Freq v Time Heatmap (Trace Data)
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The trace allows users to view patterns in frequency over time. The Freq v Time Heatmap trace is similar to the Time v Time Heatmap trace in that it provides a means of detecting deviations in a visual "heatmap" format; however, Freq v Time displays patterns in pulses across the frequency domain.
The vertical, or y-axis, is determined by the capture length of the signal. The length of each slice, in the horizontal dimension, is determined based on ENBW/RBW Resolution Band Width (RBW or ResBW): specifies the minimum frequency bandwith that two separate frequency spectra can be resolved and viewed seperately. For FFT (digital) based VSA's the process is equivalent to passing a time-domain signal through a bank of bandpass filters, whose center frequencies correspond to the frequencies of the FFT bins. For a traditional swept-tuned (non-digital) spectrum analyzer, the resolution bandwidth is the bandwidth of the IF filter which determines the selectivity., where ENBW is the Equivalent Noise Bandwidth (derived from the signal), and RBW is specified by the MeasSetup > Frequency vs. Time > ResBW parameter. This setting is specifically used for the Frequency vs. Time analysis feature, which has no effect on hardware acquisition, and is not the same as the MeasSetup>ResBW> parameter.
The Time v Time Heatmap and Freq v Time Heatmap traces process and draw a single acquisition worth of data. Every acquisition brings in new data that is drawn, and the old data is disposed.
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