Crystal FiltersGlossary

Glossary of Crystal Filter Characteristics

Terms Meaning Unit
Number of Pole The number of elements in the filter circuit pole
Insertion Loss Attenuation caused by insertion of crystal filter. dB
Operating Temperature Range Functional temperature range where the crystal filter maintains the frequency within the specified tolerance, and the filter characteristics.
Ripple Variations of the filter's loss in signal power within the passband dB
Passband Bandwidth Frequency range between the upper and lower cutoff frequencies denoting which frequencies will be passed through the filter. Attenuation will be equivalent to or below the specified value kHz
Stop Bandwidth Frequency range outside the upper and lower cutoff frequencies denoting which frequencies will not be passed through the filter. Attenuation will be above the specified value. kHz
Attenuation The gradual lose or reduction of a signal as it passes through a medium dB
Stop Band Attenuation Attenuation above the specified attenuation value that does not allow the signal to pass. dB
Termination Impedance Source impedance or load impedance viewed from the filter side, and is generally expressed by the parallel capacitance including the resistance and stray capacitance. Ω


When an input signal containing interference waves is input into a non-linear system, the frequency component (intermodulation product) generated by the linear combination of the frequency contained in the input signal will be included in the output signal.

Sufficient measures must be taken concerning the generation of one of the third-order intermodulation components 2𝑓1−𝑓2 in the passband, which leads to remarkable deterioration of the communication quality.


Type and Features of Common Matching Circuits

RC Matching

This is the simplest and common test circuit.
Since the input level is attenuated by the resistance component, it will lead to deterioration of the receiving sensitivity.
If there is low impedance it can be covered with an Amplifier.

LC/CL Matching

The features differ depending on the type of coil.
Although the Q factor of the wire wound type is favorable, the price per component is higher than the multilayer type.
The multilayer type induces a reduction of the Q factor, and deterioration of the IM.

Transformer Matching

This circuit enables extremely fine adjustments.
While the filter waveform can be improved with a screw core, the man hours taken for adjustment will increase.
Also, since the size of the transformer is large for a component, it is a drawback in meeting the downsizing requirements.

Applicable Range of Crystal Filters

Applicable Range of Crystal Filters

Technical Reference