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기타 how to confirm the impedance of the microstrip?

모아레 2010.07.10 11:16 조회 수 : 567

mckinson



Joined: 03 Sep 2003
Posts: 136
Post28 Nov 2004 15:24   

Hello ,about the 50 ohms microstrip !
Hello ,guys . Anybody knows how to confirm the impedance of the microstrip ?
For example ,I have simulated the width of the microstrip for 50 homs .But I don't
know whether the impedance of pcb tracks from pcb manufactory is correct ? How to confirm ? Best regards !
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28 Nov 2004 15:24   

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BigBoss



Joined: 17 Nov 2001
Posts: 1177
Helped: 89
Location: Earth
Post28 Nov 2004 18:38   

Re: Hello ,about the 50 ohms microstrip !
mckinson wrote:
Hello ,guys . Anybody knows how to confirm the impedance of the microstrip ?
For example ,I have simulated the width of the microstrip for 50 homs .But I don't
know whether the impedance of pcb tracks from pcb manufactory is correct ? How to confirm ? Best regards !


Connect an 50 Ohm low ESR and inductance resistor (or 2 parallel 100 Ohm) at the end of line and measure with VNA.
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vfone



Joined: 10 Oct 2001
Posts: 2578
Helped: 358
Post28 Nov 2004 22:45   

Re: Hello ,about the 50 ohms microstrip !
You don’t need any extra components. Just measure with Network Analyzer, that is connected at both ends of the line.
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sergio mariotti



Joined: 22 Dec 2003
Posts: 469
Helped: 43
Location: Italy
Post29 Nov 2004 0:03   

Re: Hello ,about the 50 ohms microstrip !
vfone wrote:
You don’t need any extra components. Just measure with Network Analyzer, that is connected at both ends of the line.

Yes, correct, but usually it may be experimented that measured Zo differ a lot from the simulated one, also in the case that all is correct and well manufactured.
This is due to end effects and ľstrip launchers.
To reduce this effect and focalize the attention to the line only, use a Time Domain VNA. Both Agilent and Anritsu have very efficent and useful TD algoritms.
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mckinson



Joined: 03 Sep 2003
Posts: 136
Post29 Nov 2004 16:14   

Hello ,about the 50 ohms microstrip !
Appreciated !Do you think that is accurate measure the character impedance Z0 by the VNA ?
Could you please tell me the detail stap for measurement ? Best regards !
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vfone



Joined: 10 Oct 2001
Posts: 2578
Helped: 358
Post29 Nov 2004 17:59   

Re: Hello ,about the 50 ohms microstrip !
By definition the main designation of VNA is to measure impedances.
Time Domain Reflectometry (TDR) is more accurate than frequency domain Vector Network Analysis (VNA), because do not depend by frequency.
But for commercial applications frequency domain is more than ok.
Check this document:
http://cp.literature.agilent.com/litweb/pdf/5968-1947E.pdf
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hitmo



Joined: 04 Jan 2005
Posts: 40
Post13 Jan 2005 18:55   

Re: Hello ,about the 50 ohms microstrip !
u can also do it with network ana. just measure inserstion loss and return loss on smith chart. return loss will tell u the impedance of the line. if the rerunloss is as close as possible to center of the smith chart its a 50ohm line

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