JP4066478B2 - Method and apparatus for measuring common mode impedance of electronic circuit board - Google Patents

Method and apparatus for measuring common mode impedance of electronic circuit board Download PDF

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JP4066478B2
JP4066478B2 JP29519297A JP29519297A JP4066478B2 JP 4066478 B2 JP4066478 B2 JP 4066478B2 JP 29519297 A JP29519297 A JP 29519297A JP 29519297 A JP29519297 A JP 29519297A JP 4066478 B2 JP4066478 B2 JP 4066478B2
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circuit board
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impedance
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common mode
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JPH11133074A (en
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孝司 笹部
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Panasonic Electric Works Co Ltd
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Matsushita Electric Works Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明は、電子回路基板のコモンモード・ノイズに対するノイズ耐量を定量的に評価するためのコモンモード・インピーダンスを測定する電子回路基板のコモンモード・インピーダンス測定方法及びその測定装置に関するものである。
【０００２】
【従来の技術】
電子回路基板やケーブルに発生するノイズには、大別してノーマルモード・ノイズとコモンモード・ノイズの二つのモードがあり、ノーマルモード・ノイズとは、電流の流れる線間に現れるノイズ成分のことであり、コモンモード・ノイズとは、各線とグランド（大地）との間に現れるノイズ成分のことである。そして、各モードについてその電流の流れ易さを表現するために設定したインピーダンスが、ノーマルモード・インピーダンスとコモンモード・インピーダンスである。
【０００３】
通常の電子回路基板は全てノーマルモード・インピーダンスであるので、ノーマルモード・インピーダンスについては、測定やシミュレーションが行われている。一方、コモンモード・ノイズについては、電子回路基板のコモンモード・インピーダンスよりも、電子回路基板に接続されたケーブルのコモンモード・インピーダンスの影響の方が支配的であると考えられており、ケーブルのコモンモード・インピーダンスについては測定が行われているが、電子回路基板のコモンモード・インピーダンスについては、測定が困難なためにその測定方法が確立されておらず、測定によって得られた計測データに基づいてコモンモード・ノイズに対する評価を行うという試みは行われてなかった。
【０００４】
しかしながら、本発明者らの研究により電子回路基板のコモンモード・インピーダンスから電子回路基板のノイズ耐性の評価が可能であることが判明し、以下のような方法を用いて、電子回路基板のコモンモード・インピーダンスを測定した。
【０００５】
図４に示すように、グランド３０面に高さが１０ｃｍ程度の木片１８を配置し、木片１８上に被測定回路基板たる電子回路基板１を載置する。グランド３０面には電子回路基板１から所定の距離を開けて断面略Ｌ字状の金属板１５を設置し、金属板１５にコネクタ１６を取り付け、コネクタ１６と電子回路基板１の入出力端子間を導電線１７で接続する。そして、ネットワークアナライザ（回路定数測定器）等のインピーダンス測定器（図示せず）をコネクタ１６に接続し、例えば反射法により電子回路基板１のコモンモード・インピーダンスを測定した。すなわち、インピーダンス測定器からコネクタ１６及び導電線１７を介して電子回路基板１に信号を印加し、その反射率を測定することによって、コモンモード・インピーダンスを測定した。
【０００６】
【発明が解決しようとする課題】
上述した電子回路基板のコモンモード・インピーダンス測定方法及びその測定装置では、コモンモード・インピーダンスの測定値の絶対値が大きいため、各電子回路基板１の間のコモンモード・インピーダンスの微小な差が測定値の誤差範囲に埋もれてしまい、基板間の差を比較することができなかった。また、開空間でコモンモード・インピーダンスを測定しているので、周囲の人体（測定者）や導体などの外乱の影響を受けやすく、コモンモード・インピーダンスの測定値がばらついて、再現性の良い測定を行うことができなかった。
