Microstrip Length

[Philip Newman]

How can I calculate the length of a line of microstrip, by using the
Effective Electrical Length and it's impedance?

I know how to calculate the width of the line, but what about the length?

I can use ADS' LineCalc to achieve this, but I wish to find a formula. What
formula does LineCalc use? I cannot find it anywhere.

Assume I know all the substrate and metallisation parameters.

Cheers

Phil

 

[Active8]

How can I calculate the length of a line of microstrip, by using the
Effective Electrical Length and it's impedance?

I know how to calculate the width of the line, but what about the length?

I can use ADS' LineCalc to achieve this, but I wish to find a formula. What
formula does LineCalc use? I cannot find it anywhere.

Assume I know all the substrate and metallisation parameters.

Cheers

Phil

Use the VP factor, 1/sqrt(e_r) where e_r is the dielectric constant
of the substrate.

l_phys = VP * l_elec

 

[Philip Newman]

Use the VP factor, 1/sqrt(e_r) where e_r is the dielectric constant
of the substrate.

l_phys = VP * l_elec

Hmm, doesn't work for my values or consistent with LineCalc. I think I may
be confusing Electrical Length with Phase Change.

I looked in my Pozar Book, and found the equations. They work out fine, so
no panick!

Cheers anyway

Phil

 

[John Larkin]

How can I calculate the length of a line of microstrip, by using the
Effective Electrical Length and it's impedance?

I know how to calculate the width of the line, but what about the length?

I can use ADS' LineCalc to achieve this, but I wish to find a formula. What
formula does LineCalc use? I cannot find it anywhere.

Assume I know all the substrate and metallisation parameters.

Cheers

Phil

Appcad reports this, based on effective dielectric constant Eef; it
gives you Eef, too.

John

 

[Mac]

Use the VP factor, 1/sqrt(e_r) where e_r is the dielectric constant
of the substrate.

l_phys = VP * l_elec

This doesn't work for microstrip. The deal with microstrip is that the
effective dielectric constant is somewhere in between that of the
dielectric medium and that of free-space (or other surrounding medium).
This sort of makes sense if you think in terms of the field lines
emmanating from the microstrip: some of them go through air (or other
surrounding medium) and some of them go through the substrate.

Pozar's book (I have _Microwave Engineering_ second edition) gives
equations, as the OP already discovered.

Mac
--

 

[danesh.8]

On Thu, 08 Apr 2004 14:46:35 +0000, Active8 wrote:

> On Thu, 8 Apr 2004 19:11:46 +0100, Philip Newman wrote:
>
>> How can I calculate the length of a line of microstrip, by using the
>> Effective Electrical Length and it's impedance?
>>
>> I know how to calculate the width of the line, but what about the length?
>>
>> I can use ADS' LineCalc to achieve this, but I wish to find a formula. What
>> formula does LineCalc use? I cannot find it anywhere.
>>
>> Assume I know all the substrate and metallisation parameters.
>>
>> Cheers
>>
>> Phil
>
> Use the VP factor, 1/sqrt(e_r) where e_r is the dielectric constant
> of the substrate.
>
> l_phys = VP * l_elec

This doesn't work for microstrip. The deal with microstrip is that the
effective dielectric constant is somewhere in between that of the
dielectric medium and that of free-space (or other surrounding medium).
This sort of makes sense if you think in terms of the field lines
emmanating from the microstrip: some of them go through air (or other
surrounding medium) and some of them go through the substrate.

Pozar's book (I have _Microwave Engineering_ second edition) gives
equations, as the OP already discovered.

Mac
--

Hi Mac,

can u share the formula that you found from pozar. chapter or the book page