JP4094843B2 - measuring device - Google Patents

Description

別の実施例においては、例えば、数２が、ジッタ量Rj、被測定電位が変化する周期のばらつき量Tj、及び補正値Mjの関係を示してもよい。
【数２】

数２において、値Djは、被測定電位が変化する周期のばらつき量Tjの測定において、測定装置の特性に起因して生じる誤差である測定ジッタの値を示す。
【００６０】
以上説明した測定装置１００により、被測定信号のばらつき量を測定することができる。本実施形態によれば、測定装置１００は、ジッタ量の測定における、被測定信号に重畳する電圧方向のノイズの影響による誤差を低減することができる。
【００６１】
図７は本発明の第２の実施形態に係る測定装置１００の構成の例を示す。測定装置１００は、入力ポート１０２、信号測定部１０４、ノイズ測定部１０６、補正部１０８、ノイズ測定指示部１１０、表示モード設定部１１２、平均値算出部１１４、信号分布算出部１１６、表示部１１８、波形表示部１２０、及び伝送路２００を備える。図７において、図１と同じ符号を付した構成要素は、図１におけるそれぞれの構成要素と同じ機能を有する。
【００６２】
伝送路２００は、被測定信号を生成する被測定信号源、又は定電圧信号を生成する定電圧信号源のいずれかと入力ポート１０２とを、ノイズ測定部の動作を制御する切換信号に応じて電気的に接続する。本実施形態において、伝送路２００は入力切換え部１２２、及び同軸ケーブル１２４を有する。
【００６３】
入力切換え部１２２は、図１に示す入力切換え部１２２と同じ機能を有する。入力切換え部１２２は同軸ケーブル１２４を介して被測定信号、又は定電圧信号のいずれかを入力ポート１０２に供給する。同軸ケーブル１２４は、被測定信号源、又は定電圧信号源のいずれかと入力ポート１０２とを電気的に接続する。同軸ケーブル１２４が電気的に接続する入力切換え部１２２と入力ポート１０２との距離は、被測定信号源と入力切換え部１２２との距離より大であってよい。
【００６４】
本実施形態において、入力ポート１０２は、同軸ケーブル１２４を介して定電圧信号を受け取るため、ノイズ測定部１０６は、同軸ケーブル１２４が伝送する信号が受けるノイズの成分を含むノイズ電位のばらつき量を算出する。よって、本実施形態によれば、測定装置１００は、同軸ケーブル１２４において被測定信号に重畳する電圧方向のノイズの影響によるジッタ測定の誤差を低減することができる。
【００６５】
図８は、伝送路２００の別の実施例を示す。本例において、伝送路２００は、入力切換え部（１２２-１〜１２２-４）、同軸ケーブル（１２４-１、１２４-２）、プリアンプ１２６、及びポストアンプ１２８を有する。プリアンプ１２６は、信号源が生成する小さい電圧の信号を増幅する増幅器であってよい。本例において、プリアンプ１２６は、被測定信号源が生成する被測定信号を増幅する。プリアンプ１２６は、被測定信号を入力切換え部１２２-３から受け取り、当該増幅した被測定信号を入力切換え部１２２-２に供給する。
【００６６】
ポストアンプ１２８は、プリアンプ１２６が増幅して出力する信号を更に増幅する増幅器であってよい。本例において、ポストアンプ１２８は、プリアンプ１２６が増幅して出力する被測定信号を更に増幅する。ポストアンプ１２８は、プリアンプ１２６が増幅した被測定信号を入力切換え部１２２-２から受け取り、当該更に増幅した信号を入力切換え部１２２-１に供給する。
【００６７】
同軸ケーブル１２４-１は、入力切換え部１２２-１と、入力ポート１０２とを電気的に接続する。同軸ケーブル１２４-１は、入力切換え部１２２-１が出力する信号を入力ポート１０２に供給する。同軸ケーブル１２４-２は、入力切換え部１２２-４と、入力切換え部１２２-３とを電気的に接続する。同軸ケーブル１２４-２は、入力切換え部１２２-４が出力する信号を入力切換え部１２２-３に供給する。
【００６８】
入力切換え部（１２２-１〜１２２-４）は、図１に示す入力切換え部１２２と同じ機能を有する。本例において、入力切換え部１２２-４は、切換信号-４に応じて、被測定信号、又は定電圧信号のいずれかを出力する。入力切換え部１２２-３は、切換信号-３に応じて、同軸ケーブル１２４を介して受け取る被測定信号、又は定電圧信号のいずれかを出力する。入力切換え部１２２-２は、切換信号-２に応じて、プリアンプ１２６が増幅した被測定信号、又は定電圧信号のいずれかを出力する。入力切換え部１２２-１は、切換信号-１に応じて、ポストアンプ１２８が更に増幅した被測定信号、又は定電圧信号のいずれかを出力する。入力切換え部（１２２-１〜１２２-４）は、切換信号-１〜切換信号-４をそれぞれノイズ測定指示部１１０から受け取ってよい。
【００６９】
本例において、入力ポート１０２は、同軸ケーブル（１２４-１、１２４-２）、プリアンプ１２６、及びポストアンプ１２８を介して定電圧信号を受け取る。ノイズ測定部１０６は、同軸ケーブル（１２４-１、１２４-２）、プリアンプ１２６、及びポストアンプ１２８が伝送する信号が受けるノイズの成分を含むノイズ電位のばらつき量を算出する。よって、本例によれば、測定装置１００は、被測定信号に同軸ケーブル（１２４-１、１２４-２）、プリアンプ１２６、及びポストアンプ１２８において重畳する電圧方向のノイズの影響による誤差を低減して、被測定信号のジッタ量を測定することができる。更に、本例によれば、入力ポート１０２が定電圧信号を受け取る経路をユーザが選択可能であるため、被測定信号の特性に合わせたノイズの影響による誤差の低減ができる。
【００７０】
以上、本発明を実施形態を用いて説明したが、本発明の技術的範囲は上記実施形態に記載の範囲には限定されない。上記実施形態に、多様な変更または改良を加えることができる。そのような変更または改良を加えた形態も本発明の技術的範囲に含まれ得ることが、特許請求の範囲の記載から明らかである。
【００７１】
【発明の効果】
上記説明から明らかなように、本発明によれば、ジッタ量の測定における、被測定信号に重畳する電圧方向のノイズの影響による誤差を低減することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る測定装置１００の構成図である。
【図２】波形表示部１２０が表示する定電圧信号の波形を示す概念図である。
【図３】波形表示部１２０が表示する被測定信号の波形を示す概念図である。
【図４】タイミング算出部４０２、及びばらつき量算出部４０４の動作を説明する図である。
【図５】波形表示部１２０が表示する信号分布上界値、及び信号分布下界値を示す概念図である。
【図６】波形表示部１２０が表示する補正信号電位を示す概念図である。
【図７】本発明の第２の実施形態に係る測定装置１００の構成図である。
【図８】第２の実施形態に係る伝送路２００の別の構成例を示す図である。
【符号の説明】
１００・・・測定装置、１０２・・・入力ポート、１０４・・・信号測定部、１０６・・・ノイズ測定部、１０８・・・補正部、１１０・・・ノイズ測定指示部、１１２・・・表示モード設定部、１１４・・・平均値算出部、１１６・・・信号分布算出部、１１８・・・表示部、１２０・・・波形表示部、１２２、１２２-１〜１２２-４・・・入力切換え部、１２４、１２４-１、１２４-２・・・同軸ケーブル、１２６・・・プリアンプ、１２８・・・ポストアンプ、４０２・・・タイミング算出部、４０４・・・ばらつき量算出部、４０６・・・電位変化率算出部、４０８・・・サンプリング測定部、８０２・・・補正値算出部、８０４・・・ジッタ算出部、４８・・・統計処理対象ウィンドウ、５０・・・ヒストグラム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a measuring apparatus. In particular, the present invention relates to a measuring apparatus that measures the amount of variation in a signal under measurement.
