JPH04315339A - Eye pattern monitor - Google Patents

Abstract

PURPOSE:To surely grasp a cause of decentralized eye patterns and also to surely judge the performance of a MODEM. CONSTITUTION:An equalizer 100 inputs a demodulated signal including in-phase and orthogonal phase components and eliminates a distortion component superimposed on the signal due to the effect of a transmission line based on the signal and outputs signals Zr, Zi from which the distortion is eliminated. In order to eliminate distortion and a noise component unable to be eliminated by the equalizer 100, a discriminator 101 discriminates a regular point closest to points of the signals Zr, Zi. Then criteria ar, ai of the discriminator 101 are used to allow a limiter 105 to decide the criteria of the Zr, Zi outputted to a waveform observing device 104. Only when the signals Zr, Zi are matched with the criteria, the limiter 105 enables a load enable signal to latches 107, 108 to permit the latch of the signals Zr, Zi. The latched signal is converted into an analog signal by D/A converts 102, 103 and the signal is observed by the waveform observing device 104 such as an oscilloscope.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art With the recent development of information and communication technology, higher speed data transmission has been realized. This high-speed data transmission method is based on CCITT Recommendation V. 27te
r and V. 29, V. There are phase keying (PSK), which is a modulation method such as No. 33, and quadrature amplitude modulation (QAM), which is a more multi-level modulation method.

The core of data transmission using such a modulation method is a modem (hereinafter referred to as a modem). In a transmission system including this modem, an eye pattern has been used as a means for observing the performance of the modem itself and the influence of noise, distortion, etc. due to the transmission path. An example of this eye pattern is shown in FIG. 9 or 10. Of these, FIG. 9 shows CCITT Recommendation V. 10 is a 9600 bps eye pattern defined in CCITT Recommendation V.29. This is an eye pattern of 14,400 bps defined in 33.

The above PSK signal and QAM signal are given by the following equations. S(t)=a1 (t)sin(ωct)+a2
(t)cos(ωct)

…(
1) However, S(t): modulation signal ωc at time t
:Carrier angular frequency a1 (t
): Amplitude a2 of the in-phase component at time t (t): Amplitude of the orthogonal component at time t The eye pattern is defined by the above formula (
1), the amplitude a1 (t) of the in-phase component is plotted on the horizontal axis, and the amplitude of the orthogonal component is plotted on the vertical axis.

As can be seen from FIGS. 9 and 10, the number of points in the eye pattern is determined by V. 29 is 16 points,
V. The number of points is 128 points in the case of No. 33, and the number of points increases exponentially as the transmission speed increases. Observing the eye pattern means observing the output signal of the equalizer that compensates for distortion on the transmission path, which is the heart of the modem receiving section.
Figure 11 shows a block diagram illustrating the observation.

[0006] Normally, inside a modem, a DSP (Digital
If digital signal processing is performed by Digital Signal Processor) and the transmission path to which the modem is connected is one that transmits analog signals, Digital-Analog (
D/A) conversion, Analog-D at the entrance of the modem receiver
digital (A/D) conversion is performed. In FIG. 11, the equalizer 100 removes the influence of distortion caused by the transmission path contained in the input signal and obtains the original transmission signal. In order to eliminate the influence of noise, etc., a regular point is determined by a determiner 101.

[0007] The eye pattern is used to observe the output signal of the equalizer 100 (in other words, the input signal of the determiner 101), and measures the in-phase component and quadrature component of the input signal converted into a digital signal, respectively. D/A converter 102, 10
3 into analog signals, and these are observed with a waveform observation device 104 such as an oscilloscope. Figures 12-1
4 is the same as V.4 above. An example of an eye pattern when noise, phase jitter, and impulse noise in No. 29 occur on a transmission path is shown. Of these, FIG. 12 shows an eye pattern when noise occurs, FIG. 13 shows a phase jitter, and FIG. 14 shows an eye pattern when impulse noise occurs. In this way, by observing the eye pattern, it is possible to know the performance of the modem, such as the influence on the signal on the transmission path and the extent to which the modem absorbs the influence.

