What is envelope detection?

When an AM signal is received, the receiver must perform a converse process to get the original signal ( Information Signal ) back .

This process is known as detection or demodulation, the simplest process which is used widely in AM radiOS is the Envelop Detector .

Envelop Detector is an electronic circuit which is used to recover ( Demodulate ) the original signal in AM systems, its constructed from just one diode, one capacitor and one resistor .

This is essentially just a halfwave rectifier which charges a capacitor to

a voltage = the peak voltage of the AM signal .

However .. the output of the detector follows the envelop of the modulated signal.

On the positive cycles of the input signal, the diode conducts and the capacitor charges

up to the peak voltage of the input signal.

As the input falls below this peak value, the diode is cut off, because the capacitor

voltage is greater than the input signal voltage, thus causing the diode to open.

The capacitor now discharges through the resistor at slow rate .

The discharge process continues until the nest positive half-cycle. When the input signal

becomes greater than the output across the capacitor, the diode conducts again and the process is repeated .