Tektronix RSA6100A Series, Help Manual

Page: 56 / 415

General Signal Viewing > DPX Spectrum DPX Primer
Table 2: Minimum signal duration speci fi cations for RSA6100A series spectrum analyzers 1 (cont.)
Span
(MHz)
RBW
(kHz) Span/RBW
Ratio
FFT
Length Spectrum/sec
MSD for
100% POI ( μ s)
110 100 1100 4096 73,242 41.0
110 30 3667 16384 18,311 163.9
110 20 5500 32768 9,155 327.7
xxx
1
With Options 110 and 200 under various combinations of control parameters.
To demonstrate the POI in action, a challenging bi-stable signal is used. A CW sinusoid sits at 2.4453 GHz
most of the time, but every 1.28 seconds, its frequency changes for about 100
μ s before returning to
normal. The duty factor of this transient is less than 0.01%.
Figure 16 shows a swept analyzer set up for a 5-second sweep of its MaxHold trace. It shows that there is
something occurring around the signal. This sweep rate was empirically determined to be the optimum rate
for reliable capture of this signal in the shortest time. Faster sweep times can reduce the probability of
intercept and result in fewer intersections of the sweep with the signal transient.
Figure 16. Swept spectrum display of the infrequent transient.
The DPX display shown in Figure 17 shows the exact same event, also captured over a 5 second period. A
lot more information can be discovered about the transient. It is obvious at
fi rst glance that the signal is
hopping by about 3 MHz, with 1.2 MHz of frequency overshoot on transitions
44
RSA6100A Series Real-Time Spectrum Analyzers Help