Ceyear 4051 Series, Руководство пользователя

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4. Operating Instruction
4.1 Function operation guide
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bandwidth, video bandwidth, sweep time, sweep type, etc., which are used to determine the access way of
spectrum data of Series Signal Analyzer and filter type. Differences may exist in other modes, please refer to
relevant user manual
1) Parameter description of 【 BW 】 key
The setting menus corresponding to the 【 BW 】 key on the front panel include [Res BW], [Video BW],
[VBW/RBW], [Span/RBW], [Filter Type] and [Filter BW].
[Res BW] is used to set and indicate the frequency resolution capability when the Series Signal Analyzer
executes the spectrum measurement. The parameters of Resolution Bandwidth (RBW) determines the
minimum frequency interval that the spectrum distinguish two signals. The smaller the resolution bandwidth
is, the higher the resolution capability is.
For a simple-frequency signal, the trace displayed by swept spectrum analysis is the frequency response shape
of checked IF filter. When the filter bandwidth is changed, the trace width displayed by analyzer will change
at the same time. For two signals with equal amplitude and very close frequency, the spectrum traces of two
signals display as one signal if the broader filter is selected; if filter narrow enough is used, these two input
signals can be distinguished and display as two separate spectrum peaks. Therefore, the signal resolution
capability is determined by the IF filter of analyzer.
When the settings of resolution bandwidth are changed, the IF filter inside the analyzer will change at the
same time. Usually, the resolution bandwidth is defined as 3 dB bandwidth of filter or as 6 dB bandwidth of
filter sometimes. To distinguish two signals with equal amplitude, the resolution bandwidth has to be less than
or equal to signal frequency interval. If the resolution bandwidth is equal to the signal interval and video
bandwidth is less than resolution bandwidth, a 3 dB dip will appear between two signals on the spectrum trace.
The smaller the resolution bandwidth is, the deeper the dip goes. Therefore, distinction between two adjacent
signals will beclearer.
The desired resolution bandwidth can be realized with IF filter by 4051 Series Signal/Spectrum Analyzer
under swept spectrum measurement mode or with FFT filter under FFT spectrum measurement mode. FFT
filter can be understood as the window function operation before executing FFT spectrum operation.
The Video Bandwidth Filter is the low-pass filter operation or average operation executed on spectrum trace,
which can smoothen the spectrum trace displayed. Under swept spectrum measurement mode, [Video BW]
(VBW) refers to the bandwidth of low-pass filter executed on spectrum trace. Under FFT spectrum
measurement mode, video bandwidth (VBW) refers to the equivalent low-pass filter bandwidth after the FFT
spectrum trace is averaged many times.
[VBW/RBW] is used to set and indicate the specific value of resolution bandwidth and video bandwidth used
by current spectrum measurement. This parameter can be set automatically or manually. The Series Signal
Analyzer is set as 1 automatically, namely the resolution bandwidth is same as video bandwidth. This
parameter only has influence on the settings of video bandwidth. When the video bandwidth is set to auto, the
VBW value of Series Signal Analyzer will be determined based on the current RBW and [VBW/RBW].
[Span/RBW] is used to set and indicate the specific value of current span and resolution bandwidth. This
parameter can be set automatically or manually. The Series Signal Analyzer is set as 106 automatically,
namely the resolution bandwidth is approximately equal to 1/106 of current span. This parameter only has
influence on the settings of resolution bandwidth. When the resolution bandwidth is set to auto, the resolution
bandwidth of Series Signal Analyzer will be determined based on the current span and [Span/RBW].
[Filter Type] is used to set whether the resolution bandwidth of Series Signal Analyzer is realized with
Gaussian filter or flat top filter.
[Filter BW] is used to set whether the resolution bandwidth is selected as 3dB, 6dB, noise bandwidth or pulse
bandwidth when the Series Signal Analyzer uses the Gaussian filter. When this parameter is changed, the
resolution bandwidth filter is fixed, and the bandwidth value in the information display zone changes.
2) Parameter description of
【
Sweep
】
key