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A
Ambient temperature:
The average temperature of the
environment immediately surrounding a device or circuit.
Ampere:
(I) A unit of electric current in the meter-kilogram-second
system. It is the steady current that, when flowing in straight parallel
wires of infinite length and negligible cross section, separated by a
distance of one meter in free space, produces a force between the wires
of 2 x 10-7 Newtons/meter of length. Also, the flow of one
coulomb per second past a given point in a circuit. I = E/R
Anti-pad:
Opening on a PCB reference plane, typically circular, around a via that
is unconnected to that plane.
ATCA:
Advanced Telecom Computing Architecture
Attenuation:
Reduction in signal strength resulting from the combined effects
of DC resistance, reflections, skin effect, and reactance in the system.
Also, a loss of optical power, typically expressed in decibels (Db) at a
specific wavelength. Also known as throughput loss.
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B
Bandwidth:
Maximum frequency which an electrical
circuit or optical fiber is capable of delivering, with no
more than 3Db (30%) attenuation. The specific permissible loss
percentage is system-dependent.
BGA:
Ball grid array. Interconnect system using reflowable solder balls to
effect a permanent electrical connection.
Bit Error Rate (BER):
The ratio between the number of erroneous bits received to the total
number of bits transmitted.
Blindmate connector:
Connector that incorporates guiding features that allow mating halves to
self-align within design tolerances. A blindmate connector is typically
used to interconnect between rail-guided modules and/or printed circuit
boards.
BOM:
Bill of material. Detailed list of components selected for use within a
system.
Breakdown voltage:
The voltage level that causes insulation failure.
Broadband:
Denotes transmission facilities capable of handling a wide range of
frequencies simultaneously, thus permitting multiple channels in data
systems, rather than direct modulation.
Broadside coupled:
A differential trace pair on adjacent signal layers in a dual stripline
configuration.
Bulk resistance:
Resistance in a connector attributed to the base material of a
connector.
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| C
Capacitance:
The property of an electric circuit or device to store an electrical
charge.
Characteristic impedance:
(Zo) Combined effect of inductance, capacitance, and resistance in a
conductive path. It is a function of the geometry and materials in the
circuit, and is independent of length.
Cladding:
The material surrounding the core of an optical waveguide. The cladding
must have a lower index of refraction to keep the light in the core.
Clearance distance:
The shortest path in air separating two conductors.
Conductivity:
A measure of the ability of a material to carry a current, the
reciprocal of resistivity.
Constriction resistance:
Resistance in a connector attributed to the compression of conductive
paths to and from microscopic asperities at the interface.
Contact resistance:
Resistance in a connector attributed to the conductivity at the
interface only. Its value is calculated with the measured voltage drop
at the rated current.
Core:
The central region of an optical fiber through which light is
transmitted.
COTS:
Commercial off-the-shelf products, as opposed to custom products.
Coupling loss:
Power loss suffered when coupling light from one optical device to
another.
Creepage distance:
The shortest distance separating two conductors as measured along an
insulating surface touching both conductors.
Crosstalk:
The amount of signal induced on one quiet line from adjacent driven
lines. It represents both a loss from the driven line, and contamination
of the quiet line. Digital systems exhibit both near-end and far-end
crosstalk, and are used as performance criteria.
Current:
The rate of transfer of electrical charge
measured in amperes. The symbol “I” is used to represent current.
Current rating:
The maximum amount of current a connector is designed to continuously
conduct in defined conditions.
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| D
DC:
Direct current; flow of electrons in one direction.
D-to-D converter:
Typically, a PCB-mounted device that converts one DC voltage to another.
Decibel (dB):
A unit of measurement of relative electrical or optical power. -10dB
represents a 10X reduction, -20dB represents a 100X reduction, etc.
De-emphasis:
Process of restoring after detection the amplitude vs. frequency
characteristics of a signal.
Derating:
Practice of applying components or devices at a lower stress level than
specified capabilities in order to reduce the occurrence of failures.
Dielectric:
An insulating material between conducting materials.
Dielectric constant:
Property of a material that determines the propagation delay of a
signal.
Dispersion:
The cause of bandwidth limitations in a
fiber. Dispersion causes a broadening of input pulses along the length
of the fiber. Three major types are: (1) modal dispersion caused by
differential optical path lengths in a multimode fiber; (2) chromatic
dispersion caused by a differential delay of various wavelengths of
light in a waveguide material; and (3) waveguide dispersion caused by
light traveling in both the core and cladding materials in single-mode
fibers.
Distributed Power Architecture (DPA):
A power distribution system that delivers one intermediate bus DC
voltage level to the PCB, where D-to-D converters reduce the voltage to
the specific levels required by devices on the board.
Differential signaling:
Digital signals transmitted as the difference in voltage of a pair of
signal lines. Offers significant noise immunity.
Dry circuit resistance:
Measurement of resistance using very low voltages. Open circuit voltages
of 20 or 50 millivolts are typically specified.
