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a) Press
【
Amplitude
】
→ [Pre Amp Off On] to turn the preamplifier on or off.
Section 4 Bandwidth Settings
This Section describes the detailed settings of the measurement bandwidth in the spectrum analyzer
mode of the S5105D/E/F microwave analyzer, including settings of resolution bandwidth, selection
of video bandwidth and detection mode. Press
【
BW
】
to open the bandwidth setting soft menu.
1
Set resolution bandwidth
Since the resolution bandwidth is subject to the bandwidth of the IF filter, the shape of trace depends on
the IF filter. The S5105D/E/F microwave analyzer supports variable resolution bandwidth settings in
the spectrum analyzer mode, ranging from 1 Hz. - 5MHz, which can be changed in steps of 1, 3, 10,
and figure keys, step keys and wheel.
What’s more, the reduction of resolution bandwidth will minimize the impact of random noise on the
measurement results. The noise based can be reduced by 10dB for every 10 times reduction in
resolution bandwidth, but setting a narrow resolution bandwidth will make the sweep time become much
longer. The impact of the resolution bandwidth from 3MHz to 300kHz on the measurement results is
shown in Figure 5-1:
Steps for setting resolution bandwidth are as follows:
a) Press
【
BW
】
→ [RBW Auto/Man] .
b) Use the numeric keys to enter the resolution bandwidth value, and select the corresponding unit in
the touch screen; and user can also Press [↑] [↓] or use the rotary knob to change the resolution
bandwidth.
After changing the resolution bandwidth, the mode of resolution bandwidth changes from automatic to
manual. In automatic mode, the resolution bandwidth will be adaptively changed based on the settings of
the span. The ratio of span and resolution bandwidth can be set by performing the following:
a) Press
【
BW
】
→ [SPAN/RBW 100] ;
b) Enter the ratio using the numeric keys and Press [OK] SPAN/RBW can be set from 1 to 500 and
defaults to 100. If the ratio is changed, the resolution bandwidth will automatically change while the
span remains the same.
3MHz
RBW
1MHz
300kHz
Figure 5-1 Impact of Resolution Bandwidth on Measurement Results
2
Set Video Bandwidth
The video bandwidth filter is used to smooth the traces, aiming to improve the ability of the microwave
analyzer and detect weak signals in noise signals. When reducing the video bandwidth, the result of the
microwave analyzer is that the noise base is compressed into a thin trace, but the position of the trace
remains unchanged. The video bandwidth does not affect the frequency resolution of the microwave
analyzer, but when measuring the low power signal, the video bandwidth improves recognition and
reproducibility, but choosing a small video bandwidth will extend the sweeping time.
