[Qucs-help] Fwd: phase or frequency modulator

[Federico M. <fm...@fc...>]

I didn't mean to modulate within Ngspice, but to create the complete FM 
signal elsewhere, for instance using Qucsator and saving the result as 
.dat, and then creating a custom file source in Ngspice. This wouldn't 
work in circuits with some feedback from the rest of the circuit to a 
node before the generation of the modulating signal.

The block diagram would be

Ngspice previous circuit ---> modulating signal ---> mod.dat ---> 
Qucsator integrator + PM modulator ---> FM.dat ---> Ngspice file source 
---> rest of the Ngspice circuit

It's a bit indirect, needing two simulator engine changes, but I guess 
it would do the job if no feedback is required

Regards,

Federico Miyara

PD: Sorry I unintentionally sent this and the previous email privately. 
May I forward them to the list just in case somebody might find them useful?


On 6/10/2025 14:04, Vadim Kuznetsov wrote:
> Hello Federico,
>
> Ngspice doesn't support modulating from external source. This task 
> cannot be resolved at GUI level. It's required to design XSPICE 
> extension for Ngspice that implements this device.
>
> On 10/6/25 19:43, Federico Miyara wrote:
>>
>> Vadim,
>>
>> Thank you, sorry, I hadn't noticed it perhaps because it is labelled 
>> SFFM instead of just FM. However these sources seem to allow 
>> sinusoidal modulating signal only. It would be very useful to be able 
>> to apply an arbitrary modulating signal, particularly the output of a 
>> previous circuit.
>>
>> One possible workaround would be to previously create the signal, 
>> save it to a .dat file and use it in a file-based source.
>>
>> Regards,
>>
>> Federico Miyara
>>
>>
>> On 6/10/2025 06:39, Vadim Kuznetsov wrote:
>>> Hello Federico,
>>>
>>> Modulated sources are available for SPICE mode too. Scroll the 
>>> sources group on the left panel to the down and look for V(SFFM) 
>>> I(SFFM), sources. These components represent frequency modulated 
>>> sources.
>>>
>>> Regards,
>>> Vadim
>>>
>>> On 10/6/25 06:18, Federico Miyara wrote:
>>>>
>>>> Dear all,
>>>>
>>>> I find that Qucs-S doesn't have a phase or frequency modulator 
>>>> source under Ngspice as is the case with Qucsator. The problem is 
>>>> when one actually needs to use SPICE. Is there a simple way to 
>>>> create such a source?
>>>>
>>>> Regards,
>>>>
>>>> Federico Miyara
>>>>
>>>
>>
>>
>


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