Keysight Technologies FieldFox A Series, User Manual

Page: 113 / 756

Keysight N9927-90001 User’s Guide 113
Time Domain – Option 010
Time Domain (Transform) Settings
Stimulus (Mode)
— There are three variations on how the Time Domain transform algorithm is
applied to the frequency domain measurement. Each method has a unique
application.
— Lowpass Impulse - Highest resolution. Most useful for seeing small
responses in devices that pass low frequencies, such as cables.
— Lowpass Step - Easiest to identify inductive and capacitive discontinuities
in devices that pass low frequencies such as cables.
In both Lowpass modes, frequencies down to DC and negative frequencies are
extrapolated. Therefore, when either Lowpass mode is selected, Set Freq.Low
Pass is automatically applied to adjust the start frequency. Learn more about
Set Frequency Lowpass below.
When the Start Frequency or resolution is changed AFTER selecting a Lowpass
mode, then Stimulus mode is set to Band Pass and Transform is disabled.
— Bandpass Impulse - Easiest method - can be used with any frequency
sweep. Most useful for measuring band limited devices such as filters and
DC blocked cables. This mode does NOT show capacitive and inductive
reactance. For the same frequency span and number of points, band pass
mode has twice the impulse width, which hides closely spaced responses
degrading the response resolution.
Set Frequency Lowpass
USE ONLY IN LOW PASS MODES. The Low Pass Start frequency is adjusted so
that the Low Pass Stop frequency is at harmonics of the Low Pass Start
frequency. Start frequency is computed by the following formula:
Low Pass Start Frequency = Stop Frequency / Number of points.
Start/Stop Time
The following settings adjust the display resolution , allowing you to zoom IN
or OUT on a response. When the start or stop time is updated, they may be
automatically adjusted to limit the display to one alias-free response on either
side of zero time.
How to set Start and Stop time
— Press Measure Setup 4
— Then Transform
— Then Transform Start Stop
This setting is made automatically when either Lowpass mode is selected.