How to couple noise to a voltage signal?!
I need to simulate a radar system in which the VCO is fed by a ramp voltage. I simulated with an ideal ramp signal, now I want to add noise to my ramp so it wouldn't appear smooth on its edge, but I'd want it look uneven. I put a voltage noise source in series with my ramp source but it didn't work, the only thing it gives out is just noise. What I want to see is a ramp voltage coupled with noise. Could anyone help me please?
Thanks,
I would think your series noise source would work. What are you using to simulate? You could try putting the noise source in parallel with the ramp, through summing resistors,
Since the noise voltage is so small, it may not be visible on the ramp signal but if you do a Phase Noise simulation, the effect of this noise contributor will absolutely be seen on the Phase Noise side-bands.
You don't have to use a ramp signal, a simple DC voltage applied to the VCO with a series connected noise signal source will contribute into the signal performance.
Thank you all, the problem is solved. I'm running Envelope simulation and it seems I needed to care about the noise bandwidth when I was setting voltage noise source. The problem was that when I give 1mV as the noise voltage what I get at the output is something in the range of 500 V! I think it was because of the bandwidth which I didn't consider. Because the dimension for the noise voltage is not Volts but Volts/square root Hz. And because the output noise was very big, it didn't let the main signal show up!
Thanks