HP 8590 E-Series User Manual page 350

sweep time
The time it takes the local oscillator to tune across the selected span. Sweep time directly
affects how long it takes to complete a measurement. It does not include the dead time
between the completion of one sweep and the start of the next. It is usually a function
of frequency span, resolution bandwidth, and video bandwidth. Resolution affects sweep
time in that the IF filters are band-limited circuits requiring finite times to charge and
discharge. The amount of time the mixing product remains in the IF filter passband is
directly proportional to the bandwidth; inversely proportional to the sweep in Hz per unit
of time. The rise time of a filter is inversely proportional to its bandwidth, and if the
proportionality constant "k" is included, then we can make the rise time equal the "k"
divided by resolution bandwidth. Mathematically, this is represented as:
Time in Passband =
Solving for sweep time:
time-gate
A time gate acts as a time filter, rejecting signals and spectra not corresponding to the
desired time. It is an RF signal switch that admits the signal to the spectrum analyzer only
while the switch, or gate, is closed. Since the spectrum analyzer receives the signal only
when passed through the gate, it will only display the measurement results from the portion
of the signal selected by the gate position in time.
title line
The area on a display where user-selected characters are displayed. These characters are
selected from the front-panel keys.
TO1
Third order intermodulation distortion occurs in a system where two signals are present.
The distortion products are a result of each signal mixing with the other's second harmonic.
If the two main signals are of equal power, the two third order distortion products will also
be of equal power. As the power of the two main signals is increased by an equal amount,
the power of the distortion products will increase three times that amount. Theoretically,
there is a power level at which the power of each distortion product equals the power of
the two main signals. (Practically, it may not be possible to reach this power level because
of compression or limiting.) The Third Order Intercept (TOI) is defined as the power at
which the third order distortion products equals the power of two equal level test signals.
trace
A trace is made up of a series of data points containing frequency and amplitude
information. The series of data points is often referred to as an array. Traces A, B, and C
are the typical names of traces that analyzer displays. The number of traces is specific to
the instrument.
Glossary-l 6
resolution bandwidth (resolution bandwidth x sweep time)
(span /sweep time) =
Rise Time =
resolution bandwidth
k x span
sweep
time =
resolution bandwidth
span
k
2