JP2907570B2 - 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 a phase modulation signal and a quadrature amplitude modulation signal.

[0002]

2. Description of the Related Art With the development of information communication technology in recent years, higher-speed data transmission has been realized. As a method of this high-speed data transmission, CCITT Recommendation V. 27te
r and V. 29, V.S. For example, there are phase modulation (PSK), which is a modulation method indicated by 33, and quadrature amplitude modulation (QAM), which is a multi-value 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 having this modem, an eye pattern is conventionally 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. An example of this eye pattern is shown in FIG. 9 or FIG. Among them, FIG. FIG. 10 shows an eye pattern of 9600 bps specified in CCITT Recommendation V.29. This is an eye pattern of 14400 bps specified by 33.

The above PSK signal and QAM signal are given by the following equations. S (t) = a ₁ (t) sin (ωct) + a ₂ (t) cos (ωct) (1) where S (t): modulated signal at time t ωc: carrier (carrier) angular 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 of the in-} phase component of the above equation (1).
(T) is plotted on the abscissa and the amplitude of the orthogonal component is plotted on the ordinate.

As can be seen from FIGS. 9 and 10, the number of points of the eye pattern is 29 is 16 points,
V. At 33, the number is 128 points, and the number of points increases exponentially as the transmission speed increases. Further, the observation of the eye pattern is to observe an output signal of an equalizer that compensates for distortion on a transmission path corresponding to the heart of a modem receiving unit.
FIG. 11 is a block diagram schematically illustrating the observation.

[0006] Normally, a DSP (Digita
l Signal Processor) performs digital signal processing, and if the transmission path to which the modem is connected transmits analog signals, a Digit is sent at the exit of the modem transmission unit.
tal-Analog (D / A) conversion, Anal at the entrance of the modem receiver
An og-Digital (A / D) conversion is performed. In FIG. 11, an equalizer 100 is for removing the influence of distortion due to a transmission path included in an input signal to obtain an original transmission signal, and the output signal is completely removed by the equalizer 100. In order to eliminate the influence of noise or the like, a legitimate point is determined by the determiner 101.

The eye pattern is for observing the output signal of the equalizer 100 (in other words, the input signal of the decision unit 101). The in-phase component and the quadrature component of the input signal converted into the digital signal are respectively D / A converter 102, 1
At 03, the signals are converted into analog signals, which are observed by a waveform observer 104 such as an oscilloscope. FIG. 29 shows an example of an eye pattern when noise, phase jitter, and impulse noise at 29 occur on a transmission path. FIG. 12 shows noise, FIG. 13 shows phase jitter, and FIG. 14 shows an eye pattern when impulse noise occurs. Thus, by observing the eye pattern, it is possible to know the effect of the signal on the transmission line and the performance of the modem such as how much the modem absorbs the effect.

[0008]

However, in an actual transmission line, noise, phase jitter, impulse noise, and the like as shown in FIGS. 12 to 14 do not occur individually, but all elements overlap. And can rarely be observed as a pattern as shown.
This situation can be easily estimated by superimposing all the patterns in FIGS.

Therefore, in the above prior art, there is no other way than to estimate the degree of influence of, for example, phase jitter from the superimposed eye pattern, and there is a problem that the cause of scattering of the eye pattern cannot be accurately detected. is there.

[0010]

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 monitoring device that monitors a phase modulation signal or a quadrature amplitude modulation signal in a two-dimensional space,
A judgment method for judging a legitimate point corresponding to an input signal point
Stages and normals determined as in-phase and quadrature components of the input point
Input signal based on the in-phase and quadrature components
No. is from the regular point determined by the determination means.
Determining means for determining whether or not it is within a predetermined range;
The input points to be monitored in the three-dimensional space are
Input determined to be within a predetermined range from a certain point
And limiting means for limiting the number of points .

Also, a phase modulation signal or quadrature amplitude modulation
Eye pattern monitor that monitors signals in two-dimensional space
And the input signal points to be monitored in the two-dimensional space
Through a regular point centered on the origin of the two-dimensional space.
Limited to input signal points within a specified range from the circle
Limiting means and output of restricted input signal points in two-dimensional space
And output means for inputting power .

[0012]

In the above arrangement, how much noise components
Accurately grasp whether eye patterns are dispersed
be able to. Also, how much eye
It is possible to accurately grasp whether patterns are dispersed.
Wear.

[0013]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic block diagram showing a configuration of an eye pattern monitoring device according to an embodiment of the present invention. In FIG. 1, an equalizer 100 receives a demodulated in-phase component signal and a quadrature component signal, removes a distortion component due to an influence of a transmission path superimposed on the signal based on the signal, and removes distortion. Output the removed signal. In the following description, the in-phase component of the output signal of the equalizer 100, and a quadrature component each Z _r, referred to as Z _i.

