How can I create a sine wave voltage source with a time-varying amplitude?

Hi Paulo,

This is relatively straight forward, have a look at the attached file. In it there is a DC source which is controlling the frequency of the sine source, by generating "theta" with the resetting integral. Theta is used by the sine block to generate a unity sine wave, this is then scaled by an offset sine wave to change the amplitude. Please look in the sources->voltage and look at the various sources that can be used to control the frequency an amplitude. Further you can generate a lookup table and drive it with the time source if you want to define an arbitrary waveform.

All in the attached file.

Is it possible to perform the calculations for amplitude and frequency by block C and then insert this data into the source?

Yes, have a look at the screen shot. simply drive the frequency component and amplitude component from c block outputs.

screenshot attached here.

Many thanks Albert for the help, I did the way you indicated and it worked perfectly !!. But I had a question, because besides changing the frequency and amplitude, I need the value of the initial angle (theta) of the sinusoidal source also to be variable, according to my need. Any suggestions on how to achieve this ?.

Again, thank you for your attention.