Hello !

Im looking for a formula impedance of conductor between two ground plane.

_________
*
h1
*
p
*
h2
*
_________

p -conductor
h1 = h2

Thank you for your help !

Goodlack ! ! !

What shape is the conductor? If it is a rectangular cross-section, do
a search on the web for "stripline impedance formula" and you should
find what you are looking for. If it's a round wire, diameter d and
symmetrically spaced between two grounded plates separated by h, and if
d .75h, to a reasonable approximation,

Z0 = 60*ln(4h/pi*d)

(per "Reference Data for Engineers"; my suspicion is that Z0 =
60*cosh^-1(2h/pi*d) is exact for lossless line, but I won't try to
prove it at the moment.) Divide by sqrt(relative dielectric constant)
if the dielectric isn't air or vacuum.

Cheers,
Tom

kretko wrote:
Hello !

Im looking for a formula impedance of conductor between two ground plane.

_________
*
h1
*
p
*
h2
*
_________

p -conductor
h1 = h2

Thank you for your help !

Goodlack ! ! !

I just posted suggesting that z0=60*cosh^-1(2h/pi*d) might be the exact
formula for the impedance. That is clearly wrong; don't use it.

Cheers,
Tom


K7ITM wrote:
What shape is the conductor? If it is a rectangular cross-section, do
a search on the web for "stripline impedance formula" and you should
find what you are looking for. If it's a round wire, diameter d and
symmetrically spaced between two grounded plates separated by h, and if
d .75h, to a reasonable approximation,

Z0 = 60*ln(4h/pi*d)

(per "Reference Data for Engineers"; my suspicion is that Z0 =
60*cosh^-1(2h/pi*d) is exact for lossless line, but I won't try to
prove it at the moment.) Divide by sqrt(relative dielectric constant)
if the dielectric isn't air or vacuum.

Cheers,
Tom

kretko wrote:
Hello !

Im looking for a formula impedance of conductor between two ground plane.

_________
*
h1
*
p
*
h2
*
_________

p -conductor
h1 = h2

Thank you for your help !

Goodlack ! ! !

kretko wrote:
Hello !

Im looking for a formula impedance of conductor between two ground plane.

_________
*
h1
*
p
*
h2
*
_________

p -conductor
h1 = h2

Thank you for your help !

Goodlack ! ! !


OK, let h=2*h1 and d= wire diameter
Then, for p/h 0,75
Zo = (138/sqrt(e))*log10(4h/(pi*d))
where pi = 3.14159.... and e = 2.7183...
Alan

Ahem. In your formula, e is the relative dielectric constant of the
dielectric between the planes and surrounding the wire, NOT the base of
natural logarithms. And I assume that "p/h 0,75" should be d/h
0,75. Then it's equivalent to what I posted earlier.

Cheers,
Tom

Alan Peake wrote:
kretko wrote:
Hello !

Im looking for a formula impedance of conductor between two ground plane.

_________
*
h1
*
p
*
h2
*
_________

p -conductor
h1 = h2

Thank you for your help !

Goodlack ! ! !


OK, let h=2*h1 and d= wire diameter
Then, for p/h 0,75
Zo = (138/sqrt(e))*log10(4h/(pi*d))
where pi = 3.14159.... and e = 2.7183...
Alan

K7ITM wrote:
Ahem. In your formula, e is the relative dielectric constant of the
dielectric between the planes and surrounding the wire, NOT the base of
natural logarithms. And I assume that "p/h 0,75" should be d/h
0,75. Then it's equivalent to what I posted earlier.

Cheers,
Tom

Ooops! - I just knew I'd get it wrong somewhe}
Yes, I meant to say d/h as that was the formula in "Reference Data for
Radio Engineers". Didn't see your post.
Must be the weather here - snowing!
Alan