Opens a submenu to search for trace segments with a bandpass or bandstop shape and determine characteristic filter parameters.
Bandfilter
search and filter parameters
Bandpass and bandstop regions can be described with the same parameter set:
A bandpass region contains a local maximum around which the magnitude of the trace falls off by more than a specified x dB Bandwidth.
A bandstop region contains a local minimum around which the magnitude of the trace increases by more than a specified x dB Bandwidth.
The analyzer locates bandpass and bandstop regions and determines their position (Center frequency) and shape (Bandwidth, LBE, UBE, Quality factor Q; see Show Results). For a meaningful definition of the x dB Bandwidth criterion, the trace format must be dB Mag.
Bandpass Search Ref to Max activates the search for a bandpass region in the active trace, starting at the absolute maximum of the active trace within the search range.
Bandstop Search activates the search for a bandstop region in the active trace, starting at the absolute minimum of the active trace within the search range.
Bandfilter Tracking causes the bandfilter search to be repeated after each sweep.
x dB Bandwidth... sets the level defining the filter bandwidth.
Search Range... confines the search to a subrange of the sweep.
Search Result Off hides the display of the bandfilter parameters in the diagram area.
Bandpass Search Ref to Marker activates the search for a bandpass region in the active trace, starting at the position of the active marker.
Bandfilter
mode can be selected for a broad range of measured quantities (Trace
– Measure),
provided that the display format is dB Mag.
To obtain real filter parameters, the measured quantity must be a transmission
S-parameter and a frequency sweep must be performed. For other quantities
(e.g reflection parameters), the Bandfilter
functions are still useful to analyze general trace properties.
In some display formats (e.g. Phase)
the bandfilter search is disabled.
Activates the search for a bandpass region on the active trace and activates bandfilter Tracking. A bandpass region is the tallest peak in the search range with a minimum excursion specified by means of the x dB Bandwidth parameter.
When Bandpass Search is activated the analyzer uses (or creates) the four markers Mkr 1 to Mkr 4 to locate the bandpass region:
Mkr 1 indicates the maximum of the peak.
Mkr 2 indicates the point on the left edge of the peak where the trace value is equal to the maximum minus x dB Bandwidth.
Mkr 3 indicates the point on the right edge of the peak where the trace value is equal to the maximum minus x dB Bandwidth.
Mkr 4 indicates the center of the peak, calculated as the arithmetic mean value of the LBE and UBE positions.
For a symmetric peak, the positions of Max and Center coincide.
The band filter search results are displayed in the bandfilter info field.
To search for a bandpass region in the vicinity of the
active marker, use Bandpass
Search Ref to Marker.
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Remote control: |
CALCulate<Chn>:MARKer<Mk>:FUNCtion:BWIDth:MODE
BPASs |
Activates the search for a bandstop region on the active trace and activates bandfilter Tracking. A bandstop region is the lowest peak (local minimum) in the search range with a minimum excursion that is specified by means of the x dB Bandwidth parameter.
When Bandstop Search is activated the analyzer uses (or creates) the four markers Mkr 1 to Mkr 4 to locate the bandstop region:
Mkr 1 indicates the minimum of the peak.
Mkr 2 indicates the point on the left edge of the peak where the trace value is equal to the minimum plus x dB Bandwidth.
Mkr 3 indicates the point on the right edge of the peak where the trace value is equal to the minimum plus x dB Bandwidth.
Mkr 4 indicates the center of the peak, calculated as the arithmetic mean value of the LBE and UBE positions.
For a symmetric peak, the positions of Max and Center coincide.
The band filter search results are displayed in the bandfilter info field.
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Remote control: |
CALCulate<Chn>:MARKer<Mk>:FUNCtion:BWIDth:MODE
BSTOP |
Causes the bandfilter search to be repeated after each sweep: When tracking mode is active the markers typically change their horizontal and their vertical positions as the measurement goes on.
Tracking for the different bandfilter search modes is enabled or disabled in a selection box. Selecting a search mode for tracking also activates this mode.
Tracking is a toggle function: Selecting the function repeatedly switches the tracking mode on and off.
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Remote control: |
CALCulate<Chn>:MARKer<Mk>:FUNCtion:EXECute
BFILter |
Opens the numeric entry bar for the minimum excursion of the bandpass and bandstop peaks.
A bandpass peak must fall off on both sides by the specified x dB Bandwidth to be considered a valid peak.
A bandstop peak must increase on both sides by the specified x dB Bandwidth to be considered a valid peak.
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Remote control: |
Opens the Search Range Dialog to confine the bandfilter search to a subrange of the sweep.
It is possible to define and store up to ten different search ranges for each trace. The bandfilter search is performed using the markers Mkr 1, ..., Mkr 4, irrespective of the selected search range.
In contrast to the marker properties defined in the Marker and Search menus, the ten search ranges are valid for the entire setup. This means that, once defined, each of them can be used for any trace in the setup, irrespective of the channel that the trace belongs to.
The default search range of each new marker is Full Span. The analyzer provides greatest flexibility in defining search ranges. In particular, two search ranges may overlap or even be identical. The search is confined to the part of the search range that belongs to the sweep range.
The following example shows how search ranges can be used to search a trace for several bandpass regions.
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Remote control: |
CALCulate<Chn>:MARKer<Mk>:FUNCtion:DOMain:USER |
Hides the info field with the results of a bandpass or a bandstop search and disables bandfiter Tracking. The info field is displayed again (and tracking re-enabled) when a new bandfilter search is performed.
The info field contains the following search results:
Bandwidth is the n-dB bandwidth of the bandpass/bandstop region, where n is the selected x dB Bandwidth. The bandwidth is equal to the difference between the Upper Bandwidth Edge (UBE) and the Lower Bandwidth Edge (LBE).
Center is the stimulus frequency where the trace reaches its absolute maximum (minimum) within the bandpass (bandstop) region.
Lower Band Edge is the closest frequency below the center frequency where the trace is equal to the center value minus n dB.
Upper Band Edge is the closest frequency above the center frequency where the trace is equal to the center value minus n dB.
The Quality Factor is the ratio between the Center frequency and the 3-dB Bandwidth; it does not depend on the selected x dB Bandwidth.
Loss
is the loss of the filter at its center frequency and is equal
to the response value of marker no. 4. For an ideal bandpass filter the
loss is zero (0 dB), for an ideal bandstop filter it is –
dB.
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Remote control: |
Activates the search for a bandpass region on the active trace and activates bandfilter Tracking, starting at the position of the active marker. A bandpass region is the closest peak in the search range with a minimum excursion specified by means of the x dB Bandwidth parameter.
In contrast to a Bandpass Search Ref to Max, the Bandpass Search Ref to Marker does not change the position of the active markers. The band filter search results are displayed in the bandfilter info field.
To search for a bandstop region in the vicinity of the
active marker, use Bandfilter
Tracking
– Bandstop
Search Ref to Marker.
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Remote control: |
CALCulate<Chn>:MARKer<Mk>:FUNCtion:BWIDth:MODE
BPRMarker | BSRMarker
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