RF filters and microwave filters are devices that pass or reject signals by frequency.

RF band pass filters are active or passive circuits that pass signals from a specific frequency band and reject signals from out-of-band frequencies.

RF band reject filters are tuned circuits that prevent the passage of signals within a specified band of frequencies.

RF low pass filters pass signals from low frequencies and reject signals from high frequencies

RF high pass filters pass signals from high frequencies and reject signals from low frequencies

Electromagnetic (EMI) filters and radio frequency interference (RFI) filters purify signals by attenuating the high-frequency RFI (typically 150kHz and up) and passing the low frequency EMI

Long pass filters transmit a wide spectral band of long wavelength radiation while blocking short wavelength radiation.