【０００７】
本発明は上記問題点に鑑みて為されたものであり、その目的とするところは、精度良く、再現性の良い測定が可能な電子回路基板のコモンモード・インピーダンス測定方法及びその測定装置を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明では、金属製の箱体からなる治具本体の内部底面に配置された誘電体ブロック上に被測定回路基板を載置し、被測定回路基板の入出力端子の少なくとも一部を短絡し、治具本体に設けられた接続部材と被測定回路基板の短絡された入出力端子とを導電線で接続し、接続部材とインピーダンス測定器とを同軸ケーブルで接続し、インピーダンス測定器から同軸ケーブルと接続部材と導電線とを介して被測定回路基板に信号を印加し、その反射率を測定することによってインピーダンスを測定しており、被測定回路基板の短絡された入出力端子とグランドとの間に信号を印加しており、被測定回路基板と治具本体、すなわち、グランドとの容量結合を高めることによって、測定値の絶対値を小さくして、被測定回路基板とグランドとの間のコモンモード・インピーダンスを精度良く測定することができる。
【０００９】
しかも、静電シールド効果を有する金属製の箱体内部に被測定回路基板を収納しているので、治具本体の周囲にある人体や導体などの外乱の影響を受けにくくすることができる。さらに、治具本体が金属から形成されているので、被測定回路基板とグランドとの容量結合を高めることができる。
【００１０】
そのうえ、被測定回路基板を誘電体ブロックを介して治具本体に配置しているので、被測定回路基板と治具本体との容量結合をさらに高めることができる。
【００１１】
請求項２の発明では、請求項１の発明において、被測定回路基板と治具本体の内部底面との間の距離を変化させて測定を行っているので、被測定回路基板と治具本体の内部底面との間の距離を、各被測定回路基板のコモンモード・インピーダンスの差が顕著となるような距離に調整して、インピーダンス測定を行うことができる。
【００１２】
請求項３の発明では、内部底面に配置された誘電体ブロック上に入出力端子間が短絡された被測定回路基板を載置した状態で収納し、一面に設けられた貫通型の同軸コネクタと被測定回路基板の短絡された入出力端子とが導電線で接続された金属製の治具と、同軸コネクタに同軸ケーブルを介して接続され、被測定回路基板に信号を印加しその反射率を測定することによって、インピーダンスを測定するインピーダンス測定器とから構成されており、被測定回路基板の短絡された入出力端子とグランドとの間に信号を印加することによって、被測定回路基板とグランドとの間のコモンモード・インピーダンスを測定することができる。さらに、治具の側面に同軸コネクタを配設しているので、治具の内側の同軸コネクタに校正治具を接続することにより、治具のインピーダンスの校正を行うことができる。
【００１３】
請求項４の発明では、請求項３の発明において、上記治具が、一面開口した治具本体と、治具本体の開口を塞ぐ蓋体とからなり、治具本体の開口端に蓋体との接触面積を大きくするためのフランジ部を設けているので、蓋体を取り外した状態で被測定回路基板の取り付けなどの作業を行うことができ、作業性を向上させることができる。さらに、治具本体の開口端にフランジ部を設けることにより、治具本体と蓋体との容量結合を高めることができる。
【００１４】
【発明の実施の形態】
本発明の電子回路基板のコモンモード・インピーダンス測定方法及びその測定装置を図１乃至図３を参照して説明する。
【００１５】
この測定装置の概略構成図を図１に、断面図を図２に示す。
【００１６】
被測定回路基板たる電子回路基板１を収納する金属製の治具３は、一面開口した略箱状の治具本体４と、治具本体４の開口を覆う蓋体５とから構成されており、電子回路基板１は治具本体４の底面に配置された高誘電率の誘電体ブロック２上に載置されている。
【００１７】
ここで、治具３に金属製のものを使用しているので、電子回路基板１を治具３全体と容量結合させることにより、電子回路基板１とグランド３０との容量性結合を高めて、コモンモード・インピーダンスの測定値の絶対値を下げることができる。また、電子回路基板１は金属製の治具３内部に収納されているので、電子回路基板１は、治具３の静電シールド効果により、治具３周囲の人体や導体などの影響を受けにくくなり、再現性の良い測定を行うことができる。さらに、電子回路基板１は誘電体ブロック２を介して治具本体４に取り付けられているので、電子回路基板１の下方に電気力線を集中させて、電子回路基板１とグランド３０との容量性結合をさらに高めることができ、コモンモード・インピーダンスの測定値の絶対値を下げて、精度の高い測定を行うことができる。
【００１８】
また、治具本体４の開口端には、蓋体５との接触面積を大きくするために幅が１ｃｍ程度のフランジ部６が設けられており、蓋体５の厚みは十分厚く形成され、その重量も重いので、治具本体４と蓋体５との接触面積が大きく、且つ、蓋体５が治具本体４に接触する接触圧が大きくなるので、治具本体４と蓋体５との充分な導電性を確保し、容量性結合を大きくして、コモンモード・インピーダンスの測定値の絶対値をさらに下げることができる。尚、蓋体５の材質がアルミの場合、蓋体５は５ｍｍ程度の厚みに形成されている。
【００１９】
