Glossary of Telecommunications Terms





Activity A qualitative measure of the amplitude of the vibration of a quartz resonator when operated in a particular oscillator circuit. 

Activity Dip

Refers to an increase in the resistance and a change in frequency of a resonator as the resonator is swept over a temperature range. It is caused by an undesired mode coupling to the desired mode.

Aging The change of frequency of a quartz resonator with time.

Alpha Quartz

A crystalline form of SiO2, which exists below 573 degrees C. is the material which is used to make resonators.

Amplitude-frequency effect The change in the frequency of a quartz crystal unit with a change in amplitude of the drive level.
Anisotrophy A phenomena where the physical properties of a crystal are dependent upon the direction in which  they are measured in the crystal.


The resonant frequency of a crystal connected in series with an external capacitor. The capacitor is referred to as the load capacitor.


A plate cut from a crystal of quartz such that the plate contains the X-axis and makes an angle of about 35 degrees with the optic or Z-axis.

Axis A direction (not a line) in a crystal. The axes are chosen arbitrarily in such a way as to make the description of the physical properties of the crystal as simple as possible. 


Bandpass Filter

A passive electronic circuit that allows a narrow range of frequencies to pass through the device while blocking or attenuating higher and lower frequencies. Crystals are used for narrow bandpass filters

Bar (Quartz)

A term used to refer to a quartz stone that has been machined into a parallelepiped.

Beta Quartz

Above 573 degrees C, crystalline quartz undergoes a change in crystal structure which is weakly piezoelectric. The structure reverts back to Alpha Quartz below 573 degrees C but will become twinned. 

Blank (Crystal)

A round or rectangular quartz crystal that has been lapped to produce very parallel major surfaces and has minor surfaces machined to the final dimensions required to build the desired resonator.  A machined disk of single crystal quartz.



Abbreviation of "Crystal Blank Manufacturing"


A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts. Usually a mineral, especially a transparent form of quartz, having a crystalline structure, often characterized by external planar faces.



Digitally Temperature Compensated Crystal Oscillator.

Dice (Quartz)

Pieces of quartz produced by sectioning quartz wafers into rectangular shapes. Dice are then further machined to produce crystal blanks.

Diopter A term used in the optical in the optical industry to measure the magnifying power of a lens. The laps used to generate spherical surfaces on lenses are marked in diopters. The diopter rating of a lens is the reciprocal of its focal length which, for a planoconvex lens, is given by D=1/f=(n-1)/R.  R is the radius of curvature and n is the index of refraction of a material.  If n = 1.5 , which is typical for glass, then D=1/2R, where R is measured in meters.

Direct Piezoelectric Effect

The generation of electricity (or electric polarity) in crystals subjected to mechanical stress.

Drive Level Dependency (DLD)

See "Starting Resistance"



A conducting metal film that is deposited on both sides of a thickness shear crystal blank.

Electrode Capacitance (Ce)

This capacitor is not a result of the acoustic vibration of the crystal blank but rather a simple capacitor formed by a dielectric with electrodes on either side.

Energy Trapping A term applied to the application of the cutoff phenomenon in wave guides to suppress undesired modes of vibration in a quartz crystal unit.
Enantiomorph (from Greek enantios, "opposite"; morphe, "form", also called Antimer, or Optical Antipode, either of a pair of objects related to each other as the right hand is to the left, that is, as mirror images that cannot be reoriented so as to appear identical. An object that has a plane of symmetry cannot be an enantiomorph because the object and its mirror image are identical. Molecular enentiomorphs, such as those of lactic acid, have identical chemical properties, except in their chemical reaction with other dissymmetric molecules and with polarized light. Enentiomorphs are important to crystallography because many crystals are arrangements of alternate right and left handed forms of a single molecule. 

Equivalent Circuit

This is a representation of a crystal expressed as a schematic diagram containing simple passive devices such a capacitors, inductors, and resistors. A simple resonator is represented by a circuit consisting of an inductor (Lm), a capacitor (Cm) and a resistor (Rm) connected in series. A second capacitor (C0) is shunted across all three elements.

