The spec Command

The spec command will create a new plot consisting of the Fourier transforms of the vectors given on the command line.

spec start_freq stop_freq step_freq vector [...]

This is based on a SPICE3 spec command by Anthony Parker of Macquarie University in Sydney Australia, which is available as part of the patch set from
http://www.elec.mq.edu.au/cnerf/spice/spice.html.

The command will create a new plot consisting of the Fourier transforms of the vectors given on the command line. Each vector given should be a transient analysis result, i.e., have time as a scale, and each should have the same time scale. The Fourier transform will be computed using the frequency parameters given, and will use a window function as given with the specwindow variable.

The following variables control operation of the spec command. Each can be set with the set command, or equivalently from the Fourier tab of the Commands tool.

spectrace
This enables messages to be printed during Fourier analysis with the spec command, for debugging purposes.

specwindow
This variable is set to one of the following strings, which will determine the type of windowing used for the Fourier transform in the spec command. If not set, the default is hanning.

bartlet	Bartlet (triangle) window
blackman	Blackman order 2 window
cosine	Hanning (cosine) window
gaussian	Gaussian window
hamming	Hamming window
hanning	Hanning (cosine) window
none	No windowing
rectangular	Rectangular window
triangle	Bartlet (triangle) window

specwindoworder
This can be set to an integer in the range 2-8. This sets the order when the gaussian window is used in the spec command. If not set, order 2 is used.