The dielectric constant is a constant (without units of measure)
used
for these calculations but.........
The value for a given material is not constant. It's shifted by
changes in temperature, moisture and frequency. You must also
know the
material's response to the operating conditions.
Andrew P. Magee - Applications Engineer
Rogers Corp - Circuit Materials Unit
Tel: (602) 917-5237
Fax: (602) 917-5256
E-Mail: [log in to unmask]
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Subject: Re: Controlled Impedance - Dielectric Constant- Comment
Author: vanech::(VANECHAA) at ~FABRIK
Date: 5/21/96 6:20 AM
From: [log in to unmask]
Date: Tue, May 21, 1996 6:20 AM
Subject: Re: Controlled Impedance - Dielectric Constant- Comment
To: Eltek Ltd.
Cc: designercouncil; technet; vanech
Avner--
If I am wrong, I hope someone out there will make me
smarter, but
the dielectric "CONSTANT" is just that--constant for that type of
material.
IMOP, when calculating impedance of microstrip or stripline, the
dielectric
constant of a material doesn't change, less the material's unique
tolerance
range REF: IPC-D-275 Table 3-2. Therefore, unless proven wrong,
the constant
DOES NOT change, but the impedance value WILL vary depending on
which
formula you are using depending on you pwb construction. Hope that
helps.
If wrong, please correct me via E-mail,
Bob Vanech
E-Mail : [log in to unmask]
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