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| E
Edge coupled:
A differential pair trace on the same signal layer.
EMC:
Electro magnetic compatibility
EMI:
Electromagnetic interference. Internally or externally generated energy
that can corrupt a signal.
EMS:
Electronic manufacturing services
EYE patterns:
An overlay of all the individual bits in a data stream that creates the
“eye” opening. The eye pattern gives a visual representation of signal
fidelity in terms of amplitude (eye opening vertically) and jitter (eye
opening horizontally).
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| F
Ferrule:
A mechanical fixture, generally a rigid tube, used to protect and align
a fiber in a connector; generally associated with fiber optic
connectors.
FPGA:
Field programmable gate array
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| G
GBIC:
Gigabit interface converter. Modular I/O interface that permits the use
of copper of fiber optic interconnect.
Gigahertz (GHz):
A unit of frequency that is equal to one billion cycles per second, 109
Hertz.
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| H
Heat sink:
Structure through which thermal energy is transferred to an external
cooling medium.
Hot Swap
(Hot mating, Hot pluggable): Ability to mate or disconnect a connector
in an energized circuit without degradation of the connector.
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| I
Inductance:
The inherent reactive property (measured in henrys, “L”) of a circuit
that opposes a change in current flow. Inductance causes current changes
to lag behind voltage changes.
Insertion loss:
A reduction in signal amplitude resulting from the insertion of a device
in a transmission line expressed in dB; also commonly referred to as
attenuation.
Intersymbol Interference (ISI):
Distortion of the received digital signal resulting from the spreading
and consequent overlap of individual pulses to the degree that the
receiver cannot reliably distinguish between changes of state.
I/O:
Input/Output
Internet Protocol (IP):
A protocol used for communicating data across a packet switched network.
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| J
Jitter:
Deviation of a signal-timing event from its ideal position.
Joule:
A
standard international unit of energy; one watt-second, 1055 Joules is
equal to 1 BTU.
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| L
LAN:
Local area network, typically with limited geography.
LGA:
Land grid array. Interconnect system using a spring-loaded contact on a
flat pad.
Loss tangent:
Measure of how much of the electromagnetic field traveling through a
dielectric is absorbed by the material, also known as dissipation
factor.
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Megahertz (MHz):
A unit of frequency that is equal to one million cycles per second.
MEMS:
Microelectromechanical system. Individual assemblies created by adding
or removing material at the atomic level.
Microstrip:
Printed circuit board surface traces referenced above a single ground or
power plane. Microstrip structures have faster propagation delays than
internal stripline, but are subject to more loss.
Minimum loss window:
In an optical fiber, the transmission frequency window at which the
attenuation coefficient is near a minimum.
Mode:
A single electromagnetic field or ray of light that travels in an
optical fiber.
Modal loss:
Loss in an optical fiber due to anomalies that cause changes in the
propagation mode of the wave.
Modal dispersion:
Spreading of a pulse caused by modal effects.
MSA:
Multisource agreement
Multimode fiber:
Optical fiber whose core diameter is large, relative to the wavelengths
propagated.
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| N
N+1 redundancy:
The design practice of having one extra element in a system to act as an
on-line replacement for an element that fails.
Nanometer (nm):
One billionth of a meter.
Normal Force:
Mechanical force applied at the point of contact. Typically measured in
grams or Newtons.
Numerical Aperture (NA):
The number that expresses the light-gathering ability of an optical
fiber; related to the acceptance angle or the difference in index of
refraction between the core and the cladding.
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| O
ODM:
Original Design Manufacturer
OEM:
Original Equipment Manufacturer
Ohm:
Unit measure of resistance (W).
The passage of one ampere through one ohm produces one volt.
Ohm’s Law:
Fundamental mathematical relationship between current (I), voltage (E),
and resistance(R). I = E/R
Operating temperature:
The range of ambient temperatures through which a connector is specified
to operate safely and to perform within specified limits.
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PAN:
Personal area network
Parallel signaling:
Each bit of a byte transmitted simultaneously on separate wires.
PCB:
Printed circuit board
POF:
Plastic optical fiber, typically 1+mm multimode fiber used in short
reach applications.
Power (P):
The rate of generating, transferring, or using energy, measured in
watts. E (voltage) X I (current) = P (power)
Propagation delay
(Tpd): Time required for a signal to travel through a portion of
a transmission line system.
Plated Through Hole (PTH):
Drilled hole in a printed circuit board that is made conductive by
deposition of metal that provides electrical connection to the copper
layers within the board.
PCI Industrial Computer Manufacturers
Group (PICMG): Industry
consortium that creates and promotes hardware and protocol standards
within the computer industry.
PMC:
PCI mezzanine card
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| R
Reflections:
Energy reflected back to its source as it encounters impedance
discontinuities in the signal path.
Resistance (R):
Property of an electric conductor by which it opposes a flow of
electricity and dissipates electrical energy away from the circuit,
usually as heat.
