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Demodulation (Detection) of Amplitude-Modulated Waves

In amplitude modulation the message to be transmitted and a carrier wave are impressed on a circuit that distorts and produces sum and difference frequencies, or sidebands, which contain the information to be transmitted. By the same process, if the carrier and sidebands are simultaneously impressed on a circuit that distorts, sum and difference frequencies are created. The difference frequencies are the desired demodulated signal and exist at audio frequencies. Demodulation was defined1,2 on page 421. Detection is2 the "process by which a wave corresponding to the modulating wave is obtained in response to a modulated wave." Fundamentally, demodulation and detection are the same process as modulation, a fact stressed in Chapter 11.



Last Update: 2011-05-30