Quartz filter

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Basically, there are two types of quartz filters the bandpass quartz filter and the bandstop quartz filter. The later is sometimes referred to as a notch quartz filter or band reject quartz filter. Both utilize piezoelectric quartz crystals as BAW (Bulk Acoustic Wave) resonators in their realization. Anatol Zeverev defines a bandpass filter as a filter that "passes the package of waves from certain lower to upper frequency limits and stops all energy out side these two limits. This filter is by far the most important and most commonly used filter in electronic equipment. Bandpass filters are used as IF Filters, SSB Filters, Comb Filters, Preselector Networks, Multiplexing Filters, Anti-Jam Filters, channel Filters or Front End Filters. The crystal notch filter is used when a certain frequency(s) has (have) to be rejected and all others have to be passed.

The quartz filter is used when a narrow passband or stopband filter is required. Because of the crystals high, unloaded Q-factor (in the range of 10,000 to 100,000) narrow band filters with low loss are achievable. Filtronetics, Inc. has designed and built discrete and monolithic quartz filters that utilize from 1 to 22 crystals. Discrete quartz filters have the advantage of offering very complex and custom designs and wider bandwidths. However, they are larger and more expensive than monolithic quartz filters. The practical frequency range for discrete quartz filters is from 5 KHz to 600 MHz. A quartz filter’s bandwidth ranges from 0.005% to 2% of the center frequency. Monolithic filters are limited to less than 150 MHz center frequency and around 0.4% maximum bandwidth.

Filtronetics, Inc. can utilize flat, polished, fundamental, overtone or inverted mesa crystals in its quartz filters. AT cut crystals and BT cut crystals are normally used for crystals over 1 MHz. X cut, SL cut, DT cut quartz crystals are used below 1 MHz. We supply quartz filters with monotonic or elliptic designs and with characteristic responses of Buterworth, Chebyshev, Cauer, Gaussian, Bessel (maximally flat delay), equal ripple delay, and Legendre as well as custom filter responses. These filters can be group delay, amplitude, or phase equalized. Amplitude, delay, or phase matching is available as well as amplitude delay or phase tracked. We have special designs for good ring-down or overshoot response as well as good IP3 or 3rd order intermodulation product, and IP2 2nd order intermodulation product characteristics.

Our quartz filters have been utilized in systems that are in space, military, undersea, airborne, testing, and commercial applications. We can produce from one to over a million quartz filters for your application. Quartz filters are available in Surface mount (SMD), Through-hole, and connectorized (BNC, TNC, SMA, or N filter) packages.