User`s guide
harmonic distortion
Undesired frequency components added to signals as a result of nonlinear behavior of the
device (for example, a mixer or an amplifier) through which signals pass. These unwanted
components are harmonically related to the original signal.
harmonic mixing
The utilization of local oscillator harmonics generated in a mixer to extend the tuning
range of a spectrum analyzer beyond the range achievable using just the local oscillator
fundamental. The mathematical algorithm is:
I;iN
=
FLO
+
FIF
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
spectrum 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 spectrum 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 spectrum 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 spectrum analyzers.
impedance
The apparent opposition in an electrical path to the flow of current. The specified nominal
input impedance of a spectrum analyzer is stated for the input connector. The most
common impedance for RF and microwave spectrum analyzers is 500. However,
750
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 spectrum analyzers is approximately 1.5 times the 3
dB
bandwidth.
incidental FM
Undesired frequency modulation on the output of a device (for example a signal source or
an amplifier) caused by or, incidental to, some other form of modulation, such as amplitude
modulation.
Glossary-7