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Modulating a square pulse

 

How can I create a voltage source in LTspice where I want the pulse to be modulated with a sine wave?
 

You could use a switch; the command signal would be a square wave (could be any kind of repetitive signal of suitable amplitude), and the switch would control the sinewave.

Le 13/12/2024 à 22:14, abid via groups.io a écrit :

How can I create a voltage source in LTspice where I want the pulse to be modulated with a sine wave?
 

Modulate period or modulate pulse width?
 
Jim

On 12/13/2024 1:14 PM PST abid via groups.io <abidsahdman@...> wrote:
 
 
How can I create a voltage source in LTspice where I want the pulse to be modulated with a sine wave?

 

What kind of modulation did you have in mind? There are at least five different methods I can thnk of off the top of my head. There are standard components that will do modulation for you. They are in the Special Functions folder and have the names "modulate" and "modulate2". You should read the help files for how they are used, but you might have to read those files more than once and experiment until you understand what is going on.
 
The MODULATE device is a voltage controlled oscillator. See the example schematic .\examples\Educational\PLL.asc. The instantaneous oscillation frequency is set by the voltage on the FM input. The conversion from voltage to frequency is linear and set by the two instance parameters, mark and space. Mark is the frequency when the FM input is at 1V and space is the frequency when the input is at 0V. The amplitude is set by the voltage on the AM input and defaults to 1V if that input is unused(connected to the MODULATE common).
 
Good luck,
 
 

Or amplitude?
 

On 12/13/2024 1:53 PM PST James Wagner <wagnejam99@...> wrote:
 
 
Modulate period or modulate pulse width?
 
Jim
On 12/13/2024 1:14 PM PST abid via groups.io <abidsahdman@...> wrote:
 
 
How can I create a voltage source in LTspice where I want the pulse to be modulated with a sine wave?

 

Or amplitude?

On Fri, December 13, 2024 2:53 pm, Jim Wagner via groups.io wrote:
Modulate period or modulate pulse width?

Jim

On 12/13/2024 1:14 PM PST abid via groups.io
<abidsahdman@...> wrote:


How can I create a voltage source in LTspice where I want the pulse to
be modulated with a sine wave?





--
Not sent from an iPhone.
 

On Fri, Dec 13, 2024 at 03:53 PM, Jim Wagner wrote:
Modulate period or modulate pulse width?

Could you please explain for both the cases? Thanks.
 

Not much to explain.  Pulse Width varies the width (an equivalent name is duty cycle) with the external signal, leaving the period constant. Period varies the period of the square wave, leaving the pulse width constant. This also changes the duty cycle ( duty cycle = width/period). That is it.
 
Jim

On 12/13/2024 2:57 PM PST abid via groups.io <abidsahdman@...> wrote:
 
 
On Fri, Dec 13, 2024 at 03:53 PM, Jim Wagner wrote:
Modulate period or modulate pulse width?

Could you please explain for both the cases? Thanks.

 

On Fri, Dec 13, 2024 at 03:34 PM, Jerry Lee Marcel wrote:
You could use a switch; the command signal would be a square wave (could be any kind of repetitive signal of suitable amplitude), and the switch would control the sinewave.
Could you please tell me how to do that?
 

On Fri, Dec 13, 2024 at 06:36 PM, abid wrote:
Could you please tell me how to do that?
I really am uncomfortable when someone wants the keys to be handed to them, while they do nothing.
 
Have you considered how someone might build both kinds of modulators in real life?  That is often the best starting point.  Imagine how it would be done with actual hardware, then make a simulation model that does the same thing, only simpler.
 
Have you thought about how you would make either kind of modulator?  Using one's imagination to achieve an aim, is a great way to begin.
 
Do you actually want to simulate this modulator, or is this an academic exercise that serves no purpose?  It is beginning to sound like one.
 
Andy
 
 

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