JPH01121772A - Characteristic impedance measuring circuit - Google Patents
Characteristic impedance measuring circuitInfo
- Publication number
- JPH01121772A JPH01121772A JP27975987A JP27975987A JPH01121772A JP H01121772 A JPH01121772 A JP H01121772A JP 27975987 A JP27975987 A JP 27975987A JP 27975987 A JP27975987 A JP 27975987A JP H01121772 A JPH01121772 A JP H01121772A
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- transmission line
- characteristic impedance
- output
- impedance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000005540 biological transmission Effects 0.000 claims abstract description 35
- 238000005259 measurement Methods 0.000 claims abstract description 17
- 238000010586 diagram Methods 0.000 description 2
- 238000002847 impedance measurement Methods 0.000 description 2
Landscapes
- Measurement Of Resistance Or Impedance (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は特性イノピーダンスの測定回路、特にパルスを
用いて伝送線路の特性インピーダンスを測定する測定回
路に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measuring circuit for measuring characteristic inopedance, and particularly to a measuring circuit for measuring the characteristic impedance of a transmission line using pulses.
従来のこの種の特性インピーダンス測定回路は。 This type of conventional characteristic impedance measurement circuit.
出力レベルに無関係に一定な出力インピーダンス（一般
には５０Ωが多い）を持つ駆動回路を用いてステップパ
ルスあるいはパルス巾を待ったノ（ルスで被測定伝送線
路を駆動し、伝送線路の遠端に接続し九可変抵抗回路を
調整して、伝送線路遠端での反射波がなくなったときの
可変抵抗回路の抵抗値を伝送線路め特性インピーダンス
とする回路が一般に用いられる、反射波の＠側は駆動回
路の出力で行なう。Using a drive circuit with a constant output impedance (generally 50Ω) regardless of the output level, drive the transmission line under test with a step pulse or a pulse width pulse, and connect it to the far end of the transmission line. Generally, a circuit is used in which a variable resistance circuit is adjusted and the resistance value of the variable resistance circuit when the reflected wave at the far end of the transmission line disappears is the characteristic impedance of the transmission line.The @ side of the reflected wave is connected to the drive circuit. Do this with the output of
しかし、上述した従来の特性インピーダンス測定回路は
、駆動回路の出力インピーダンスが伝送線路の特性イン
ピーダンスと同等かあるいは小さい念めに、駆動回路の
出力端で観測する電圧は到来する反射電圧と同等かある
いは小さくなる。それは駆動回路の出力端での反射係数
が零の付近かあるいは負になるためである。この結果、
反射波の有無の判定が難かしく特性インピーダンスの測
定精度が悪いという欠点がめった。However, in the conventional characteristic impedance measurement circuit described above, the output impedance of the drive circuit is equal to or smaller than the characteristic impedance of the transmission line, and the voltage observed at the output end of the drive circuit is equal to or smaller than the incoming reflected voltage. becomes smaller. This is because the reflection coefficient at the output end of the drive circuit is close to zero or negative. As a result,
The drawbacks were that it was difficult to determine the presence or absence of reflected waves and the measurement accuracy of characteristic impedance was poor.
−万、出力端での反射係数を正にして、反射波を大きく
するｔめに駆動回路の出力インピーダンスを大きくする
と、駆動回路の駆動電圧は、出力インピーダンスと特性
インピーダンスとで分圧される念め、伝送線路の駆動電
圧が小さくなり、したがって反射電圧も小さくなって測
定精度はあがらない。- If you make the reflection coefficient at the output terminal positive and increase the output impedance of the drive circuit to increase the reflected wave, the drive voltage of the drive circuit will be divided by the output impedance and the characteristic impedance. Therefore, the driving voltage of the transmission line becomes smaller, and therefore the reflected voltage also becomes smaller, and the measurement accuracy does not improve.
