Markers provide a numerical readout of measured data, a search capability for specific values, and can change stimulus settings. There are 15 regular markers and one Reference marker (used with Delta markers) available per trace. This topic discusses all aspects of markers.
Note: Marker Readout can be turned ON/OFF and customized from the Customize Display dialog box. Learn more.
Marker Functions (Change Instrument Settings)
SA Analysis Markers (Spectrum Analyzer channel markers)
Note: Marker Readout can be turned ON / OFF and customized from the View/Display menu. Learn more.
To move a marker, make the marker active by selecting its number in any of the previous 3 methods. The active marker appears on the analyzer display as Ñ. All of the other markers are inactive and are represented on the analyzer display as D. Then change the stimulus value using any of the following methods:
Type a value.
Scroll to a stimulus value using the up / down arrows. The resolution can not be changed.
Click the stimulus box, then use the front-panel knob.
Click and Drag Markers using a finger (touchscreen) or by left-clicking and holding a marker symbol. Then drag the marker to any point on the trace. This feature is NOT allowed in Smith Chart or Polar display formats or with a Fixed Marker type.
Move the mouse cursor over the stimulus box, then use the mouse scroll wheel.
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Marker Specifies the current (active) marker number that you are defining. On Check to display the marker and corresponding data on the screen. Stimulus Specifies the X-axis value of the active marker. To change stimulus value, type a value, use the up and down arrows, click in the text box and use the front-panel knob, or drag the marker on the screen. Note: When the sweep type is set to CW Time, the marker can not be set to 0 (first point of the trace on the x-axis) because the marker indicates the time to acquire the first point of the trace. Delta (and Reference) Markers Check to make the active marker display data that is relative to the reference (R) marker. There is only one reference marker per trace. All other markers can be regular markers or delta markers. When a delta marker is created, if not already displayed, the reference marker is displayed automatically. A delta marker can be activated from the Marker dialog box or the Marker Toolbar. See Also: Number of General Purpose and Reference Markers. Discrete Marker Check to display values at only the discrete points where data is measured. Clear to display values that are interpolated from the data points. The interpolated marker will report y-axis data from ANY frequency value between the start and stop frequency. Fixed Check to cause the marker to have a fixed X-axis and Y-axis position based on its placement on the trace when it was set to fixed. It does NOT move with trace data amplitude. It can be scrolled left and right on the X-axis by changing the marker stimulus value. Use this marker type to quickly monitor "before and after" changes to your test device. For example, you could use fixed markers to record the difference of test results before and after tuning a filter. Clear the box to create a Normal marker, which has a fixed stimulus position (X-axis) and responds to changes in data amplitude (Y-axis). It can be scrolled left and right on the X-axis by changing the marker stimulus value. Use this marker type with one of the marker search types to locate the desired data. (Marker) Format Displays the marker data in a format that you choose. The Trace Default setting has the same marker and grid formats. Choose from the following:
Noise Marker Format ( SA measurement classes only) - For comparison purposes, electronic noise measurements are often displayed as though the measurement was made in a 1 Hz Res BW. However, making an actual measurement at a 1 Hz Res BW is impossible, and at 10 Hz, extremely slow. A Noise Marker mathematically calculates the noise measurement at that single data point as though it were made using a 1 Hz bandwidth. To accurately measure noise, the Noise Marker should NOT be placed on, or too close to, a signal. The distance from a signal depends on several factors. To know if an accurate reading is being made, move the Noise Marker until consistent measurements are displayed in adjacent data points. All Off Switches OFF all markers on the active trace. The coupled markers feature causes markers on different traces to line up with the markers on the selected trace. Markers are coupled by marker number, 1 to 1, 2 to 2, 3 to 3, and so forth. If the x-axis domain is the same (such as frequency or time), coupling occurs. Trace markers in a different x-axis domain will not be coupled. If a trace marker has no marker to couple with on the selected trace, the marker remains independent. Coupling Method - Determines the scope of coupling. Choose from the following:
Coupled Markers Model This model simulates the use of coupled markers in the analyzer :
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You can use markers to search and return data for the following trace criteria:
Max and Min: find the highest or lowest points on the trace
Peak, then move to other peaks (left, right, next highest)
Target Value: find a specific Y-axis value
Bandwidth (Filters)
Notch (Filters)
Compression Point (Amplifiers)
Power Saturation (Amplifiers)
Power Normal Operating Point (Amplifiers)
How to Search with Markers |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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Marker Specifies the marker that you are defining. Not available for search types that deploy specific markers. Search Range Defines the area where the marker can move or search. For full span, the marker searches for specified values within the full measurement span. For user span, the marker searches for specified values within a measurement span that you define. Learn more about Search Range. Search TypeNote You must either press Target Search or check Tracking to initiate all search types. If there is no valid data match for the search type, the marker will not move from its current position.
