Design RF choke

[Juang231]

I new at design LNA, i want to design rf choke for the LNA with radial stub for 3GHz LNA but i stuck with calculate for the L and W for Stub, can anyone help me

 

[biff44]

So you want to emulate a lumped element bias line, to get the broadest bandwidth.
To make a series inductor out of a microstrip line, you make it as high an impedance as possible. so practically, you do not want a line width W1 smaller than 5mils, so you choose that size. make it quarter wavelength long.
Then to emulate the shunt capacitance, you use a open circuited quarter wave line as wide as is practical. I would choose a width W2 of say 75 mils. and again, make it quarter wave long.

you can replace the W2 line with a radial stub, and get a little more bandwidth out of it, but to keep the aspect ratio right, no more than say a 30 degree arc. and the width at the biggest piece, not too wide if you are at high frequency, or it will no longer act like an open circuited transmission line, but instead some sort of rectangular resonator