[0002]
[Prior art]
Conventionally, a digital oscilloscope has been used in jitter measurement of a signal under measurement. A sampling oscilloscope, which is a form of digital oscilloscope, stores voltage measurement data at a number of sample points. In jitter measurement by a sampling oscilloscope, jitter is measured by statistically processing measurement data at a large number of sampling points.
[0003]
[Problems to be solved by the invention]
However, jitter measurement using an oscilloscope has a problem that an error occurs in the jitter value calculated by statistical processing due to the influence of noise in the voltage direction superimposed on the signal under measurement.
[0004]
Then, this invention aims at providing the measuring apparatus which can solve said subject. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous specific examples of the present invention.
[0005]
[Means for Solving the Problems]
That is, according to the first aspect of the present invention, the input port to which the signal under measurement is to be input and the signal under measurement When the signal source is active, A signal measuring unit that measures the potential to be measured, which is the potential of the input port, and calculates the amount of variation in the measurement results; When the signal source of A noise measurement unit that calculates a variation amount of the noise potential generated in the input port; and a correction unit that calculates a variation amount of the signal under measurement based on the variation amount of the measurement result and the variation amount of the noise potential. A measuring device is provided.
[0006]
Further, it is preferable that the signal measuring unit calculates a variation amount of a cycle in which the measured potential changes as a variation amount of the measurement result, and the correction unit calculates a jitter amount of the measured signal as a variation amount of the measured signal. . The input port is the signal under measurement Input when the signal source is in standby The noise measurement unit measures the potential of the input port when the input port receives the constant voltage signal as the noise potential and calculates the variation amount of the noise potential. It's okay. In this case, the input port preferably receives the ground potential as a constant voltage signal.
[0007]
Further, the signal measurement unit includes a timing calculation unit that calculates a crossover timing, which is a timing at which the potential to be measured indicates a predetermined threshold voltage, and a variation amount calculation unit that calculates a variation amount of the period based on the crossover timing. It is preferable to have. Further, the signal measuring unit further includes a potential change rate calculating unit for calculating a crossing slew rate that is a rate of change of the measured potential at the crossing timing, and the correcting unit calculates the value of the variation amount of the noise potential by the crossing slew rate. It is preferable to have a correction value calculation unit that calculates a value obtained by dividing the value as a correction value, and a jitter calculation unit that calculates the square root of a value obtained by subtracting the square value of the correction value from the square value of the variation amount of the period as the jitter amount. .
[0008]
Furthermore, the signal measurement unit has a sampling measurement unit that measures the measured potential at a predetermined cycle, stores the measurement timing and the measured potential at the measurement timing in association with each other and stores them as sampling measurement data. It is preferable that the calculation unit calculates the crossover timing based on the sampling measurement data. The sampling measurement unit may store a phase value indicating the time from the predetermined timing in the cycle of the signal under measurement to the time of measurement as the measurement timing. In addition, the sampling measurement unit When the signal source of It is preferable that the noise potential measured at the predetermined period is stored as noise measurement data, and the noise measurement unit calculates the variation amount of the noise potential based on the noise measurement data.
[0009]
Furthermore, a noise measurement instructing unit that generates a switching signal for controlling the operation of the noise measuring unit based on a user instruction is provided, and the noise measuring unit has a noise potential variation amount when the switching signal shows a predetermined value. Is preferably calculated.
[0010]
Furthermore, it is preferable to further include a display unit for displaying the value of the jitter amount. The display unit may display the value of the variation amount of the period or the value of the jitter amount in accordance with a display instruction signal that instructs the content displayed by the display unit. In this case, it is preferable to further include a display mode setting unit that generates a display instruction signal based on a user instruction.
[0011]
Further, for a predetermined range of phase values, a first axis coordinate value indicating the phase value stored by the sampling measurement unit and a second axis coordinate value indicating the measured potential corresponding to the phase value are shown. It is preferable to provide a waveform display unit that displays a signal waveform including coordinate points. In this case, among the phase values stored by the sampling measurement unit, the average value for calculating the average value of the measured potential corresponding to the phase value substantially equal to the one phase value as the average signal potential corresponding to the one phase value A signal distribution for calculating a value obtained by adding the variation amount of the noise potential to the average signal potential as a signal distribution upper bound value and calculating a value obtained by subtracting the variation amount of the noise potential from the average signal potential as a signal distribution lower bound value And a waveform display unit including a coordinate value of a first axis indicating one phase value and a second axis indicating a signal distribution upper bound value or a signal distribution lower bound value corresponding to the one phase value. It is preferable to display coordinate points indicating the coordinate values.
[0012]
Further, the signal distribution calculation unit calculates a corrected signal potential obtained by correcting the measured potential corresponding to one phase value based on the average signal potential, the signal distribution upper limit value, and the signal distribution lower limit value, and the waveform display unit It is preferable to display a coordinate point indicating the coordinate value of the first axis indicating one phase value and the coordinate value of the second axis indicating the correction signal potential corresponding to the one phase value. When the measured potential corresponding to one phase value is larger than the signal distribution upper limit value, the signal distribution calculation unit corrects the value obtained by subtracting the difference between the signal distribution upper limit value and the average signal potential from the measured potential. When the measured potential corresponding to one phase value is smaller than the signal distribution lower bound value, the value calculated by adding the difference between the average signal potential and the signal distribution lower bound value is the corrected signal potential. May be calculated as
[0013]
Further, the average value calculation unit calculates an average value of the measured potential corresponding to the phase value substantially equal to the other phase value among the phase values stored in the sampling measurement unit, and the average signal potential corresponding to the other phase value. The signal distribution calculation unit calculates a signal distribution upper bound value and a signal distribution lower bound value corresponding to the other phase value based on the variation amount of the average signal potential and the noise potential, and displays the waveform. The coordinate point indicates the coordinate value of the first axis indicating the other phase value and the coordinate value of the second axis indicating the signal distribution upper bound value or the signal distribution lower bound value corresponding to the other phase value. May be displayed.
