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Demodulation is the process of extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated carrier wave. [1] There are many types of modulation, and there are many types of ...
Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave.In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to that of the message signal, such as an audio signal.
A demodulator (sometimes detector) is a circuit that performs demodulation, the inverse of modulation. A modem (from mod ulator– dem odulator), used in bidirectional communication, can perform both operations.
The capture effect can occur at the signal limiter, or in the demodulation stage for circuits that do not require a signal limiter. [1] Some types of radio receiver circuits have a stronger capture effect than others. The measurement of how well a receiver rejects a second signal on the same frequency is called its capture ratio.
The easiest type of demodulation to understand is AM demodulation, used in AM radios to recover the audio modulation signal, which represents sound and is converted to sound waves by the radio's speaker. It is accomplished by a circuit called an envelope detector (see circuit), consisting of a diode (D) with a bypass capacitor (C) across its ...
A major category of AM demodulation technique involves envelope detection, since the envelope of an AM signal is the original signal. A diode detector is a type of simple envelope detector. It consists of a diode connected between the input and output of the circuit, with a resistor and capacitor in parallel from the output of the circuit to ...
In the case of AM, φ(t) (the phase component of the signal) is constant and can be ignored. In AM, the carrier frequency is also constant. Thus, all the information in the AM signal is in R(t). R(t) is called the envelope of the signal. Hence an AM signal is given by the function
In the DSB-SC modulation, unlike in AM, the wave carrier is not transmitted; thus, much of the power is distributed between the side bands, which implies an increase of the cover in DSB-SC, compared to AM, for the same power use. DSB-SC transmission is a special case of double-sideband reduced carrier transmission. It is used for radio data systems