIG. 6, reference numeral 100 denotes an equalizer that removes the influence of distortion due to transmission from an input signal via a transmission path to obtain an original transmission signal. This output signal is removed by the equalizer. In order to remove the influence of noise or the like that could not be removed, the decision unit 101 decides a regular point.

The eye pattern is for observing the output signal (input signal of the discriminator) of the equalizer 100. The in-phase component and the quadrature component of the digital signal are converted into analog signals by the D / A converters 102 and 103. It is converted and observed as shown in the oscilloscope 104.

FIGS. 7 to 9 show CCITT Recommendation V. 5 shows an eye pattern when noise, phase jitter, and impulse noise in a 29 standard modem occur on a transmission line. Fig. 7 each
8 shows an example of an eye pattern displayed on the oscilloscope 104 when noise occurs on the transmission line, FIG. 8 shows a case where phase jitter occurs on the transmission line, and FIG. 9 shows a case where impulse noise occurs on the transmission line. I have.

As shown in FIGS. 7 to 9, by observing the eye pattern, it is possible to observe the effects on the transmission path and the performance of the modem such as how much the modem absorbs the effects.

[0010]

However, as shown in FIG. 5, when higher-speed data transmission is considered (for example, in the case of a CCITT standard V.33 modem), the number of points to be observed increases exponentially. It is becoming difficult to determine the influence of noise, phase jitter, impulse noise, and the like while observing the whole.

Further, when the noise component increases, the distance between adjacent points also becomes short, making it difficult to determine a regular point and also making observation difficult. Furthermore,
If it is desired to focus on points and observe, only a part of all pattern points needs to be enlarged by the oscilloscope 104. However, in this case, in particular, it has a drawback that a legitimate point is difficult to judge, and accurate and prompt observation cannot be performed.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has, for example, the following arrangement as one means for solving the above-mentioned problems. That is, an eye pattern monitor device of the multi-level phase modulated signal or multilevel quadrature Fuhaba modulated signal, positive corresponding to the input signal point
Determining means for determining a regular point;
Within the symbol interval during which the
To alternate between the input signal point and the determined normal point.
And display means for displaying the information.

[0013]

[0014]

In the above construction, one point of the eye pattern
Within the symbol interval during which
Alternate display of force signal points and determined normal points
The input signal based on the regular points.
Accurately grasp the extent to which issue points are dispersed
Can be .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below in detail with reference to the drawings. An outline of the present invention is that, when displaying an eye pattern, means for alternately outputting an eye pattern affected by noise or the like and a determination value obtained by determining the eye pattern at a normal position when outputting one pattern is provided. is there.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS. 2 and 3 show examples of eye patterns displayed on a display screen according to the present embodiment. FIG. 1 is a diagram showing the configuration of an eye pattern generation unit subsequent to the equalizer of a modem, similar to FIG.

In FIG. 6, reference numeral 100 denotes a received signal (usually an in-phase component and a quadrature component of a demodulated baseband signal), and estimates and removes a distortion component added by a transmission line from the signal. This is an equalizer (adaptive equalizer) that outputs a transmission signal that would have occurred. 101 is an equalizer 10
This is a determiner that removes the influence of noise or the like that cannot be completely removed by 0 and determines a legitimate point.

The normal eye pattern is obtained by observing the output signal of the equalizer 100 (input signal of the discriminator) as shown in FIG. (This is usually called "symbol interval"
This period is controlled by a symbol rate clock having this period. 2), the output signal of the equalizer 100 and the output signal of the determiner 101 indicating a normal point are alternately output to the D / A converters 102 and 103 and displayed on the display screen of the oscilloscope 104.

Hereinafter, the configuration of this embodiment will be described in detail with reference to FIG. Reference numerals 105 and 106 denote selectors that receive the output of the equalizer 100 and the output of the determiner 101 and output an equalizer output or a determiner output selected by an external signal. As a selection signal of the selector, a symbol rate clock having the above-described symbol interval as a cycle is used. For example, during a period when the symbol rate clock is “High”, the selectors 105 and 106 output an output signal from the equalizer 100, and “ During the period of “LOW”, the output signal from the determiner 101 is output to the D / A converters 102 and 103, respectively.