Maximum Marker locates the maximum (highest) data value. Minimum Marker locates the minimum (lowest) data value. Peak - See below. Next Peak - Marker locates the peak with the next lower amplitude value relative to its starting position. Peak Right - The marker locates the next valid peak to the right of its starting position on the X-axis. Peak Left - The marker locates the next valid peak to the left of its starting position on the X-axis. Multi Peak - A function that search for peaks that match the multi-peak search excursion value and multi-peak polarity value. Learn more about Multi Peak Search.
Target - A function that searches for a target that matches the pre-defined target value and transition types (positive, negative or both (positive and negative)) and then moves the marker to that target. Learn more about Multi Target Search. Target Left - A function executes the search from the current marker position to the smaller stimulus values and moves the marker to first target encountered. Target Right - A function executes the search from the current marker position to the larger stimulus values and moves the marker to first target encountered. Multi Target - A function that search for targets that are of the multi-target value and multi target transition value. Learn more about Multi Target Search.
Compression - A function used the active marker to find the specified gain Compression Level. Learn more about Compression Search.
Bandwidth and Notch searches are accessed by pressing Search > Bandwidth & Notch > BW Ref to or Search > Bandwidth & Notch > Notch Ref to.
Bandwidth - A function for determining the bandwidth of the trace, center frequency, cut-off points (on the higher frequency and the lower frequency sides), Q and insertion loss based on the position of the active marker (if search mode set to Marker) or the peak marker (if search mode set to Peak). Learn more about Bandwidth Search.
Notch - A function is used to obtain the bandwidth, center frequency, cutoff points (high-frequency side and low-frequency side), Q and insertion loss of a trace based on the position of the active marker (if search mode set to Marker) or the peak (if search mode set to Peak). Learn more about Notch Search.
The default behavior for searches based on the active marker or peak marker can be set using the Marker: On Preset, set BW/Notch search reference to Peak preference. Power Saturation - Learn more about PSAT Search.
Normal Operating Pt - The output power where the input is offset from the back-off input power by the Pin Offset. Learn more about PNOP Search.
Spurious Search (Phase Noise only) Phase Noise marker searches are accessed by pressing Search > Spurious or by selecting the search marker from the Search Type pulldown menu in the Marker Search dialog. The Phase Noise application has marker search function types similar to a standard channel. In addition, it has marker search types specific to a Phase Noise channel. Spur analysis must be enabled to use the Spurious search functions. See Enable Spur Analysis. Spurious Search - Searches for spurious signals based on spurious settings. Spurious Right >> Search - Searches for the next spurious signal to the right. << Spurious Left Search - Searches for the next spurious signal to the left. Multi Spurious Search - Searches for multiple spurious signals. Spur Sensibility - Sets the spurious sensibility number. Learn more.
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How to create Maximum and Minimum Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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You can search for the maximum or minimum measured value on the trace and move a marker to that point.
Search for maximum (Max Search) |
Move active marker to point on trace where measured value is greatest. |
Search for minimum (Min Search) |
Move active marker to point on trace where measured value is lowest. |
Note: When the data format is in Smith chart or polar format, execute the search only for the main response value.
