:FUNCtion:PARameters:FFT:DISPlay

FFT Parameters Commands

Specifies the output format of an FFT operator (:FUNCtion:FOPerator) to be one of the following types:

  • DBM — dBm
  • DBV — dBV
  • DBMV — dBmV
  • DB — dB (Normalized)
  • DBPHz — dBm/Hz (NSD). For Noise Spectral Density (NSD) measurements where a constant will be subtracted from the FFT function.
  • MAGNitude — Linear Magnitude
  • PHASe — Phase
  • UPHase — Unwrapped Phase
  • GDELay — Group Delay

When phase (PHASe), unwrapped phase (UPHase), or group delay (GDELay) is selected, use the :FUNCtion:PARameters:FFT:PREFerence command to set the FFT phase reference to left, center, or manual. If you select manual, use the :FUNCtion:PARameters:FFT:PREFerence:TORigin command to enter the FFT origin in seconds.

If the input is an optical signal and dBV (Electrical) is selected, use the :FUNCtion:PARameters:FFT:TFACtor command to enter the voltage conversion factor (V/W).

To ensure that enough data is available to construct a useful FFT, set Infiniium's timebase scale equal to the waveform's period. This will display 10 waveform cycles. For example, for a 5 GHz (200 ps) reference clock, enter a scale setting of 200 ps/division.

Content Windows

The FFT waveform is automatically displayed in the appropriate type of content window, which is listed in the following table and displayed in the above picture. For the DBHertz, DHERtz, and SHERtz arguments, you can optionally move the waveform to an additional content window of the same type using the :FUNCtion:CWINdow command. For example,

:FUNCtion1:FOPerator FFT  // Create an FFT function.
:FUNCtion1:OPERand1 CHAN1_1  // Assign input waveform.
:FUNCtion1:PARameters:FFT:DISPlay GDELay  // Select output waveform type. Waveform is automatically assigned to content window GDELay1. 
:FUNCtion1:CWINdow GDELay2  // Display content window GDELay2 (Delay 2) and re-assign output waveform from GDELay1 to GDELay2.
Command Arguments and Resulting Waveform Content Window
Argument Equivalent
GUI Selection		 Displayed
Content Window		 Number of
Available Windows		 Scale Units
Via
Front Panel		 Programmatically
DBM dBm Decibels (Hz) 1 4 Y-Axis: dBm (logarithmic scale)
X-Axis: Hertz
DBV dBV Y-Axis: dBV (logarithmic scale)
X-Axis: Hertz
DBMV dBmV Y-Axis: dBmV (logarithmic scale)
X-Axis: Hertz
DB dB (Normalized) Y-Axis: dB (logarithmic scale)
X-Axis: Hertz
DBPHz dBm/Hz (NSD) Y-Axis: dBm/Hz (logarithmic scale)
X-Axis: Hertz
MAGNitude Linear Magnitude Waveform 1 4 Y-Axis: Volts or Watts (linear scale)
X-Axis: Hertz
PHASe Phase Degrees (Hz) 1 4 Y-Axis: phase (°)
X-Axis: Hertz
UPHASe Unwrapped Phase
GDELay Group Delay Seconds (Hz) 1 4 Y-Axis: seconds
X-Axis: Hertz

Example Command Sequence

:FUNCtion2:FOPerator FFT
:FUNCtion2:PARameters:FFT:DISPlay DBM
:FUNCtion2:PARameters:FFT:WINDow HANNing
:FUNCtion2:COLor TCOLor4
:FUNCtion2:DISPlay ON
*OPC?
…  //  Your code to synchronize execution timing.