Tektronix RSA6100A Series, Help Manual

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General Signal Viewing > Time Overview Trace Tab
Detection
Trace Detection occurs when the trace is being decimated by the measurement. For example, if the
maximum number of trace points is 100,000, and the selected analysis region is 200,000 samples, the
measurement must decimate the 200,000 resulting trace points by 2 to prevent exceeding the 100,000 trace
point limit. Since only one value can be selected for each trace point, an algorithm must be used to select
(detect) the appropriate value to use.
The IQ samples in a data acquisition can be detected in a variety of ways. The number of IQ samples
available to each trace point varies with both analysis length and trace length. For example, with Spectrum
Length set to ‘Auto’ in the Analysis menu, the instrument analyzes just enough samples to produce one
IQ sample pair per trace point. In this case, the detection method chosen has very little effect, as the
+Peak, -Peak, Avg (VRMS) and Sample values are all equal. Changing the Spectrum Length causes the
available detection methods to differ in value because they have a larger set of samples for the various
detection methods to process.
The available detection methods (depending on the display) are:
+Peak – Each point on the trace is the result of detecting the positive peak value present in the set of
IQ samples available to that trace point.
-Peak – Each point on the trace is the result of detecting the negative peak value present in the set of
IQ samples available to that trace point.
+/-Peak – Selects the highest and lowest values of all the samples contained in two consecutive
acquisition intervals.
Avg (VRMS)
[Average V
RMS
] – Each point on the trace is the result of determining the RMS Voltage
value for all of the IQ samples available to the trace point. When displayed in either linear (Volts,
Watts) or Log (dB, dBm), the correct RMS value results. When the averaging function is applied to a
trace, the averaging is performed on the linear (Voltage) values, resulting in the correct average
for RMS values.
Sample – The result is calculated based on the fi rst sample available in the set of IQ samples for
each trace point.
Trace Processing
Traces can be processed to display in different ways. The Function setting controls trace processing.
Normal - Each new trace is displayed and then replaced by the next trace. Each data point contains a
single vertical value.
Average - Multiple traces are averaged together to generate the displayed trace. There is one vertical
value for each underlying frequency data point. Once the speci fi ed number of traces have been
acquired and averaged to generate the displayed trace, each new trace takes the place of the oldest
trace in the calculation. The
Number of Traces setting speci fi es how many traces averaged.
RSA6100A Series Real-Time Spectrum Analyzers Help
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