5120A/5115A Operations and Maintenance Manual 33
The following phase noise settings can be configured:
Plot Scale (see page 33)
Data Markers (see page 35)
Test Mask (see page 38)
Display Tools, including Time Constant (see page 41)
5.1.1 Scaling the Phase Noise Plot
The phase noise plot can be scaled logarithmically or linearly in the following ways:
Automatically scale the y axis:
• Sets the dB/division to the closest values that allow display of all data.
• Sets the top grid line to a multiple of the selected dB/division value.
Manually scale the y axis:
• Allows for shifting the displayed values from a maximum of 60 dBc/Hz to a minimum
of -240 dBc/Hz.
• Lets you increase or decrease the dB/division allowing the following values: 0.5, 1,
1.5, 2, 5, 10, 15, 20, 25, and 30.
Automatically scale the x axis:
• Sets the x scale to logarithmic.
• Sets the minimum and maximum frequency to fit all data.
Fixed logarithmic scale x:
• Shows from 1 to 9 decades.
• Allows the following values (Hz): 10
–4
, 10
–3
, 10
–2
, 10
–1
10
0
, 10
1
, 10
2
, 10
3
, 10
4
, 10
5
,
and 10
6
.
Fixed linear scale x:
• Forces minimum x value of 0 Hz.
• Allows the following maximum values (Hz): 10
–3
,10
–2
, 10
–1
10
0
, 10
1
, 10
2
, 10
3
, 10
4
,
10
5
, and 10
6
.
The 5120A-01 cannot measure phase noise at offset frequencies greater than 100
kHz when either of the signals connected to the front panel signal input ports has
a frequency less than 2 MHz. When signals with lower frequencies are attached,
the plot can still be scaled to include the 1 MHz offset frequency, but no data will
be plotted from 100 kHz to 1 MHz. Both of the internal oscillators produce
frequencies greater than 2 MHz.
To scale the plot using softkeys:
1. Navigate to the Phase Noise Plot. See “3.1.1 Navigation” on page 12 for details.