RMS value:
Root mean Square, the heating effect of an AC voltage comparable to a DC
voltage.
Return loss:
A summation of all reflected signal energy coming back to the end where
it originated, and is a result of the dissimilarity between impedances
in metallic transmission lines and loads. Expressed in dB as a reduction
in amplitude of the reflected to forward energy, and varies with
frequency. In optic systems, the amount of optic power reflected at the
connector interface, expressed in dB. Values range from minus 15 to
minus 60 dB. Higher numbers reflect better performance. Also known as
back reflection loss.
Risetime (tr):
Time required for a digital signal to reach 90 percent of its maximum
amplitude. Some differential applications use an 80 percent value.
RoHS:
Restriction on the use Of Hazardous Substances driven by the European
Parliament. Seeks to eliminate a number of materials used in electronic
equipment, including lead.
RTM:
Rear transition module. Small daughter plugged into the back of a
midplane that is used to adapt signals for the I/O interface.
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| S
S-parameter:
Scattering parameter. Matrix of amplitude and phase data that can
quantify signal fidelity. The S12 parameter that plots attenuation vs.
frequency is one of the most common used to document connector
performance, and is also known as insertion loss.
SERDES:
Serializer/Deserializer. Device that creates a high-speed serial bit
stream by combining data from multiple parallel lines.
Serial signaling:
Sequential transmission of all bits of a byte over one wire if single
ended, or a pair of wires if differential.
SFP:
Small form factor pluggable. Smaller, higher speed GBIC.
SIG:
Special interest group
Signal integrity (SI):
Process of analyzing and making appropriate system design decisions that
result in optimal high-speed system performance.
Single ended signaling:
Signals transmitted over one wire using a common ground return.
Single mode fiber:
Optical fiber whose core diameter is so small, relative to the
wavelength of light, that only one mode is propagated.
Skew:
Difference in propagation delay between two conductors through a
high-speed circuit, causing loss of fidelity.
·
Differential
skew: Difference in
propagation time between signals in a differential pair.
·
Channel
skew: Difference in
propagation time between two differential pairs.
Skin effect:
Loss of signal due to the tendency for high-speed signals to propagate
on the surface of conductors. Resistance increases as the conductor size
is reduced (e.g. reduced PCB trace widths).
Smith Chart:
Used to convert between impedance and S-parameters.
Spectral loss curve:
A plot of attenuation as a function of wavelength.
SPICE:
Simulated Program with Integrated Circuit Emphasis. An analog circuit
analysis program that is used to predict the high-speed performance of
digital circuits. SPICE is a time domain tool.
Stripline:
A signal trace structure between two reference planes, either power or
ground. Striplines are used for internal signal layers in PCBs.
Supertemperature:
Temperature at the individual asperity contact points on an electrical
interface.
Surge/inrush current:
Instantaneous spike in current that occurs in a circuit as it is
switched on, and persists until the capacitive characteristics of the
circuit have been charged.
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TDR:
Time domain reflectometer. Instrument used to identify impedance
discontinuities in a transmission line system and measure their
reflection coefficients.
Telematics:
The integration of wireless communications, vehicle monitoring systems,
and location devices in transportation-related applications.
Thermal runaway:
A condition in a separable interface where an increase in temperature
increases power loss, causing a further increase in temperature; a
spiraling effect which may lead to connector and system failure. Heat
generated is greater than heat dissipated.
Transmission line:
Signal path where the rise time of the signal is less than the
round-trip time of flight of the signal.
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U
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| V
Vertical-cavity surface-emitting laser (VCSEL):
Semiconductor laser diode that produces a laser beam emission
perpendicular to the top surface of the device.
Via:
In PCB design, via refers to a pad with a
plated hole that connects copper tracks from one layer of the board to
other layers. In IC design, a via is a small opening in an insulating
oxide layer that allows metallic interconnect on different interconnect
layers to form a connection.
VME:
Versa Module Eurocard system bus structure
VoIP:
Voice-over-Internet Protocol
Volt (V):
A unit of electromotive force in the International System of Units that
will produce a current of 1 ampere in a circuit that has resistance of 1
ohm.
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| W
Watt
(W):
a
standard unit of power defined as one Joule of energy transferred or
dissipated in one second. One watt is the amount of power that is
delivered to a component of an electric circuit when a current of 1
ampere flows through the component and a voltage of 1 volt exists across
it. W = E (volts) X I (amps)
Wavelength:
The distance between two successive points of an electromagnetic
waveform, usually measured in nanometers (nm).
Wavelength-Division Multiplexing:
Transmission method where several signals are transmitted simultaneously
at different wavelengths (colors) over a single fiber.
WiMax:
Worldwide Interoperability for Microwave Access
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Y
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Are we missing a term that you need? Send
any suggestions for additional terms to atanghe@connectorsupplier.com.
Bishop
& Associates, Inc. © 2011 |
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