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HP-IB
The abbreviation for Hewlett-Packard Interface Bus. It is a Hewlett-
Packard proprietary parallel interface that allows you to “daisy-chain”
more than one device to a port on a computer or instrument.
IF
The abbreviation for intermediate frequency. An IF frequency is a
frequency to which a signal wave is shifted locally as an intermediate step
in transmission or reception. On analyzers, this is the frequency resulting
from conversion before demodulation.
IF gain/IF attenuation
A control that adjusts the vertical position of displayed signals without
affecting the signal level at the input mixer. When changed, the value of
the reference level is changed accordingly.
IF feedthrough
A condition that results in a rise in amplitude of the baseline trace. This
occurs as a result of an input signal at the intermediate frequency (IF)
passing through the input mixer. This a usually only a potential problem
on nonpreselected analyzers. The entire baseline trace rises because the
signal is always at the IF. (Mixing with the local oscillator is not required.)
image response
A displayed signal that is actually twice the intermediate frequency (IF)
away from the frequency indicated by the analyzer. For each harmonic of
the local oscillator there is an image pair. One is below the local oscillator
frequency by the IF and the other is above. Images usually only appear
on nonpreselected analyzers.
impedance
The apparent opposition in an electrical path to the flow of current. The
specified nominal input impedance of an analyzer is stated for the input
connector. The most common impedance for RF and microwave analyzers
is 500. However,
7562
is typically used for cable television (CATV) work.
impulse bandwidth
The width of a rectangular filter that has the same peak voltage
output as the actual analyzer filter. The impulse bandwidth of
the synchronously-tuned, Gaussian-like resolution filters in the
Hewlett-Packard analyzers is approximately 1.5 times the 3
dB
bandwidth.
Glossary-12