[SI-LIST] Re: [SI-LIST]: Which tool is the best - LINPARdiscussion
- From: Raj Raghuram <raj.raghuram@xxxxxxxxxxxxxxx>
- To: levinpa@xxxxxxxxxxxxx
- Date: Tue, 20 Apr 2004 08:04:49 -0700
Apart from the cost, here are some technical pros and cons of ApsimRLGC
and Linpar.
1. Linpar uses the Boundary Element method. This is Method of Moments
based and uses free space Green's functions. Where there is boundary
between dielectrics, interface charge needs to be added and solved for.
This can add to the simulation time. Where there are a number of
dielectric layers, it can affect the accuracy as well. Apsim RLGC
(method=1) also uses the Method of Moments. However, because it uses the
Spectral Domain method, it does not need to model and solve for the
interface charge at the boundaries between dielectrics.
2. If two conductors are very close together (normally not true in
typical PCBs), the LINPAR answer for the mutual capacitance may be more
accurate because the charge on the edges is modeled better compared to
ApsimRLGC (method = 1).
3. If you use a closed geometry with non rectangular conductors (say a
co-ax cable with two inner conductors), neither Apsim RLGC (method=1)
nor LINPAR is probably suitable. ApsimRLGC has a Finite Difference base
solver (method = 2), which is good for arbitrary closed geometries.
4. ApsimRLGC has a quick Via model extractor which LINPAR does not have.
It is also based on the Spectral Domain technique uisng cylindrical
co-ords and circular symmetry.
5. One minor disadvantage of the Boundary Element method in LINPAR (at
least in the earlier version) was that a homogenous medium such as
stripline could give forward crosstalk. For forward crosstalk to be
absent, the even and odd mode velocities must match exactly. A very
minor error in the L and C matrices of a coupled line could destroy this
match. The numerical techniques in ApsimRLGC automatically achieve this
match even if there are minor errors in L and C matrices.
6. ApsimRLGC was originally intended to provide matrices for
transmission line simulation in ApsimSPICE format and not as a
standalone program. Some of the notation is still less than obvious for
this reason.
Warm Regards,
Paul Levin wrote:
>Dear Abe, et al.,
>
>Sorry, I've never played with LINPAR v1. Considering the price,
>I'd just recommend that you spring for v2.
>
>Regards,
>
>Paul
>________________________
>
>Abe Riazi wrote:
>
>
>
>>Dear Paul,
>>
>>Can you comment on some of the differences between LINPAR v2 and
>>the free version LINPAR v1 ?
>>
>>Thank you.
>>
>>Abe
>>
>>
>>-----Original Message-----
>>From: Paul Levin [SMTP:levinpa@xxxxxxxxxxxxx]
>>Sent: Monday, April 19, 2004 2:49 PM
>>To: Raymond.Anderson@xxxxxxx
>>Cc: si-list@xxxxxxxxxxxxx; vrbanacm@xxxxxxxxxx
>>Subject: [SI-LIST] Re: [SI-LIST]: Which tool is the best -
>>LINPARdiscussion
>>
>>Dear All,
>>
>>LINPAR v2 (what I've got) will indeed handle dielectric above
>>the uppermost layer of conductors (solder mask) in the multi-
>>layered planar structure mode, as well as several others.
>>
>>The one caveat is that the top surface of each dielectric layer
>>is flat, so solder mask thickness changes drastically depending
>>on whether the mask is above copper or simply above dielectric
>>(and the mask must be thick enough to that at least 5% of the
>>layer thickness is covering the copper.) Alternately, you could
>>force the top conductors to bury themselves into the dielectric
>>just below the conductors so that the dielectric and conductors
>>have a smooth top surface on top of which you could put a uniform
>>covering of dielectric. (Gee, for this it would be nice to use
>>the new text plotting capability, but I don't have the time to
>>download, let alone, learn the software.)
>>
>>User-defined input file mode would indeed permit you to define
>>trapezoidal conductor cross sections and conformal coat solder
>>mask. I must admit that I have never tried to use a User-Defined
>>Input File, however.
>>
>>That said, I have found the program to be really useful and, as
>>others have noted, an incredible bargain. My two cents. . .
>>
>>Regards,
>>
>>Paul
>>
>>
>>
>>
>>
>
>
>
--
Raj Raghuram
Berkeley Design Automation (http://berkeley-da.com)
2902 Stender Way,
Santa Clara, CA-95054
PH: (408)-496-6600 ext.203
Cell: (408)-390-7614
EMAIL: raj.raghuram@xxxxxxxxxxxxxxx
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