Term
|
Definition
|
|
A
|
| 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. |
|
Anti-resonance
|
The resonant frequency of a crystal connected in series with an
external capacitor. The capacitor is referred to as the load capacitor.
|
|
AT-Cut
|
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. |
|
B
|
|
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.
|
|
C
|
|
C.B.M.
|
Abbreviation of "Crystal Blank Manufacturing"
|
|
Crystal
|
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.
|
|
D
|
|
D.T.C.X.O.
|
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"
|
|
E
|
|
Electrode
|
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. |
|
F
|
| Face |
One of the natural surfaces which
develop on a crystal during the growth process. Often called a
"natural face". |
|
Frequency
|
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. |
| G |
|
H
|
|
Holder Capacitance (Ch)
|
The sum of the stray capacity contributed by the crystal connected
between the two leads of the resonator.
|
|
Hydrothermal
|
A method of growing synthetic quartz using a pressure vessel, calcium
chloride or sodium chloride, and a quantity of natural quartz material.
|
|
I
|
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I.B.P.
|
"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.
|
| J |
| K |
|
L
|
|
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.
|
|
M
|
|
M.C.F.
|
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 |
| n |
Often the small letter n is used to
designate the overtone number of a crystal unit. |
|
O
|
|
O.C.X.O.
|
Oven Compensated Crystal Oscillator
|
|
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. |
|
P
|
|
PhotoQuartz Strip
|
A strip resonator built with a photolithographic method where the blank
is shaped by using chemical enchants.
|
|
Piezoelectricity
|
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. |
| Q |
|
Q
|
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
|
| 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. |
|
R.B.A.
|
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. |
|
Resonance
|
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.
|
|
Resistance
|
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.
|
|
Resonator
|
Usually a quartz crystal device made to be used in a crystal
oscillator.
|
|
S
|
|
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.
|
|
S.M.
|
Surface Mount
|
|
S.M.F.
|
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
|
| T/C |
Temperature vs. Frequency
characteristic of a crystal resonator. |
|
T.C.X.O.
|
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.
|
|
Twinning
|
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".
|
| U |
| V |
|
W
|
|
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
|
| X-Cut |
A quartz wafer with the major
surface of the wafer perpendicular to the X crystallographic axis. |
|
X.O.
|
Crystal Oscillator
|
|
Xtal
|
Crystal
|
| Y |
| Y-Cut |
A quartz wafer with the major
surface of the wafer perpendicular to the Y crystallographic axis. |
|
Z
|
| 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.
|
