Glossary of Terms D-2 Glossary of Terms
S412E UG PN: 10580-00318 Rev. P D-5
CW : Continuous Wave (CW)
DANL : Displayed Average Noise Level (DANL): Displayed average noise level
is sometimes confused with the term Sensitivity. While related, these
terms have different meanings. Sensitivity is a measure of the
minimum signal level that yields a defined signal-to-noise ratio (SNR)
or bit error rate (BER). It is a common metric of radio receiver
performance. Spectrum analyzer specifications are always given in
terms of the DANL. One of the primary uses of a spectrum analyzer is to
search out and measure low-level signals. The limitation in these
measurements is the noise generated within the spectrum analyzer
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. 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.
Demodulate : To extract information from a transmitted (modulated) signal.
Demodulor : A device that extracts information from a transmitted (modulated)
signal.
To Next Page
Loading...