[0014]
Further, either the signal source to be measured for generating the signal to be measured or the constant voltage signal source for generating the constant voltage signal and the input port are electrically connected in accordance with the switching signal for controlling the operation of the noise measuring unit. A transmission path may be further provided. The transmission line may include a coaxial cable that electrically connects either the signal source to be measured or the constant voltage signal source and the input port.
[0015]
The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and all combinations of features described in the embodiments are the solution of the invention. It is not always essential to the means.
[0017]
FIG. 1 shows an example of the configuration of a measuring apparatus 100 according to the first embodiment of the present invention. The measuring apparatus 100 is a measuring apparatus that measures the amount of variation in a signal under measurement, and includes an input port 102, a signal measuring unit 104, a noise measuring unit 106, and a correcting unit 108. In the present embodiment, the measurement apparatus 100 further includes a noise measurement instruction unit 110, a display unit 118, a display mode setting unit 112, a waveform display unit 120, an average value calculation unit 114, a signal distribution calculation unit 116, and an input switching unit 122. Prepare. The measuring apparatus 100 may be a sampling oscilloscope, for example. The measuring apparatus 100 may be a test apparatus that tests an electronic device. The input port 102 is a terminal to which a signal under measurement is to be input. In the present embodiment, the input port 102 receives a constant voltage signal indicating a predetermined potential in a state where the signal under measurement is not operating. The input port 102 preferably receives the ground potential as a constant voltage signal.
[0018]
The signal measuring unit 104 measures a measured potential that is the potential of the input port 102 in a state where the measured signal is operating, and calculates a variation amount of the measurement result. In the present embodiment, the signal measuring unit 104 calculates a variation amount of a cycle in which the measured potential changes as a variation amount of the measurement result.
[0019]
In another embodiment, the signal measuring unit 104 may calculate, for example, a variation amount of the measured potential with respect to time as the variation amount of the measurement result. The signal measuring unit 104 may calculate the variation amount of the potential of the signal under measurement at a predetermined timing as the variation amount of the measurement result. The signal measuring unit 104 may calculate a variation amount of timing at which the signal under measurement indicates a predetermined potential as the variation amount of the measurement result.
[0020]
The noise measuring unit 106 calculates a variation amount of the noise potential generated in the input port 102 in a state where the signal under measurement is not operating. In the present embodiment, the noise measurement unit 106 measures the potential of the input port 102 when the input port 102 receives a constant voltage signal as the noise potential, and calculates the variation amount of the noise potential. The noise measurement unit 106 may calculate the variation amount of the noise potential when the switching signal for controlling the operation of the noise measurement unit 106 shows a predetermined value. In the present embodiment, the noise measurement unit 106 receives a switching signal from the noise measurement instruction unit 110. The noise measuring unit 106 calculates the variation amount of the noise potential when the logical value of the switching signal is 1.
[0021]
The correction unit 108 calculates the variation amount of the signal under measurement based on the variation amount of the measurement result calculated by the signal measurement unit 104 and the variation amount of the noise potential calculated by the noise measurement unit 106. In the present embodiment, the correction unit 108 calculates the variation amount of the signal under measurement by correcting the variation amount of the measurement result with the variation amount of the noise potential. The correcting unit 108 calculates the jitter amount of the signal under measurement as the variation amount of the signal under measurement.
[0022]
The noise measurement instruction unit 110 receives a user instruction and changes the value of a switching signal for controlling the operation of the noise measurement unit 106 based on the user instruction. The noise measurement instruction unit 110 may change the logical value of the switching signal to 0 or 1 based on a user instruction. The noise measurement instruction unit 110 may further generate a signal that instructs the correction unit 108 to start calculating the jitter amount based on a user instruction. The noise measurement instruction unit 110 may receive a user instruction by, for example, an operation button operable by the user or a touch panel.
[0023]
The display unit 118 displays the value of the jitter amount. In the present embodiment, the display unit 118 displays the value of the variation amount of the period or the value of the jitter amount in accordance with a display instruction signal that instructs the content displayed by the display unit 118. The display unit 118 may further display the value of the variation amount of the noise potential. The display unit 118 receives a display instruction signal from the display mode setting unit 112. It is preferable that the display mode setting unit 112 receives a user instruction and generates a display instruction signal based on the user instruction. The display mode setting unit 112 may receive a user instruction, for example, by an operation button operable by the user or a touch panel.
[0024]
The waveform display unit 120 displays the waveform of the signal measured by the measurement apparatus 100. In the present embodiment, the waveform display unit 120 displays the waveform of the signal under measurement measured by the measuring apparatus 100 as a sampling oscilloscope while the signal under measurement is operating. The waveform display unit 120 displays the waveform of the constant voltage signal measured by the measuring apparatus 100 as a sampling oscilloscope while the signal under measurement is not operating.
[0025]
The average value calculator 114 calculates an average signal potential at each phase value of the signal under measurement. The signal distribution calculation unit 116 calculates a range in which the value of the measured potential varies based on the average signal potential and the variation amount of the noise potential. In the present embodiment, the signal distribution calculation unit 116 calculates the range as a signal distribution upper bound value and a signal distribution lower bound value.
[0026]
The input switching unit 122 supplies either the signal under measurement or the constant voltage signal to the input port 102 according to the switching signal. The input switching unit 122 includes a first input terminal that receives a signal under measurement, a second input terminal that receives a constant voltage signal, and an output terminal that is electrically connected to one of the first and second input terminals. And have. The input switching unit 122 supplies the signal under measurement to the input port 102 when the logical value of the switching signal is zero. When the logical value of the switching signal is 1, the input switching unit 122 supplies a constant voltage signal to the input port 102. The input switching unit 122 receives the signal under measurement from, for example, a signal under measurement source that is a photodiode that generates the signal under measurement based on an optical signal.
[0027]
As described above, the measuring apparatus 100 calculates the jitter amount of the signal under measurement by correcting the variation amount of the cycle in which the potential under measurement changes with the amount of noise potential variation. In another embodiment, the measuring apparatus 100 calculates the variation amount of the measured potential when the measured signal source that generates the measured signal is in the first state as the first variation amount, and the measured signal source However, the variation amount of the potential to be measured in a second state different from the first state may be calculated as the second variation amount. In this case, the measuring apparatus 100 corrects the second variation amount with the first variation amount and calculates the variation amount of the signal under measurement. The measuring apparatus 100 calculates the first variation amount in a state where one component included in the signal source to be measured is not operating, and the second variation in a state where the one component is operating. The amount may be calculated.
