Low-pass Filter is a filter that passes signals with a frequency lower than a selected cutoff frequency
It than also attenuates signals with frequencies higher than the cutoff frequency
These filters are usually applied after RF amplifiers like MMIC, Gain-block and Class C amplifiers
It is used for suppression of high-order harmonics of radio-frequency signals
They can also be placed at the mixer output to filter high frequency interference that plays a role in frequency selection