Design of DC bias network in GHz range

[winglj]

Hi, everyone. I am wondering how to design the DC bias network for varactor in GHz range. I saw many literatures using the radial stub with a very narrow microstrip line as the bias pads. Anyone has some recommendation references of this type of DC bias network and any other topologies? Thanks.

 

[rfmw]

How many GHz and bandwidth are we talking about here? Did you consider a simple 0603 10-47k resistor?

 

[winglj]

Hi, rfmw.
The desired frequency is about 2GHz.
Can you give me some layout/circuit example for using the 0603 resistor?

I think the most difficult part is the RF choke for the DC bias, I tried the 0804 440nH inductor as the RF choke, but it seems the isolation between the DC feed to the RF port is still too low.

 

[bobmcnamara]

If your application is sufficiently narrowband, you can use quarter wave lines
to form a bias tee. See the example given in **broken link removed**

One quarter wave line is used as an RF choke to keep RF out of the bias network.
The other line prevents the bias network from loading the RF signal.