Monolithic Crystal Filters: Terms and Definitions

Monolithic Crystal Filter (MCF):  MCF represents the ideal low-insertion loss pass band filters featuring sharp selectability within a narrow pass band.  It has outstanding temperature and aging stability.  MCF has been widely used in mobile radio communications, automobile telephone, cordless telephone, Pager, and measuring equipments.

Holder:  A case housing a thin plate of quartz crystal with vacuum-evaporated metal electrodes and terminals for connections. 

Nominal Frequency:  This refers to the nominal value of the center frequency given in the specification, to which other frequencies may be referenced.  Normally, the nominal frequency indicates the center frequency and the carrier frequency. 

Pass Bandwidth:  The pass bandwidth in which the attenuation is equal to or less than a specified values of stop band attenuation.  It is expressed as a range of frequencies attenuated less than the specified value, typically specified at 3 dB. 

Stopband:  Stopband is a band of frequencies in which the relative attenuation of a filter is equal or great than specified values.  It is expressed as a range of frequencies attenuated by more than some specified minimum, such as 60 dB.

Insertion Loss:  The logarithmic ratio of the power delivered to the load impedance before insertion of the filter to the power delivered to the load impedance after insertion of the filter.

(Passband) Ripple:  The ripple is the difference between the maximum and minimum attenuation within the pass band.  It is a design parameter, not a specified parameter.

Guaranteed Attenuation:  The maximum attenuation guaranteed at the specified frequency range.

Spurious Response:  It is the minimum attenuation caused by extraordinary response in the stop band.  Spurious response usually appears at a frequency higher than the center frequency.

Group Delay Distortion:  It is the difference between the maximum and minimum group delay within pass bandwidth unless otherwise specified.

Termination Impedance:  It is the required impedance to be seen on input and load side of the filter to maintain a good characteristic response.  Typically, it is specified as a series resistance with a parallel capacitance that should also include the stray capacitance of the circuit board.