[0028]
For example, the measuring apparatus 100 calculates the first variation amount based on the signal under measurement generated in the standby state by the signal source under measurement, and the first measurement based on the signal under measurement generated in the active state by the signal source under measurement. The variation amount of 2 may be calculated. The signal source under measurement may be, for example, a modulation signal generator having a power supply circuit and a modulator. In this case, the modulation signal generator may stop the operation of the modulator in the standby state. According to this example, the measuring apparatus 100 can correct the measurement result in the active state with the noise component measured in the standby state, and calculate the variation amount of the signal under measurement.
[0029]
Hereinafter, the signal measurement unit 104, the noise measurement unit 106, the correction unit 108, and the waveform display unit 120 will be described in more detail. The signal measurement unit 104 includes a sampling measurement unit 408, a timing calculation unit 402, a variation amount calculation unit 404, and a potential change rate calculation unit 406.
[0030]
The sampling measurement unit 408 measures the potential to be measured at a predetermined cycle, associates the measurement timing with the potential to be measured at the measurement timing, and stores it as sampling measurement data. In the present embodiment, the sampling measurement unit 408 stores, as measurement timing, a phase value indicating a time from measurement at a predetermined timing in the cycle of the signal under measurement to measurement. The sampling measurement unit 408 may store the time from the timing of crossing the zero point to the timing of sampling measurement as the phase value, for example, while the potential of the signal under measurement increases. The sampling measurement unit 408 measures the potential to be measured with the same function as the sampling oscilloscope, and stores a set of sample point data as a result of one sampling measurement as sampling measurement data.
[0031]
Further, the sampling measurement unit 408 may further store the noise potential measured at the predetermined cycle as the noise measurement data in a state where the signal under measurement is not operating. The sampling measurement unit 408 may store the noise potential in association with the measurement timing at which the noise potential is measured. In the present embodiment, the sampling measurement unit 408 measures the noise potential with the same function as the sampling oscilloscope, and stores a set of noise sample point data as a result of one sampling measurement as noise measurement data. The sampling measurement unit 408 preferably measures the noise potential by the same function as measuring the potential to be measured. The sampling measurement unit 408 preferably stores noise measurement data with the same function as storing sampling measurement data.
[0032]
The timing calculation unit 402 calculates a crossover timing that is a timing at which the potential to be measured indicates a predetermined threshold voltage. The timing calculation unit 402 preferably calculates the crossing timing based on the sampling measurement data. The timing calculation unit 402 may set the threshold voltage based on a user instruction. For example, the timing calculation unit 402 may set the potential indicated by the voltage axis marker displayed by the waveform display unit 120 as the threshold voltage based on a user instruction. The timing calculation unit 402 may calculate a suitable threshold voltage based on the sampling measurement data. For example, the sampling measurement unit 408 calculates the potential of the high potential (high level) and the low potential (low level) based on the sampling measurement data, and sets the average value of both potentials as the threshold voltage. It's okay.
[0033]
The variation amount calculation unit 404 calculates the variation amount of the cycle in which the measured potential changes based on the crossover timing. The variation amount calculation unit 404 may calculate the standard deviation of the crossover timing as the variation amount of the period. The variation amount calculation unit 404 may calculate a value obtained by multiplying the standard deviation of the crossover timing by a predetermined constant as the variation amount of the period. For example, the variation amount calculation unit 404 may calculate a value twice the standard deviation of the crossover timing as the variation amount of the period.
[0034]
In this embodiment, the variation amount calculation unit 404 calculates a frequency distribution of phase values corresponding to sample point data existing in the statistical processing target window. The variation amount calculation unit 404 calculates the standard deviation of the frequency distribution as the variation amount of the period.
[0035]
The potential change rate calculation unit 406 calculates a crossing slew rate that is a change rate of the potential to be measured at the crossing timing. The potential change rate calculation unit 406 is a first average value of phase values corresponding to sample point data indicating a potential to be measured that is substantially equal to the first potential among sample point data in a predetermined phase value range. An average phase value and a second average phase value that is an average value of phase values corresponding to sample point data indicating a measured potential that is substantially equal to the second potential are calculated, and the second potential and the first potential are calculated. A value obtained by dividing the difference by the difference between the second average phase value and the first average phase value may be calculated as the crossing slew rate.
[0036]
The potential change rate calculation unit 406 has, as a predetermined phase value range, substantially the same phase value indicating the rising end timing of the signal waveform to be measured from a phase value substantially equal to the phase value indicating the rising start timing of the signal waveform to be measured. A range up to the phase value may be set. The potential change rate calculation unit 406 may set a potential lower than the threshold voltage as the first potential. In this case, the potential change rate calculation unit 406 preferably sets a potential higher than the threshold voltage as the second potential.
[0037]
The noise measuring unit 106 calculates the variation amount of the noise potential. In the present embodiment, the noise measurement unit 106 calculates the variation amount of the noise potential based on the noise measurement data stored in the sampling measurement unit 408. The noise measurement unit 106 may calculate the variation amount of the noise potential based on the noise sample point data included in the noise measurement data. In the present embodiment, the noise measurement unit 106 calculates the standard deviation of the noise potential distribution of the noise sample point data as the noise potential variation amount. The noise measuring unit 106 may calculate a value obtained by multiplying the standard deviation by a predetermined constant as the variation amount of the noise potential. For example, the noise measurement unit 106 may calculate a value twice as large as the standard deviation as the variation amount of the noise potential. In another embodiment, the noise measurement unit 106 may store the maximum value and the minimum value of the noise potential measured a plurality of times. In this case, the noise measurement unit 106 may calculate the difference between the maximum value and the minimum value as the variation amount of the noise potential.
[0038]
The correction unit 108 includes a correction value calculation unit 802 and a jitter calculation unit 804. The correction value calculation unit 802 calculates a value obtained by dividing the value of the variation amount of the noise potential by the crossing slew rate as a correction value. The jitter calculation unit 804 calculates the square root of a value obtained by subtracting the square value of the correction value from the square value of the variation amount of the period in which the measured potential changes, as the jitter amount.
[0039]
The waveform display unit 120 corresponds to the coordinate value of the time axis that is the first axis indicating the phase value stored by the sampling measurement unit 408 and the phase value for the display phase value range that is a predetermined range of phase values. A signal waveform including a coordinate point indicating the coordinate value of the voltage axis which is the second axis indicating the potential to be measured is displayed. The waveform display unit 120 may display the coordinate point by two-dimensional orthogonal coordinates having the time axis and the voltage axis.
