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# A question about Lange coupler

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#### patriot

##### Member level 5
6 finger lange coupler

How much is the power capacity of Lange coupler?
the parameters are as follows:
width of the finger=190um
space between two fingers=27um
thickness of conductor(Cu)=35um

can i use it for a power combiner of 20 Watts?

high power lange coupler

can anyone give me suggestions?
many thanks!

lange coupler em

What is the frequency range? The power is high, what about theS parameters of this Lange?

simulation lange coupler 4 fingers

freq:1350MHz-1850MHz
Er=2.65
thickness of dieelectricity=0.41mm
thickness of conductor(Cu)=35um
s21=s31=-3db (Hybrid coupler)

the space between the finger is 27 um,i am afraid it will breakdown when combining 20 Watts power in balanced amplifier

Hi patriot,

To understand more details on Lange Coupler, go through the followinng detailed post available in EDA board with lot of documents...

---Manju---

I also want to know its answer

lange coupler calculating

You need to consider maximum current through the traces. You can use a 2.5D EM simulator too look at current density (use Sonnet because Momentum current visulatization is flawed). You can also just use coupled line models in a HB simulator and measure the maximum current. Find skin depth so you can calculate cross section of trace that current flows through. Then find fusing current of conductor for that cross-section and make sure you are below it. The fusing current is for a wire in air so it is worst case. Heat dissipation on Alumina or Aluminum Nitride will be better.

Again use HB simulation so find maximum voltage between lines and be sure this is below breakdown of air. You can also use 2.5D EM simulation by placing a high resistivity layer just above and below your conductors and with this you can see the electric field; I have not used this for this application, just fooled around with it.

If you have HFSS and ePhysics you can perform thermal simulations. I have used this for verifying thin film loads.

lange coupler em

Hi,

you must have wire bonds accross the fingers as integral part of Lange coupler. I would expect these to be the bottle-neck for handling high power.

flyhigh

lange coupler

Hi Patriot,

Assume that your system is 50 Ohms, according to Onderdonk's fusing current formular:

I=.188*A/(√t) (where I is in Amp, t is in second & A is in Mil²)

Then your trace will last only 24.35 seconds under 20Watts of power before it melts.

I=20W/50Ω= 0.4A
A= (35e-6/25.4e-3)*(190e-6/25.4e-3)=10.5 Mil²
t=(.188*10.5/.4)²=24.35 sec

Krytar

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