Some terms often used in connection with LC filters are explained below.
Insertion loss is sometimes abbreviated as IL.
Insertion loss is the amount of loss of signal power in the desired frequency band, expressed in decibels (dB), that occurs when the signal passes through the product. If the insertion loss characteristics are good, the filter has little loss of signal power and can be said to have low insertion loss. If the insertion loss characteristics are poor, there is significant loss of signal power as it passes through the product and in serious cases the signal may not be able to pass through at all.
For this reason, products with good insertion loss characteristics are superior.
Attenuation is sometimes abbreviated as ATT.
Attenuation is the amount of reduction of signal power in the undesired frequency band, expressed in decibels (dB), that occurs when the signal passes through the product. If the attenuation characteristics are good, the amount of reduction of signal power caused by the filter is large, and it can be said to have high attenuation. If the attenuation characteristics are poor, noise, etc., in the undesired frequency band can pass through the product.
When the design focuses on insertion loss, there is a tendency for attenuation characteristics to suffer. For this reason, filter developers strive to maintain a balance between insertion loss and attenuation characteristics.
Return loss is sometimes abbreviated as RL.
Return loss is the amount of reflection of the signal, expressed in decibels (dB), that occurs when it is input to the product. If the return loss characteristics are good, the amount of reflection of the desired signal band by the filter is small, allowing more of the signal to pass through the filter without being reflected.
Return loss and insertion loss are related characteristics, and products with good insertion loss characteristics tend also to have good return loss characteristics.
Bandwidth is sometimes abbreviated as BW.
Bandwidth is the frequency band of the signal that passes through the filter, expressed in hertz (Hz). One thousand hertz is 1 kHz, one million hertz is 1 MHz, and one billion hertz is 1 GHz.
A frequency of 1 Hz represents an AC signal with a waveform that alternates between positive and negative once per second. A frequency of 1 MHz represents a waveform that alternates between positive and negative one million times per second.