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Passband modulation. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a separate signal called the modulation signal that typically contains information to be transmitted. [1] For example, the modulation signal might be an audio signal ...
Continuous phase modulation (CPM) is a method for modulation of data commonly used in wireless modems.In contrast to other coherent digital phase modulation techniques where the carrier phase abruptly resets to zero at the start of every symbol (e.g. M-PSK), with CPM the carrier phase is modulated in a continuous manner.
Demodulation is 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 so there are many types of demodulators.
[1] [2] [3] Heterodyning is used to shift signals from one frequency range into another, and is also involved in the processes of modulation and demodulation. [ 2 ] [ 4 ] The two input frequencies are combined in a nonlinear signal-processing device such as a vacuum tube , transistor , or diode , usually called a mixer .
A satellite modem or satmodem is a modem used to establish data transfers using a communications satellite as a relay. A satellite modem's main function is to transform an input bitstream to a radio signal and vice versa. There are some devices that include only a demodulator (and no modulator, thus only allowing data to be downloaded by ...
A modulator-demodulator, commonly referred to as a modem, is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio.
The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying wave forms (passband transmission), using a digital modulation method. The passband modulation and corresponding demodulation (also known as detection) is carried out by modem equipment.
v. t. e. In telecommunications, direct-sequence spread spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference. The direct-sequence modulation makes the transmitted signal wider in bandwidth than the information bandwidth. After the despreading or removal of the direct-sequence modulation ...