Duty Cycle Folower

[Frosty_47]

An FM square wave that will follow the duty cycle of the intelligence. That is, if the intelligence is 25% Duty Square wave, when modulated, the resultant FM wave will have 25% duty cycle. Is this feasible in modern age of electronics?

Also, the duty of intelligence will change with every cycle

All suggestions are very much appreciated

 

[BrownOut]

Fascinating! Who's intelligence are we talking about?

 

[crutschow]

What does duty cycle mean with respect to FM modulation?

 

[KMoffett]

Pulse width modulation of an FM carrier?

Ken

 

[Ubergeek63]

An FM square wave that will follow the duty cycle of the intelligence. That is, if the intelligence is 25% Duty Square wave, when modulated, the resultant FM wave will have 25% duty cycle. Is this feasible in modern age of electronics?

Also, the duty of intelligence will change with every cycle

All suggestions are very much appreciated

that is an oxymoron. there is FM (frequency modulation) and there is PWM (duty cycle modulation if you will). You can modulate an FM carrier with a PWM signal, but why bother?

 

[Frosty_47]

that is an oxymoron. there is FM (frequency modulation) and there is PWM (duty cycle modulation if you will). You can modulate an FM carrier with a PWM signal, but why bother?

PWM does not have a carrier. FM on the other hand consists of intelligence + carrier. I need a wave of roughly 110Khz that will have the same duty cycle as the intelligence wave...
That is if the sensitivity of the receiver is 1Khz/Volt, and there is a 1Khz @ 1 Volt intelligence square wave with 25% duty, the resultant FM wave will be 109Khz - 111Khz FM at 25% duty cycle...
I apologies if this is not clear enough,

 

[Frosty_47]

Yes in a way it is. I can manually adjust the duty on an FM wave, but what I want is a system that will automatically output PWM based on the input wave (intelligence)

 

[Frosty_47]

Pulse width modulation of an FM carrier?

Ken

Yes in a way it is. I can manually adjust the duty on an FM wave, but what I want is a system that will automatically output PWM based on the input wave (intelligence)

 

[Ubergeek63]

Yes in a way it is. I can manually adjust the duty on an FM wave, but what I want is a system that will automatically output PWM based on the input wave (intelligence)

you are missing the point, that is NOT "F"requency "M"odulation. Nothing says you can not phase lock to a PWM carrier, but that does not make it frequency modulated.

what you have just described is a simple PWM... compare your input wave to a ramp and you get a PWM based on the input wave, but that has nothing to do with FM

 

[KMoffett]

Frosty,

I think it might make it a little more clear to us if you could explain what the real project is.

Right now it looks to me like you have a PWM signal that is modulated by some signal (intelligence).
You want to modulate an FM signal (carrier?) with the modulated PWM signal.
Somewhere, the FM signal is demodulated to recover the PWM signal, and that is demodulated to recover the "intelligence".

Ken

 

[crutschow]

Sounds like you want to step modulate the FM with the PWM signal. If that's so, just drive the FM modulator with the PWM signal and adjust the modulator gain to give the desired FM deviation. The FM receiver will demodulate that back to the PWM signal. You may want to run the demodulated output through a comparator to square up the signal, depending upon the output frequency response of the receiver.