Etch Channel Density E.C.D. The number of Line dislocations in synthetic quartz contained in a one centimeter square area. The channels are made visible by deeply etching a sample of the material and counting the now visible channels under a microscope. 


Face One of the natural surfaces which develop on a crystal during the growth process. Often called a "natural face".


The number of complete cycles an alternating current or voltage will complete in one second.

Fundamental Frequency

The lowest frequency at which the crystal can vibrate.


Holder Capacitance (Ch)

The sum of the stray capacity contributed by the crystal connected between the two leads of the resonator.


A method of growing synthetic quartz using a pressure vessel, calcium chloride or sodium chloride, and a quantity of natural quartz material.



"Itty Bitty Package" Refers to the round compression weld package used to enclose early strip resonators.

Indirect Piezoelectric Effect

Generation of a mechanical stress in crystals subjected to an electric field

Inflection Point

An AT Cut crystal has a temperature vs. frequency characteristic that can be represented by a third order polynomial. This curve has a point where the slope is zero and the slope is positive on one side and negative on the other side. This point is defined as the inflection point.

Infinite Plate Design

A quartz crystal that has a diameter to thickness ratio greater than 60. This type of design is simpler in comparison to a finite plate design.

Infra-Red (I.R.) A frequency of light with a slightly longer wavelength than the visible spectrum of light. 

Intermediate Frequency (I..F.)

Abbreviation for "intermediate frequency". A frequency used by a radio to process the received signal. It is below the received R.F. frequency and above the audio voice frequency, thereby the name.



Load Capacity

Crystal resonators are often operated with a capacitor connected in series with the crystal resonator. The value of this capacitor is the load capacity.



Monolithic Crystal Filter

Mechanical Strip

A strip resonator built utilizing mechanical shaping of the crystal blank.

Monolithic Crystal Filter

A crystal with two or more electrodes where energy is coupled between the electrodes by way of the vibrating quartz structure.

Motional Capacitance (Cm)

A quantity related to the charge held by the crystal. The actively vibrating area of the crystal and the thickness of the crystal blank set this value. It is a result of the elasticity of the crystal structure. It is represented in the electrical circuit as a capacitor.

Motional Inductance (Lm)

A quantity related to the energy stored by the crystal. The actively vibrating mass of the crystal determines this value. It is represented in the electrical circuit as an inductor.

Motional Resistance (Rm)

The energy lost within the vibrating area of the crystal resonator. (See resistance). Does not include any loss external to the vibrating crystal. It is represented in the electrical circuit as a resistor.

n Often the small letter n is used to designate the overtone number of a crystal unit. 



Oven Compensated Crystal Oscillator


Electronic circuit which generates an alternating voltage or current when a steady voltage is applied to the circuit. Usually the circuit is designed to produce a specific frequency. Crystal oscillators use a crystal resonator to control the frequency of the alternating voltage.

Overtone Crystals can vibrate at many harmonic frequencies. Frequencies which are multiples of the lowest or fundamental frequency are referred to as overtone frequencies. The overtones are usually referred to by the number of the overtone.  


PhotoQuartz Strip

A strip resonator built with a photolithographic method where the blank is shaped by using chemical enchants.


Electrical polarization produced by certain classes of crystals when the crystal is mechanically stressed.

Piezoid A body of some special shape cut from a crystal having piezoelectric properties and used as an electromechanical transducer.
Plateback Mass deposited on a piezoid to reduce it's frequency to a desired value.  This is normally done by controlling the thickness of electrodes deposited on the major faces of a resonator.


Quality Factor is the ratio of energy stored in a system divided by the energy dissipated in the system. Used to characterize the acoustic loss in quartz crystal resonators.

Quartz usually refers to alpha quartz which is crystalline SiO2.


r face One of the three smaller faces which occur at the ends of the natural quartz crystal.
R face One of the three larger faces which occur at the ends of the natural quartz crystal.