本発明の特性イノピーダンス測定回路は、出カイ／ピー
ダンスを伝送線路の特性インピーダンスに比べて小さい
値と十分大きい値とに変化させる機能を有し、又、伝送
線路の往復伝搬遅延時間より小さいパルス巾のパルス信
号を伝送線路に駆動する駆動回路と、伝送線路の遠端に
接続する可変抵抗回路と、駆動回路の出力に接続される
測定端子とから構成され、
少なくともパルス信号の出力している間は出力インピー
ダンスｔ−特性インピーダンスより小さくし、又パルス
信号の反射波が駆動回路の出力に到達する時間より以前
に出力インピーダンスを特性インピーダンスより十分大
きくすること全特徴としている。The characteristic inopedance measurement circuit of the present invention has a function of changing the output power/pedance between a value smaller than the characteristic impedance of the transmission line and a value sufficiently large, and also has a function of changing the output power/pedance between a value smaller than the characteristic impedance of the transmission line and a value sufficiently large. It consists of a drive circuit that drives a wide pulse signal onto a transmission line, a variable resistance circuit that is connected to the far end of the transmission line, and a measurement terminal that is connected to the output of the drive circuit, and outputs at least a pulse signal. The output impedance is made smaller than the t-characteristic impedance, and the output impedance is made sufficiently larger than the characteristic impedance before the reflected wave of the pulse signal reaches the output of the drive circuit.
次に１本発明について図面を参照して説明する。 Next, one embodiment of the present invention will be explained with reference to the drawings.
第１図は本発明の一実施例金示す回路図であり、入力端
子５からのパルス信号を入力し又入力端子６からの出力
インピーダンスを制御する制御信号を入力する駆動回路
１と、駆動回路１の出力に接続する測定端子２と、被測
定伝送厳賂３と、伝送線路３の遠端と接地間に接続する
可変抵抗回路４とから構成される。FIG. 1 is a circuit diagram showing an embodiment of the present invention, and includes a drive circuit 1 to which a pulse signal from an input terminal 5 is input and a control signal for controlling output impedance from an input terminal 6 is input, and a drive circuit. 1, a transmission line to be measured 3, and a variable resistance circuit 4 connected between the far end of the transmission line 3 and ground.
駆動回路１の出カイ／ピーダンスは、制御信号により、
伝送線路３の特性インピーダンスより小さいかあるいは
十分大きい値に変化する機能を有する。The output power/pedance of the drive circuit 1 is determined by the control signal.
It has a function of changing to a value smaller than or sufficiently larger than the characteristic impedance of the transmission line 3.
伝送線路３は不平衡型を例としており帰線の両端は接地
している。The transmission line 3 is an unbalanced type, and both ends of the return line are grounded.
出力インピーダンスを変化させる機能を持つ駆動回路１
は、３ステ一ト出力機能を持つ汎用の駆動用集積回路（
例えばテキサス・インストルメント社製 ８Ｎ７４３６
５Ａ） ｔ−使用することにより容易に実現できる。Drive circuit 1 with the function of changing output impedance
is a general-purpose drive integrated circuit (
For example, Texas Instruments 8N7436
5A) It can be easily realized by using t-.
第２図は本実施例の動作を説明するための電圧波形を示
したものであり、第２図（ａ）は測定端子２の点での波
形、第２図（ｂ）は伝送線路３の遠端での反射パルス、
４２１ｇ（Ｃ１は出力インピーダンスの制Ｙ・
御信号波形をそれだれ示している。FIG. 2 shows voltage waveforms for explaining the operation of this embodiment. FIG. 2(a) shows the waveform at the measurement terminal 2, and FIG. 2(b) shows the waveform at the transmission line 3. reflected pulse at the far end,
421g (C1 shows the output impedance control signal waveform.
駆動回路１の出力インピーダンスは、制御信号が低レベ
ルの場合は特性インピーダンスて比べて小さくなり、制
御信号が高レベルの場合は十分大きくなる。初めは制御
信号を低レベルにし、出力インピーダンスを小さくした
状態にする。The output impedance of the drive circuit 1 is smaller than the characteristic impedance when the control signal is at a low level, and becomes sufficiently large when the control signal is at a high level. Initially, the control signal is set to a low level and the output impedance is kept small.
伝送線路３の往復の伝搬遅延時間Ｔ２よりも小さいパル
ス巾Ｔ１のパルス信号を入力端子５に入力すると、駆動
回路１は低出力インピーダンスで伝送線路３ｔ−駆動す
る。When a pulse signal with a pulse width T1 smaller than the round-trip propagation delay time T2 of the transmission line 3 is input to the input terminal 5, the drive circuit 1 drives the transmission line 3t with a low output impedance.