[0040]
In the present embodiment, the waveform display unit 120 includes a time axis coordinate value indicating one phase value, and a signal distribution upper bound value corresponding to the one phase value or a voltage axis coordinate value representing a signal distribution lower bound value. Further, coordinate points indicating are displayed. The waveform display unit 120 is a coordinate point indicating the coordinate value of the time axis indicating another phase value and the coordinate value of the voltage axis indicating the signal distribution upper bound value or the signal distribution lower bound value corresponding to the other phase value. May be further displayed. The waveform display unit 120 further displays a coordinate point indicating the coordinate value of the time axis indicating one phase value and the coordinate value of the voltage axis indicating the correction signal potential corresponding to the one phase value.
[0041]
FIG. 2 is a conceptual diagram illustrating a waveform of a constant voltage signal displayed by the waveform display unit 120 described with reference to FIG. The waveform display unit 120 displays coordinate points indicating noise sample point data included in the noise measurement data stored in the sampling measurement unit 408 described with reference to FIG. 1 as the waveform of the constant voltage signal.
[0042]
The coordinate points (22-1 to 22-11) indicate a part of the coordinate points displayed by the waveform display unit 120. The coordinate points (22-1 to 22-11) have a time axis coordinate value indicating the measurement timing and a voltage axis coordinate value indicating the noise potential. The alternate long and short dash lines 24 and 26 are virtual lines indicating the upper and lower bounds of the potential range where the coordinate points indicating the noise sample point data exist with a predetermined probability. In the present embodiment, the waveform display unit 120 does not display the virtual line. In another embodiment, the waveform display unit 120 may display the virtual line as a solid line. The alternate long and short dash line 24 may be, for example, a value obtained by adding the value of the standard deviation of the measured noise potential to the average value of the measured noise potential. The alternate long and short dash line 26 may be, for example, a value obtained by subtracting the standard deviation value of the noise potential from the average value of the noise potential. In FIG. 2, the difference between the potential indicated by the one-dot chain line 24 and the potential indicated by the one-dot chain line 26 is equal to twice the noise potential variation ΔVn calculated by the noise measurement unit 106.
[0043]
FIG. 3 is a conceptual diagram showing the waveform of the signal under measurement displayed by the waveform display unit 120 described with reference to FIG. The waveform display unit 120 displays coordinate points indicating sample point data included in the sampling measurement data stored in the sampling measurement unit 408 described with reference to FIG. 1 as the waveform of the signal under measurement.
[0044]
The coordinate point 32 is a coordinate point indicating one sample point data. The coordinate point 32 has a coordinate value on the time axis indicating the measurement timing and a coordinate value on the voltage axis indicating the potential to be measured. The alternate long and short dash lines 34 and 36 are virtual lines indicating the upper and lower boundaries of the potential range where the coordinate points indicating the sample point data exist with a predetermined probability in each phase value on the time axis. In the present embodiment, the difference between the potential indicated by the alternate long and short dash line 34 and the potential indicated by the alternate long and short dash line 36 in the phase value at which the potential to be measured indicates a low level is equal to twice the noise potential variation ΔVn. In FIG. 3, the difference between the phase value in which the voltage axis coordinate value of the alternate long and short dash line 36 indicates the threshold voltage Vt and the phase value in which the voltage axis coordinate value of the alternate long and short dash line 34 indicates the threshold voltage Vt has been described with reference to FIG. It is equal to twice the variation amount Tj of the period in which the measured potential calculated by the variation amount calculation unit 404 changes.
[0045]
FIG. 4 is a diagram illustrating the operations of the timing calculation unit 402 and the variation amount calculation unit 404 described with reference to FIG. FIG. 4 shows a part of the waveform of the signal under measurement shown in FIG. The coordinate point 42 is a coordinate point indicating one sample point data. A one-dot chain line 44 indicates a part of the one-dot chain line 34 illustrated in FIG. 3. A one-dot chain line 46 indicates a part of the one-dot chain line 36 shown in FIG.
[0046]
In the present embodiment, the timing calculation unit 402 measures the potential to be measured in a range from a threshold voltage window lower limit value VtL indicating a potential lower than the threshold voltage Vt to a threshold voltage window upper limit value VtH indicating a potential higher than the threshold voltage Vt. Is extracted from the sampling measurement data, and the phase value corresponding to the extracted sample point data is calculated as the crossover timing. The timing calculation unit 402 may set the threshold voltage window lower limit value VtL and the threshold voltage window upper limit value VtH based on a user instruction.
[0047]
The timing calculation unit 402 sets the threshold voltage window lower limit value VtL or the difference between the threshold voltage window upper limit value VtH and the threshold voltage Vt based on a user instruction, and sets the threshold voltage based on the difference and the threshold voltage Vt. The window lower limit value VtL or the threshold voltage window upper limit value VtH may be calculated. The timing calculation unit 402 calculates a potential in a state where the potential to be measured is high (high level) and a state in which the potential to be measured is low (low level) based on the measurement result of the potential to be measured, and multiplies the difference between both potentials by a certain ratio. The calculated value may be calculated as the difference. For example, the timing calculation unit 402 may calculate a value indicating 1% of the difference between the two potentials as the difference. The timing calculation unit 402 has a sample point at which the average value of the phase values corresponding to the sample point data indicating the measured potential approximately equal to the threshold voltage window lower limit value VtL indicates the measured potential approximately equal to the threshold voltage window upper limit value VtH. It is preferable to set the threshold voltage window lower limit value VtL and the threshold voltage window upper limit value VtH to be substantially equal to the average value of the phase values corresponding to the data.
[0048]
The timing calculation unit 402 further extracts, from the extracted sample point data, sample point data whose phase value is in the range from the phase value window lower bound value TL to the phase value window upper bound value TH. It is preferable to calculate the phase value corresponding to the point data as the crossover timing. For example, the timing calculation unit 402 sets the phase value substantially equal to the phase value indicating the rising start timing of the measured signal waveform indicated by the waveform display unit 120 as the phase value window lower bound value TL, and indicates the rising end timing of the measured signal waveform. A phase value substantially equal to the phase value may be used as the phase value window upper bound value TL.
[0049]
The timing calculation unit 402 may set the phase value window lower bound value TL and the phase value window upper bound value TH based on a user instruction. The sampling measurement unit 408 may detect the rising timing of the signal waveform under measurement based on the sampling measurement data, and calculate the phase value window lower bound value TL and the phase value window upper bound value TH based on the timing.
[0050]
In the present embodiment, the timing calculation unit 402 has a measured potential not less than the voltage window lower limit value VtL and not more than the threshold voltage window upper limit value VtH, and the phase value not less than the phase value window lower limit value TL and on the phase value window. A range that is less than or equal to the boundary value TH is set as the statistical processing target window 48. The timing calculation unit 402 extracts sample point data existing in the statistical processing target window 48, and calculates a phase value corresponding to the extracted sample point data as a crossover timing. The timing calculation unit 402 shows a measured potential that is substantially equal to the threshold voltage Vt, and has as many sampling point data as possible to indicate the phase value in the range from the phase value window lower limit value TL to the phase value window upper limit value TH. The value window lower bound value TL and the phase value window upper bound value TH are preferably set. The timing calculation unit 402 has a phase value window so that the sampling point data indicating a measured potential that is substantially equal to the threshold voltage Vt and a phase value that is substantially equal to the lower limit value TL of the phase value window or the upper limit value TH of the phase value window is small. It is preferable to set the lower limit value TL and the phase value window upper limit value TH.
