JP4048556B2 - Jitter analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital jitter analyzer (hereinafter referred to as a jitter analyzer), and more particularly to a jitter analyzer that obtains a jitter value by digital processing.
[0002]
[Prior art]
The jitter analyzer is a measuring device that measures a time required for a specific signal change of a signal under measurement, calculates a jitter value based on the measured time, and displays the jitter value with an analog meter.
[0003]
FIG. 5 is a block diagram of a conventional jitter analyzer. The measurement time setting unit 1 inputs the gate time set in consideration of the operation speed of the designated device to the time measurement unit 2 as measurement control information 102. The time measurement unit 2 measures the time of the signal under measurement 101 according to the gate time of the measurement control information 102 and stores the measurement data 103 in the acquisition memory 10. The jitter calculation unit 3 reads the measurement data 103, calculates the jitter value, and stores it in the jitter value memory 4 as the measurement jitter value 104. The meter control unit 5 reads the measured jitter value 104 from the jitter value memory 4, converts it into a voltage value 105, and inputs it to the meter unit 6. The meter unit 6 drives the pointer of the analog meter based on the voltage value 105.
[0004]
[Problems to be solved by the invention]
In the conventional jitter analyzer described above, the gate time specified by the measurement time setting unit 1 is set to about several hundreds of milliseconds in consideration of the time necessary for calculating the jitter value. Here, the pointer of the meter unit 6 fluctuates every gate time when the jitter value is updated, and the pointer of the meter unit 6 moves discretely according to this, so that the measurement feeling by the analog meter cannot be satisfied.
[0005]
The present invention has been made in order to solve the above-described problems of the prior art, and provides a jitter analyzer capable of obtaining a highly accurate measurement value and continuously viewing a measurement change. For the purpose.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a jitter analyzer according to the present invention is specified in a jitter analyzer that measures a time required for a specific signal change of a signal under measurement and calculates a jitter value based on the measured time. A measurement time setting unit for setting a plurality of measurement times divided so that the change of the pointer of the analog meter can be visually recognized as a continuous movement with respect to the gate time, and time measurement of the signal under measurement based on the set measurement time A time measurement unit that sequentially performs measurement, a measurement data storage unit that stores measurement data sequentially obtained by the time measurement unit, and when measurement data is newly obtained for the one measurement time by the time measurement unit, analog Mae outputting a jitter calculating unit that calculates a jitter value based on the measurement data obtained within the gate time, the jitter value calculated by the jitter calculating unit And an outputting unit having a.
[0007]
Jitter analyzer of the present invention, since the process of the measurement data from the digitizing until obtaining the voltage value are all digitally processing a high jitter value calculated et be the measurement accuracy, and, in several gate time Since the jitter value is updated for each divided measurement time, the pointer of the analog meter of the output unit is visually recognized smoothly, and the measurement feeling by analog display is satisfied.
[0008]
In the jitter analyzer according to the present invention, it is preferable that the measurement data storage unit discards all of the storage when the designation of the gate time is changed. In this case, even if the gate time is changed during measurement, a correct jitter value corresponding to the gate time is output.
[0009]
It is also a preferred embodiment of the present invention that pre-Symbol output unit comprises a D / A converter and the output circuit. In this case, the output waveform of a smooth jitter signal can be observed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The jitter analyzer of the present invention will be described below with reference to the drawings based on the embodiments of the present invention. FIG. 1 is a block diagram of a jitter analyzer according to an embodiment of the present invention. The jitter analyzer according to the present embodiment includes a measurement time setting unit 1 that sets a signal measurement time and the number of measurement divisions based on a specified gate time, a time measurement unit 2 that performs time measurement of a signal under measurement, and a jitter value. Jitter calculation unit 3 for calculating the jitter value, jitter value memory 4 for holding the obtained jitter value, meter control unit 5 for converting the jitter value into an analog signal, meter unit 6 having an analog meter, division number memory for holding the division number 7. Counter memory 8 for holding the number of measurement times, addition memory 9 for holding data obtained by adding all measurement data, and 10 acquisition memories (measurement data storage units) 11 for holding individual measurement data separately ~ 21.
