[SI-LIST] Re: 回复： Re: How to measure the actual impedance of a stripline with DSA8200(TDR)

  • From: John Lee <venussoso@xxxxxxxx>
  • To: " Hithesh \(GE Intelligent Platforms\)Nijagunamurthy" <hithesh@xxxxxx>
  • Date: Thu, 13 Jan 2011 22:57:28 +0800 (CST)

Thank you very much, Hithesh,
I have tryed the calculator which you recommended, and the result is about 
57ohm.
The actual trace width = 3.3mil, trace thickness = 0.5mil, distance between 
traces = 4mil, distance to top ref layer = 5mil, and distance to bottom ref 
layer 9.4mil,and dielectric constant is about 4.3 (which i have doubt about it).
Best Regards!
John Lee

--- 11å¹´1æ??13æ?¥ï¼?å?¨å??, Nijagunamurthy, Hithesh (GE Intelligent Platforms) 
<hithesh@xxxxxx> å??é??ï¼?


å??件人: Nijagunamurthy, Hithesh (GE Intelligent Platforms) <hithesh@xxxxxx>
主é¢?: RE: å??å¤?ï¼? [SI-LIST] Re: How to measure the actual impedance of a 
stripline with DSA8200(TDR)
�件人: "John Lee" <venussoso@xxxxxxxx>
æ?¥æ??: 2011å¹´1æ??13æ?¥,å?¨å??,ä¸?å??7:16



I use a calculator on the web and also calculate using the tool in the SI 
software I use - Sisoft.
I usually have come across same 
ref planes  ( Vdd on either side of the strip line or Ground on either side of the strip line)
 
You can try the calculator by AWR. Try using this - 
http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=util_pcb_imp_stripline_dual
 
If you can tell me the trace width, trace thickness, distance between 
traces, distance to top ref layer and bottom ref layer and dielectric 
constant, I can calculate in my SI software.
 
-Hithesh
 




From: John Lee [mailto:venussoso@xxxxxxxx] 
Sent: Thursday, January 13, 2011 3:36 PM
To: Nijagunamurthy, Hithesh (GE Intelligent Platforms)
Subject: RE: å??å¤?ï¼? [SI-LIST] Re: How to measure the actual impedance of a 
stripline with DSA8200(TDR)







Hi, Hithesh,
I just use the POLAR CITS25 to simulate the impedance, maybe i have missed 
something..
And how do you measure the stripline in your site?

Best Regards!
John Lee

--- 11å¹´1æ??13æ?¥ï¼?å?¨å??, Nijagunamurthy, Hithesh (GE Intelligent Platforms) 
<hithesh@xxxxxx> å??é??ï¼?


å??件人: Nijagunamurthy, Hithesh (GE Intelligent Platforms) <hithesh@xxxxxx>
主é¢?: RE: å??å¤?ï¼? [SI-LIST] Re: How to measure the actual impedance of a 
stripline with DSA8200(TDR)
�件人: "John Lee" <venussoso@xxxxxxxx>
æ?¥æ??: 2011å¹´1æ??13æ?¥,å?¨å??,ä¸?å??5:55



John,
 
Are you considering it as a strip line or a microstrip?
In the strip lines I have seen, the signal line has same reference 
layers(usually ground) on either side of the signal.
But in your case, one reference layer is Vcc and the other is gnd.
I am not sure how to calculate impedance. Can you tell me.
 
-Hithesh



From: John Lee [mailto:venussoso@xxxxxxxx] 
Sent: Thursday, January 13, 2011 3:13 PM
To: SI LIST; Nijagunamurthy, Hithesh (GE Intelligent Platforms)
Subject: å??å¤?ï¼? [SI-LIST] Re: How to measure the actual impedance of a 
stripline with DSA8200(TDR)







Hi, Hithesh,
I calculated the value by POLAR CITS25.

Best Regards!
John Lee

--- 11å¹´1æ??13æ?¥ï¼?å?¨å??, Nijagunamurthy, Hithesh (GE Intelligent Platforms) 
<hithesh@xxxxxx> å??é??ï¼?


å??件人: Nijagunamurthy, Hithesh (GE Intelligent Platforms) <hithesh@xxxxxx>
主�: [SI-LIST] Re: How to measure the actual impedance of a stripline with 
DSA8200(TDR)
�件人: "John Lee" <venussoso@xxxxxxxx>, "SI LIST" <si-list@xxxxxxxxxxxxx>
æ?¥æ??: 2011å¹´1æ??13æ?¥,å?¨å??,ä¸?å??4:42



How did you calculate the theoretical value?
Did you get the value from the fab or use the Strip line formula?

-Hithesh


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of John Lee
Sent: Thursday, January 13, 2011 1:17 PM
To: SI LIST
Subject: [SI-LIST] How to measure the actual impedance of a stripline with 
DSA8200(TDR) 

Hi, SI experts,
I have a question about impedance measurement for DDR3 register memory.
I have a register memory that uses 10layers stack-up as follows:
L1 signal        ----
L2 Vdd        -----------
L3 signal        ----        target layer
L4 signal        ----
L5 Vss       ------------
L6~L10     symmetry 
 
Now I want to measure the impedance of L3's signal, so i got a PCB (without any 
resisters, or DRAMs) to do the test, but no matter Vdd or Vss I choose for the 
reference plane, the result is only about a half of theoretical value (for 
instance, the theoretical value is 60ohm, but the measurement result is more or 
less 28ohm).
 
Is there anything i missed during the measurement? And how to get the actual 
impedance in this situation?
 
Any reply will be appreciated, thanks in advance.
Best Regards!
John Lee


      
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