JPH03252562A - Instrument for measuring erlang variance - Google Patents
Instrument for measuring erlang varianceInfo
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- JPH03252562A JPH03252562A JP5141690A JP5141690A JPH03252562A JP H03252562 A JPH03252562 A JP H03252562A JP 5141690 A JP5141690 A JP 5141690A JP 5141690 A JP5141690 A JP 5141690A JP H03252562 A JPH03252562 A JP H03252562A
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- 230000005611 electricity Effects 0.000 claims 1
- 238000005259 measurement Methods 0.000 abstract description 24
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Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、アラン分散の測定器（アラン分散測定器又は
アラン分散測定装置ともいう、）に係る。DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an Allan dispersion measuring device (also referred to as an Allan dispersion measuring device or an Allan dispersion measuring device).
このアラン分散の測定器は、発振器のもつごくわずかな
周波数ゆらぎを高精度に測定する装置であり、通信計測
分野においてはマイクロ波によるヘテロダイン通信装置
あるいは測距用マイクロ波発振器の周波数安定度評価装
置に、また光計測分野においては高安定なレーザ光源の
周波数安定度評価装置として利用される。さらに、つぎ
の世代の通信方式として研究が進められている光ヘテロ
ダイン通信用レーザ光源の周波数安定度の評価にも用い
られる。This Allan dispersion measuring device is a device that measures the very slight frequency fluctuation of an oscillator with high precision. Furthermore, in the field of optical measurement, it is used as a frequency stability evaluation device for highly stable laser light sources. Furthermore, it can also be used to evaluate the frequency stability of laser light sources for optical heterodyne communications, which are being researched as a next-generation communications system.
アラン分散は、発振器の周波数安定度を表す一つの指標
であり、一般に次のように定義される。Allan dispersion is one index representing the frequency stability of an oscillator, and is generally defined as follows.
第４図に示すように、まず時間的に周波数が変化してい
る信号源において、その周波数のτ時間平均値ν、を順
次得る。連続する２個の周波数のτ時間の平均値ν１と
ν２についての標本標準偏差の２乗は、
＝ −・−（１
）となるが、アラン分散はこれをＮ個の平均値ν□に対
し計算を行ない、、それらを平均したもので、Ｎ
ｌｋ″＋２
で表される。ここで、丁 は信号源のτ時間におτ
ける公称周波数である。As shown in FIG. 4, first, for a signal source whose frequency changes over time, the time average value τ of the frequency ν is sequentially obtained. The square of the sample standard deviation for the average values ν1 and ν2 of the τ times of two consecutive frequencies is = −・−(1
), but the Allan variance is calculated for N average values ν□, and is the average of them.
lk″+2, where d is the nominal frequency of the signal source at time τ.
一般に周波数安定度を表すにはσ（τ）すなわち、（２
）式の平方根が用いられている。アラン分散は、（２）
式に示されるように、平均された周波数データ数Ｎと積
分時間τの二つの変数の関数で表され、さらに定義とし
て測定の空き時間、すなわち第４図でν、とシア、Ｉの
積分領域の境界部分の時間がゼロであることが要求され
ている。Generally, to express frequency stability, σ(τ), that is, (2
) is used. The Allan variance is (2)
As shown in the equation, it is expressed as a function of two variables, the averaged frequency data number N and the integration time τ, and is further defined as the measurement free time, that is, the integral area of ν, shear, and I in Fig. 4. It is required that the time at the boundary part of is zero.
第５図は、従来のアラン分散測定器の構成を示す一実施
例で、入力信号Ｓａは波形整形機能を存する検出器１に
より矩形波信号ｓｂに変換される。この信号ｓｂを周波
数カウンタ部２で計数し、メモリ３に一旦データを蓄え
た後、データ処理部４でアラン分散値を計算する方法が
用いられている。FIG. 5 shows an example of the configuration of a conventional Allan dispersion measuring device, in which an input signal Sa is converted into a rectangular wave signal sb by a detector 1 having a waveform shaping function. A method is used in which the frequency counter section 2 counts this signal sb, the data is temporarily stored in the memory 3, and then the data processing section 4 calculates the Allan variance value.
