What is an RF Low Pass Filter?

A Low Pass Filter (LPF) is a device that passes low frequency signals and blocks signals above a certain frequency. The point up to which it passes signals is called the cut off frequency. Signals beyond this cutoff frequency are attenuated. Low-pass filters are designed to reject or heavily attenuate signals that operate at a frequency above the cut-off frequency.

When looking for a low pass RF filter, keep the following parameters in mind:

Cut off Frequency: This is the frequency below which the signal is passed with minimal losses. Any signal above this frequency is attenuated.

Passband or Bandwidth: This is the frequency below the cut-off frequency.

Stopband: This is the frequency above the cut-off frequency.

Insertion Loss: This is the loss the signal will experience in the pass band of the filter. This is usually very low and is represented in dB.

Attenuation/ Rejection: The attenuation gives the measurement of how well a filter can reject the unwanted frequency components. So it is the loss in signal above the cut-off frequency. It is represented in dB. A higher attenuation is always preferred.

Power Level: This is the maximum input power that a filter can handle.