治具本体４の側面には貫通型のＮ型同軸コネクタ７が配設されており、貫通型のＮ型同軸コネクタ７には同軸ケーブル９が配線されたＮ型同軸コネクタ８が接続され、インピーダンス測定器たる回路定数測定器（ネットワークアナライザ）２０はＮ型同軸コネクタ８及び同軸ケーブル９を介して貫通型のＮ型同軸コネクタ７に接続される。また、電子回路基板１の入出力端子１３の少なくとも一部はジャンパー線１４により短絡される。Ｎ型同軸コネクタ１０に配線された導電線１１はジャンパー線１４に電気的に接続され、Ｎ型同軸コネクタ１０を貫通型のＮ型同軸コネクタ７に接続することによって、短絡された入出力端子１３が貫通型のＮ型同軸コネクタ７の内部導体に接続される。而して、同軸ケーブル９の内部導体は電子回路基板１の入出力端子１３に電気的に接続され、同軸ケーブル９の外部導体は貫通型のＮ型同軸コネクタ７を介して治具３に電気的に接続される。尚、治具３のインピーダンス等の校正は、治具３の側面に配設された貫通型のＮ型コネクタ７の治具３内部側に、適当な校正治具１２１，１２２を接続することによって行う。
【００２０】
ここで、回路定数測定器２０は、同軸ケーブル９及び導電線１１を介して電子回路基板１に信号を印加し、その反射率を測定し、計算によって電子回路基板１のグランド３０に対するコモンモード・インピーダンスを求めている。
【００２１】
以下に、本実施形態の電子回路基板のコモンモード・インピーダンス測定方法を説明する。まず、治具本体４の底面に誘電体ブロック２を配置し、誘電体ブロック２上に電子回路基板１を載置する。次に、電子回路基板１の入出力端子１３の少なくとも一部をジャンパー線１４で短絡し、ジャンパー線１４とＮ型同軸コネクタ１０に配線された導電線１１とを電気的に接続し、Ｎ型同軸コネクタ１０を治具本体４の側面に配設された貫通型のＮ型同軸コネクタ７に接続して、電子回路基板１の短絡された入出力端子１３とＮ型同軸コネクタ７の内部導体とを電気的に接続する。さらに、貫通型のＮ型同軸コネクタ７に同軸ケーブル９が配線されたＮ型同軸コネクタ８を接続して、回路定数測定器２０と貫通型のＮ型同軸コネクタ７とを電気的に接続する。その後、回路定数測定器２０から電子回路基板１に信号を印加し、その反射率を測定することによって、回路定数測定器２０は電子回路基板１のグランド３０に対するコモンモード・インピーダンスを測定する。ここで、治具３は治具本体４と蓋体５とから構成されており、治具３内に電子回路基板１を取り付ける際は、蓋体５を外した状態で作業を行うことができ、取付作業の作業性が向上する。
【００２２】
また、誘電体ブロック３の高さを調節するなどして、電子回路基板１の設定位置（すなわち、電子回路基板１と治具３との間の距離）を変化させることができるので、電子回路基板１とグランド３０との容量性結合を変化させ、各電子回路基板１のコモンモード・インピーダンスの測定値の差が顕著となるような位置に電子回路基板１を設置して、コモンモード・インピーダンスの測定を行うことができ、各電子回路基板１のコモンモード・インピーダンスの差を精度良く、定量的に測定することができる。
【００２３】
【発明の効果】
上述のように、請求項１の発明は、金属製の箱体からなる治具本体の内部底面に配置された誘電体ブロック上に被測定回路基板を載置し、被測定回路基板の入出力端子の少なくとも一部を短絡し、治具本体に設けられた接続部材と被測定回路基板の短絡された入出力端子とを導電線で接続し、接続部材とインピーダンス測定器とを同軸ケーブルで接続し、インピーダンス測定器から同軸ケーブルと接続部材と導電線とを介して被測定回路基板に信号を印加し、その反射率を測定することによってインピーダンスを測定しており、被測定回路基板の短絡された入出力端子とグランドとの間に信号を印加しているので、被測定回路基板と治具本体、すなわち、グランドとの容量結合を高めることによって、測定値の絶対値を小さくして、被測定回路基板とグランドとの間のコモンモード・インピーダンスを精度良く測定できるという効果がある。しかも、静電シールド効果を有する金属製の箱体内部に被測定回路基板を収納しているので、治具本体の周囲にある人体や導体などの外乱の影響を受けにくくすることができ、再現性の良い測定を行うことができるという効果がある。さらに、治具本体が金属から形成されているので、被測定回路基板とグランドとの容量結合を高めることができ、インピーダンス測定値の絶対値を下げて、精度の高い測定を行うことができるという効果がある。そのうえ、被測定回路基板を誘電体ブロックを介して治具本体に配置しており、被測定回路基板と治具本体との容量結合をさらに高めることができるので、インピーダンス測定値の絶対値を下げて、精度の高い測定を行うことができるという効果がある。
【００２４】
請求項２の発明は、被測定回路基板と治具本体の内部底面との間の距離を変化させて測定を行っており、被測定回路基板と治具本体の内部底面との間の距離を、各被測定回路基板のコモンモード・インピーダンスの差が顕著となるような距離に調整して、インピーダンス測定を行うことができるので、各被測定回路基板のコモンモード・インピーダンスの差を精度良く、定量的に測定できるという効果がある。
【００２５】
請求項３の発明は、内部底面に配置された誘電体ブロック上に入出力端子間が短絡された被測定回路基板を載置した状態で収納し、一面に設けられた貫通型の同軸コネクタと被測定回路基板の短絡された入出力端子とが導電線で接続された金属製の治具と、同軸コネクタに同軸ケーブルを介して接続され、被測定回路基板に信号を印加しその反射率を測定することによって、インピーダンスを測定するインピーダンス測定器とから構成されており、被測定回路基板の短絡された入出力端子とグランドとの間に信号を印加することによって、被測定回路基板とグランドとの間のコモンモード・インピーダンスを測定できるという効果がある。さらに、治具の側面に同軸コネクタを配設しているので、治具の内側の同軸コネクタに校正治具を接続することにより、治具のインピーダンスの校正を行うことができるという効果がある。