さらに詳しく述べると、前記検出器１を通して矩形化さ
れた矩形波信号ｓｂは前記周波数カウンタ部２内のカウ
ンタ５に入力され、立上り信号数が計数・累積される。More specifically, the rectangular wave signal sb rectangularized through the detector 1 is input to the counter 5 in the frequency counter section 2, and the number of rising signals is counted and accumulated.
このカウンタ５に累積された立上り信号数の計数値ｆｃ
は計数タイミング信号発生器６において設定された周期
τ秒のラッチ信号Ｓｃにより、τ秒毎にラッチ回路７に
送られる。Count value fc of the number of rising signals accumulated in this counter 5
is sent to the latch circuit 7 every τ seconds by a latch signal Sc with a cycle of τ seconds set in the counting timing signal generator 6.
ここで、立上り信号の度数を計数する前記カウンタ５は
前記ラッチ信号Ｓｃとは無関係に、前記矩形波信号ｓｂ
の立上り信号の度数を計数し続けており、従って時間τ
の計数と次の時間τの計数との間には、アラン分散の定
義どおり、空き時間は発生しない方法がとられている。Here, the counter 5 that counts the frequency of the rising signal receives the rectangular wave signal sb regardless of the latch signal Sc.
continues to count the number of rising signals of , and therefore the time τ
As defined by the Allan distribution, a method is adopted in which no idle time occurs between the counting of time τ and the counting of the next time τ.
しかしながら、第６図に示すように、この立上り信号を
計数する場合、設定時間τの計数開始時あるいは計数終
了時のタイミングのずれにより、１カウントの数え落し
、あるいは、数え過ぎによる±１の丸め誤差が発生する
ことは避けられない構成になっていた。However, as shown in Fig. 6, when counting this rising signal, due to a timing shift at the start or end of counting for the set time τ, one count may be missed or there may be a rounding error of ±1 due to overcounting. The situation was such that it was inevitable that this would occur.
この丸め誤差により、アラン分散の測定器の安定度測定
限界が決定され、その値は、
σ□、！１ ＝ □・ τ−１・・ （３）ｆＬ
となる、ここでｆＬは１秒間の入力信号１の公称周波数
である０例えば、ｆＬが５ ＭＨｚの周波数入力の場合
、τ＝ｉ秒の積分時間では２ Ｘ １０”のアラン分散
平方根以下の安定度は測定不能となる。This rounding error determines the stability measurement limit of the Allan variance measuring instrument, whose value is σ□,! 1 = □・τ-1... (3) fL, where fL is the nominal frequency of input signal 1 for 1 second 0 For example, if fL is a frequency input of 5 MHz, then τ=integration for i seconds In time, stability below the square root of the Allan variance of 2 x 10'' becomes unmeasurable.
アラン分散測定装置に関する文献としては、次のものカ
ヤ知られている。The following documents are known regarding the Allan dispersion measuring device.
（１）「レーザ周波数安定度の実時間測定装置」椎尾、
大津、田幸：電子通信学会技術研究報告ＯＱＥ ＰＰ
、 ８２−５２ （１９８１）（２）「レーザ周波数安
定度の実時間測定装置の試作」 椎尾、大津、田幸：電
子通信学会論文誌６４−Ｃ，（１９８１） Ｐ２Ｏ４
（３）「周波数オフセットロックシステムの性能評価」
加藤、久保木、大津：レーザ・原子発振器の周波数制
御と応用、第２回シンポジウム予稿 （１９８７）
〔発明が解決しようとする課題］
本発明は、従来技術において発生する±１カウントの丸
め誤差を低減することを課題とし、この丸め誤差により
制限されていた安定度測定限界を改善したアラン分散の
測定器を実現することを目的としている。(1) “Real-time measurement device for laser frequency stability” Shiio,
Otsu, Tayuki: Institute of Electronics and Communication Engineers Technical Research Report OQE PP
, 82-52 (1981) (2) "Prototype of real-time measurement device for laser frequency stability" Shiio, Otsu, Tayuki: Transactions of the Institute of Electronics and Communication Engineers 64-C, (1981) P2O4 (3) "Frequency offset lock system performance evaluation”
Kato, Kuboki, Otsu: Frequency Control and Applications of Lasers and Atomic Oscillators, 2nd Symposium Proceedings (1987) [Problems to be Solved by the Invention] The present invention reduces the rounding error of ±1 count that occurs in the conventional technology. The purpose of this study is to realize an Allan dispersion measuring instrument that improves the stability measurement limit that was limited by this rounding error.