[0011]
FIG. 2 shows a front view of the jitter analyzer of FIG. In the jitter analyzer, a meter unit 6 constituting an analog meter is disposed on the left side of the front surface, an operation panel portion of the measurement time setting unit 1 is disposed on the upper right side of the front surface, and a data input unit 31 that constitutes an input of the time measurement unit 2 and The clock input unit 32 is disposed on the lower right side of the front surface. The measurer inputs a signal under measurement from the data input unit 31 and the clock input unit 32 and designates a predetermined gate time from the operation panel portion of the measurement time setting unit 1.
[0012]
FIG. 3 is a flowchart showing the time measurement operation by the jitter analyzer of FIG. The measurement time setting unit 1 determines whether or not a new gate time is designated (step S11). If “YES”, the measurement time and the number of divisions are set for the new gate time. Here, the optimum time of the meter operation in which the operation of the analog meter can be visually recognized is generally about 100 ms. The specified gate time is 300 ms. The time setting unit 1 sets the value of the measurement time to 100 ms, which is the same as the meter operation optimum time, sets the number of divisions to 3, and converts the 300 ms gate time into three 100 ms measurement times. The measurement time setting unit 1 stores the division number “3” in the division number memory 7 and resets the counter memory 8 to “0”.
[0013]
The measurement time setting unit 1 inputs a measurement time of 100 ms and a control command for the time measurement unit 2 to the time measurement unit 2 as measurement control information 102. The time measuring unit 2 decodes the measurement control information 102 and clears the stored contents of the acquisition memories 11 to 21 and the addition memory 9 when the measurement start control command is a control command for starting measurement. The time measurement unit 2 reads “3” stored in the division number memory 7, selects the three acquisition memories 11 to 13 as memories for storing the measurement data 103 for three times, and sets the acquisition memory 11 to the first time. In addition, the acquisition memory 12 is set to be used for the second time, and the acquisition memory 13 is set to be used for the third time (step S12).
[0014]
The time measuring unit 2 reads “0” stored in the counter memory 8 and increments the stored content in the counter memory 8 by 1 to “1”. Here, when the storage content of the counter memory 8 becomes larger than the storage content of the division number memory 7, it is forcibly reset to "1". The time measuring unit 2 recognizes that the next time measurement is the first time, measures the measured signal 101 based on the measurement time of 100 ms, and stores the first measurement data 103 in the acquisition memory 11. (Step S13). The time measuring unit 2 adds all the contents stored in the three acquisition memories 11 to 13 and stores them in the addition memory 9 (step S14).
[0015]
The jitter calculation unit 3 reads the storage contents of the addition memory 9 and performs jitter calculation, and stores the measured jitter value 104 in the jitter value memory 4 (step S15). The meter control unit 5 converts the stored contents of the jitter value memory 4 into a read voltage and inputs the voltage to the meter unit 6 as a voltage value 105. The meter unit 6 drives the pointer of the analog meter based on the voltage value 105 (step S16).
[0016]
Next, returning to step S11, the measurement time setting unit 1 determines whether or not a new gate time is specified. In the case of “NO”, the jitter analyzer recognizes that the next time measurement is the second time, and executes steps S13 to S16 in the same manner, and also in the second time and thereafter.
[0017]
FIGS. 4A to 4D show first to fourth trial examples of time measurement in FIG. In the first to fourth time measurement, the stored contents of any one of the acquisition memories 11 to 13, the addition memory 9, and the counter memory 8 are updated at a measurement time period of 100 ms.