【００２６】
請求項４の発明は、上記治具が、一面開口した治具本体と、治具本体の開口を塞ぐ蓋体とからなり、治具本体の開口端に蓋体との接触面積を大きくするためのフランジ部を設けているので、蓋体を取り外した状態で被測定回路基板の取り付けなどの作業を行うことができ、作業性が向上するという効果がある。さらに、治具本体の開口端にフランジ部を設けることにより、治具本体と蓋体との容量結合を高めることができるという効果もある。
【図面の簡単な説明】
【図１】本実施形態のインピーダンス測定装置を示す概略構成図である。
【図２】（ａ）は同上の治具の断面図であり、（ｂ）は同上の治具を校正するための校正治具を示す図である。
【図３】同上の電子回路基板の接続状態を示す上面図である。
【図４】従来のインピーダンス測定装置を示す側面図である。
【符号の説明】
１ 電子回路基板
２ 誘電体ブロック
３ 治具
４ 治具本体
５ 蓋体
７，８，１０ Ｎ型同軸コネクタ
９ 同軸ケーブル
１１ 導電線
２０ 回路定数測定器
３０ グランド[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring a common mode impedance of an electronic circuit board and a measuring apparatus for measuring the common mode impedance for quantitatively evaluating noise immunity against common mode noise of the electronic circuit board.
[0002]
[Prior art]
Noise generated on electronic circuit boards and cables can be broadly divided into two modes: normal mode noise and common mode noise. Normal mode noise is a noise component that appears between current lines. Common mode noise is a noise component that appears between each line and the ground (ground). And the impedance set in order to express the easiness of the current flow about each mode is a normal mode impedance and a common mode impedance.
[0003]
Since all normal electronic circuit boards have normal mode impedance, measurement and simulation are performed for normal mode impedance. On the other hand, for common mode noise, the influence of the common mode impedance of the cable connected to the electronic circuit board is considered to be more dominant than the common mode impedance of the electronic circuit board. Although common mode impedance has been measured, the measurement method has not been established for the common mode impedance of electronic circuit boards because measurement is difficult. Based on the measurement data obtained by measurement No attempt was made to evaluate common mode noise.
[0004]
However, the present inventors have found that it is possible to evaluate the noise resistance of the electronic circuit board from the common mode impedance of the electronic circuit board. Using the following method, the common mode of the electronic circuit board can be evaluated.・ Impedance was measured.
