The amplitude shift keying modulated signal has the signal information in its envelope. The actual digital signal can be recovered from the received signal by rectifying the received signal and then low pass filtering the rectified waveform. Figure 1 shows the block diagram for the amplitude shift keying receiver.

Figure 1: Block diagram of amplitude shift keying receiver

Figure 2 shows the rectified and low pass filtered results of the ASK modulated signal. The waveform is shown for 8-bit data word.

Figure 2: Amplitude shift keying demodulation

At the end of this experiment, students are instructed to apply amplitude shift keying demodulation technique to different analog waveforms and observe the results on the oscilloscope.