本発明では、上記課題に対して次の技術手段を用いて解
決している。In the present invention, the above problem is solved using the following technical means.
従来の技術は、第５図に示すように、入力信号Ｓａを波
形整形機能を有する検出器１に通して矩形波信号ｓｂに
変換し、この矩形波信号ｓｂの立上りをカウンタ５によ
り計数していたのに対し、本発明のアラン分散の測定器
は、第１図に示すように、入力信号Ｓａの周波数ｆＬよ
りも十分高い周波数ｆｌの電気信号を出力する発振器８
の出力信号の立上りをカウンタ５で計数し、矩形波に整
形された前記入力信号Ｓａをラッチ信号Ｓｃとして、該
カウンタ５で計数された計数値をラッチ回路７にラッチ
する。In the conventional technique, as shown in FIG. 5, an input signal Sa is passed through a detector 1 having a waveform shaping function to be converted into a rectangular wave signal sb, and a counter 5 counts the rise of this rectangular wave signal sb. On the other hand, the Allan dispersion measuring device of the present invention, as shown in FIG.
A counter 5 counts the rising edge of the output signal, and the input signal Sa, which has been shaped into a rectangular wave, is used as a latch signal Sc, and the count value counted by the counter 5 is latched into a latch circuit 7.
このラッチされた計数値をもとにしてデータ処理部４に
よりアラン分散値を計算する。Based on this latched count value, the data processing section 4 calculates the Allan variance value.
このような方式により、前記入力信号Ｓａの周波数安定
度を測定した場合、該入力信号Ｓａの公称周波数ｆＬの
逆数すなわち、入力信号Ｓａの周期を積分時間τとして
測定していることになり、測定すべき入力信号Ｓａの周
波数ゆらぎは、この積分時間τのゆらぎとして前記発振
器８の出力信号を計数して測定する。この際に発生する
丸め誤差は、前記カウンタ５により計数された該発振器
８の計数値に含まれる±１カウントであるが、この誤差
は前記入力信号Ｓａの周波数ｆＬに対する丸め誤差Ｅに
換算すると、
Ｅ ＝ ｆＬ ／ ｆ＊
−・ （４）となる。When the frequency stability of the input signal Sa is measured by such a method, the reciprocal of the nominal frequency fL of the input signal Sa, that is, the period of the input signal Sa is measured as the integral time τ, and the measurement The frequency fluctuation of the input signal Sa to be measured is measured by counting the output signal of the oscillator 8 as the fluctuation of the integration time τ. The rounding error that occurs at this time is ±1 count included in the count value of the oscillator 8 counted by the counter 5, but when this error is converted to the rounding error E with respect to the frequency fL of the input signal Sa, E = fL/f*
−・(4) becomes.
したがって、（４）式で得られる丸め誤差に制限される
本発明のアラン分散の測定器の安定度測定限界は、
となる０例えば、前記発振器８の出力周波数ｆいを１０
０Ｍ Ｈｚ に設定した場合、その安定度測定限界は
τ＝１秒の場合でｌＸｌ０−”の安定度が得られる。Therefore, the stability measurement limit of the Allan dispersion measuring device of the present invention, which is limited to the rounding error obtained by equation (4), is as follows: 0 For example, if the output frequency f of the oscillator 8 is 10
When set to 0 MHz, the stability measurement limit is τ=1 second, and a stability of lXl0-'' is obtained.
この値は、従来技術における ｆＬ＝ ５ ＭＨ２の場
合の安定度測定限界２Ｘ１０−’に比べ１桁程度の向上
が得られることになる。This value is about one order of magnitude better than the stability measurement limit 2X10-' in the case of fL=5 MH2 in the prior art.
第１図に示す構成図は、本発明のアラン分散の測定器に
係る基本的な第１の実施例であり、第２図は本発明によ
る第２の実施例の構成図である。The block diagram shown in FIG. 1 is a basic first embodiment of the Allan dispersion measuring instrument of the present invention, and FIG. 2 is a block diagram of a second embodiment of the present invention.
