you guys are both right
sorry for the contradiction
yaniel
Added after 2 minutes:
No, it is AM modulation but using a class C amplifier. The idea is that the power amplfier, amplitude modulates the signal. It has two inputs, the RF signal and the modulated voltage from a PWM system with a low pass filter at its output. If it is still unclear, please let me know
Yaniel
Added after 8 minutes:
the system is like this
an analog signal ( your voice) is used as an input to the microphone. Then, comes PWM. Afterwards, a high power electronic switch raise the voltage level of the PWM. Then it is pass through a low pass filter and afterwards is used as input power supplied to the power amplifier.
On the other side, an oscillator generates the carrier wave. The power amplifier thus has two input the RF signal and the modulated voltage.
the power amplifier design is then bounded by this constraints.
since we are using a microcontroller to implement the oscillator, our carrier wave has a frequency of 0.8Mhz.
the modulated voltage must be between 12V and 15V. The ouput power could be as low as 1W
Using a class C amplifier to implement power amplifier in amplitude modulation requires a low pass filter at its output to reduce the harmonics since often transformer are use to match impedances.
please guys if you have any idea, or opinion let me know, I really appreaciate it
thanks
Yaniel