[0005]
As shown in FIG. 4, a piece of wood 18 having a height of about 10 cm is disposed on the surface of the ground 30, and the electronic circuit board 1 that is a circuit board to be measured is placed on the piece of wood 18. A metal plate 15 having a substantially L-shaped cross section is installed on the surface of the ground 30 at a predetermined distance from the electronic circuit board 1, a connector 16 is attached to the metal plate 15, and between the connector 16 and the input / output terminals of the electronic circuit board 1 Are connected by a conductive wire 17. Then, an impedance measuring device (not shown) such as a network analyzer (circuit constant measuring device) was connected to the connector 16, and the common mode impedance of the electronic circuit board 1 was measured by, for example, a reflection method. That is, the common mode impedance was measured by applying a signal from the impedance measuring instrument to the electronic circuit board 1 via the connector 16 and the conductive wire 17 and measuring the reflectance.
[0006]
[Problems to be solved by the invention]
In the above-described method and apparatus for measuring the common mode impedance of an electronic circuit board, since the absolute value of the measured value of the common mode impedance is large, a minute difference in the common mode impedance between the electronic circuit boards 1 is measured. It was buried in the value error range, and the difference between the substrates could not be compared. In addition, since the common mode impedance is measured in an open space, it is easily affected by disturbances from the surrounding human body (measurement person) and conductors, and the measurement value of the common mode impedance varies, making it a highly reproducible measurement. Could not do.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for measuring a common mode impedance of an electronic circuit board capable of measuring with high accuracy and good reproducibility, and a measuring apparatus therefor. There is to do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a circuit board to be measured is placed on a dielectric block disposed on the inner bottom surface of a jig body made of a metal box, and the circuit board to be measured. At least a part of the input / output terminal is short-circuited, the connection member provided on the jig body and the shorted input / output terminal of the circuit board to be measured are connected by a conductive wire, and the connection member and the impedance measuring instrument are coaxial. The impedance is measured by connecting a cable, applying a signal from the impedance measuring instrument to the circuit board to be measured through the coaxial cable, the connecting member, and the conductive wire, and measuring the reflectance. A signal is applied between the shorted input / output terminal and the ground, and the absolute value of the measured value is reduced by increasing the capacitive coupling between the circuit board to be measured and the jig body, that is, the ground. The common mode impedance between the measured circuit board and the ground can be accurately measured.
[0009]
In addition, since the circuit board to be measured is housed inside a metal box having an electrostatic shielding effect, it can be made less susceptible to disturbances such as a human body or a conductor around the jig body . Furthermore, since the jig body is made of metal, the capacitive coupling between the circuit board to be measured and the ground can be enhanced.
[0010]
In addition, since the circuit board to be measured is disposed on the jig body via the dielectric block , the capacitive coupling between the circuit board to be measured and the jig body can be further enhanced.
[0011]
In the invention of claim 2, in the invention of claim 1, since the measurement is performed by changing the distance between the circuit board to be measured and the inner bottom surface of the jig body, the circuit board to be measured and the jig body are Impedance can be measured by adjusting the distance from the inner bottom surface to such a distance that the difference in common mode impedance of each circuit board to be measured becomes significant.
[0012]
In a third aspect of the present invention, a circuit board to be measured in which the input / output terminals are short-circuited is placed on a dielectric block arranged on the inner bottom surface, and the through-type coaxial connector provided on one surface is stored. A metal jig connected to the shorted input / output terminal of the circuit board to be measured with a conductive wire and a coaxial connector connected to the circuit board via a coaxial cable. It is composed of an impedance measuring instrument that measures impedance by measuring, and by applying a signal between the shorted input / output terminal of the circuit board to be measured and the ground, the circuit board to be measured and the ground The common mode impedance between can be measured. Further, since the coaxial connector is disposed on the side surface of the jig, the impedance of the jig can be calibrated by connecting the calibration jig to the coaxial connector inside the jig.
[0013]
In the invention of claim 4, in the invention of claim 3, said jig is made up of a jig body that one side opening, a lid for closing an opening of the jig body, and a lid to the open end of the jig body Since the flange portion for increasing the contact area is provided, work such as attachment of the circuit board to be measured can be performed with the lid removed, and workability can be improved. Further, by providing the flange portion to the open end of the jig main body, it is possible to increase the capacitive coupling between the jig body and a lid.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A method and apparatus for measuring a common mode impedance of an electronic circuit board according to the present invention will be described with reference to FIGS.
