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[SOLVED] electromagnetic coupling : rules of thumb

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louay

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Helo every body,
I am a beginner in RF design. I have designed a CMOS LNA at 2.4GHz and i have finished the layout. Unfortunately, i did not have access to an electromagnetic simulation tool and i must make the necessary precautions to prevent the magnetic coupling between inductances between them, and each inductor with other interconnects.
So is there a method to avoid these couplings that can degrade the performances of the LNA after the fabrication. Or is there a design rule (rule of thumb) that i can follow to avoid this coupling.
Thanks a lot
Best Regards
 

Radike

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Hi,

Usually I do the EM simulation and check whether there is coupling. Sometimes foundry provides some Design rules for distance between each inductors and lines. I am not sure whether this is related to coupling.
 

jiripolivka

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In any amplifier like yours at 2.4 GHz where there are inductors at input and output which can magnetically couple and cause instability, use partitions.
If you print the inductors on a PCB, you can never be sure about the coupling. If you use wire coils (I use such coils in my designs to adjust an optimum response) you can adjust them while observing if there is any coupling effect. Setting coils' axes perpendicular to each other looks easy but sometimes you can force a LNA to oscillate. Again, a partition is the best solution to use with a LNA or with a power amplifier.
 

vfone

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Yes, there is a rule placing inductors to avoid unwanted coupling between them.
Inductors have large magnetic fields around them and should not be placed close together, or in parallel, unless you want magnetinc field coupling.
Separate the inductors by minimum one times body height, or place perpendicular to one another.
 

louay

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Thanks lot for your replies
 

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