[0051]
The histogram 50 shows a frequency distribution of phase values corresponding to sample point data existing in the statistical processing target window 48. In the present embodiment, the variation amount calculation unit 404 calculates the standard deviation of the histogram 50 as the variation amount Tj of the cycle in which the measured potential changes.
[0052]
FIG. 5 shows the coordinate values of the time axis indicating one phase value and the coordinate values of the voltage axis indicating the signal distribution upper bound value or the signal distribution lower bound value corresponding to the one phase value displayed by the waveform display unit 120. It is a conceptual diagram which shows the coordinate point which shows a value. The coordinate point 52 is a coordinate point indicating one sample point data. A one-dot chain line 54 indicates a part of the one-dot chain line 34 illustrated in FIG. 3. A one-dot chain line 56 indicates a part of the one-dot chain line 36 illustrated in FIG. 3. A dotted line 58 is an imaginary line connecting coordinate points indicating the average signal potential at each phase value.
[0053]
In the present embodiment, the average value calculation unit 114 described with reference to FIG. 1 is the average value of the measured potential corresponding to the phase value substantially equal to one of the phase values stored in the sampling measurement unit 408. Is calculated as an average signal potential corresponding to the one phase value. The average value calculation unit 114 calculates the average value of the measured potential corresponding to the phase value substantially equal to the other phase value among the phase values stored by the sampling measurement unit 408, and the average signal potential corresponding to the other phase value. It is preferable to further calculate as In the present embodiment, the average value calculation unit 114 calculates an average signal potential for each phase value in a display phase value range that is a phase value range in which the waveform display unit 120 displays a waveform. In another embodiment, the average value calculation unit 114 may calculate the average signal potential for each phase value corresponding to the sample point data included in the sampling measurement data.
[0054]
A solid line 70 is a line connecting coordinate points indicating the signal distribution upper bound value. A solid line 72 is a line connecting coordinate points indicating the lower bound value of the signal distribution. In the present embodiment, the signal distribution calculation unit 116 described with reference to FIG. 1 includes an upper bound value and a lower bound value indicating a range in which the value of the measured potential varies due to noise in the voltage direction superimposed on the measured signal. Are calculated as a signal distribution upper bound value and a signal distribution lower bound value. The signal distribution calculation unit 116 calculates an upper bound value and a lower bound value indicating a range in which the value of the measured potential varies with a predetermined probability due to the noise as a signal distribution upper bound value and a signal distribution lower bound value. It's okay. In this embodiment, the signal distribution calculation unit 116 outputs a value obtained by adding the variation amount ΔVn of the noise potential to the average signal potential as a signal distribution upper limit value, and subtracts the variation amount ΔVn of the noise potential from the pre-uniform signal potential. The value is calculated as the signal distribution lower bound value. The signal distribution calculation unit 116 may further calculate a signal distribution upper bound value and a signal distribution lower bound value corresponding to other phase values based on the average signal potential and the variation amount ΔVn of the noise potential. In the present embodiment, the signal distribution calculation unit 116 calculates a signal distribution upper bound value and a signal distribution lower bound value for the phase values corresponding to the sample point data in the display phase value range, respectively.
[0055]
In the present embodiment, the difference between the potential indicated by the solid line 70 and the potential indicated by the solid line 72 at each phase value is equal to twice the noise potential variation ΔVn. The difference between the phase value in which the voltage axis coordinate value of the solid line 72 indicates the threshold voltage Vt and the phase value in which the voltage axis coordinate value of the solid line 70 indicates the threshold voltage Vt is the correction value calculation unit described in relation to FIG. 802 is equal to the double value of the correction value Mj calculated.
[0056]
FIG. 6 shows coordinate points indicating a time axis coordinate value indicating one phase value and a voltage axis coordinate value indicating a correction signal potential corresponding to the one phase value displayed by the waveform display unit 120. It is a conceptual diagram. A solid line 64 is a line connecting coordinate points indicating average signal potentials at respective phase values. A solid line 66 and a solid line 68 are lines indicating the amount of variation in the signal under measurement. In the present embodiment, the solid line 68 translates the point where the voltage axis coordinate value of the solid line 64 indicates the threshold voltage Vt by the jitter amount Rj calculated by the jitter calculation unit 804 described with reference to FIG. Including the points. The solid line 66 includes a point in which the voltage axis coordinate value of the solid line 64 indicates the threshold voltage Vt and is translated in the time axis direction by −Rj. The solid line 66 and the solid line 68 may be parallel to the solid line 64 at a phase value in which each voltage axis coordinate value is substantially equal to the phase value indicating the threshold voltage Vt.
[0057]
The coordinate point 62 is a coordinate point indicating one phase value and the correction signal potential at the one phase value. The signal distribution calculation unit 116 described with reference to FIG. 1 generates a corrected signal potential obtained by correcting the measured potential corresponding to one phase value based on the average signal potential, the signal distribution upper bound value, and the signal distribution lower bound value. calculate. In the present embodiment, the signal distribution calculation unit 116 calculates a correction signal potential for each phase value in the display phase value range. When the measured potential corresponding to one phase value is larger than the signal distribution upper limit value, the signal distribution calculating unit 116 calculates a value obtained by subtracting the difference between the signal distribution upper limit value and the average signal potential from the measured potential. Calculated as the correction signal potential, and if the measured potential corresponding to one phase value is smaller than the signal distribution lower bound value, the correction signal is obtained by adding the difference between the average signal potential and the signal distribution lower bound value to the measured potential. Calculated as potential. When the measured potential corresponding to one phase value is larger than the signal distribution upper limit value, the signal distribution calculating unit 116 calculates a value obtained by subtracting the noise potential variation ΔVn from the measured potential as the corrected signal potential. When the measured potential corresponding to one phase value is smaller than the signal distribution lower bound value, a value obtained by adding the variation amount ΔVn of the noise potential to the measured potential may be calculated as the correction signal potential. The signal distribution calculation unit 116 may calculate the average signal potential as the correction signal potential when the measured potential corresponding to one phase value is larger than the signal distribution lower bound value and smaller than the signal distribution upper bound value. .
[0058]
In FIG. 6, the difference between the phase value in which the voltage axis coordinate value of the solid line 68 indicates the threshold voltage Vt and the phase value in which the voltage axis coordinate value of the solid line 66 indicates the threshold voltage Vt is the jitter amount Rj calculated by the jitter calculating unit 804. Is equal to twice the value.
