What is demodulation?
The process of separating the original information or SIGNAL from the MODULATED CARRIER. In the case of AMPLITUDE or FREQUENCY MODULATION it involves a device, called a demodulator or detector, which produces a signal corresponding to the instantaneous changes in amplitude or frequency, respectively. This signal corresponds to the original modulating signal
What term means changing the characteristics of a signal as when a modem changes a digital pulse into an analog audio signal?
Which device connects a computer with a telephone line by providing modulation and demodulation of incoming and outgoing data?
Demodulation takes place to extract the low-frequency signal from the high-frequency carrier, using a nonlinear process that produces components at the signal frequency. The LP filter is used to eliminate the high-frequency carrier component from the signal so that it does not cause problems at a later stage in the amplification of the signal.
The diagonal clipping in Amplitude Demodulation (using envelop detector) can be avoided if RC time-constant of the envelope detector satisfies the following condition, where W is message bandwidth and w is carrier frequency both in rad/sec: The time contant t should be always in between ( 1/w) and ( 1/W) [without including ( 1/w) and ( 1/W) ]
In Coherent demodulation the incoming signal are in phase with the local oscillator signal. This type of detection used in satellite standards because direct uplink and downlink transmission and reception respectively through earth station hub. But in non coherent demodulation there is a phase discontinuouty due fading of the channel. This type of detection used in terrestrial applications (mobile wireless standards).