How to create Peak Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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A peak is a measurement point whose value is greater or smaller than the adjoining measurement points on its right and left sides. Peaks are classified into the following two types depending on the difference in magnitude from the measurement points on either side of it.
You define what the analyzer considers a "peak" by selecting the following two peak criteria settings:
Threshold - Minimum amplitude (dB). To be considered valid, the peak must be above the threshold level. The valley on either side can be below the threshold level.
Excursion - The vertical distance (dB) between the peak and the valleys on both sides. To be considered a peak, data values must "fall off" from the peak on both sides by the excursion value.
Definition: |
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Positive |
A peak whose measured value is greater than those of the measurement points on either side of it. Detect positive peaks which are larger than Threshold. |
Negative |
A peak whose measured value is smaller than those of the measurement points on either side of it. Detect negative peaks which are smaller than Threshold. |
Both |
A peak whose measured value is smaller and greater than those of the measurement points on either side of it. Threshold value is not used when polarity is set to both. |
The peak excursion value is the smaller of the differences in measured values from the adjoining peaks of the opposite polarity.
The following 3 methods are available for executing the peak search:
Next Peak |
Moves the marker to the maximum peak when peak polarity is Positive or Both. Moves the marker to the minimum peak when peak polarity is Negative. |
Peak Left |
Executes the search from current marker position to the smaller stimulus values and moves the marker to first peak encountered. |
Peak Right |
Executes the search from current marker position to the larger stimulus values and moves the marker to first peak encountered. |
Note: Peak right, peak left and next peak may not be tracked. If these searches are selected and then tracking is turned on, the peak tracking is enabled.
When the data format is in Smith chart or polar format, execute the search for the main response value of the two marker response values.
Changing the settings of peak excursion value or peak polarity executes new search for multiple peak.
Example:
Threshold Setting: -10dB
Excursion Setting: 1dB
Scale = 1 dB / Division
Mouse over the graphic to find a valid peak.
Peak A = Valid Peak (Above Threshold and Excursion Settings)
Peak B = Invalid Peak (Below Excursion Setting)
Peak C = Invalid Peak (Below Threshold Setting)
How to create Multi Peak Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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The multi peak search function enables you to display markers on multiple peaks on traces. Depending on the number of detected peaks, markers 1 through 15 are displayed from the start frequency. The reference marker is not affected.
Multiple peak search has threshold, excursion and polarity as user defined values. This search may have tracking enabled.
When the multiple peak search is executed, previous markers search and tracking are disabled and the settings for the multiple peak search are used.
Note: Do not use individual marker settings or marker domain.
Put markers on each valid peak, using up to 15 markers.
How to create Target Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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The target search is a function that searches for a target that matches the pre-defined target value and transition types (positive, negative or both positive and negative) and then moves the marker to that target.
A target is a point that has a specific measured value on the trace. Targets can be divided into the 3 groups shown below depending on their transition type.
Transition Type: |
Function: |
Positive |
The target value is larger than the measured value immediately preceding it. |
Negative |
The target value is smaller than the measured value immediately preceding it. |
Both |
The conditions for either Positive or Negative transition are satisfied. |
The following 3 methods are available for executing the target search:
Target Left |
Executes the search from the current marker position to the smaller stimulus values and moves the marker to first target encountered. |
Target Right |
Executes the search from the current marker position to the larger stimulus values and moves the marker to first target encountered. |
Multi Target |
Executes the search for targets that are of the multi-target value and multi target transition value. See Multi Target Search. |
Note: Target right and target left cannot have tracking enabled. If target left or target right is the selected search and then tracking is enabled, target tracking is enabled.
When the data format is in Smith chart or polar format, execute the search for the main response value of the 2 marker response values.
Changing the settings of target value or transition type executes new search for multiple target.
The marker moves to the first occurrence of the Target value to the right of its current position. Subsequent presses of the Target Search softkey cause the marker to move to the next value to the right that meets the Target value. When the marker reaches the upper end of the stimulus range, it will "wrap around" and continue the search from the lower end of the stimulus range (left side of the window).
