help on characteristic impedance

[tieuquaybk]

in most datasheet that i read ( for ex. LNA9M403 ) , used PCB FR4 with ε = 4.6 ,h = 0.5 mm W = 0.5 mm and they said that the characteristic impedance of microtrip is 50 0hm . But after using all formulas for microtrip , i can't get that value . Can someone tell me how to obtain it .

 

[dpsman]

with the following formula you get close to 50 (about 45) with ε = 4.6.
Check ´Signal Integrity Issues and Printed Circuit Board Design´
By Douglas Brooks (I´ve downloaded it from this board I think) Just post me if you can´t find it.

 

[tieuquaybk]

hi! thank dpsman for replying
oh ,this mean that T is sizeable (maybe in this case T= 0.5 mm = H = W !! ) . Just because i don't know exactly the thickness of copper T ,and used the value of 18 - 36 µm which is << 0.5 mm (i found this value by searching on google ) .
Once more question is : how to make connection between components on microwave frequency ? as i see ,it use microstrip too . But still have some dout on it . And if we use the microstrip ,then its lenght and width are choosen by which standard ? and how it affect on circuit matching

 

[tieuquaybk]

dpsman ! i' ve found the book you said . thanhks a lot