Keysight N9923-90001 User’s Guide65Time Domain – Option 010Time Domain (Transform) SettingsStimulus (Mode)— There are three variations on how the Time Domain transform algorithm isapplied to the frequency domain measurement. Each method has a uniqueapplication.— Lowpass Impulse - Highest resolution. Most useful for seeing smallresponses in devices that pass low frequencies, such as cables.— Lowpass Step - Easiest to identify inductive and capacitive discontinuitiesin devices that pass low frequencies such as cables.In both Lowpass modes, frequencies down to DC and negative frequencies areextrapolated. Therefore, when either Lowpass mode is selected, Set Freq.LowPass is automatically applied to adjust the start frequency. Learn more aboutSet Frequency Lowpass below.When the Start Frequency or resolution is changed AFTER selecting a Lowpassmode, then Stimulus mode is set to Band Pass and Transform is disabled.— Band pass- Easiest method - can be used with any frequency sweep. Mostuseful for measuring band limited devices such as filters and DC blockedcables. This mode does NOT show capacitive and inductive reactance. Forthe same frequency span and number of points, band pass mode has twicethe impulse width, which hides closely spaced responses degrading theresponse resolution.Set Frequency LowpassUSE ONLY IN LOW PASS MODES. The Low Pa ss Start frequency is adjusted sothat the Low Pass Stop frequency is at harmonics of the Low Pass Startfrequency. Start frequency is computed by the following formula:Low PassStart Frequency = Stop Frequency / Number of points.Start/Stop TimeThe following settings adjust the d isplay resolution, allowing you to zoom INor OUT on a response. When the start or stop time is updated, they may beautomatically adjusted to limit the display to one alias-free response on eitherside of zero time.How to set Start and Stop time— Press Measure Setup 4— Then Transform— Then Transform Start StopThis setting is made automatically when either Lowpass mode is selected.