[0059]
Equation 1 shows the relationship among the jitter amount Rj, the variation amount Tj (see FIG. 3) of the period in which the measured potential changes, and the correction value Mj (see FIG. 4) in this embodiment.
[Expression 1]

In another embodiment, for example, Equation 2 may indicate the relationship between the jitter amount Rj, the variation amount Tj of the period in which the measured potential changes, and the correction value Mj.
[Expression 2]

In Equation 2, the value Dj indicates the value of measurement jitter, which is an error caused by the characteristics of the measuring apparatus in measuring the variation amount Tj of the cycle in which the potential to be measured changes.
[0060]
With the measuring apparatus 100 described above, the amount of variation in the signal under measurement can be measured. According to the present embodiment, the measuring apparatus 100 can reduce errors due to the influence of noise in the voltage direction superimposed on the signal under measurement in the measurement of the jitter amount.
[0061]
FIG. 7 shows an example of the configuration of the measuring apparatus 100 according to the second embodiment of the present invention. The measurement apparatus 100 includes an input port 102, a signal measurement unit 104, a noise measurement unit 106, a correction unit 108, a noise measurement instruction unit 110, a display mode setting unit 112, an average value calculation unit 114, a signal distribution calculation unit 116, and a display unit 118. A waveform display unit 120 and a transmission line 200. In FIG. 7, components having the same reference numerals as those in FIG. 1 have the same functions as the respective components in FIG. 1.
[0062]
The transmission line 200 electrically connects either the signal source to be measured that generates the signal to be measured or the constant voltage signal source that generates the constant voltage signal and the input port 102 in accordance with the switching signal that controls the operation of the noise measuring unit. Connect. In the present embodiment, the transmission line 200 includes an input switching unit 122 and a coaxial cable 124.
[0063]
The input switching unit 122 has the same function as the input switching unit 122 shown in FIG. The input switching unit 122 supplies either the signal under measurement or the constant voltage signal to the input port 102 via the coaxial cable 124. The coaxial cable 124 electrically connects either the measured signal source or the constant voltage signal source to the input port 102. The distance between the input switching unit 122 and the input port 102 to which the coaxial cable 124 is electrically connected may be greater than the distance between the signal source under measurement and the input switching unit 122.
[0064]
In the present embodiment, since the input port 102 receives a constant voltage signal via the coaxial cable 124, the noise measurement unit 106 calculates the variation amount of the noise potential including the noise component received by the signal transmitted by the coaxial cable 124. To do. Therefore, according to the present embodiment, the measuring apparatus 100 can reduce jitter measurement errors due to the influence of noise in the voltage direction superimposed on the signal under measurement in the coaxial cable 124.
[0065]
FIG. 8 shows another embodiment of the transmission line 200. In this example, the transmission line 200 includes an input switching unit (122-1 to 122-4), coaxial cables (124-1 and 124-2), a preamplifier 126, and a post-amplifier 128. The preamplifier 126 may be an amplifier that amplifies a low voltage signal generated by the signal source. In this example, the preamplifier 126 amplifies the signal under measurement generated by the signal source under measurement. The preamplifier 126 receives the signal under measurement from the input switching unit 122-3 and supplies the amplified signal under measurement to the input switching unit 122-2.
[0066]
The postamplifier 128 may be an amplifier that further amplifies the signal that is amplified and output by the preamplifier 126. In this example, the postamplifier 128 further amplifies the signal under measurement output by the preamplifier 126 after amplification. The post amplifier 128 receives the signal under measurement amplified by the preamplifier 126 from the input switching unit 122-2 and supplies the further amplified signal to the input switching unit 122-1.
[0067]
The coaxial cable 124-1 electrically connects the input switching unit 122-1 and the input port 102. The coaxial cable 124-1 supplies a signal output from the input switching unit 122-1 to the input port 102. The coaxial cable 124-2 electrically connects the input switching unit 122-4 and the input switching unit 122-3. The coaxial cable 124-2 supplies the signal output from the input switching unit 122-4 to the input switching unit 122-3.
[0068]
The input switching unit (122-1 to 122-4) has the same function as the input switching unit 122 shown in FIG. In this example, the input switching unit 122-4 outputs either a signal under measurement or a constant voltage signal in response to the switching signal-4. The input switching unit 122-3 outputs either a signal under measurement received via the coaxial cable 124 or a constant voltage signal in response to the switching signal-3. The input switching unit 122-2 outputs either the signal under measurement amplified by the preamplifier 126 or the constant voltage signal in accordance with the switching signal-2. The input switching unit 122-1 outputs either the signal under measurement or the constant voltage signal further amplified by the post amplifier 128 according to the switching signal- 1. The input switching units (122-1 to 122-4) may receive the switching signals-1 to 4 from the noise measurement instruction unit 110, respectively.
[0069]
In this example, the input port 102 receives a constant voltage signal via the coaxial cables (124-1, 124-2), the preamplifier 126, and the postamplifier 128. The noise measuring unit 106 calculates a variation amount of noise potential including noise components received by signals transmitted by the coaxial cables (124-1, 124-2), the preamplifier 126, and the postamplifier 128. Therefore, according to this example, the measuring apparatus 100 reduces an error due to the influence of noise in the voltage direction superimposed on the coaxial signals (124-1, 124-2), the preamplifier 126, and the postamplifier 128 on the signal under measurement. Thus, the jitter amount of the signal under measurement can be measured. Furthermore, according to this example, since the user can select a path through which the input port 102 receives the constant voltage signal, it is possible to reduce errors due to the influence of noise in accordance with the characteristics of the signal under measurement.
[0070]
As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.
[0071]
【The invention's effect】
As is apparent from the above description, according to the present invention, errors due to the influence of noise in the voltage direction superimposed on the signal under measurement can be reduced in measuring the jitter amount.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a measuring apparatus 100 according to a first embodiment of the present invention.
2 is a conceptual diagram showing a waveform of a constant voltage signal displayed by a waveform display unit 120. FIG.
3 is a conceptual diagram showing a waveform of a signal under measurement displayed by a waveform display unit 120. FIG.
FIG. 4 is a diagram for explaining operations of a timing calculation unit 402 and a variation amount calculation unit 404;
FIG. 5 is a conceptual diagram showing a signal distribution upper bound value and a signal distribution lower bound value displayed by a waveform display unit 120;
6 is a conceptual diagram showing a correction signal potential displayed by a waveform display unit 120. FIG.
FIG. 7 is a configuration diagram of a measuring apparatus 100 according to a second embodiment of the present invention.