[0015]
A schematic configuration diagram of this measuring apparatus is shown in FIG. 1, and a sectional view thereof is shown in FIG.
[0016]
A metal jig 3 that houses an electronic circuit board 1 that is a circuit board to be measured includes a substantially box-shaped jig body 4 that is open on one side, and a lid 5 that covers the opening of the jig body 4. The electronic circuit board 1 is placed on a dielectric block 2 having a high dielectric constant disposed on the bottom surface of the jig body 4.
[0017]
Here, since the jig 3 is made of metal, the capacitive coupling between the electronic circuit board 1 and the ground 30 is enhanced by capacitively coupling the electronic circuit board 1 with the entire jig 3. The absolute value of the measured value of common mode impedance can be reduced. Further, since the electronic circuit board 1 is housed in the jig 3 made of metal, the electronic circuit board 1 by the electrostatic shielding effect of the jig 3, affected by the jig 3 around the human body and conductor This makes it difficult to measure with good reproducibility. Further, since the electronic circuit board 1 is attached to the jig body 4 via the dielectric block 2, the electric lines of force are concentrated below the electronic circuit board 1, and the capacitance between the electronic circuit board 1 and the ground 30. Sexual coupling can be further increased, and the absolute value of the measured value of the common mode impedance can be lowered to perform highly accurate measurement.
[0018]
In addition, a flange 6 having a width of about 1 cm is provided at the opening end of the jig body 4 in order to increase the contact area with the lid 5, and the lid 5 is formed with a sufficiently large thickness. the weight is also heavy, large contact area between the jig body 4 and the lid 5, and, since the contact pressure lid 5 is in contact with the jig main body 4 is increased, the jig body 4 and the lid 5 Sufficient conductivity can be ensured, capacitive coupling can be increased, and the absolute value of the measured value of common mode impedance can be further reduced. In addition, when the material of the lid 5 is aluminum, the lid 5 is formed with a thickness of about 5 mm.
[0019]
A through-type N-type coaxial connector 7 is disposed on the side surface of the jig body 4, and an N-type coaxial connector 8 to which a coaxial cable 9 is wired is connected to the through-type N-type coaxial connector 7. A circuit constant measuring device (network analyzer) 20 serving as a measuring device is connected to a through-type N-type coaxial connector 7 via an N-type coaxial connector 8 and a coaxial cable 9. Further, at least a part of the input / output terminal 13 of the electronic circuit board 1 is short-circuited by the jumper wire 14. The conductive wire 11 wired to the N-type coaxial connector 10 is electrically connected to the jumper wire 14, and the input / output terminal 13 is short-circuited by connecting the N-type coaxial connector 10 to the through-type N-type coaxial connector 7. Is connected to the inner conductor of the through-type N-type coaxial connector 7. Thus, the inner conductor of the coaxial cable 9 is electrically connected to the input / output terminal 13 of the electronic circuit board 1, and the outer conductor of the coaxial cable 9 is electrically connected to the jig 3 via the through-type N-type coaxial connector 7. Connected. Incidentally, the calibration impedance, etc. of the jig 3, the jig 3 the inner side of the N-type connector 7 feedthrough disposed on a side surface of the jig 3, to connect the appropriate calibration jig 12 1, 12 2 By doing.
[0020]
Here, the circuit constant measuring device 20 applies a signal to the electronic circuit board 1 via the coaxial cable 9 and the conductive wire 11, measures the reflectance thereof, and calculates the common mode signal to the ground 30 of the electronic circuit board 1 by calculation. Finding impedance.
