opus-banner
previous | back | home | next
CACD Group
updated 2006.5.22
Author: Mike Smith

spec: generate a Fourier transform vector

General Form spec start_frequency stop_frequency frequency_step vector Calculates a new vector containing the Fourier transform of the input vector. This vector should be the output of a transient analysis. This command takes note of the following shell variables which can be set using the set command:
Variable Type Description
specwindow String Specifies the windowing function. Possible values are:
none
hanning or cosine
rectangular
hamming
triangle or bartlet
blackman
gaussian
If this variable is not defined, the hanning window is used.
specwindoworder Number Specifies the window order for the gaussian window only.
Note that the time axis of the input vector should be linearised first by using the linearize command because Spice does not produce a linear time axis for transient analyses. After using the spec command, the spectrum can be displayed by plotting the magnitude of the resultant vector. For instance, after a transient analysis resulting in transient vector v(1), the spectrum can be plotted with the following commands: linearize 1us
spec 10Hz 100kHz 5kHz v(1)
plot mag(v(1))
previous | back | home | next