FIG. 8 is a diagram illustrating another configuration example of a transmission line 200 according to the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Measuring apparatus, 102 ... Input port, 104 ... Signal measuring part, 106 ... Noise measuring part, 108 ... Correction | amendment part, 110 ... Noise measurement instruction | indication part, 112 ... Display mode setting unit, 114 ... average value calculation unit, 116 ... signal distribution calculation unit, 118 ... display unit, 120 ... waveform display unit, 122, 122-1 to 122-4 ... Input switching unit, 124, 124-1, 124-2 ... Coaxial cable, 126 ... Preamplifier, 128 ... Postamplifier, 402 ... Timing calculation unit, 404 ... Variation amount calculation unit, 406 ... potential change rate calculation unit, 408 ... sampling measurement unit, 802 ... correction value calculation unit, 804 ... jitter calculation unit, 48 ... statistic processing target window, 50 ... histogram

Claims (20)

A measuring device for measuring the amount of variation in a signal under measurement,
An input port to which the signal under measurement is to be input; and
A signal measuring unit that measures a measured potential that is a potential of the input port when the signal source of the measured signal is in an active state, and calculates a variation amount of a result of the measurement;
A noise measuring unit that calculates a variation amount of a noise potential generated in the input port when the signal source of the signal under measurement is in a standby state ;
A measuring apparatus comprising: a correction unit that calculates a variation amount of the signal under measurement based on a variation amount of the measurement result and a variation amount of the noise potential. The signal measuring unit calculates a variation amount of a cycle in which the measured potential changes as a variation amount of the measurement result,
The measuring apparatus according to claim 1, wherein the correction unit calculates a jitter amount of the signal under measurement as a variation amount of the signal under measurement. The input port receives a constant voltage signal indicating a predetermined potential as an input when the signal source of the signal under measurement is in a standby state ,
The noise measurement unit measures the potential of the input port when the input port receives the constant voltage signal as the noise potential, and calculates a variation amount of the noise potential. The measuring device described.   The measurement apparatus according to claim 3, wherein the input port receives a ground potential as the constant voltage signal. The signal measuring unit calculates a crossover timing that is a timing at which the measured potential indicates a predetermined threshold voltage; and
The measurement apparatus according to claim 2, further comprising a variation amount calculation unit that calculates a variation amount of the period based on the crossover timing. The signal measuring unit further includes a potential change rate calculating unit that calculates a crossing slew rate that is a rate of change of the measured potential at the crossing timing,
The correction unit is
A correction value calculation unit that calculates a value obtained by dividing the value of the variation amount of the noise potential by the crossing slew rate, as a correction value;
The measurement apparatus according to claim 5, further comprising: a jitter calculation unit that calculates a square root of a value obtained by subtracting a square value of the correction value from a square value of the variation amount of the period as the jitter amount. The signal measuring unit further includes a sampling measuring unit that measures the potential to be measured at a predetermined cycle and stores the measurement timing and the measured potential at the measurement timing in association with each other as sampling measurement data. ,
The measurement apparatus according to claim 5, wherein the timing calculation unit calculates the crossover timing based on the sampling measurement data.   The measurement according to claim 7, wherein the sampling measurement unit stores, as the measurement timing, a phase value indicating a time from the predetermined timing in the cycle of the signal under measurement to the time when the measurement is performed. apparatus. The sampling measurement unit stores, as noise measurement data, the noise potential measured at the predetermined period when the signal source of the signal under measurement is in a standby state ,
The measurement apparatus according to claim 7, wherein the noise measurement unit calculates a variation amount of the noise potential based on the noise measurement data. A noise measurement instruction unit that generates a switching signal for controlling the operation of the noise measurement unit based on a user instruction;
The measurement apparatus according to claim 1, wherein the noise measurement unit calculates the amount of variation in the noise potential when the switching signal shows a predetermined value.   The measurement apparatus according to claim 2, further comprising a display unit that displays the value of the jitter amount.   12. The display unit according to claim 11, wherein the display unit displays the value of the variation amount of the period or the value of the jitter amount in accordance with a display instruction signal instructing contents to be displayed by the display unit. measuring device.   The measurement apparatus according to claim 12, further comprising a display mode setting unit that generates the display instruction signal based on a user instruction. About the predetermined range of the phase value,
A signal waveform including a coordinate point indicating a coordinate value of the first axis indicating the phase value stored by the sampling measurement unit and a coordinate value of the second axis indicating the potential to be measured corresponding to the phase value is displayed. The measuring apparatus according to claim 8, further comprising a waveform display unit. Of the phase values stored in the sampling measurement unit, an average value of the measured potential corresponding to the phase value substantially equal to the one phase value is calculated as an average signal potential corresponding to the one phase value. An average value calculator;
A signal distribution that outputs a value obtained by adding the variation amount of the noise potential to the average signal potential as a signal distribution upper bound value, and calculates a value obtained by subtracting the variation amount of the noise potential from the average signal potential as a signal distribution lower bound value A calculation unit,
The waveform display unit includes a first axis coordinate value indicating the one phase value and a second axis coordinate value indicating the signal distribution upper bound value or the signal distribution lower bound value corresponding to the one phase value. 15. The measuring device according to claim 14, wherein coordinate points indicating are displayed. The signal distribution calculating unit calculates a corrected signal potential obtained by correcting the measured potential corresponding to the one phase value based on the average signal potential, the signal distribution upper bound value, and the signal distribution lower bound value;
The waveform display unit displays a coordinate point indicating a coordinate value of the first axis indicating the one phase value and a coordinate value of the second axis indicating the correction signal potential corresponding to the one phase value. The measuring apparatus according to claim 15. When the measured potential corresponding to the one phase value is larger than the signal distribution upper limit value, the signal distribution calculating unit calculates the signal distribution upper limit value and the average signal potential from the measured potential. A value obtained by subtracting the difference is calculated as the correction signal potential,
When the measured potential corresponding to the one phase value is smaller than the signal distribution lower bound value, a value obtained by adding a difference between the average signal potential and the signal distribution lower bound value to the measured potential is the correction signal. The measurement apparatus according to claim 16, wherein the measurement apparatus calculates the potential. The average value calculator corresponds to the average value of the measured potential corresponding to the phase value substantially equal to the other phase value among the phase values stored in the sampling measurement unit, to the other phase value. Further calculating the average signal potential
The signal distribution calculation unit further calculates the signal distribution upper bound value corresponding to the other phase value and the signal distribution lower bound value based on the variation amount of the average signal potential and the noise potential,
The waveform display unit includes a first axis coordinate value indicating the other phase value, and a signal distribution upper boundary value corresponding to the other phase value, or a second axis coordinate value indicating the signal distribution lower boundary value. The measuring device according to claim 15, further displaying a coordinate point indicating the above.   Either the measured signal source for generating the measured signal or the constant voltage signal source for generating the constant voltage signal and the input port are electrically connected according to a switching signal for controlling the operation of the noise measuring unit. The measuring apparatus according to claim 3, further comprising a transmission path to be connected.   The measurement apparatus according to claim 19, wherein the transmission line includes a coaxial cable that electrically connects either the measured signal source or the constant voltage signal source and the input port.

Images