DC blocking caps selection for a Filter(Band pass)

[Bsr]

Hi,

I am going to use the below Filter in my RF application. One thing I could not understand is: finding out the DC blocking capacitors' values which are recommended as a part of supporting circuit. Please, let me know if I should use the DC blocking caps, if yes, what can be the recommended capacitors values??

https://www.johansontechnology.com/datasheets/0868LP15A020/0868LP15A020.pdf


TIA!

 

[FvM]

It's not clear to me under which circumstances blocking capacitors are needed at all, I guess if the signal has a DC bias, e.g. amplifier output.

I would use something like 1nF 0402.

 

[akhilpaulv]

you can use around 200 pf capacitor, which provide around 0.8 Ohm impedance at 880 Mhz . in pratical there will be some parasitic resistance and inductance will comes across the component so you can use around 60-100 pf capacitor. if you have network analyzer you can plot the impedance on the smith chart and find optimum value

 

[biff44]

the prototype filter test circuit uses blocking caps, so one could suppose the input is a DC short circuit. So you need the caps IF that port is connected to an active device that has DC bias on it.

800 MHz, it is hard to get a capacitor that will not work well...since the frequency is so low. If you were at 20 GHz...they you would need to use either one specifically designed for microwaves, or test a lower cost version to make sure it did not resonate.

200 pf should work fine, as stated above