I would like to have the envelope from a signal using a simple circuit composed of a diode and a low pass filter.
I know :
*Tam > t >> Tcarrier
*The diode must be a germanium diode because of the Vthreshold
*A germanium diode
*R = 1k
*C = 4.7nF
The wave is generate from a GBF :
*fcarrier = 1MHz *fam = 20 kHz
I took a capture from the oscloscope measuring the signal accross the resistance. My signal is shown bellow :
My questions are:
- How can I have a clean modulating signal?
- Some books talk about a High pass filter, why it could be necessary? (I tried and it's not better)
- The circuit is currently designed for a specific carrier but if my carrier has a defined range (in my case I will have a range between 1MHz to 7MHz), how could I adapt the circuit (or is there another circuit)?
- Is the type of the capacitor change something?