Sample Detection

The bucket concept is important, as it will help us differentiate the six
detector types:

Sample
Positive peak (also simply called peak)
Negative peak
Normal
Average
Quasi-peak

The first 3 detectors, sample, peak, and negative peak are easily understood
and visually represented in Figure 2-19. Normal, average, and quasi-peak
are more complex and will be discussed later.

Figure 2-19. Trace point saved in memory is based on
detector type algorithm

Let's return to the question of how to display an analog system as faithfully
as possible using digital techniques. Let's imagine the situation illustrated in
Figure 2-17. We have a display that contains only noise and a single CW signal.

Sample detection
As a first method, let us simply select the data point as the instantaneous level
at the center of each bucket (see Figure 2-19). This is the sample detection
mode. To give the trace a continuous look, we design a system that draws
vectors between the points. Comparing Figure 2-17 with 2-20, it appears that
we get a fairly reasonable display. Of course, the more points there are in the
trace, the better the replication of the analog signal will be. The number of
available display points can vary for different analyzers. On ESA and PSA Series
spectrum analyzers, the number of display points for frequency domain traces
can be set from a minimum of 101 points to a maximum of 8192 points. As
shown in figure 2-21, more points do indeed get us closer to the analog signal.

Figure 2-20. Sample display mode using ten points to display the signal
of Figure 2-17

Figure 2-21. More points produce a display closer to an analog display