Relative Bechmann Angle is the apparent angle of orientation of an AT crystal blank, which is derived from a plot of the temperature vs. frequency characteristic of a crystal resonator.

R.F. Abbreviation for "radio frequency". Often used in conjunction with a component name to indicate operation at high frequencies. (i.e. R.F. Crystal)
Reference edge The edge of a blank or wafer identified for use in orienting the blank or wafer on an x-ray chuck for making orientation measurements.
Reference flat A flat edge on an otherwise circular blank for use as a reference edge. Called an X-flat  when perpendicular to the X-axis.


The frequency at which a simple crystal resonator appears to be purely resistive and exhibits zero phase shift. Oscillator circuits are designed to operate at various resonance points to obtain maximum frequency stability.


The opposition of a body or substance to current passing through it, resulting in a change of electrical energy into heat or another form of energy.


Usually a quartz crystal device made to be used in a crystal oscillator.


S.C. Cut

A doubly rotated crystal cut plate (theta = 34 degrees and seven minutes and phi = 21 degrees and fifty six minutes) that is used in precision oscillators. It is placed in an oven and operated at the crystals lower turning point around 100 C.

Series Resonance

The operating frequency at which the impedance of the Cm and the Lm cancel out causing the crystal to look like a simple resistor Rm.


Surface Mount


Surface Mount Filter

Shunt Capacity (Co)

The shunt capacity of the crystal is the sum of the holder capacity (Ch) and the capacity of the capacitor formed by the resonator electrodes separated by the quartz dielectric (Ce).

Sleeping Sickness

See "Starting Resistance"

Spur or Spurious Mode

An undesired resonance in the vicinity of the resonator's desired resonant frequency. These modes are usually higher order thickness shear vibrations, which occur above the main frequency of the resonator.

Starting Resistance

The non-linear change in the resistance of a crystal as a function of the power level used to drive the crystal.

Stone (Quartz)

A term used to describe a quartz crystal before any machining operations have been done. The synthetic single crystals grown in the Hydrothermal Process are referred to as a "Stone".

Strip Resonator

A small AT cut crystal whose width is much smaller than it's length. The crystal is a finite plate design requiring exact mathematical analysis to achieve good performance. The length of the resonator can be parallel to either the X or Z axis of quartz.


T/C Temperature vs. Frequency characteristic of a crystal resonator.


Temperature Compensated Crystal Oscillator

Turning Point

An AT Cut crystal has a temperature vs. frequency characteristic that can be represented by a third order polynomial. The turning points are points of zero slope where the slope reverses sign. Usually there is a lower turning point around -4 C and an upper turning point around +55 C. Often ovenized oscillators hold the temperature of the crystal at the upper turning point to obtain maximum temperature stability.


Crystalline quartz can exist in a right handed and left handed form. A single piece of quartz material, which contains both left and right handed regions, is said to be "twinned".



Wafer (Quartz)

Term used to describe the flat, thin pieces of quartz produced when a dicing saw cuts a bar of quartz. Refers to a slab of quartz sawed from the stone but not yet shaped to form a blank or resonator.

Wave Number Wave number (k) = 2p / l Where l is the wave length of the light wave.  Wave number is proportional to the number of peaks  per unit distance


X-Cut A quartz wafer with the major surface of the wafer perpendicular to the X crystallographic axis.


Crystal Oscillator



Y-Cut A quartz wafer with the major surface of the wafer perpendicular to the Y crystallographic axis.


Z-Cut A quartz wafer with the major surface of the wafer perpendicular to the Z crystallographic axis.

ZZ' Angle

The angle between the plane of the blank and the optic axis in quartz. The optic axis is the Z or c axis.  This angle determines the frequency vs. temperature characteristic of the finished crystal resonator.

Zero Angle

The angle of cut that will result in a resonator that has zero temperature vs. frequency slope at the inflection point. For a fundamental, AT-cut crystal this angle is about 35 degrees and 15 minutes of arc.



Updated: 11/15/2010


Copyright   2001 thru 2013  by Theodore Lind