HP 70000 series, Руководство пользователя

Страница: 408 / 447

rear panel of many Hewlett-P ackard computers , including the HP 9000 Series 200 and 300
computers .
HP-MSIB
See address map.
IF feedthrough
Since the spectrum analyzer is a heterodyne receiver , an input signal equal in frequency
to the rst IF lifts the entire baseline , regardless of the frequency-control settings . This
phenomenon known as IF feedthrough obscures the display and can completely submerge
other signals present. T o eliminate any gap in the analyzer frequency coverage , an alternate
IF with appropriate ltering must be available and the two IFs must not be harmonically
related. A preselector also eliminates IF feedthrough.
input number
Input ports (for measuring input signals) are numbered consecutively starting with 1.
instrument window
P ortion of screen dedicated as the display for a modular measurement system instrument.
Size of window is determined by
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
ASSIGN WINDOW (press 4 DISPLA Y 5 to access it) or IWINDOW
programming command. See graphics window.
interferometer
See Mach-Zehnder interferometer (MZI).
internal attenuation
Attenuation located inside the spectrum analyzer , after the RF INPUT .
internal memory
See user memory.
item
A series of programming commands which form a shape for repeated graphics applications .
Created with the IT command.
key
Spectrum-analyzer functions are accessed by front-panel keys . The keys surrounding the
graticule are called softkeys and access all the spectrum-analyzer functions . Commonly
used functions can be executed with the keys on the instrument keypad, located beneath
the display on some models , such as the HP 70004A Display .
Any group of keys that can be accessed at one time form a menu. Menus are organized in
levels . The highest-levels are accessed with the 4 USER 5 , 4 MENU 5 , or 4 DISPLA Y 5 keys .
limit line
A limit line is a test limit consisting of a series of line segments positioned according to
frequency and amplitude in the spectrum-analyzer measurement range . Two limit lines can
be dened, one for the upper limit, another for the lower limit. Once dened, trace data
can be compared to the limit lines as the spectrum analyzer sweeps . When the trace data
exceeds the upper or lower limits , the spectrum analyzer beeps or returns test results to the
computer .
limit-line le
User-memory le that contains limit-line table entries . When recalled with
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
recall to...
or LO AD programming command, limit-line table is cleared and contents of le are loaded
into the limit-line table . See limit line.
Glossary-9