[0014] determination unit 101, the above Z _r, the Z _i as an input signal, Z _r, superimposed on the Z _i signal, the equalizer 100
In order to remove distortion and noise components that could not be removed,
Z _r, is to determine the point closest normal to Z _i signal points. Note that the in-phase component and the quadrature component of the output signal of the determiner 101 are called a _r and a _i , respectively. Traditionally, eye pattern, signal Z _r as described above, converted into an analog signal at each D / A converter Z _i, and measure it in the waveform observation device such as an oscilloscope.

However, in this embodiment, as will be described later,
Fixed value a_r , A_i And a waveform observer at the limiter 105
Z to output to 104_r , Z_i Determine signal limiting conditions
You. And the limiter 105 is Z_r , Z_i Signal is a limiting condition
, And only when the latch 107 and the latch 10
8 by enabling the load enable signal to
_r , Z_i Allows the signal to be latched. Latched
The converted signals are converted into analog signals by the D / A converters 102 and 103.
To a waveform observation device 104 such as an oscilloscope.
Observe at

[0016] On the other hand, if Z _r, Z _i signal is other than limiting conditions, Z _r, Z _i signal is not input to the latch 107, before that satisfies the condition latch signal is latched Since it is in the state as it is, the signal is sent to the waveform observer 104 again. Next, a method of actually limiting the eye pattern output to only noise components will be described. FIG.
FIG. 3 is a block diagram showing the internal configuration of the limiter 105 in FIG. 1 corresponding to the case where the eye pattern output is limited to only noise components. FIG. 3 is a flowchart showing the operation procedure of the limiter 105.

In FIG. 12 shown as the prior art, the variance of the eye pattern due to noise spreads in a circle with respect to a normal point, so that the actual eye pattern on which elements other than noise are superimposed is in-phase from the normal point. It can be seen that if only the distances of the orthogonal components and the orthogonal components are separated by a small distance, almost only the noise components can be observed.

Referring to FIG. 2, a subtractor 201 includes an equalizer 1
The subtracter 202 calculates the difference between the in-phase component Z _r of the output signal of 00 and the in-phase component a _r of the output signal of the decision unit 101, and the subtractor 202 calculates the quadrature component Z _i of the output signal of the equalizer 100 and the The difference between the output signal and the orthogonal component a _i is calculated. Then, the output of each subtractor is input to the next absolute value unit 203 or 204 to obtain its absolute value, and the output is input to the comparator 205 or 206.

The comparators 205 and 206 compare a predetermined threshold value with an input value as described later, and only when the result of the comparison satisfies the AND condition in the AND circuit 207, the load enable signal (LE signal). ) Is output.
Next, in accordance with the flowchart shown in FIG.
The operation procedure of No. 5 will be described. Referring to FIG.
In the output Z _r of the equalizer 100, Z _i and the determination value a _r, subtracting the component of each of a _i in the subtractor 201 and 202, signals S and absolute value of the signal by the absolute value unit 203, 204 _r = |
_{Z r -a r |, S i} = | Z i -a i | obtained. The signals S _r and S _i indicate the absolute value distance of the normal point of the eye pattern. In step S2, the comparator 205 compares the signal S _r with a predetermined minute distance (Sth). In step S3, the comparator 206 compares the signals S _i and Sth.

At steps S2 and S3, the signal S_r , S_i But
If both are determined to be less than or equal to Sth, the process proceeds to step S4.
Then, through the AND circuit 207, the latches 107 and 10
8 enable load enable (LE) signal
State. This gives Z _r , Z_i The signal is latch 10
7, 108, and D / A converters 102, 1
03 is output to the waveform observation device 104 after D / A conversion
You.

FIG. 7 shows an example in which only the noise component is extracted from the actual eye pattern output shown in FIG. 6. As described above, an eye pattern in which only the noise component is extracted from the eye pattern in which elements other than noise are also superimposed. Is observed. Next, a case where only the phase jitter component is extracted from the eye pattern output will be described.

FIG. 4 is a block diagram showing the internal structure of the limiter 105 in FIG. 1 corresponding to the case where the output of the eye pattern is limited to only the phase jitter component. FIG. From FIG. 13, it can be seen that the variance of the eye pattern due to the phase jitter component spreads on a circle centered on the origin with respect to a normal point at the same distance from the origin. Therefore, these points, Z _r, Z _i signal normalization point a
_It suffices to calculate whether or not they are on a circle centered on the origin of _r and a _i , but if only the components on the circle are extracted, the number of observation points becomes extremely small and the observation itself becomes difficult. Considering that, here, a point near the circle is observed.

