Crystal and frequency control glossary
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A radio relay station that orbits the Earth. A complete satellite communications
system also includes earth stations that communicate with each other
via the satellite.
A telecommunications service provided via one or more satellite
relays and their associated uplinks and downlinks.
A kind of antenna used to pick up transmissions broadcast from a satellite.
A radio link between a transmitting
Earth station and
a receiving Earth station through one satellite.
Abbreviation for surface acoustic wave.
The frequency spectrum near 2 GHz
used for land-based microwave and some mobile satellite communications.
A double rotated
crystal cut good for ovenized
application with good aging rates
and low phase noise.
SC stands for Stress Compensated.
SC-cut crystals have an improved temperature and frequency characteristic
for ovenized applications (OCXO). The frequency vs. temperature curve
is a sine with the inflection temperature at ~ +95°C. This crystal
operates in the thickness shear mode. Preferred for ovenized oscillators
(OCXO) such as space systems, and Global Positioning Satellite Systems
Abbreviation for signal code modulation.
The basic unit of measure of time, equivalent to "the duration
of 9,192,631,770 periods of the radiation corresponding to the transition
between the two hyperfine levels of the ground state of the cesium-133
atom." For our purposes, one "second" is 1/60th of a
Secondary frequency standard
A frequency standard that does not have inherent accuracy, and therefore
must be calibrated against a primary
The condition that exists when a crystal unit is operated without the
presence of load capacitance.
Series resonance is frequently shortened to the word series. See load
Series vs. parallel load resonance
A crystal can be used in
an oscillator circuit to operate in either of two resonant modes: Series
Resonance or Parallel Load Resonance (also known as antiresonance).
The crystals used in these two types of modes are physically the same
crystal, but calibrated to slightly different frequencies.
When a crystal is placed into an oscillator
circuit, they oscillate together at a tuned frequency. This frequency
is dependent upon the crystal design and the amount of load capacitance,
if any, the oscillator circuit presents to the crystal. Specified in
picoFarads (pF), load
capacitance is comprised of a combination of the circuit’s
discrete load capacitance, stray board capacitance, and capacitance
from semiconductor Miller effects.
Short messaging service (SMS)
A service for sending messages of up to 160 characters (224 characters
if using a 5-bit mode) to mobile phones that use Global System for Mobile
Abbreviated as C0. A parameter associated with a quartz crystal unit,
used to identify the capacitance resulting from the presence of the
electrodes plus stray capacitance associated
with the holder. The static capacitance
between the crystal terminals. Measured in picoFarads
(pF), shunt capacitance is present whether the device is oscillating
or not (unrelated to the piezoelectric
effect of the quartz). Shunt capacitance is derived from the dielectric
of the quartz, the area of the crystal electrodes, and the capacitance
presented by the crystal holder.
The bands of frequency
above and below a carrier frequency that are produced by its modulation.
Abbreviation for silicon-germanium.
Detectable transmitted energy that can be used to carry information.
As applied to electronics, any transmitted electrical impulse.
Signal frequency shift
Any change in frequency. Any change in the frequency
of a radio transmitter or
Signal to noise ratio (S/N)
Relative power of the signal to the noise. As the ratio decreases on
a line, it becomes more difficult to distinguish between information
and non-information (noise). S/N deteriorates with distance because
the noise builds every time the signal is repeated.
Signal to noise ratio (SNR)
The ratio of the amplitude of the desired signal to the amplitude of
noise signals at a given point in time. SNR is usually expressed in
A periodic wave that can be represented by a sine curve. The amplitude
of such a wave is a function of the sine of a linear quantity such as
phase or time.
Interference caused by a single-frequency source.
Abbreviation for silicon dioxide.
An antenna system whose technology enables it to focus its beam on
a desired signal to reduce interference. A wireless
network would employ smart antennas at its base stations in an effort
to reduce the number of dropped calls, improve call quality and improve
Abbreviation for surface mount device. See surface
Abbreviation for surface-mount filter.
Abbreviation for surface-mount package.
Abbreviation for small-outline integrated circuit.
Abbreviation for single-pole double-throw.