[0008]

[Problem to be Solved by the Invention] However, in actual transmission lines, noise, phase jitter, impulse noise, etc. shown in Figs. 12 to 14 do not occur individually, but all elements overlap. It is rare that the pattern shown in the figure can be observed. This situation can be easily estimated by superimposing all the patterns in FIGS. 12 to 14.

[0009] Therefore, in the above-mentioned conventional technology, the only way is to estimate the degree of influence of, for example, phase jitter, from the superimposed eye patterns, and there is a problem that the cause of eye pattern scattering cannot be accurately determined. be.

0010

[Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and has the following configuration as a means for solving the above-mentioned problems. That is, the eye pattern monitoring device monitors a phase modulation signal or a quadrature amplitude modulation signal in a two-dimensional space, and adjusts the dispersion range of the eye pattern to a predetermined region based on the in-phase component and quadrature component of the input signal. The eye pattern includes a limiting means for limiting the area, and a means for outputting the eye pattern whose area is limited on two-dimensional coordinates.

Preferably, the limiting means limits the output points of the eye pattern to only points that are a predetermined distance away from the normal points. Preferably, the limiting means limits the output points of the eye pattern to only a range that is a predetermined distance away from a circle passing through a regular point centered on the origin of the two-dimensional coordinates.

0012

[Operation] With the above configuration, the cause of eye pattern dispersion can be accurately grasped.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic block diagram showing the configuration of an eye pattern monitoring device according to an embodiment of the present invention. In the same figure, an equalizer 100 inputs demodulated in-phase and quadrature component signals, and based on these signals, removes distortion components due to the influence of the transmission path superimposed on the signals, thereby reducing distortion. Output the removed signal. In the following description, the in-phase component and quadrature component of the output signal of the equalizer 100 will be referred to as Zr and Zi, respectively.

The determiner 101 receives the above-mentioned Zr and Zi as input signals, and selects the Zr and Zi signal points in order to remove distortion and noise components that are superimposed on the Zr and Zi signals and cannot be removed by the equalizer 100. It determines the regular point closest to . Note that the in-phase component and quadrature component of the output signal of the determiner 101 are respectively ar and ai
It is called. Conventionally, the eye pattern is based on the signal Z as described above.
Each of r and Zi is converted into an analog signal by a D/A converter, and the signal is observed by a waveform observation device such as an oscilloscope.

However, in this embodiment, as will be described later, the limiter 105 uses the determination values ar and ai to determine the limiting conditions for the Zr and Zi signals to be output to the waveform observer 104. Then, the limiter 105 enables the load enable signals to the latch 107 and the latch 108 to permit the Zr and Zi signals to be latched only when the Zr and Zi signals meet the limiting conditions. The latched signal is sent to D/A converters 102 and 103.
The signal is converted into an analog signal, and the signal is observed using a waveform observation device 104 such as an oscilloscope.

On the other hand, when the Zr and Zi signals are outside the limiting conditions, the Zr and Zi signals are closed to the latches 107 and 108.
Since the signal that was not input to the waveform and was latched before satisfying the condition remains latched, that signal is sent to the waveform observation device 104 again. Next, a method of actually limiting the eye pattern output to only noise components will be explained. FIG. 2 is a block diagram showing the internal configuration of the limiter 105 in FIG. 1, which corresponds to the case where the eye pattern output is limited to only noise components, and FIG. 3 is a flowchart showing the operating procedure of the limiter 105. It is.

In FIG. 12, which is shown as a prior art, the dispersion of the eye pattern due to noise spreads in a circular shape with respect to the regular points, so the in-phase difference from the regular points is greater than the actual eye pattern on which elements other than noise are superimposed. , and the orthogonal components, if only those separated by a certain minute distance are extracted, it is possible to observe almost only the noise component.

