28
/
78
Figure 3-7 Distinguished Two Equal-Amplitude Signal
（
2
）
When the resolution is decreased, the sweep time will increased and the displayed signal will be
smoother at the same time. For the fastest measurement, use the maximum resolution bandwidth
as much as possible. In factory setting, resolution bandwidth and sweep span is coupling.
Distinguish the Small Signal from the Big Signal
This example shows that use a narrow resolution bandwidth to distinguish two signal with frequency
difference 10 kHz, amplitude difference 50dBm.
1. As shown in Figure 3-4, connect two signal sources to input port of the spectrum analyzer.
2. Set the frequency and amplitude of one signal source to 300Mz, -10dBm, another signal source is
set to 300.01MHz
，
-60dBm and turn on signal output.
3. Follow the steps to set spectrum analyzer:
Press
[Default]>Reset
Press
[FREQ]>Center Frequency>300>MHz
、
Span>200>kHz
Press
[BW]>30>kHz
4. Set 300MHz signal as the reference level:
Press
[Peak]>Marker→>Ref Lvl
Note
UTS3000B/A’s filter has 4:8:1 shape factor. With a resolution bandwidth of 30 kHz, its 60dB
bandwidth is 144 kHz. Half of this bandwidth (77 kHz) is greater than the frequency
difference of two signals (10 kHz), so the two input signals cannot be distinguished.
