DC blocking caps selection for a Filter(Band pass)
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/d...68LP15A020.pdf
TIA!
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.
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
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