As described above, the output signals of the selectors 105 and 106 alternately output the output signal of the equalizer 100 and the output signal of the decision unit 101 representing a normal point at every symbol interval. Are converted into analog signals by D / A (digital / analog) converters 102 and 103 and displayed on an oscilloscope 104 for observation.

Here, the output signal of the equalizer 100 and the decision unit 1
Consider the possible values of the 01 output signal. As described above, the output signal of the equalizer 100 is a signal obtained by adding components such as noise and phase jitter in the transmission path to the original transmission signal.
Output almost all points on the two-dimensional plane of the pattern to be displayed. That is, the output value may be close to infinity.

On the other hand, the output signal of the decision unit 101 is
As shown in FIGS. 29 and V.I. At 33, only 16 points and 128 points can be taken, respectively. Therefore, when observed with the oscilloscope 104, it is natural that most of the normal points, which are the outputs of the determiner 101, are almost always output, and the display rate to the normal points is high, and the luminance of the normal points appears relatively high.

FIGS. 2 and 3 show this state. FIG. 29 shows a display example of an eye pattern when all points 29 are observed, and FIG. 3 shows a display example when an arbitrary point of the eye pattern is enlarged. As you can see from the figure,
The luminance at the portion of the regular point (the output signal of the determiner 101) increases, and the distinction between the regular point and the dispersed point can be recognized at a glance.

Therefore, as shown in FIG. 3, even when an arbitrary point is enlarged and observed, accurate dispersion with respect to a normal point can be accurately achieved (for example, in the case of FIG. 3, noise and phase jitter are added). You can understand at a glance), you can grab.

[0025]

Other Embodiments In the embodiments described above, the selectors 105 and 106, the D / A converters 102 and 103, etc. are constituted by hardware, and are completely separate from the equalizer 100, the decision unit 101, etc. Although the image can be provided outside the modem device, the present invention is not limited to this, and the same means may be provided integrally inside the modem device. In this case, processing inside the device (modem, modem) is usually processed by software using a digital signal processor (DSP), and a part of the means of the present invention can be processed by software. .

The present invention may be applied to a system composed of a plurality of devices or to an apparatus composed of one device. Needless to say, the present invention can also be applied to a case where the above is achieved by supplying a program to a system or an apparatus.

[0027]

As described above, according to the present invention, the symbol interval to output one point of the eye pattern
During the period, the input signal point and the determined normal poi
The regular points are displayed by alternately displaying
As a criterion, how scattered the input signal points are
Can be accurately grasped, and the cause of dispersion can be accurately grasped.
Can be grasped .

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a display example of an eye pattern displayed on a display screen according to the embodiment.

FIG. 3 is a diagram illustrating an enlarged display example of an eye pattern displayed on a display screen according to the embodiment.

FIG. 4. CCITT Recommendation V. 9600 specified by 29
It is a figure showing an eye pattern of bps.

FIG. 5: CCITT Recommendation V. 144 specified by 33
It is a figure showing an example of an eye pattern of 00bps.

FIG. 6 is a diagram showing a configuration of an eye pattern generation unit after an equalizer of a conventional modem.

FIG. 7: CCITT Recommendation V. FIG. 4 is a diagram illustrating an eye pattern when noise occurs in a transmission line in a 29 standard modem.

FIG. 8: CCITT Recommendation V. FIG. 3 is a diagram showing an eye pattern when phase jitter occurs on a transmission line in a 29 standard modem.

FIG. 9: CCITT Recommendation V. FIG. 3 is a diagram showing an eye pattern in a case where impulse noise occurs on a transmission line in a 29 standard modem.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Equalizer 101 Judge 102, 102 D / A converter 104 Oscilloscope 105, 106 Selector

Claims (1)

(57) [Claims] An eye pattern monitoring apparatus for a multi-level phase modulation signal or a multi-level quadrature amplitude modulation signal , wherein a judgment means for judging a normal point corresponding to an input signal point is provided.
The stage and the symbol interface to output one point of the eye pattern
Input signal point and the determined normal
An eye pattern monitor device comprising: display means for alternately displaying points .