Can I change frequency of SIN voltage source using "alter" command?

[simpletk]

I have this netlist:

• first line is ignored
  V1 1 0 DC 0 AC 0 0 SIN(0 1 440 0 0 0)
  R1 1 0 1k2

I can change "AC 0" using alter command like this:

.control
alter V1 AC = 5
.endc

But is it possible to change VA and FREQ of SIN (...)? Something like:

.control
alter V1 VA = 5
alter V1 FREQ = 1234
.endc

ngspice-36

[Holger Vogt]

See manual, page 358.

[simpletk]

I tried this but amplitude is still 0.1 and I got error: Error: Only a single param - value pair supported.

• changing amplitude and freq of sine voltage source
  V1 1 0 DC 0 AC 1 0 SIN(0 0.1 192 0 0 0)
  R1 1 0 1k2
  .control
  set nobreak
  set nopage
  let newamp = 5
  let newfreq = 440
  alter @v1[sin] [0 $&newamp $&newfreq]
  set newamp = 6
  set newfreq = 1234
  .endc
  .tran 10u 10m 0
  .print tran v(1)
  .end

[Holger Vogt]

You may change either amplitude or frequency, but not both.

Edit: See next post.

[Holger Vogt]

My previous post was not correct.

The manual states the following in chapter 17.5.3:

For specifying a list of parameters as values, start it with ‘[’, followed by the values in
the list, and end with ‘]’. Be sure to place a space between each of the values and before
and after the ‘[’ and ‘]’.

So the line in your netlist should read
alter @v1[sin] [ 0 $&newamp $&newfreq ]
(see the additional spaces).

Then everything should be o.k.

[simpletk]

Thanks.

[dick freebird]

If you want to change amplitude in real time you could use a poly vcvs as an analog multiplier, from a secondary (multiplier) DC source that has a variable or time-varying value. Keep all of that ground-referred and do any level shifting, after you're happy with gain control.

I wonder if you could similarly use a multiplier as mixer, to alter applied frequency (might also need a co-scaled vcvs amplitude corrector?). I'd go with high side injection, low side might require more carrier cycles to stabilize?