CBSE NOTES CLASS 12 PHYSICS
CHAPTER 15 COMMUNICATION SYSTEMS
Detection of amplitude modulated wave
The transmitted message gets attenuated in propagating through the channel. The receiving antenna is therefore to be followed by an amplifier and a detector.
To facilitate further processing, the carrier frequency is usually changed to a lower frequency by an intermediate frequency (IF) stage preceding the detection.
The detected signal may not be strong enough to be made use of and hence is required to be amplified.
Block diagram of receiver
Detection is the process of recovering the modulating signal from the modulated carrier wave. The modulated carrier wave contains the frequencies ωc and ωc ± ωm.
Block diagram of AM wave detector