If Discrete Marker is OFF, the marker locates the interpolated data point that equals the target value.
If Discrete Marker is ON and there are two data points on either side of the target value, the marker locates the data point closest to the Target value
How to create Peak Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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The multi target search is a function that searches for targets that match to pre-defined target value and transition types (positive, negative or both of positive and negative) and displays markers on the targets being searched.
Depending on the number of detected targets, markers 1 through 15 are displayed from the start frequency. The reference marker is not affected.
When the multi target search is executed, search and tracking settings for markers 1 through 15 are ignored and the settings for the multi target search are used.
Note: Put markers on each found target value, using up to fifteen markers. Reference marker is not affected. Do not use individual marker settings or marker domain. Search range is applied.
Multiple target search has target and transition types as user defined values. This search may have tracking enabled. When this search is executing, previous marker searches are disabled.
Bandwidth and notch search behavior depends on whether the preference called Marker: Use single marker for marker search is set or not. When set, only one marker is used for a marker search. Sub markers are displayed and used for Bandwidth and Notch searches. When cleared, multiple markers are used for a marker search. The default is cleared.
How to create Bandwidth and Notch Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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The bandwidth search is a function for determining the bandwidth of the trace, center frequency, cut-off points (on the higher frequency and the lower frequency sides), Q and insertion loss based on the position of the active marker or peak marker. The definitions of the parameters determined through the bandwidth search are shown in below.
The notch search function is used to obtain the bandwidth, center frequency, cutoff points (high-frequency side and low-frequency side), Q and insertion loss of a trace based on the active marker or peak marker position. The notch search function starts from the left side of the active marker position and ends when points that meet the conditions are found.
The figure and the table below shows the definition of parameters obtained by notch search function. The notch value in figure below must be specified by the user.
The following values are displayed for Bandwidth and Notch Search:
Bandwidth/Notch Parameter: |
Definition: |
Bandwidth (BW) |
The difference in frequency between the higher frequency cut-off and lower frequency cut-off points (High - Low). |
Center frequency (cent) |
Frequency at the middle point between the lower frequency cut-off and higher frequency cut-off points. (High + Low)/2. |
Lower frequency cut-off point (Low) |
Lower frequency of 2 measurement points, both separated by the defined bandwidth / notch value from the active marker position. |
Higher frequency cut-off point (High) |
Higher frequency of 2 measurement points, both separated by the defined bandwidth / notch value from the active marker position. |
Q |
Ratio of Center Frequency to Bandwidth (Center Frequency / Bandwidth). |
Insertion loss (loss) |
The measured value of the position of the center frequency at the time the bandwidth/notch search is executed. |
Bandwidth / Notch Search can be used ONLY with Log Mag display format.
To use Bandwidth Search on a peak or valley other than the maximum or minimum values, change the Search Domain.
Uses the active marker to find the specified gain Compression Level.
Note: Valid ONLY for S21 (Gain) measurements with a Power Sweep.
How to create Compresssion Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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Linear gain is defined as the Y-axis value (gain) of the first data point of the Search Domain (Full Span by default).
Marker > N - X-axis value and Y-axis value.
Comp Pin - Input power (marker X-axis value).
Comp Pout - Output power (Pin + gain).
Comp Level - Compression level found.
When Discrete is OFF (default setting), the marker finds the exact specified compression, interpolated between the two closest data points and calculates the Comp Pin and Comp Pout value for that point.
The marker can move from one actual measurement point to another. Because it is interpolated, it can also move in the space between measurement points.
When Discrete is ON (not interpolated), the marker resides on the closest data point to the requested compression level.
A marker moves only between actual measurement points. When a specific marker stimulus value is specified as a numerical value, the marker is placed at the measurement point closest to the specified value. A marker that is placed between interpolated points with the discrete mode off automatically moves to the nearest measurement point when the discrete mode is turned on.
Comp. Not Found - Displayed when the requested compression level is not found.
