what is microstrip

Hi All,

I wanna know something about Microstrips?
Are they some sort of external components like resistors etc or they are formed by varying the thinkness and length of copper traces on a PCB?
I want to have a 50 Ω microstrip on my FR4 PCB operating @ RF(900MHz)
So how can I implement it?

Thanks in Advance![/b]

Microstrip is build in a following way. for example you have 2-sided pcb where the bottom layer is left as a ground plane. Then on the top side you have a copper trace. Between these bottom and top layer is of course the pcb substrate. Now, changing the width of the copper trace affest on the characteristic impedance of this microstip. So you have to do some math in calculating the trace width, since it is affected also by the dielectric constant of the substrate and the thickness of the substrate. And if we are really accurate, then we should also take into account the thickness of the top copper trace. Take a look some microwave engineering book (li Pozar) and find out those equations to calculate microstrio trace width. Or you can find ready made calculator from the web... which suits you better

Hope this heps

Hi,

The description provided by karote is very good. The characteristics of microstrip lines depends greatly on the material and even something as trivial as the conductor plating thickness plays a role. Furthermore if you need to be really accurate you need to include the fact that @ RF the waves are no longer TEM (transverse electromagnetic) and thus all of the equations derived using the TEM assumption is false.

If you need some more info I can mail you a chapter from Microwave transistors by Gonzales discussing the design of Microstrip lines.

Cheers
Slayer

Microstrip is a line made on some substrate to generate filter or antenna....

How is microstrip related to antenna ?

there are some freeware tools provided by Microwave Office and ADS to calculate the required width and length for impedance that you required.
Microwave Office is Txline Calculator.
ADS, i forgot.

THE TOOLS IN ADS IS CALLED LINECALC ON SCHEMATIC, AND YOU CAN STUDY THE HAMMERSTAD METHOD DESIGN OR WHELER ON CAMPUTER AID DESIGN BOOK.

Just Calculate the width and the FR4 height to satisfy your impedance requirement.

Hello Slayer,

Can you please upload or mail me the said chapter. Also, if you have some tutorials on RF PCB Design and if you can give me than it would be a great help.

Thanks

use this:

http://www.hp.woodshot.com/