What is the role of capacitor in AM envelope detector?
The capacitor in the circuit stores up charge on the rising edge, and releases it slowly through the resistor when the signal falls. The diode in series rectifies the incoming signal, allowing current flow only when the positive input terminal is at a higher potential than the negative input terminal.
Why do we need to demodulate the signals?
The process of recovering the original signal from the modulated wave is known as demodulation or detection. When the modulated wave is picked up by the radio receiver, it is necessary to recover the audio signal from it. This process is accomplished in the radio receiver and is called demodulation.
Why do you need a capacitor in a demodulator?
The capacitor is not required for the demodulator to work. However it does improve its operation is two ways:-. By charging up to the peak signal amplitude and holding most of that charge between peaks, it increases the audio output voltage.
How does a capacitor affect the audio output?
By charging up to the peak signal amplitude and holding most of that charge between peaks, it increases the audio output voltage. Without any capacitance after the diode, the average output voltage of a half wave rectifier is Vpeak*0.318. With a suitably sized capacitor the audio output voltage increases closer to the peak value.
When to start demodulating an AM waveform?
We start with a peak detector, which is just a diode followed by a capacitor. The diode conducts when the input signal is at least ~0.7 V above the voltage on the capacitor, and otherwise it acts like an open circuit.
What kind of circuitry is used for demodulation?
Demodulation circuitry ranges from something as simple as a modified peak detector to something as complex as coherent quadrature downconversion combined with sophisticated decoding algorithms performed by a digital signal processor. We’ll use LTspice to study techniques for demodulating an AM waveform.