入力信号Ｓａを波形整形機能を有する検出器ｌで検知し
、入力信号Ｓａと同じ周波数ｆＬの繰返し周波数を持つ
矩形波信号ｓｂに変換する。また、入力信号Ｓａの周波
数ｆｔより十分高い発振周波数ｆ３の電気信号が３発振
器８から入力信号Ｓａとは独立して出力される。The input signal Sa is detected by a detector l having a waveform shaping function, and converted into a rectangular wave signal sb having a repetition frequency of the same frequency fL as the input signal Sa. Furthermore, an electrical signal having an oscillation frequency f3 sufficiently higher than the frequency ft of the input signal Sa is output from the three oscillators 8 independently of the input signal Sa.
カウンタ５は、この入力信号Ｓａを常に計数・累積し続
けており、この計数値は計数タイミング信号発生器６の
出力信号であるラッチ信号Ｓｃによりラッチ回路７にラ
ッチされる。この計数タイミング信号発生器６からのラ
ッチ信号Ｓｃの出力タイミングは、入力信号Ｓａを検出
器１で波形整形した矩形波信号ｓｂの立ち上がりを計数
タイミング信号発生器６で計数し、入力信号Ｓａの周期
の整数倍の時間に対応し、かつ、設定されたアラン分散
を測定する積分時間τのうち最小時間単位τ、、、、に
対応するｎ計数毎にラッチ信号Ｓｃを出力する。The counter 5 keeps counting and accumulating this input signal Sa, and this count value is latched into the latch circuit 7 by the latch signal Sc which is the output signal of the count timing signal generator 6. The output timing of the latch signal Sc from the counting timing signal generator 6 is determined by counting the rising edge of a rectangular wave signal sb obtained by shaping the input signal Sa by the detector 1, and calculating the period of the input signal Sa. The latch signal Sc is output every n counts corresponding to the minimum time unit τ of the integration time τ for measuring the set Allan dispersion.
すなわち、入力信号Ｓａの周波数ｆ、が５Ｍ１ｌｚで最
小積分時間τ、轟、を１／１０００秒から測定しようと
する場合、入力信号Ｓａが波形変換された矩形波信号ｓ
ｂの５０００波数の計数で １／１０００秒の時間範囲
となるためｎは５０００となる。前記ラッチ回路７にラ
ッチされた前記カウンタ５の計数値は、ラッチが更新さ
れる毎にメモリ３に記憶される。That is, when the frequency f of the input signal Sa is 5M1lz and the minimum integration time τ is to be measured from 1/1000 seconds, the input signal Sa is converted into a rectangular wave signal s.
Since the time range of 1/1000 seconds is obtained by counting 5000 wave numbers of b, n is 5000. The count value of the counter 5 latched by the latch circuit 7 is stored in the memory 3 every time the latch is updated.
このラッチ回路７による計数値のラッチと、その記憶の
動作は、前記ラッチ信号Ｓｃを計数する測定データ数計
数器９の計数値が、Ｍ（アラン分散を測定する最大積分
時間τａｍ ｘが、最小積分時間τ、五、を何回集めて
構成できるか、また何回の最大積分時間τａｍ ｘの測
定によりアラン分散を算出するかで決定される）の値に
等しくなるまで続けられる。したがって、Ｍは
τ −凰 ８
である。The latch circuit 7 latches the count value and stores the count value such that the count value of the measurement data number counter 9 that counts the latch signal Sc is M (maximum integration time τam x for measuring Allan dispersion is the minimum This process is continued until it becomes equal to the value (determined by how many integration times τ, 5) can be collected and how many times the maximum integration time τam x is to be measured to calculate the Allan variance. Therefore, M is τ −凰 8 .
すなわち、τ１１、が１／１００秒で、τ５．１が１０
秒であり、τ、、うの測定回数が１０回である場合のＭ
の値は１０，０００である。このＭにラッチ信号Ｓｃの
計数値が等しくなったとき、前記測定データ数計数器９
はデータ処理部４にデータ処理開始信号Ｓｄを出力する
。データ処理開始信号Ｓｄを受ｅ１４ Ｌ−たデータ処
理部４は、前記メモリ３に記憶されている計数値のデー
タを基にアラン分散の算出を行う。That is, τ11 is 1/100 seconds and τ5.1 is 10
seconds, and the number of measurements of τ, , is 10 times, M
The value of is 10,000. When the count value of the latch signal Sc becomes equal to this M, the measurement data number counter 9
outputs a data processing start signal Sd to the data processing section 4. Upon receiving the data processing start signal Sd, the data processing section 4 calculates the Allan variance based on the count value data stored in the memory 3.