[0023] In limiter shown in FIG. 4, Z _r, Z
_i, a _r, a _i signals are squared by multipliers 300 to 303 respectively, and Z _r ² and Z _i ² of which are added by the adder ^{_{304 S 0 = Z r 2 +}} Z i 2 Is output as Also,
a _r ² and a _i ² are added by the adder 305, and S ₁ = a _r ²
Is output as + a _i ^2. Then, after these S ₀ and S ₁ are subtracted by the subtractor 306, the absolute value
Its absolute value is calculated.

The comparator 308 compares the absolute value calculated by the absolute value calculator 307 with a predetermined threshold, and outputs a load enable signal (LE signal) based on the result. Next, an operation procedure of the limiter 105 will be described according to the flowchart shown in FIG. In the figure, in step S11, as described above, the adder 304 makes the multiplier 30
The sum S _{0 of} the Z _r and Z _i signals squared at 0 and 301
= Calculates the Z _r ² + Z _i ^2, in step S12, a _r, a
sum of squares of the _i signal S ₁ = calculates the a _r ² + a _i ^2.

In step S13, the subtractor 306
The subtraction of S ₀ and S ₁ and the absolute value of the subtraction value by the absolute value unit 307 are performed, and J = | S ₀ −S ₁ | is obtained. This J indicates the distance from the above-mentioned circle, and the closer to the circle the closer to zero. Then, step S14
Then, the value of J is compared with a certain minute distance Jth by the comparator 308, and the step S1 is performed only when J ≦ Jth.
In step 5, a load enable (LE) signal is output to the latches 107 and 108.

FIG. 8 shows an eye pattern when only the phase jitter component is extracted from the actual eye pattern output shown in FIG. Although a method of extracting only impulse noise from an actual eye pattern output is not specifically shown,
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 other than noise is recognized, it can be determined that the error is due to impulsive noise or the like and a sudden event.

As described above, according to this embodiment,
By restricting the eye pattern output to only noise components or extracting only the phase jitter component and restricting the observation pattern, pattern observation can be performed for each cause of eye pattern dispersion, and the causes of dispersion can be accurately grasped, and There is an effect that it becomes easy to specify. In the above embodiment, the eye pattern output range is limited outside the modem. However, the limitation may be performed inside the modem. In this case, since the processing of the modem is usually processed by software using a DSP, the limitation of the eye pattern output range is also processed by software.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device.

[0029]

As described above, according to the present invention,
A regular poi determined as the in-phase and quadrature components of the input point
Input signal points based on the in-phase and quadrature components of the
Is within a predetermined range from the determined normal point.
Means to determine whether or not
The input point to be monitored is the regular point determined by the determination means.
To the input point determined to be within a predetermined range from the point
By providing limiting means to limit the noise component
How accurately the eye patterns are dispersed
Can be grasped. Also, monitor in two-dimensional space
The input signal point to be exponential should be normalized with respect to the origin of the two-dimensional space.
Input signal within a predetermined range from a circle passing through a
Nominal point, how much phase jitter
Accurately grasp whether eye patterns are dispersed
be able to.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a 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 an operation procedure of a limiter when limiting to a noise component;

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

FIG. 5 is a flowchart showing an operation procedure of a limiter when limiting to a phase jitter component;

FIG. 6 is a diagram showing an actual eye pattern;

FIG. 7 is a diagram showing only noise components extracted from an actual eye pattern output;

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

FIG. 9: CCITT Recommendation V. 9600 specified by 29
Figure showing bps eye pattern,

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

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

FIG. FIG. 29 is a diagram illustrating an example of an eye pattern when noise occurs on a transmission path in 29

FIG. FIG. 29 is a diagram showing an example of an eye pattern when phase jitter occurs on a transmission path in 29.

FIG. FIG. 29 is a diagram illustrating an example of an eye pattern in a case where impulse noise occurs on a transmission path at 29.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Equalizer 101 Judge 102, 103 D / A converter 104 Waveform observer 105 Limiter 107, 108 Latch 205, 206, 308 Comparator

Claims (2)

(57) [Claims] 1. An eye pattern monitoring device for monitoring a phase modulation signal or a quadrature amplitude modulation signal in a two-dimensional space , wherein a determination means for determining a normal point corresponding to an input signal point.
The stage and the normal points determined as the in-phase and quadrature components of the input point.
Input signal points based on the in-phase and quadrature components of the
Is determined from the legitimate points determined by the determination means.
Determining means for determining whether or not the input point is within the range; and an input point to be monitored in the two-dimensional space,
An entry determined to be within a predetermined range from a regular point
An eye pattern monitor device comprising: a limiting unit that limits the point of force . 2. A phase modulation signal or a quadrature amplitude modulation signal.
Is an eye pattern monitor that monitors
I, the input signal point to be monitored by on a two-dimensional space, two-dimensional sky
From a circle passing through a regular point centered on the origin between
Limiting means for limiting input signal points existing within a fixed range, and an output means for outputting the limited input signal points to a two-dimensional space
Eye pattern monitor device, characterized in that it comprises a stage.