Tektronix RSA6100A Series, Help Manual

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General Signal Viewing > DPX Spectrum DPX Primer
Figure 7. Color-coded low-resolution example (left) and a real DPX display (right).
In addition to the choice of palette, there are z-axis scaling adjustments for Maximum, Minimum, and
Curve. Maximum sets the occurrence value that will be mapped to the highest color in the palette.
Minimum sets the occurrence value for the lowest color. In the “temperature” palette, the highest color is
deep red and the lowest is dark blue. Occurrence values less than the selected Minimum are represented
with black pixels, while pixels that exceed the selected Maximum are red in hue but somewhat transparent.
Values between Maximum and Minimum are represented by the other colors of the palette.
Adjusting the Minimum above the black default allows you to concentrate most of your color resolution
over a small range of medium or higher occurrence rates to visually discriminate between different signals
that have nearly equal probability values.
To see why adjustable color scaling is useful compare Figures 8 and 9. On the Scale tab, the Max control is
set to 100% in Figure 8. The range of colors now covers the full z-axis range of densities from 0 to 100%.
The signals used to create this bitmap are fairly diffused in both frequency and amplitude, so most pixels
have low occurrence counts or density values and the upper half of the color palette is unused.
Figure 8. DPX spectrum bitmap with default color scale settings.
RSA6100A Series Real-Time Spectrum Analyzers Help
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