[SI-LIST] Re: The crosstalk of transmission line when it is completelymatched
- From: "Scott McMorrow" <scott@xxxxxxxxxxxxx>
- To: zhang_kun@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Thu, 05 Dec 2002 19:38:00 -0800
Zhangkun,
You are getting reflected reverse crosstalk off of the driver. You will
need to match the driver impedance to the transmission line impedance to
eliminate this reflection. Since the driver is a perfect source, your
reflection coefficient is -1.
scott
--
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
Zhangkun wrote:
>Hi all:
>
>This morning, I do some crosstalk simulation. I find something interesting.
>The following is what I do.
>
>1. Create diffline.rlgc from rlgc.sp
>2. Calculate the Z_diff and Z_comm from diffline.rlgc
>3. Match the diffline and simulate it by match_2.sp
>
>I find the near end crosstalk and the far end crosstalk are equal. This is not
>same to the general crosstalk theory. I want to know why.
>
>rlgc.sp
>.OPTION PROBE POST
>VIMPULSE in1 gnd PULSE 0v 5v 5n 2n 2n 20n
>W1 in1 in2 gnd out1 out2 gnd FSmodel=cond2_sys N=2 l=1000mil
>Rin2 in2 gnd 49
>Rout1 out1 gnd 49
>Rout2 out2 gnd 49
>.MATERIAL diel DIELECTRIC ER=4.5
>.SHAPE rect RECTANGLE WIDTH=7mil, HEIGHT=2mil,
>.LAYERSTACK stack1,
>+LAYER=(PEC,20mil), LAYER=(diel,22mil),
>+LAYER=(PEC,20mil)
>.FSOPTIONS opt1 PRINTDATA=YES
>.MODEL cond2_sys W MODELTYPE=FieldSolver,
>+LAYERSTACK=stack1, FSOPTIONS=opt1
>+RLGCFILE=diffline.rlgc
>+CONDUCTOR=(SHAPE=rect, ORIGIN=(0,30mil)),
>+CONDUCTOR=(SHAPE=rect, ORIGIN=(14mil,30mil))
>.TRAN 0.5n 100n
>.PROBE v(out1)
>.END
>
>diffline.sp
>*SYSTEM_NAME : cond2_sys
>*
>* ------------------------------------ Z = 0.0015748
>* //// Top Ground Plane //////////////
>* ------------------------------------ Z = 0.0010668
>* diel H = 0.0005588
>* ------------------------------------ Z = 0.000508
>* //// Bottom Ground Plane ///////////
>* ------------------------------------ Z = 0
>
>* N (number of signal conductors)
>*********************************
>2
>
>* Lo (H/m)
>*********************************
>3.42622e-07
>6.40120e-08 3.42622e-07
>
>
>* Co (F/m)
>*********************************
>1.50678e-10
>-2.82540e-11 1.50678e-10
>
>
>* Ro (Ohms/m)
>*********************************
>0.00000e+00
>0.00000e+00 0.00000e+00
>
>
>* Go (S/m)
>*********************************
>0.00000e+00
>-0.00000e+00 0.00000e+00
>
>match_2.sp
>the simple diff transmissionline
>
>.options list node post
>.op
>.tran 0.5n 100n
>
>*driver
>vp in1 gnd pulse 0 5 1n 1n 1n 3n 8n
>*vn in2 gnd pulse 10 0 1n 1n 1n 3n 8n
>rin2 in2 gnd 47.69
>
>*transmission line
>Wcable in1 in2 gnd out1 out2 gnd RLGCfile=diffline.rlgc n=2 l=5000mil
>
>*receiver
>rout1 out1 node1 39.4598
>rout2 out2 node1 39.4598
>rcon node1 gnd 9.0864
>
>.end
>
>Z_diff=78.9195 Z_comm=28.8163
>rou1=rout2=Z_diff/2
>rcon=(2*Z_comm-Z_diff/2)/2
>
>Best Regards
>Zhangkun
>2002.12.06
>
>
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