Commonly used AM demodulators and simulation with Python and NumPy

In a previous article, AM modulator and a simple demodulator were explained and simulated with Python. However, there are different techniques to extract the information from the AM signal, each of them used for different applications depending on the performance and cost of the receiver. Some of the most common demodulator are:

• Diode amplitude detector: the simplest and cheapest demodulator, which has been already described and simulated in this article. Mainly, a diode gets absolute value of the received signal, which is then low pass filtered, removing the high frequency component. This is the simplest way to demodulate an AM signal, but it is also the worst (it introduces higher distortion into the demodulated signal).
• Power amplitude detector: similar to the previous one but using the power instead of the absolute value. This detector provides the square of the input signal (another way of extracting the positive part of the signal), and low pass filtering. The output of this demodulator is better than the diode detector, and it is still simple.

Product detector

• Synchronous demodulator: this demodulator multiplies the received signal by a local oscillator, which replicates the carrier signal used in the transmitter. In electronics, the element which carries out this multiplication is called…