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Amplitude-Shift Keying

    Last Modified: February 6, 2018

    Amplitude-shift keying (ASK) refers to a type of amplitude modulation that assigns bit values to discrete amplitude levels. The following table shows the supported M-ary number for ASK.

    Modulation Type M-ary
    ASK 2, 4, 8

    On-off keying (OOK) is equivalent to two-level ASK (0, 1), that is, a sinusoidal carrier signal on and off with a unipolar binary signal. The following image shows a unipolar binary baseband signal and the resulting OOK modulated signal.

    The ASK demodulator uses the discrete levels in the carrier amplitude as the default symbol map. The carrier amplitude of the recovered symbol closest to the ideal symbol in the map decides the bits it represents. The bits mentioned in the symbol map are read as blog2M)-1 ... b0.

    The bit stream returned after analyzing the complete waveform is reported as follows:

    {b0 ... blog2M)-1}0 {b0 ... blog2M)-1}1 ... {b0 ... blog2M)-1}n-1

    where M is the M-ary and n is the number of symbols analyzed.

    The amplitude levels are as shown below.

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