How is an AM diode detector an envelope demodulator?

How is an AM diode detector an envelope demodulator?

The AM diode detector is an envelope detector – it provides an output of the envelope of the signal. As such the diode detector or demodulator is able to provide an output proportional to the amplitude of the envelope of the amplitude modulated signal.

How is the demodulation of an AM signal done?

The AM demodulation is done using a low pass filter which can filter out the high frequency carrier from the AM wave in such a way that only the envelope of the carrier wave appears at the output of the filter. The amplitude of the filtered wave has variations corresponding to the amplitude of the modulating low frequency signal.

Can a diode envelope detector detect selective fading?

The diode envelope detector is not able to combat the effects of this in the way that some other detectors are able, and as a result, distortion occurs when selective fading occurs. Sensitivity: The diode detector is not as sensitive as some other types.

What are the advantages of an envelope detector?

Envelope detector advantages: Low cost: The diode detector only requires the use of a few low cost components. This made it ideal for use in transistor (and valve / vacuum tube ) radios using discrete components. Simplicity: Using very few components, the Diode AM detector was easy to implement.

What kind of detector is used for amplitude demodulation?

Classification of Amplitude Demodulation or Detector. Detector may be of two types: Square law diode detector utilize nonlinear portion of dynamic current-voltage characteristic of an electron device and is used for detecting modulated carriers of small magnitude. Linear diode detector uses the rectification property of a diode.

What is the total impedance of amplitude demodulation?

Since the applied voltage is of large magnitude, the operation takes place essentially over the linear region of the dynamic current-voltage characteristic of the diode. Assuming capacitor C to be absent, the total impedance in the series circuit is (R f + R) where R f is the dynamic anode resistance of the diode.

How to see the results of envelope detectors?

When you run the model, you will see the original signal and the results of both envelope detectors. This example shows the results of the two different envelope detectors for two different types of input signals.

Why does the amplitude of the envelope not match the signal?

In the plots, for the envelope detection method using Hilbert transform the envelope amplitude does not match the actual signal, because the Hilbert transform which was implemented using the FIR filter is not ideal. That is, the magnitude response is not one for all frequencies.

Can a Simulink model be used for envelope detection?

Note that the Analytic Signal block found in the DSP System Toolbox™ could also be used to implement this envelope detection design. The all-platform floating-point version of the Simulink model is shown below. When you run the model, you will see the original signal and the results of both envelope detectors.