calculate the min coupling

[rameshrai]

Hello,

I need to calculate minimum coupling between two microstrip line and the gap required for this, how do i do this?

is there any tool?

hoping for reply
ramesh

 

[ronv]

Something like this?

**broken link removed**

 

[rameshrai]

Re

thanks for link, but no good. I needed gap distance between two microstrip on the same plane i.e horizontal. the calculators in the link calculates only vertical.

 

[steveB]

Hello,

I need to calculate minimum coupling between two microstrip line and the gap required for this, how do i do this?

is there any tool?

The usual method is to calculate the fields using field theory and then calculate coupling using mode coupling theory. The coupling usually is related to the difference between propagation constants (small difference means more efficient coupling) and the amount of integrated field overlap, meaning that orthogonal modes tend not to couple well.

But, maybe you are looking for formulas that have already been calculated or approximated from this theory, or you are looking for a simulation tool that will do the calculations?

However, call me crazy, but wouldn't an infinite gap between the lines give the minimum coupling? It seems the problem and/or geometry/constraints need to be more clearly defined?

 

[ronv]

So if there is no ground plane it would just be 2 parallel "plates"

Cpf= .0085XDCXAmm/Dmm

Capacitance in pf = .0085 X dielectric constant of air multiplier X area in mm / distance apart in mm.

So I make a 2" trace with 1 oz. copper spaced at 10 mils to be .12 pf. Could be right.

See what Steve gets.

 

[rameshrai]

The amount of coupling is dependent on the electromagnetic field surrounding the conductor. The amount of EM field depends upon the amount of current or charge flowing through the microstrips lines. If there is no current then the coupling is zero. Hence coupling is dependent on the current amount and its rate which in turn depends upon the frequency and other factors.

But in board sense there is always finite amount of coupling.

I think Ronv is referring to the parallel capacitor formula. If so I think this would not be accurate in microwave frequency domain.

I want to calculate gap distance required between two microstrip for minimum effects on each other, which i believe is the term coupling.

There are so much advanced formulation in textbooks regarding this problem and the topic is broad itself, so I wanted to ask designers here what formula is used in my case.

 

[ronv]

Microwave frequencies have their own set of rules. I have no experience there. The only thing I would think is further apart is less coupling.

 

[Frank3point14]

Well
you could check out this site **broken link removed**

Thanks...

 

[remon7]

Minimum coupling between two micro strip lines and the gap required for this, coupling theory, Micro strip coupled transmission lines have been studied extensively for applications as couplers and filter. I have attached necessary Pdf about Microstrip.

 

[mathew hopkin]

Not sure if this will work but https://easycalculation.com/engineering/electrical/microstrip-line-calculator.php They say they've got something like you need.