Function:window - Agilent Technologies InfiniiVision 5000 Series Programmer's Manual

5
Commands by Subsystem

:FUNCtion:WINDow

Command Syntax
:FUNCtion:WINDow <window>
<window> ::= {RECTangular | HANNing | FLATtop | BHARris}
The :FUNCtion:WINDow command allows the selection of four different
windowing transforms or operations for the FFT (Fast Fourier Transform)
function.
The FFT operation assumes that the time record repeats. Unless an
integral number of sampled waveform cycles exist in the record, a
discontinuity is created between the end of one record and the beginning
of the next. This discontinuity introduces additional frequency components
about the peaks into the spectrum. This is referred to as leakage. To
minimize leakage, windows that approach zero smoothly at the start and
end of the record are employed as filters to the FFTs. Each window is
useful for certain classes of input signals.
• RECTangular — useful for transient signals, and signals where there are
• HANNing — useful for frequency resolution and general purpose use. It
• FLATtop — best for making accurate amplitude measurements of
• BHARris (Blackman- Harris) — reduces time resolution compared to the
Query Syntax
:FUNCtion:WINDow?
The :FUNCtion:WINDow? query returns the value of the window selected
for the FFT function.
Return Format
<window><NL>
<window> ::= {RECT | HANN | FLAT | BHAR}
See Also •
244
(see page 658)
an integral number of cycles in the time record.
is good for resolving two frequencies that are close together, or for
making frequency measurements. This is the default window.
frequency peaks.
rectangular window, but it improves the capacity to detect smaller
impulses due to lower secondary lobes (provides minimal spectral
leakage).
"Introduction to :FUNCtion Commands"
Agilent InfiniiVision 5000 Series Oscilloscopes Programmer's Guide
on page 230