How to calculate the RF-RLC package size?

[breitfuss]

Hello!

I´d like to design a low pass filter for ~900Mhz. The C and L-values are not the problem.
What componentsize I should choose? 0805, 0603...
How I can calculate the recommended package size (L,C)?

I´ve placed a series resistor in the inputmachting path (PA). How I can calculate this recommended package size?

nice greetings

 

[madengr]

RF-RLC package size

You really don't "calculate" package size.

In general for capacitors, the smaller the case the higher the self resonant frequency and less shunt capacitance, but the trade off is lower breakdown voltage and higher loss (not always though).

For inductors, the smaller the footprint the higher the self resonance but lower current handling. For really small inductors the Q gets worse since they are not air core. For instance Coilcraft 0603 has higher Q than 0402, but the SRF is lower.

Of course those are just rules of thumb and there are always exceptions, and as you move to dielectrics like X7R things get nonlinear.

For your case though, use parts that are maybe 3/2 higher in SRF than your operating frequency, then choose the higher Q, unless big parts create problems with shunt capacitance from the pads, but at 900 MHz that won't be too much of a problem.

I like Coilcraft inductors and ATC capacitors (specifically the 600S and 600L series).

 

[kspalla]

RF-RLC package size

If you select a component let say from murata then they give you the model too.
This way you can simulate the component with package effects.