User`s guide

126 Agilent E5505A User’s Guide
5 Absolute Measurement Fundamentals
4
Press the [[DEFINE TRACE]]
a press the [[and the MATH FUNCTION keys.
Using the --> key on the RF analyzer, offset the marker by the PLL
bandwidth. Read the offset frequency and noise level indicated at the
bottom of the display. (If the noise level falls below the bottom of the
display, the marker reading is still correct.)
5 To increase the vertical scale
a press [[VERT SCALE]]
b press [[, DEFINE DB/DIV]], and enter 20 dB.
6 Compare the average noise level at the PLL bandwidth offset to the small
angle criterion level shown on the graph in Figure 82. The average noise
level of the signal must remain below the small angle line at all offset
frequencies beyond the PLL bandwidth. (The small angle line applies only
to the level of the average noise. Spur levels that exceed the small angle line
do not degrade measurement accuracy provided they do not exceed
—
⋅ 40 dBc.)
7 Continue moving the marker to the right to verify that the average noise
level remains below the small angle line.
8 Increase the span by a factor of ten by selecting FREQ and DEFINE SPAN.
Continue comparing the noise level to the graph.
9 Continue to increase the span width and compare the noise level out to
100 kHz. (If the noise level exceeds the small angle line at any offset
frequency beyond the PLL bandwidth, note the offset frequency and level of
the noise. Use the graph in Figure 83 on page 127 to determine the Peak
Figure 82 Graph of small angle line and spur limit