Glossary of Terms
MS20xxC UG PN: 10580-00305 Rev. J H-3
itself. This noise, generated by the random electron motion in various
circuit elements, is amplified by multiple gain stages in the analyzer
and appears on the display as a noise signal. On a spectrum analyzer,
this noise is commonly referred to as the Displayed Average Noise
Level, or DANL 1. While there are techniques to measure signals
slightly below the DANL, this noise power ultimately limits our ability
to make measurements of low-level signals.
dB : Decibel or deciBel (dB) is a unit for measuring relative power ratios in
terms of gain or loss. The units of dB are expressed in terms of the
logarithm to base 10 of a ratio and typically are expressed in watts. For
example, a -3dB loss indicates a 50% loss in power; a +3dB reading is a
doubling of power; 10 dB indicates an increase (or a loss) by a factor of
10; 20 dB indicates an increase (or a loss) of a factor of 100; 30 dB
indicates an increase (or a loss) by a factor of 1000.
dBc : Decibels referenced to the carrier (dBc) is a technique for expressing a
power measurement in logarithmic form using the carrier power as a
reference. The units are used to describe how far down signals and noise
are relative to a known signal. A typical use of this term is to describe
spurious signals and noise compared to a desired transmit signal.
dBm : dBm is a decibel value referenced to a milliWatt (dBm) This is a
technique for expressing a power measurement in logarithmic form
using 1 mW as a reference. dBm is a decibel ratio (log 10) of
Watts (W) to one milliwatt (1mW). dBm therefore represents
absolute power.
DTF : Distance-To-Fault (DTF) DTF is the distance from the
instrument output connector (or the end of a test lead) to a problem
area, as indicated by a peak in the displayed signal.
FFT : Fast Fourier Transform (FFT) is an efficient algorithm to compute the
Discrete Fourier transform (DFT) and its inverse. FFTs are of great
importance to a wide variety of applications, from digital signal
processing to solving partial differential equations to algorithms for
quickly multiplying large integers.
Flash Memory : Flash memory is a non-volatile solid state storage device that is
packaged as a chip. It can be electrically erased and reprogrammed. It is
primarily used in memory cards, USB flash drives, MP3 players, and
solid-state drives for general storage and transfer of data between
computers and other digital products. It is a specific type of EEPROM
(electrically erasable programmable read-only memory) that is erased
and programmed in large blocks.
GPS : The Global Positioning System (GPS) is a space-based global navigation
satellite system (GNSS) that provides reliable location and time
information in all weather and at all times when and where an
unobstructed line of sight is available to four or more GPS satellites.
The system is maintained by the United States government and is
freely accessible by anyone with a GPS receiver. The Global Positioning
System is making it possible for people using ground receivers to
determine their geographic location within 10 to 100 meters. The
satellites use simple mathematical calculations to broadcast
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