第２図（ａ）に示す駆動パルスＶＤは、伝送線路３を伝
搬してゆき可変抵抗回路４に到達する。伝送線路３の特
性インピーダンスｔＺａ、可変抵抗回路４の抵抗値′ｔ
−ＦＬＹとし、説明をわかりやすくするために、伝送線
路３は無損失とすると、伝送線路３の遠熾での反射パル
スＶＲ１は、
と表わされる。The drive pulse VD shown in FIG. 2(a) propagates through the transmission line 3 and reaches the variable resistance circuit 4. Characteristic impedance tZa of the transmission line 3, resistance value 't of the variable resistance circuit 4
-FLY, and assuming that the transmission line 3 is lossless to make the explanation easier to understand, the reflected pulse VR1 at the far end of the transmission line 3 is expressed as follows.
反射パルスｖＲ１は逆方向に伝搬してゆき測定端子２に
到達する。測定端子２には、反射パルスｖＲ１１とその
駆動回路１の出力での再反射パルスが電なった電圧が璃
われる。駆動回路１の出力インピーダンスｔ−ＥＬＬと
すると、測定端子２で測定されるパルス電圧ｖｎ、２は
と表わされる。The reflected pulse vR1 propagates in the opposite direction and reaches the measurement terminal 2. A voltage generated by the reflected pulse vR11 and its re-reflected pulse at the output of the drive circuit 1 is applied to the measurement terminal 2. When the output impedance of the drive circuit 1 is t-ELL, the pulse voltage vn,2 measured at the measurement terminal 2 is expressed as follows.
反射パルスＶＢ１が駆動回路ｌの出力に戻る前に制御信
号金高レベルにして、出力インビーダノスＲＬｉ％−性
インピーダンス２・に比べて十分大きくする。この結果
により、（２）式の第２項はほぼ反射パルスＶＢ、ｔと
なる、
ＶＢ、２″：ｌ：１ＶＲｘ
（３１となり、測定端子２における測定パルスＶＢ２は
反射パルスＶ Ｒ１の２倍の値で−ｊ定できることにな
る。Before the reflected pulse VB1 returns to the output of the drive circuit 1, the control signal is set to a high level to make it sufficiently large compared to the output impedance RLi%-characteristic impedance 2. According to this result, the second term of equation (2) becomes approximately the reflected pulse VB,t, VB,2'':l:1VRx
(31, and the measurement pulse VB2 at the measurement terminal 2 can be determined by -j at twice the value of the reflected pulse VR1.
特性インピーダンスＺ０は、可変抵抗回路４を可変して
、反射パルスＶＢ１がなくなったときの抵抗１１［Ｂｕ
ｖｔ″測定すること尤より求められる。そのとも抵抗［
ＲＶは特性インピーダンス２・に等しくなり、（１）式
より反射パルスＶＲＩは零となり、（３）式より測定パ
ルスＶｆＬ２は同じく零となる。The characteristic impedance Z0 is determined by changing the variable resistance circuit 4 to the resistance 11 [Bu
It is highly desirable to measure the resistance [
RV becomes equal to the characteristic impedance 2·, the reflected pulse VRI becomes zero from equation (1), and the measurement pulse VfL2 also becomes zero from equation (3).
抵抗値几Ｖと特性インピーダンスｚ０との差による反射
波ＶＢ１の２倍の電圧値が測定端子２で測定できるとい
うことは、特性インピーダンスＺ０の測定精度も２倍に
向上するということである。The fact that a voltage value twice the reflected wave VB1 due to the difference between the resistance value V and the characteristic impedance Z0 can be measured at the measurement terminal 2 means that the measurement accuracy of the characteristic impedance Z0 is also doubled.
駆動回路ｌの制御信号を低レベルにした時は出力インピ
ーダンスは小さいため、伝送線路３の駆動電圧を大きく
することができる。出力インピーダンスと特性インピー
ダンスとの分圧による駆動電圧の低下が小さいからであ
る。When the control signal of the drive circuit 1 is set to a low level, the output impedance is small, so the drive voltage of the transmission line 3 can be increased. This is because the drop in drive voltage due to voltage division between the output impedance and the characteristic impedance is small.
