HP 8590 E-Series User Manual page 346

persistence
See CRT persistence.
personality
Applications available on a memory card or other electronic media that extends the
capability of an instrument for specific uses. Examples include digital radio personalities
and cable TV personalities.
phase noise
Refer to noise sidebands.
position units
The position unit describes the location of a point along the horizontal axis of a trace.
Position unit values of a trace begin on the left-hand side of the graticule and increase to
a predefined value (specific to the spectrum analyzer model) on the right-hand side of the
graticule.
positive peak
The maximum, instantaneous value of an incoming signal. On digital displays, each
displayed point of the signal indicates the maximum value of the signal for that part of the
frequency span or time interval represented by the point.
preamplifier
An external, low-noise-figure amplifier that improves system (preamplifier/spectrum
analyzer) sensitivity over that of the analyzer itself.
predefined trace
Trace A, B, or C of a spectrum analyzer. Refer also to trace.
preselector
A tunable bandpass filter placed ahead of a frequency converter, or mixer, of a spectrum
analyzer. It tracks the appropriate mixing mode and passes signals of a desired frequency
and reduces others. Preselectors are typically used only above 2 GHz. They essentially
eliminate multiple and image responses and, for certain signal conditions, improve dynamic
range.
quasi-peak detector
A detector circuit designed with time constants that give a weighted value to the amplitude
of a detected signal. The displayed signal output is an indication of the degree to which the
detected signal would impair the intelligibility of a desired signal. The time constants (rise,
fall, average) for EM1 purposes are based on the recommendations of CISPR that are in turn
based on subjective tests. Interference limits for commercial EM1 tests are often given in
quasi-peak values.
random-access memory
RAM (random-access memory) or read-write memory, is a storage area allowing access to
any of its storage locations. Data can be written to or retrieved from RAM, but data storage
is only temporary. When the power is removed, the information disappears. User-generated
information appearing on a display is RAM data.
raster display
A television-like display in which the image is formed by scanning the electron beam
rapidly across and slowly down the CRT face and gating the beam on as appropriate. The
scanning rates are fast enough to produce a flicker-free display. Refer also to vector
display and sweep time.
Glossary-l 2