[0018]
As shown in FIG. 5A, in the first time measurement, the first measurement data is stored in the acquisition memory 11 and “1” is stored in the counter memory 8. Only the first measurement data is available. As shown in FIG. 5B, in the second time measurement, the second measurement data is stored in the acquisition memory 12 and “2” is stored in the counter memory 8. This is the total value of the first measurement data and the second measurement data.
[0019]
As shown in FIG. 6C, in the third time measurement, the third measurement data is stored in the acquisition memory 13 and “3” is stored in the counter memory 8. This is the total value of the first to third measurement data. As shown in FIG. 4D, in the fourth time measurement, the fourth measurement data is stored in the acquisition memory 11 and “1” is stored in the counter memory 8. This is the total value of the second to fourth measurement data.
[0020]
Since the voltage value 105 changes in a cycle of 100 ms when the addition memory 9 is updated, the pointer of the analog meter of the meter unit 6 moves smoothly as compared with the conventional case where the voltage value 105 changes in a cycle of 300 ms.
[0021]
Note that a smooth output waveform of a jitter signal can be similarly observed when a jitter value is converted into an analog voltage by a DA converter and output to the outside as a jitter signal.
[0022]
According to the above embodiment, since the process from digitizing the measurement data to obtaining the voltage value is digitally processed, a jitter value with high measurement accuracy is obtained, and the gate time is divided into several times. Since the jitter value is updated at every measurement time, a continuous change in the jitter value can be visually recognized.
[0023]
Although the present invention has been described based on the preferred embodiment, the jitter analyzer of the present invention is not limited to the configuration of the above embodiment, and various modifications can be made from the configuration of the above embodiment. In addition, a modified jitter analyzer is also included in the scope of the present invention.
[0024]
【The invention's effect】
As described above, in the jitter analyzer of the present invention, the entire process from digitizing measurement data to obtaining a voltage value is digitally processed, so that a jitter value with high measurement accuracy can be obtained and the gate time can be obtained. Since the jitter value is updated every measurement time divided into several times, a continuous change in the jitter value can be visually recognized.
[0025]
In addition, since a jitter value with high measurement accuracy can be output to the outside as a jitter signal having a smooth change, the communication interface and the program are not required for taking in the data from the outside to the computer.
[Brief description of the drawings]
FIG. 1 is a block diagram of a jitter analyzer according to an embodiment of the present invention.
2 shows a front view of the jitter analyzer of FIG.
FIG. 3 is a flowchart showing a time measurement operation by the jitter analyzer of FIG. 1;
4A to 4D show first to fourth trial examples of time measurement in FIG. 3;
FIG. 5 is a block diagram of a conventional jitter analyzer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Measurement time setting part 2 Time measurement part 3 Jitter calculation part 4 Jitter value memory 5 Meter control part 6 Meter part 7 Division number memory 8 Counter memory 9 Addition memory 10-21 Acquisition memory (measurement data storage part)
101 Measurement Signal 102 Measurement Control Information 103 Measurement Data 104 Measurement Jitter Value 105 Voltage Value

Claims (3)

In a jitter analyzer that measures the time required for a specific signal change of a signal under measurement and calculates a jitter value based on the measured time,
A measurement time setting unit for setting a plurality of measurement times divided so that a change in the pointer of the analog meter can be visually recognized as a continuous movement with respect to a specified gate time, and a signal under measurement based on the set measurement time A time measurement unit that sequentially performs time measurement, a measurement data storage unit that stores measurement data sequentially obtained by the time measurement unit, and when measurement data is newly obtained for one measurement time by the time measurement unit, A jitter calculation unit that calculates a jitter value based on measurement data obtained within the previous gate time; and an output unit that includes an analog meter that outputs the jitter value calculated by the jitter calculation unit. A featured jitter analyzer. The jitter analyzer according to claim 1, wherein the measurement data storage unit discards all of the storage when the designation of the gate time is changed. The jitter analyzer according to claim 1, wherein the output unit includes a D / A converter and an output circuit.

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