[0021]
Hereinafter, a method for measuring the common mode impedance of the electronic circuit board according to the present embodiment will be described. First, the dielectric block 2 is disposed on the bottom surface of the jig body 4, and the electronic circuit board 1 is placed on the dielectric block 2. Next, at least a part of the input / output terminal 13 of the electronic circuit board 1 is short-circuited by the jumper wire 14, the jumper wire 14 and the conductive wire 11 wired to the N-type coaxial connector 10 are electrically connected, and the N-type The coaxial connector 10 is connected to a through-type N-type coaxial connector 7 disposed on the side surface of the jig body 4 so that the short-circuited input / output terminal 13 of the electronic circuit board 1 and the inner conductor of the N-type coaxial connector 7 are connected. Are electrically connected. Further, an N-type coaxial connector 8 in which a coaxial cable 9 is wired is connected to the through-type N-type coaxial connector 7, and the circuit constant measuring device 20 and the through-type N-type coaxial connector 7 are electrically connected. Thereafter, by applying a signal from the circuit constant measuring instrument 20 to the electronic circuit board 1 and measuring the reflectance thereof, the circuit constant measuring instrument 20 measures the common mode impedance with respect to the ground 30 of the electronic circuit board 1. Here, the jig 3 includes a jig body 4 and a lid 5, and when the electronic circuit board 1 is mounted in the jig 3, the work can be performed with the lid 5 removed. The workability of the mounting work is improved.
[0022]
In addition, since the setting position of the electronic circuit board 1 (that is, the distance between the electronic circuit board 1 and the jig 3) can be changed by adjusting the height of the dielectric block 3, the electronic circuit The capacitive coupling between the board 1 and the ground 30 is changed, and the electronic circuit board 1 is installed at a position where the difference in the measured value of the common mode impedance of each electronic circuit board 1 becomes significant. The difference in common mode impedance of each electronic circuit board 1 can be measured accurately and quantitatively.
[0023]
【The invention's effect】
As described above, according to the first aspect of the present invention, the circuit board to be measured is placed on the dielectric block disposed on the inner bottom surface of the jig body made of a metal box, and the input / output of the circuit board to be measured is performed. Short-circuit at least part of the terminals, connect the connection member provided on the jig body and the shorted I / O terminal of the circuit board to be measured with a conductive wire, and connect the connection member and the impedance measuring instrument with a coaxial cable Then, the impedance is measured by applying a signal from the impedance measuring instrument to the circuit board to be measured through the coaxial cable, the connecting member, and the conductive wire, and measuring the reflectance, and the circuit board to be measured is short-circuited. Since the signal is applied between the input / output terminal and the ground, the absolute value of the measured value is reduced by increasing the capacitive coupling between the circuit board to be measured and the jig body, that is, the ground. Measurement times The common mode impedance between the substrate and the ground there is an effect that can be accurately measured. In addition, since the circuit board to be measured is housed inside a metal box that has an electrostatic shielding effect, it can be made less susceptible to disturbances such as the human body and conductors around the jig body. There is an effect that measurement with good characteristics can be performed. Furthermore, since the jig body is made of metal, the capacitive coupling between the circuit board to be measured and the ground can be increased, and the absolute value of the impedance measurement value can be lowered to perform highly accurate measurement. effective. In addition, the circuit board to be measured is arranged on the jig body via the dielectric block , and the capacitive coupling between the circuit board to be measured and the jig body can be further increased, so the absolute value of the impedance measurement value is lowered. Thus, there is an effect that measurement with high accuracy can be performed.
[0024]
According to a second aspect of the invention, and subjected to measurement distance by changing the between the inner bottom surface of the circuit under test board and the jig body, the distance between the inner bottom surface of the circuit under test board and the jig body Since the impedance can be measured by adjusting the distance so that the difference in common mode impedance of each circuit board to be measured becomes significant, the difference in common mode impedance of each circuit board to be measured can be accurately determined. There is an effect that it can be measured quantitatively.
[0025]
According to a third aspect of the present invention, there is provided a through-type coaxial connector provided on one surface, which is housed in a state in which a circuit board to be measured whose input and output terminals are short-circuited is placed on a dielectric block disposed on the inner bottom surface. A metal jig connected to the shorted input / output terminal of the circuit board to be measured with a conductive wire and a coaxial connector connected to the circuit board via a coaxial cable. It is composed of an impedance measuring instrument that measures impedance by measuring, and by applying a signal between the shorted input / output terminal of the circuit board to be measured and the ground, the circuit board to be measured and the ground The common mode impedance can be measured. Furthermore, since the coaxial connector is disposed on the side surface of the jig, the impedance of the jig can be calibrated by connecting the calibration jig to the coaxial connector inside the jig.
[0026]
A fourth aspect of the present invention, the jig comprises a jig body that one side opening, consists of a lid for closing an opening of the jig body, in order to increase the contact area with the lid in the open end of the jig body Since the flange portion is provided, work such as attachment of the circuit board to be measured can be performed with the lid removed, and the workability is improved. Furthermore, there by providing a flange on the open end of the jig body, also an effect that it is possible to increase the capacitive coupling between the jig body and a lid.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an impedance measuring apparatus according to an embodiment.
