Why mutual inductance coupling is high in microstrip line

[hioyo]

Dear Team,

I was learning about crosstalk in PCB from the High-speed signal propagation book by Howard Johnson.
It says mutual inductance coupling is high in microstrip line compared to mutual capacitive coupling.
May I know why it is like that

Regards
HAri

 

[BigBoss]

Isn't that normal ? Distributed Inductance along Line Length and Magnetic Coupling due to this reason is dominate. Capacitive Coupling occurs at fringe sides of the Line and it's ( Electrical Coupling ) relatively low compare to Magnetic Coupling.

 

[hioyo]

Thank you...
May I know what you mean by fringe sides of the Line

 

[D.A.(Tony)Stewart]

Stripline impedance is vertical to ground plane with nH/mm and pF/mm such that a w:h ratio in FR4 of 2:1 is about 50 Ohms from Zo=sqrt(L/C) There is lateral flux coupling from coplanar tracks by M being a fraction of L and C due to the thin edge crosstalk which is about 50% of the voltage for a 0.1ns risetime (near 4GHz) when the geometry for l:w:h = 10:1:1.

Directional couplers vary in design but depend on the controlled power ratio of the coupling and directional properties.

Microwaves101 | Microstrip "3 dB" Coupler

Microwaves101 | Microstrip "3 dB" Coupler

www.microwaves101.com

Microwaves101 | Even and Odd Mode Impedances

Microwaves101 | Even and Odd Mode Impedances

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Microwaves101 | Book: Microwave Engineering by Kaul and Wolff

Microwaves101 | Book: Microwave Engineering by Kaul and Wolff

www.microwaves101.com