Compression measurements based on the Pout vs Pin curves are common in the satellite test industry. In the case of Travelling Wave Tube (TWT) amplifiers, PSAT markers identify the normal operating point near saturation, and the amplifiers are operated with the power slightly backed-off approximately 0.03 to 0.1 dB. For TWT amplifiers, the saturation curve always "folds over" and produces a maximum power out.
For Solid State Power Amplifiers (SSPA), the saturation is not as well defined. A common reference is the Normal Operating Point, which is a power backed-off by 8 to 10 dB from the maximum power. In this case, the normal operating point marker replaces the Psat with the PNOP values. Also, because the backoff is important, the backoff output and input powers are displayed (PBO Out), (PBO in) as well as gain at back off (PBO Gain).
If the Marker: Use single marker for marker search preference is cleared, this search uses Markers 1, 2, and 3 to quickly identify output power saturation parameters of an amplifier. If the Marker: Use single marker for marker search preference is set, then only one marker is used for the search and 2 notational markers are displayed. The notational markers may not be moved. These markers are for display purposes only.
Back-off is a point at which the output power is sufficiently lower than the saturated output power so that the device under test behaves in a more linear fashion.
Note: Valid ONLY for Power IN vs Power OUT measurements.
How to make Power IN (X-axis) vs Power OUT (Y-axis) measurement |
Using Hardkey/SoftTab/Softkey |
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How to create PSAT Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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This setting uses three markers to calculate and display 10 values.
The three markers:
Marker 1: Linear gain; the first data point in the sweep.
Marker 2: Specified output power Back-off from max power.
Marker 3: Max Power output; usually the last data point.
The 9 displayed values:
Param |
Description |
Calculated from... |
PSat Out |
Output power at the saturation point. |
Marker 2 Y-axis value |
PSat In |
Input power at the saturation point. |
Marker 2 X-axis value |
Gain Sat |
Gain at the saturation point. |
Psat Out - Psat In |
Comp Sat |
Compression at the saturation point. |
Gain Sat - Gain Linear |
PMax Out |
Maximum output power. |
Marker 3 Y-axis value |
PMax In |
Input power at the maximum output power. |
Marker 3 X-axis value |
Gain Max |
Gain at the maximum output power. |
PMax Out - PMax In |
Comp Max |
Compression at the maximum output power. |
Gain Max - Gain Linear |
Gain Linear |
Linear gain at the first data point. |
Marker 1 - Y-axis value MINUS X-axis value |
Comp. Not Found is displayed when the requested Back-off point is not found.
When Discrete marker is NOT selected (the default setting), the three markers find an interpolated value between the two closest data points.
When Discrete marker is selected (NOT interpolated), the three markers reside on the closest data points.
If the Marker: Use single marker for marker search preference is cleared, this search uses Markers 1, 2, 3, and 4 to quickly identify Normal Operating Point parameters of an amplifier. If the Marker: Use single marker for marker search preference is set, then only one marker is used for the search and 2 notational markers are displayed. The notational markers may not be moved. These markers are for display purposes only.
Back-off is a point at which the output power is sufficiently lower than the saturated output power so that the device under test behaves in a more linear fashion.
The power normal operating point is the output power where the input is offset from the back-off input power by the Pin Offset.
Note: Valid ONLY for Power IN vs Power OUT measurements.
See Power Saturation to learn how to make a Power IN (X-axis) vs Power OUT (Y-axis) measurement.
How to create PNOP Search |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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This setting uses four markers to calculate and display 12 values.
The four markers:
Marker 1: Linear gain; the first data point in the sweep.
Marker 2: Max Output Power MINUS the specified Output (Y-axis ) Back-off value in dB.
Marker 3: Max Output Power; usually the last data point in the sweep.
Marker 4: X-axis value of Back-off (Marker 2) plus the Pin Offset (X-axis) value in dB.
