244 Keysight N9927-90001 User’s GuideIQ Analyzer (IQA) – Option 351 (CPU2 Only)I/Q Analyzer (IQA) Mode Settings— Res BW (Spectrum only) – Sets the resolution bandwidth of the FFTanalysis. Changing this value changes the FFT window size, analysislength, and the sweep time (data acquisition capture length). Thissoftkey is only available when IQA is set to Spectrum (Freq Domain).When the resolution bandwidth value is set to Auto (default) theFieldFox automatically sets the optimum resolution bandwidth value.(Default: 200 kHz, Minimum: 0.1 Hz, maximum: 3 MHz).— Analysis Length Sets the FFT analysis length that is the length of thecomplex I/Q data points (I/Q–pairs) vector that is used for spectrumanalysis, expressed in the number of samples. (Couplings: In Auto,this setting is directly coupled to the Res BW and to Span. Minimum:8, Maximum: 524,288. Where each FFT length "point" is equal to 1 Iand 1 Q point. So, 237 is equal to 237 I and 237 Q points).— FFT Window Sets the FFT filtering window (spectrum analysiswindow) shape for the I/Q data. Default: Flat TopThen select one of the following:There is a significant difference between resolution BW in FFTmeasurements and the resolution BW of a traditional "sweeping"spectrum analyzer (SA) measurement. The resolution BW in FFTmeasurements does not directly control the IF BW like a traditional SAswept measurement. Resolution bandwidth is directly related to theanalysis length (window) and or data acquisition capture length (sweeptime).FFT Window DescriptionUniform No windowingTriangular Barlett windowingHanning This is a Hann window, sometimes called Hanning or "raisedcosine".Hamming This window has lower side-lobe peaks than the Hann window,but has worse main-lobe flatness and poor side-lobe roll-off.Blackman This window is similar to the three-term Blackman-Harriswindow, but it has simpler fixed-form coefficients and betterside-lobe roll-off.Blackman Harris 3 This is the three-term Blackman-Harris window. This has theminimum side-lobe level for a three-term cosine window.Blackman Harris This is the four-term Blackman-Harris window. This has theminimum side-lobe level for a four-term cosine window with60 dB/decade roll-off.Gaussian Top This is a five-term cosine window that resembles a Gaussianwindow.
