Error detection in a signal in amplitude modulation

An amplitude demodulator, comprising:

• a first element for filtering a signal received in amplitude modulation to provide a signal to be interpreted;
• a second filtering element having a time constant smaller than that of the first filtering element to determine an average value of the received signal;
• two first elements for comparing the amplitude of the signal to be interpreted with respect to two values surrounding said average value;
• at least two second elements for comparing the amplitude of the signal to be interpreted with respect to two second values surrounding the average value and ranging between the first two values;
• and
• a circuit for interpreting the results of the comparison elements indicating an insufficient modulation factor if the received signal ranges between at least two of said values.

An amplitude demodulator comprising:

• an element for filtering a signal received in amplitude modulation;
• a capacitive element for filtering a first D.C. component provided by the filtering element;
• an element for adding a second D.C. component corresponding to half the supply voltage of the demodulator to the signal resulting from the capacitive element;
• two first elements of comparison of the amplitude of the signal to be interpreted with respect to two values surrounding half of said supply voltage;
• and comprising:
• at least two second elements or comparing the amplitude of the signal to be interpreted with respect to two second values surrounding half of said supply voltage and ranging between the two first values;
• and
• a circuit for interpreting the results of the comparison elements indicating an insufficient modulation factor if the received signal ranges between at least two of said values.