This schematic is the manufacturers dev-board design for the RFID-IC power Supply, using a large power inductor at 4A I_RMS and 22uH.
Calculating this design as an RLC filter, yields fc~2kHz (low-pass). Since for this design the power supply noise is superimposed on the antenna signal, any noise in the range of up to 20kHz (per datasheet) is critical for high read sensitivity. The RFID-tag modulates the Antenna field at ~4kHz, which to me seems the most critical frequency range.
The current rating of the inductor seems excessive, the antenna driver has a maximum at ~250mA which is well below the 4A rating of the inductor. Can a smaller inductor be chosen? I think the I_RMS rating is only relevant for maximum power handling and doesn't take into account effects of saturation. As far as I understand, the filtering properties will be lost when the inductor reaches saturation (however not very clear on this, if someone can recommend some literature I'd be grateful). The ripple on the input is in the range of +-150mV.
Is there a better/smaller/more elegant way to achieve comparable or better filtering between, let's say 200-20kHz?