二の算出はτ＋ｓｉｎからτ、、８までの所定のτ値に
対して行われ、該メモリ３に記憶されている計数値は前
記カウンタ５の累積値であるため、あらかじめ１つの累
積計数値からその直前のτ、ｉゎで計数した累積値を引
き、実際にτａｔ ｎの時間で計数した値りに変換する
。所定のτ値の間の計数値はτ／τ１１．，１個のＤ値
の和であるから、この和によりτ時間の計数値を算出し
、τ時間のアラン分散の計算に必要なτ時間におけるＮ
個の計数値データを作成する。The second calculation is performed for a predetermined τ value from τ+sin to τ, , 8, and since the counted value stored in the memory 3 is the cumulative value of the counter 5, it is calculated in advance from one cumulative counted value. The cumulative value counted at the immediately preceding time τ, iゎ is subtracted and converted into the value actually counted at the time τatn. The count value between predetermined τ values is τ/τ11. , 1 D value, calculate the count value of τ time using this sum, and calculate N in τ time necessary for calculating the Allan variance of τ time.
Create count value data.
このようにして算出したτ時間の計数値は、前記発振器
８の計数値であるから、前記入力信号Ｓａと該発振器８
の周波数比である ｆｔ／ｆ＊の係数を各τ時間の計数
値に乗算して、入力信号のτ時間における周波数計数値
νを算出した後（２）式を使ってアラン分散値を算出し
て測定する。Since the count value of the τ time calculated in this way is the count value of the oscillator 8, the input signal Sa and the oscillator 8
After calculating the frequency count value ν at the input signal τ time by multiplying the count value of each τ time by the coefficient of ft/f*, which is the frequency ratio of Measure.
第３図に、入力信号５ ＭＨｚ時における、従来技術と
本発明によるアラン分散の測定器の安定度測定限界の比
較を示す。第３図において、ａが従来技術による測定限
界を示す直線で、ｂが本発明による発振器の周波数を１
００Ｍ Ｈｚに設定した場合の測定限界を示す直線であ
る０図に示されているように従来技術における±１カウ
ントの丸め誤差に起因する安定度測定限界を、本発明の
丸め誤差を低減する手法を用いることにより測定限界を
１桁程度向上させることができた。この限界は、発振器
の周波数を高めることによりさらに改善することが可能
である。FIG. 3 shows a comparison of the stability measurement limits of the Allan dispersion measuring instruments according to the prior art and the present invention when the input signal is 5 MHz. In FIG. 3, a is a straight line indicating the measurement limit according to the prior art, and b is a straight line indicating the frequency of the oscillator according to the present invention.
As shown in Figure 0, which is a straight line showing the measurement limit when the frequency is set to 00MHz, the stability measurement limit due to the rounding error of ±1 count in the conventional technology can be reduced by using the method of reducing the rounding error of the present invention. This made it possible to improve the measurement limit by about one order of magnitude. This limit can be further improved by increasing the oscillator frequency.
また、本発明と従来技術のアラン分散測定器を組み合わ
せることにより安定度の非常に悪い発振器から高い精度
の発振器までの安定度が測定できるダイナミックレンジ
の広いアラン分散測定器を実現できる。Moreover, by combining the present invention with the conventional Allan dispersion measuring device, it is possible to realize an Allan dispersion measuring device with a wide dynamic range that can measure the stability of oscillators ranging from extremely unstable oscillators to highly accurate oscillators.