The 11 displayed values:
Param |
Description |
Calculated from... |
Pnop Out |
Output power at the power normal operating point. |
Marker 4 Y-axis value |
Pnop In |
Input power at the power normal operating point. |
Marker 4 X-axis value |
Pnop Gain |
Gain at the power normal operating point. |
Pnop Out - Pnop In |
Pnop Comp |
Compression at the power normal operating point. |
Pnop Gain - Linear Gain* |
PMax Out |
Maximum output power. |
Marker 3 Y-axis value |
PMax In |
Input power at the maximum output power. |
Marker 3 X-axis value |
Gain Max |
Gain at the maximum output power. |
PMax Out - PMax In |
Comp Max |
Compression at the maximum output power. |
Gain Max - Linear Gain* |
PBO Out |
Output power at the back-off point. |
Marker 2 Y-axis |
PBO In |
Input power at the back-off point. |
Marker 2 X-axis |
PBO Gain |
Gain at the back-off point. |
PBO Out - PBO In |
*Linear Gain (not shown): Marker 1 - Y-axis value MINUS X-axis value
PNOP Not Found is displayed when the requested back-off level is not found.
When Discrete marker is NOT selected (the default setting), the four markers each find an interpolated value between the two closest data points.
When Discrete marker is selected (NOT interpolated), the four markers each reside on the closest data point.
Search domain settings restrict the stimulus values (X-axis for rectangular format) to a specified span. Set the User Start and User Stop stimulus settings of these User spans. If User Start is greater than User Stop, the marker will not move. Learn how to set Search Range.
The default domain of each new marker is "full span".
There are 16 user-defined domains for every channel.
The user-defined domains can overlap.
More than one marker can use a defined domain.
Search Domain settings are shared with Trace Statistics User Ranges
The graphic below shows examples of search domains.
A search range will be indicated with a pair of small, outlined triangles sitting on the X-axis. Although there can be multiple search ranges in use on various markers, only the current-selected search range for the active marker is displayed. This rule prevents the possibility of the X-axis being cluttered with many search range triangles. This rule applies even when there are multiple traces in a window.
Only one search range will be displayed on a grid at any time. The displayed search range will correspond to the active trace and active marker. The color of the range indicators will match that of the active trace.
Range indicators will appear automatically when appropriate and cannot be disabled. The mouse or touchscreen can't be used to “click-and-drag” the position of the range indicators which will alter the search range definition.
The zoomed frequency range becomes the User 16 Search Domain span.
A marker is created if not already present on the trace. If markers are already present on the trace, the lowest marker is moved to the found value.
Left-click the mouse or use a finger, then drag across a portion of a trace.
Release the mouse or lift the finger.
Select Search Within.
Then choose from the following:
Max - A marker moves to the HIGHEST value within the zoomed range.
Min - A marker moves to the LOWEST value within the zoomed range.
Target - A marker moves to the first value within the zoomed range that is currently set in the Marker Search 'Target' setting. The same Discrete Marker rules apply as those for the standard Target Marker Search.
Marker Functions - Change Instrument Settings
The following settings change the relevant analyzer settings to the position of the active maker.
How to change Instrument settings using markers |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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Note: Marker Functions do not work with channels that are in CW or Segment Sweep mode. Marker =>Start Sets the start sweep setting to the value of the active marker. Marker =>Stop Sets the stop sweep setting to the value of the active marker. Marker =>Center Sets the center of the sweep to the value of the active marker. Marker =>Ref Level Sets the screen reference level to the value of the active marker. Marker =>Delay The phase slope at the active marker stimulus position is used to adjust the line length to the receiver input. This effectively flattens the phase trace around the active marker. Additional Electrical Delay adjustments are required on devices without constant group delay over the measured frequency span. You can use this to measure the electrical length or deviation from linear phase. This feature adds phase delay to a variation in phase versus frequency; therefore, it is only applicable for ratioed measurements. See Measurement Parameters. Marker =>Span Sets the sweep span to the span that is defined by the delta marker and the marker that it references. Unavailable if there is no delta marker. Marker =>CW Freq Sets the CW frequency to the frequency of the active marker. NOT available when the channel is in CW or Power Sweep. Use this function to first set the CW Frequency to a value that is known to be within the current calibrated range, THEN set Sweep Type to Power or CW. |
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Note: Some Marker Functions do not work with channels that are in certain Sweep Types.