2 (a) is a sectional view of the jig of the same, (b) is a diagram showing a calibration jig for calibrating the jig of the same.
FIG. 3 is a top view showing a connection state of the electronic circuit board.
FIG. 4 is a side view showing a conventional impedance measuring apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electronic circuit board 2 Dielectric block 3 Jig 4 Jig body 5 Lid 7, 8, 10 N type coaxial connector 9 Coaxial cable 11 Conductive wire 20 Circuit constant measuring device 30 Ground

Claims (4)

金属製の箱体からなる治具本体の内部底面に配置された誘電体ブロック上に被測定回路基板を載置し、被測定回路基板の入出力端子の少なくとも一部を短絡し、治具本体に設けられた接続部材と被測定回路基板の短絡された入出力端子とを導電線で接続し、接続部材とインピーダンス測定器とを同軸ケーブルで接続し、インピーダンス測定器から同軸ケーブルと接続部材と導電線とを介して被測定回路基板に信号を印加し、その反射率を測定することによってインピーダンスを測定することを特徴とする電子回路基板のコモンモード・インピーダンス測定方法。A circuit board to be measured is placed on a dielectric block arranged on the inner bottom surface of a jig body made of a metal box, and at least a part of the input / output terminals of the circuit board to be measured is short-circuited. The connection member provided in the circuit board and the shorted input / output terminal of the circuit board to be measured are connected by a conductive wire, the connection member and the impedance measuring instrument are connected by a coaxial cable, and the coaxial cable and the connecting member are connected from the impedance measuring instrument. A method of measuring a common mode impedance of an electronic circuit board, comprising: measuring a impedance by applying a signal to a circuit board to be measured through a conductive wire and measuring a reflectance thereof. 被測定回路基板と治具本体の内部底面との間の距離を変化させて測定を行うことを特徴とする請求項１記載の電子回路基板のコモンモード・インピーダンス測定方法。2. The method of measuring a common mode impedance of an electronic circuit board according to claim 1, wherein the measurement is performed by changing a distance between the circuit board to be measured and the inner bottom surface of the jig body. 内部底面に配置された誘電体ブロック上に入出力端子間が短絡された被測定回路基板を載置した状態で収納し、一面に設けられた貫通型の同軸コネクタと被測定回路基板の短絡された入出力端子とが導電線で接続された金属製の箱体からなる治具と、同軸コネクタに同軸ケーブルを介して接続され、被測定回路基板に信号を印加しその反射率を測定することによって、インピーダンスを測定するインピーダンス測定器とから構成されることを特徴とする電子回路基板のコモンモード・インピーダンス測定装置。 A circuit board to be measured with the input / output terminals short-circuited is placed on a dielectric block placed on the bottom of the internal circuit in a state where it is placed, and the through-type coaxial connector provided on one surface and the circuit board to be measured are short-circuited. A jig made of a metal box connected to the input / output terminals with conductive wires, and connected to the coaxial connector via a coaxial cable, applying a signal to the circuit board to be measured and measuring its reflectivity An apparatus for measuring the common mode impedance of an electronic circuit board, comprising: an impedance measuring instrument for measuring impedance. 上記治具が、一面開口した治具本体と、治具本体の開口を塞ぐ蓋体とからなり、治具本体の開口端に蓋体との接触面積を大きくするためのフランジ部を設けたことを特徴とする請求項３記載の電子回路基板のコモンモード・インピーダンス測定装置。The jig is composed of a jig body that opens on one side and a lid that closes the opening of the jig body, and a flange portion is provided at the opening end of the jig body to increase the contact area with the lid. The common mode impedance measuring apparatus for an electronic circuit board according to claim 3.
JP29519297A 1997-10-28 1997-10-28 Method and apparatus for measuring common mode impedance of electronic circuit board Expired - Fee Related JP4066478B2 (en)

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JP29519297A JP4066478B2 (en) 1997-10-28 1997-10-28 Method and apparatus for measuring common mode impedance of electronic circuit board

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JP2005233833A (en) * 2004-02-20 2005-09-02 Sony Corp Electromagnetic interference measuring system
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JP5470820B2 (en) * 2008-11-28 2014-04-16 株式会社村田製作所 High frequency measurement method and apparatus
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