第１図は本発明の第１の実施例の構成図、第２図は本発
明の第２の実施例の構成図、第３図は安定度測定限界に
ついて従来技術と本発明の比較を示す図、第４図は時間
的に周波数が変化する信号を示す図、第５図は従来技術
によるアラン分散測定器の構成を示す図、第６図は従来
技術によるアラン分散測定器の丸め誤差を説明する図で
ある。
図中、１は検出器、２は周波数カウンタ部、３ばメモリ
、４はデータ処理部、５はカウンタ、６は計数タイミン
グ信号発生器、７はラッチ回路、８は発振器、９は測定
データ数計数器、Ｓａは入力信号、ｓｂは矩形波信号、
Ｓｃはラッチ信号、Ｓｄはデータ処理開始信号、ａは従
来技術による周波数安定度測定限界を示す直線、ｂは本
発明による周波数安定度測定限界を示す直線をそれぞれ
示す。
第１図Fig. 1 is a block diagram of a first embodiment of the present invention, Fig. 2 is a block diagram of a second embodiment of the present invention, and Fig. 3 is a comparison of the conventional technology and the present invention regarding stability measurement limits. Figure 4 shows a signal whose frequency changes over time, Figure 5 shows the configuration of a conventional Allan dispersion measuring device, and Figure 6 explains the rounding error of the conventional Allan dispersion measuring device. This is a diagram. In the figure, 1 is a detector, 2 is a frequency counter section, 3 is a memory, 4 is a data processing section, 5 is a counter, 6 is a counting timing signal generator, 7 is a latch circuit, 8 is an oscillator, and 9 is the number of measured data Counter, Sa is input signal, sb is square wave signal,
Sc is a latch signal, Sd is a data processing start signal, a is a straight line showing the frequency stability measurement limit according to the prior art, and b is a straight line showing the frequency stability measurement limit according to the present invention. Figure 1
Claims (1)
値の電気信号を出力する検出器（１）と、該検出器（１
）の出力信号のパルス周期よりも短い周期の周波数信号
を出力する発振器（８）と、該発振器（８）の出力信号
周波数を計数するカウンタ（５）と、 該検出器（１）の出力電気信号によりラッチ信号を形成
し、該カウンタ（５）の出力信号をラッチするラッチ回
路（７）と、 該ラッチ回路（７）の出力信号を受領し、前記周波数の
揺らぎを持つ入力信号のアラン分散値を計算するデータ
処理部（４）とを備え、 前記入力信号の周波数の揺らぎを１波数以内の誤差でア
ラン分散値を測定するアラン分散の測定器。[Claims] Receiving an input signal with frequency fluctuations and shaping the waveform,
a detector (1) that outputs an electrical signal of a value;
), an oscillator (8) that outputs a frequency signal with a shorter period than the pulse period of the output signal of the oscillator (8), a counter (5) that counts the output signal frequency of the oscillator (8), and an output electricity of the detector (1). a latch circuit (7) that forms a latch signal according to the signal and latches the output signal of the counter (5); and a latch circuit (7) that receives the output signal of the latch circuit (7) and performs Allan dispersion of the input signal having frequency fluctuations. A data processing unit (4) that calculates a value, and an Allan dispersion measuring device that measures an Allan dispersion value with an error within one wave number of frequency fluctuations of the input signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2051416A JPH081448B2 (en) | 1990-03-02 | 1990-03-02 | Alan dispersion measuring instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2051416A JPH081448B2 (en) | 1990-03-02 | 1990-03-02 | Alan dispersion measuring instrument |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03252562A true JPH03252562A (en) | 1991-11-11 |
| JPH081448B2 JPH081448B2 (en) | 1996-01-10 |
Family
ID=12886326
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2051416A Expired - Fee Related JPH081448B2 (en) | 1990-03-02 | 1990-03-02 | Alan dispersion measuring instrument |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH081448B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006038485A (en) * | 2004-07-22 | 2006-02-09 | Anritsu Corp | Frequency stability measuring instrument |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57127860A (en) * | 1981-01-31 | 1982-08-09 | Nec Home Electronics Ltd | Measuring apparatus for input signal frequency in computer system |
-
1990
- 1990-03-02 JP JP2051416A patent/JPH081448B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57127860A (en) * | 1981-01-31 | 1982-08-09 | Nec Home Electronics Ltd | Measuring apparatus for input signal frequency in computer system |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006038485A (en) * | 2004-07-22 | 2006-02-09 | Anritsu Corp | Frequency stability measuring instrument |
| JP4593993B2 (en) * | 2004-07-22 | 2010-12-08 | アンリツ株式会社 | Frequency stability measuring device |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH081448B2 (en) | 1996-01-10 |
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