Marker Function |
Sweep Type |
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Lin/Log Freq. |
Segment |
Power |
CW Time |
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Start, Stop, Center |
S |
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S |
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Span |
S |
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S |
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Ref Level |
S |
S |
S |
S |
Delay |
S |
S |
S |
S |
CW Freq. |
S |
S |
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S: Available in only Standard Class
The following markers are specific to Spectrum Analyzer measurement channels.
Spectrum Analysis markers |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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Band Power – Provides a readout of the total power obtained by integrating over the specified frequency range defined by Band Span, centered at the marker position.
The Average detector type makes the display more consistent with Band Power markers. With this detector type the marker readouts and the estimated power values or delta from the display have a good match. Many legacy spectrum analyzers need to set the detector type to average to do band power measurements. analyzer -SA does not need to select the average detector to compute the right band power measurements, it’s only useful to check the values between marker readouts and display estimates.
Band Density – Selections are Off, Noise, Power, Tone, NPR, or ACPR
Noise – Provides a readout of the noise-power density (dBm/Hz) at the marker position, obtained by integrating over the specified frequency range defined by Band Span, and normalizing to the same frequency range.
Power – Provides a readout of the power density (dBm/Hz) at the marker position, obtained by integrating over the specified frequency range defined by Band Span, and normalizing to the bandwidth defined by Equivalent Span.
Tone – Provides a readout of the power density (dBm/tone) at the marker position, obtained by integrating over the specified frequency range defined by Band Span, and normalizing to the bandwidth defined by Density BW and Equivalent Span. When Density BW is set to the tone spacing of the multitone signal, and Equivalent Span is the same as Band Span, Tone Density gives dBm/tone. This feature is useful for measuring the power density of the signals inside and outside the notch for Noise Power Ratio (NPR) measurements. For example, for measuring a 10 MHz notch with -50 dBm band power and 100 kHz tone spacing (number of tones = 10 MHz/100 kHz = 100), setting the Band Span and Equivalent Span to 10 MHz and the Density BW to 100 kHz, the result shows that each tone would be -70 dBm (-50 dBm - 10*Log10[100]). Tone band density can also be used to measure Adjacent-Channel-Power-Ratio (ACPR).
NPR – Uses the same calculation method as Tone, but provides a simpler readout consisting only of marker frequency and NPR value.
ACPR - Uses the same calculation method as Tone, but provides a simpler readout consisting only of marker frequency and ACPR value.
Note: The band-density markers can be set to Delta ON mode which is very useful for NPR and ACPR, which are defined as distortion power in a specified band divided by in-band power. For these ratioed measurements, the reference marker can be set to Tone Band Density, with a Band Span that covers the in-channel bandwidth (for NPR, see Equivalent Span below to account for the reduction in channel power due to the notch). The ACPR and NPR delta markers will have a Band Span defined by the adjacent-channel bandwidth or the notch bandwidth respectively.
Band Span – Sets the frequency range over which Band Power and Band Density measurements are calculated.
Equivalent Span – Sets the frequency range over which Power and Tone Band Density measurements are normalized. This feature is useful for calculating the power density of a wideband signal with a notch (or multiple notches), where the power in the notch(es) is significant and cannot be ignored. Adjusting the Equivalent Span is essential for calculating the correct tone powers of a noise-power-ratio (NPR) signal. For example, for a 100 MHz signal with a 10 MHz notch, the Equivalent Span would be 90 MHz. For measuring the power in the notch, the Equivalent Span and Band Span are the same (10 MHz in this example).
Density BW – Sets the frequency range over which Tone Band Density measurements are calculated.
Occupied BW – Enables/disables the frequency range that contains a defined percentage of the overall band power as specified by OBW Percent.
OBW Percent – Sets the percentage used to calculate Occupied BW.