以上説明したように本発明は、伝送線路を駆動するとき
は低出力インピーダンスとして大きな振巾で駆動し、又
伝送線路の遠端からの反射波が戻るときには高出力イン
ピーダンスだして反射波を大きくする駆動回路を使うこ
とにより、伝送線路の特性インピーダンスを高精度で測
定できる効果がある。As explained above, in the present invention, when driving a transmission line, the transmission line is driven with a low output impedance and with a large amplitude, and when the reflected wave from the far end of the transmission line returns, it is driven with a high output impedance to increase the reflected wave. By using a drive circuit, the characteristic impedance of the transmission line can be measured with high precision.
第１図は本発明の実施例を示す回路図、第２図は動作を
説明するための電圧波形である。
１・・・・・・駆動回路、２・・・・・・測定端子、３
・・・・・・伝送線路、４・・・・・・可変抵抗回路、
５，６・・・・・・入力端子。
代理人 弁理士 内 原 音
道 １ 図FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a voltage waveform for explaining the operation. 1...Drive circuit, 2...Measurement terminal, 3
...Transmission line, 4...Variable resistance circuit,
5, 6... Input terminal. Agent Patent Attorney Otomichi Uchihara 1 Figure
Claims (1)
比べて小さい値と十分大きい値とに変化させる機能を有
し、又、前記伝送線路の往復伝搬遅延時間より小さいパ
ルス巾のパルス信号を前記伝送線路に駆動する駆動回路
と、 前記伝送線路の遠端に接続する可変抵抗回路と、前記駆
動回路の出力に接続される測定端子とから構成され、 少なくとも前記パルス信号が出力している間は前記出力
インピーダンスを前記特性インピーダンスより小さくし
、又前記パルス信号の反射波が前記駆動回路の出力に到
達する時間より以前に前記出力インピーダンスを前記特
性インピーダンスより十分大きくすることを特徴とする
特性インピーダンス測定回路。[Claims] It has a function of changing the output impedance between a value smaller than the characteristic impedance of the transmission line and a value sufficiently larger, and also generates a pulse signal with a pulse width smaller than the round-trip propagation delay time of the transmission line. It is comprised of a drive circuit that drives the transmission line, a variable resistance circuit that is connected to the far end of the transmission line, and a measurement terminal that is connected to the output of the drive circuit, and that operates at least while the pulse signal is being output. The characteristic impedance is characterized in that the output impedance is made smaller than the characteristic impedance, and the output impedance is made sufficiently larger than the characteristic impedance before the reflected wave of the pulse signal reaches the output of the drive circuit. measurement circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27975987A JPH01121772A (en) | 1987-11-04 | 1987-11-04 | Characteristic impedance measuring circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27975987A JPH01121772A (en) | 1987-11-04 | 1987-11-04 | Characteristic impedance measuring circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01121772A true JPH01121772A (en) | 1989-05-15 |
Family
ID=17615510
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27975987A Pending JPH01121772A (en) | 1987-11-04 | 1987-11-04 | Characteristic impedance measuring circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01121772A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2655738A1 (en) * | 1989-12-11 | 1991-06-14 | Itis | Method and apparatus for electrical measurement |
| JP2004233336A (en) * | 2003-01-08 | 2004-08-19 | Toppan Printing Co Ltd | Characteristic impedance measuring method and device |
| JP2008157360A (en) * | 2006-12-25 | 2008-07-10 | Fukushima O-Two Co Ltd | Connection joint and oxygen supply device using the same |
| JP2009294101A (en) * | 2008-06-05 | 2009-12-17 | Mitsubishi Electric Corp | Apparatus and method of inspecting printed board |
-
1987
- 1987-11-04 JP JP27975987A patent/JPH01121772A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2655738A1 (en) * | 1989-12-11 | 1991-06-14 | Itis | Method and apparatus for electrical measurement |
| JP2004233336A (en) * | 2003-01-08 | 2004-08-19 | Toppan Printing Co Ltd | Characteristic impedance measuring method and device |
| JP2008157360A (en) * | 2006-12-25 | 2008-07-10 | Fukushima O-Two Co Ltd | Connection joint and oxygen supply device using the same |
| JP2009294101A (en) * | 2008-06-05 | 2009-12-17 | Mitsubishi Electric Corp | Apparatus and method of inspecting printed board |
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