An envelope detector is a device which is used to demodulate AM signals. The original message is decoded from the envelope of the modulated signal.
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2 Diode Detector
3 Precision detector
- x(t) = R(t)cos(ωt+φ(t))
- x(t) = (C + m(t))cos(ωt)
The simplest form of envelope detector is the diode detector. To construct a diode detector, simply connect a diode between the input and output of a circuit, and connect a resistor and capacitor in parallel from the output of the circuit to the ground. If the resistor and capacitor are correctly chosen, the output of this circuit should approximate a voltage-shifted version of the original signal. A simple filter can then be applied to filter out the DC component.
The envelope detector has several drawbacks
Most of these drawbacks are relatively minor and are usually acceptable tradeoffs for the simplicity and low-cost of using an envelope detector.