Special cut crystals
Special cut crystals are those crystals that have been cut at a different
angle of orientation to enhance performance for specific needs. Typical
special cuts would include BT
cut crystals, SC cut crystals, IT
cut crystals, and FC cut
Special emergency radio service
A Private Land Mobile Radio Service employed by persons or organizations
engaged in emergency medical and rescue service, health care or similar
Specialized mobile radio (SMR)
A two-way radio service provided within a designated portion of the
800 and 900 MHz frequency bands.
The frequency specified by the customer.
The electromagnetic radio spectrum. The FCC grants authorizations and
licenses to private and governmental entities to use specified portions
under certain conditions.
Federal government authorization for use of specific frequencies
or frequency pairs within a given allocation, usually at stated a geographic
location(s). Mobile communications authorizations are typically granted
to private users, such as oil companies.
Telecommunications techniques in which a signal
is transmitted in a bandwidth
considerably greater than the frequency
content of the original information.
Abbreviation for Simulation Program with Integrated
A substitution for the term spurious frequency response. The word "spur"
is used to refer to a frequency occurring at some point higher than
the desired mode, but lower than the next overtone.
Spurious frequency response
In radio reception, a response
in the receiver intermediate
frequency (IF) stage produced by an undesired emission in which
frequency (or harmonics above the fundamental frequency) of the
undesired emission mixes with the fundamental or harmonic of the receiver
Abbreviation for single sideband. Single-sideband modulation is a communications system in which one of the two sidebands used in amplitude-modulation is suppressed.
Abbreviation for solid state power amplifiers.
The change in the oscillator
frequency, referred to the desired oscillator frequency,
caused by temperature changed.
Standard calibration tolerance
The allowable deviation from nominal, expressed in parts per million
— ppm, at a specific temperature
at +25 °C.
The specified time from oscillator power-up to the time the oscillator
reaches steady state oscillation.
The non-linear change in the resistance
of a crystal as a function
of the power level used to drive the crystal.
See shunt capacitance.
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
The part of the frequency
spectrum that is subjected to specified attenuation of signal strength
by a filter. See attenuation.
Storage temperature range
The minimum and maximum temperatures that the device can be stored
or exposed to when in a non-oscillation state. After exposing or storing
the device at the minimum or maximum temperatures for a length of time,
all of the operating specifications are guaranteed over the specified
A small AT cut crystal whose width
is much smaller than its 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.
The most widely used type of radio receiver, in which all incoming modulated radio-frequency signals are converted to a common intermediate-frequency or IF carrier value for additional amplification and selectivity prior to demodulation. The advantage to this method is that most of the radio's signal path has to be sensitive to only a narrow range of frequencies. The diagram below shows the basic elements of a single conversion superheterodyne receiver.
The DC input voltage necessary for oscillator operation, specified
Surface mount (SM)
A component, either active or passive, having no separate leads but
which is part of the component body to permit direct mounting on a printed
Surface-mount technology or surface-mount toroidal (SMT)
A surface mount device is a component, either active or passive, having
no separate leads but which is part of the component body to permit
direct mounting on a printed circuit board.
Symmetry is defined as the ratio of amount of time the voltage is in
the logic "1" state compared to the time in the logic "0"
state. The measurements are taken at the 50% points of the voltage transition
between the two logic states. The time period of one cycle of the waveform
is calculated first as below.
1/Frequency in Hertz = Time Period in Seconds
Next, the time period of the logic "1" state is measured
from the 50% point of the waveform's positive voltage transition to
the 50% point of the waveform’s negative voltage transition, then
compared to the total waveform period. The calculation for symmetry
is shown below:
Logic "1" Time in Symmetry/Period of One Cycle X 100 = %
For the % symmetry of the logic "0" state, subtract the logic
"1" symmetry from 100%. For example, 40/60% means that the
waveform is in its logic "1" state 40% and in the logic "0'
state 60% of the total waveform time period.
Synchronous digital hierarchy (SDH)
A standard technology for synchronous data transmission on optical
media. It is the international equivalent of Synchronous Optical Network.
Synchronous optical network (SONET)
Abbreviation for synchronous optical network.
An interface standard for synchronous optical-fiber transmission, applicable
to the Physical Layer of the OSI Reference Model.
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