Language Reference

TWNDOW

Example

170

OUTPUT 723;"CENTERWL 750NM;"

Set measurement range .

 

180

OUTPUT 723;"SP 0;ST 50MS;"

 

 

190

OUTPUT 723;"TWNDOW TRC,FLATTOP;"

Store ￿at-top-window algorithm

 

 

 

in trace C.

 

200

OUTPUT 723;"CLRW TRB;BLANK TRA;"

Measure with trace B . Blank

 

 

 

trace A.

 

210

OUTPUT 723;"SNGLS;TS;"

Sweep once .

 

220

OUTPUT 723;"FFT TRA,TRB,TRC;"

Perform fast-F ourier trans-

 

 

 

form on trace B and store the

 

 

 

results in trace A.

 

230

OUTPUT 723;"BLANK TRB;VIEW TRA;"

Blank trace B . Store and view

 

 

 

trace A.

Description The TWNDOW function formats a trace array with real values for use with the fast Fourier transform function (FFT). Execute TWNDOW on a trace that

has the same length as the trace you wish to transform with FFT.

The window function weights the contents of a trace array according to four algorithms, called trace windows: uniform, Hanning, Hamming, or ￿at-top. Three of the ￿lters are shown below as graphs in the time domain. The TWNDOW command multiplies a trace array with one of these windows. If the prede￿ned windows do not meet your measurement needs, use the TRA, TRB, TRC commands to build your own window function.

Hanning, Flat top, and Uniform Trace Window Shapes

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