NPR Measurement Example
Noise-Power-Ratio (NPR) measurements are displayed using a fixed reference marker (set to Tone Band Density) that calculates the power density of the main signal, and a delta marker (set to NPR Band Density) that calculates the power density of the distortion signals within the notch. The Equivalent Span of the main signal is set to the Band Span minus the notch bandwidth – for example, for a 100 MHz wide NPR signal with a 10 MHz notch, the Equivalent Span would be 100 MHz - 10 MHz = 90 MHz. For the notch in this same example, the Equivalent Span would be set to 10 MHz.
Calculations for Band Power and Density Markers
All the band-power and band-density markers are computed from Discrete Fourier Transform (DFT) data, before the data is processed into the display points shown on the screen as traces. As a result, these markers are not affected by the number of display points, or by the detection algorithm used (average, sample, peak, etc.). There are two ways to access the DFT data if a user wishes to do their own calculations of power, or to perform other mathematical processing:
Set the Detector Type to Bypass, which works if the number of DFT points is below 100,003 (the trace-size limit).
Use the SA Data feature (accessed via the Advanced tab of the SA Setup dialog). In general, the display points do not provide an accurate representation of band-power or band-density values.
There are many more DFT data points than display points, and the data reduction performed by the detection algorithm causes band-power accuracy to degrade at signal discontinuities, where there is a wide change in power values. In addition, when using peak detection, the algorithm takes the largest power value of the DFT data-set to produce a single display point, so the displayed value does not represent the average power of the band covered for that point. For these reasons, it is impossible to compute an accurate band-power or band-density value from display points using the peak detector. This is why the SA band-power and band-density markers are computed from the underlying DFT data.
The marker display dialog allows you to change how markers and the associated readout is displayed on the analyzer screen. Several marker display features also apply to Statistics display.
How to change Marker Display settings |
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Using Hardkey/SoftTab/Softkey |
Using a mouse |
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The following settings apply to readouts of ALL currently-displayed marker, bandwidth, and trace statistics. These settings revert to their defaults on Preset but ARE stored with Instrument State and User Preset. Marker ReadoutChecked - Shows readout information. Cleared - Shows NO readout information. Large ReadoutChecked - Shows the marker readout in large font size for easy reading. However, all readout lines may not be visible. Cleared - Shows the marker readout in normal font size. Active Trace OnlyChecked - Shows the marker readout for the active trace only. Cleared - Shows all marker readouts. Readouts Per TraceChoose the quantity of marker readouts to show in the window for each trace. Choose to display up to 16 readouts per trace, up to 20 readouts per window. When more markers are present than the specified quantity of readouts, the marker numbers for which readouts are displayed can change depending on the marker number that is active. Readouts Per Trace can be set independently for each window. SymbolChoose from the following marker symbols.
Line symbols are NOT used on Smith or Polar display formats. Symbols can be set independently for each window. Symbols Above TraceCleared - ONLY the active marker is displayed above the trace. Inactive markers are displayed below the trace. Checked - ALL marker symbols are displayed above the trace. The active marker is always filled solid. Decimal PlacesChoose the marker readout resolution to display. These values also apply to the readouts that are displayed in the marker table. Decimal Places can be set independently for each window. Stimulus (X-axis) - Choose from 2 to 6 places after the decimal point. Default is 3. Response (Y-axis) - choose from 1 to 4 places after the decimal point. Default is 2. Readout PositionChoose where to place the marker readouts. Marker readouts are right-justified on the specified X-axis and Y-axis position. The default position (10.0, 10.0) is the upper-right corner of the grid. Position (1.0,1.0) is the lower-left corner. Readout position can also be set independently for each window. Note: Readout Position can also be changed using a mouse by left-clicking on the top readout and dragging to the new position. Marker Colors Starts the Display Colors dialog with only the marker colors available. Learn more. |
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You can display a table that provides a summary of marker data for the active trace. The marker data is displayed in the specified format for each marker.
How to view the Marker Table |
Using Hardkey/SoftTab/Softkey |
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