In FIG. 2, the subtracter 201 is equalizer 1
The subtracter 202 calculates the difference between the in-phase component Zr of the output signal of 00 and the in-phase component ar of the output signal of the determiner 101, and the subtracter 202 calculates the difference between the orthogonal component Zi of the output signal of the equalizer 100 and the in-phase component ar of the output signal of the determiner 101.
01 and the orthogonal component ai of the output signal is calculated. Then, the output of each subtracter is sent to the absolute value unit 20 of the next stage.
3 or 204 and its absolute value is taken,
Furthermore, the output is input to comparator 205 or 206.

Comparators 205 and 206 compare a predetermined threshold value with an input value as described later, and only when the result of this comparison satisfies the AND condition in AND circuit 207, the load enable signal (LE signal ) is output. Next, according to the flowchart shown in FIG.
The operating procedure of step 5 will be explained. In the same figure, step S1
The outputs Zr, Zi of the equalizer 100 and the judgment values ar, a
Each component of i is subtracted by subtracters 201 and 202, and the resulting signal is converted into an absolute value by absolute value units 203 and 204 to obtain a signal S.
r = |Zr −ar |, Si = |Zi −ai
Get ｜. These signals Sr, Si indicate the absolute value distance of the regular points of the eye pattern, and are
In step 2, the comparator 205 compares the signal Sr with a predetermined minute distance (Sth), and the step S
In step 3, the comparator 206 compares the signals Si and Sth.

[0020] In steps S2 and S3, the signals Sr and Si
If both are determined to be less than or equal to Sth, step S
4, the latch 107,
The load enable (LE) signal for 108 is enabled. As a result, the Zr and Zi signals are latched by the latches 107 and 108, and the D/A converter 1
After D/A conversion by 02 and 103, the signal is output to the waveform observation device 104.

FIG. 7 shows an eye pattern in which only noise components are extracted from the actual eye pattern output shown in FIG. It can be seen that is observed. Next, a case will be described in which only the phase jitter component is extracted from the eye pattern output.

FIG. 4 is a block diagram showing the internal configuration of the limiter 105 in FIG. 1, which corresponds to the case where the eye pattern output is limited to only the phase jitter component, and FIG. 5 shows the operating procedure of the limiter 105. This is a flowchart showing the following. From FIG. 13, it can be seen that the dispersion of the eye pattern due to the phase jitter component spreads on a circle centered on the origin with respect to regular points at the same distance from the origin. Therefore, these points are point a where Zr and Zi signals are normal.
It is only necessary to calculate whether or not it lies on a circle centered on the origin of r and ai, but if only the components on the circle are extracted, the number of observation points will be extremely small, making the observation itself difficult. Considering this, here we observe points near the circle.

In the limiter shown in FIG. 4, Zr, Z
The i, ar, and ai signals are sent to multipliers 300 to 3, respectively.
03, Zr2 and Zi2 are added together in an adder 304, and outputted as S0=Zr2+Zi2. Further, ar2 and ai2 are added by an adder 305 and output as S1=ar2+ai2. After these S0 and S1 are subtracted by a subtracter 306, the absolute value thereof is calculated by an absolute value unit 307.

The comparator 308 compares the absolute value calculated by the absolute value unit 307 with a predetermined threshold value, and outputs a load enable signal (LE signal) based on the result. Next, the operating procedure of the restrictor 105 will be explained according to the flowchart shown in FIG. In the figure, in step S11, the adder 304 is replaced by the multiplier 30, as described above.
The sum value S0 = Zr2 + Zi2 of the Zr and Zi signals squared by 0.301 is calculated, and in step S12, the sum value S1 = ar2 of the square values of the ar and ai signals is calculated.
+ai2 is calculated.

In step S13, the subtracter 306 calculates
These S0 and S1 are subtracted, and the subtracted value is converted into an absolute value by the absolute value unit 307, and J=|S0 - S1
Get ｜. This J indicates the distance from the above-mentioned circle, and the closer it is to the circle, the closer it becomes to 0. Then, in step S14, the comparator 308 calculates the value of J and a certain minute distance J.
Then, only when J≦Jth, a load enable (LE) signal is output to the latches 107 and 108 in step S15.

