>> Hello,
>>
>> For a transient simulation I want to specify the input signal as, e.g.,
>> a modulated Gaussian pulse. How can I do that? I'm using MacSpice.
>>
>> Background:
>> My aim is to simulate a lumped element circuit that models 'free space'
>> and then visualize wave propagation. So space is discretized into cubes,
>> each modelled e.g. by
formatting link
then 100*100*100
>> cells create the simulation volume. I've created the respective netlist
>> using a script which works nicely.
>>
>> So now I want to impress between two nodes an input signal that is a
>> modulated gaussian pulse and 'measure' the voltages across the circuit
>> in order to get the data for visualizing wave propagation.
>>
>> Any pointers welcome!
>>
>> Michael
>
>
> (?? previous attempt at a reply didn't show up...sorry if this ends up
> being a duplicate.)
>
> I assume by "modulated gaussian pulse" you mean something of the form
> A*sin(2*pi*f*t)*exp(-k*(t-t0)^2)). If that's the case, you can do it
> in SPICE3-based simulators with the B nonlinear dependent source
> component. Dunno if your MacSpice has that or not. It's easy to
> generate a variable that's proportional to time: the current through
> an inductor connected to a constant voltage source, or the voltage
> across a capacitor connected to a constant current source. Start the
> inductor current or capacitor voltage with zero initial condition.
>
> Cheers,
> Tom
Gosh, i was going to suggest a peice-wise-liner (PWL) approximation. It could be written with a script, and you could study the value of the coarse to fine adjustments of the script created waveform on the simulation result.