FIG. 8 shows an eye pattern obtained when only the phase jitter component is extracted from the actual eye pattern output shown in FIG. Although the method for extracting only impulse noise from the actual eye pattern output is not particularly illustrated,
In the case of this impulse noise, observe the noise extraction screen,
By examining the error rate of the modem output signal, if an increase in the error rate is found to be due to something other than noise, it can be determined that this is due to impulsive noise or a sudden event.

As explained above, according to this embodiment,
By limiting the eye pattern output to only the noise component or extracting only the phase jitter component and limiting the observation pattern, it is possible to observe patterns for each cause of eye pattern variance, and it is possible to accurately understand the cause of variance. This has the effect of making identification easier. In the above embodiment, the eye pattern output range is limited outside the modem, but it may also be done inside the modem. In this case, since modem processing is usually done by software using a DSP, the restriction of the eye pattern output range is also done by software.

Furthermore, the present invention may be applied to a system made up of a plurality of devices, or to a device made up of one device.

[0029]

[Effects of the Invention] As explained above, according to the present invention,
By limiting the display range of each point of the output eye pattern, causes of eye pattern dispersion such as noise and phase jitter can be accurately grasped. Furthermore, the performance of the modem can be accurately observed from the dispersion of the eye pattern, and there is an effect that evaluations at the time of manufacturing the modem and evaluations of the modem in the field can be performed accurately and easily.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the configuration of an eye pattern monitoring device according to an embodiment of the present invention;

FIG. 2 is a block diagram showing the internal configuration of a limiter when limiting the eye pattern output to only noise components;

FIG. 3 is a flowchart showing the operation procedure of the limiter when limiting to noise components;

FIG. 4 is a block diagram showing the internal configuration of a limiter when limiting the eye pattern output to only the phase jitter component;

[Figure 5
] Flowchart showing the operating procedure of the limiter when limiting to the phase jitter component,

[Figure 6] Diagram showing an actual eye pattern,

[Fig. 7] A diagram showing only the noise component extracted from the actual eye pattern output,

FIG. 8 is a diagram showing an eye pattern when only the phase jitter component is extracted from the actual eye pattern output,

[Figure 9]C
CITT Recommendation V. A diagram showing an eye pattern of 9600 bps defined in 29,

FIG. 10: CCITT Recommendation V. 144 specified in 33
A diagram showing an eye pattern of 00bps,

FIG. 11 is a block diagram schematically illustrating the observation of the output signal of the equalizer,

FIG. 12: V. A diagram showing an example of an eye pattern when noise occurs on the transmission path in No. 29,

FIG. 13: V. A diagram showing an example of an eye pattern when phase jitter occurs on the transmission path in No. 29,

FIG. 14: V.
29 is a diagram showing an example of an eye pattern when impulse noise occurs on a transmission path in No. 29. FIG.

[Explanation of symbols]

100 Equalizer 1
01 Determiner 10
2,103 D/A converter 104
Waveform observation device 105
limiter 107,
108 Latch 205, 206, 3
08 Comparator

Claims (3)

[Claims] 1. An eye pattern monitor device for monitoring a phase modulated signal or a quadrature amplitude modulated signal in a two-dimensional space, wherein a dispersion range of an eye pattern is determined based on an in-phase component and a quadrature component of an input signal. What is claimed is: 1. An eye pattern monitoring device comprising: limiting means for limiting the area to an area; and means for outputting the area-limited eye pattern on two-dimensional coordinates. 2. The eye pattern monitoring device according to claim 1, wherein the limiting means limits the output points of the eye pattern to only points that are a predetermined distance away from a normal point. 3. The limiting means limits the output points of the eye pattern to only a range that is a predetermined distance from a circle passing through a regular point centered on the origin of the two-dimensional coordinates. The eye pattern monitor device according to item 1.