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FM signals can be generated using either direct or indirect frequency modulation: Direct FM modulation can be achieved by directly feeding the message into the input of a voltage-controlled oscillator. For indirect FM modulation, the message signal is integrated to generate a phase-modulated signal.
Digital modulation schemes are possible because the transmitter-receiver pair has prior knowledge of how data is encoded and represented in the communications system. In all digital communication systems, both the modulator at the transmitter and the demodulator at the receiver are structured so that they perform inverse operations.
Frequency modulation is widely used for FM broadcasting of radio programming, and largely supplanted amplitude modulation for this purpose starting in the 1930s, with its invention by American engineer Edwin Armstrong in 1933. [4] FM also has many other applications, such as in two-way radio communications, and in FM synthesis for music ...
Phase modulation (PM) is a modulation pattern for conditioning communication signals for transmission. It encodes a message signal as variations in the instantaneous phase of a carrier wave . Phase modulation is one of the two principal forms of angle modulation , together with frequency modulation .
Combination of AM and FM or PM F: Frequency modulation (e.g. FM broadcast radio) G: Phase modulation: H: Single-sideband modulation with full carrier (e.g. as used by CHU) J: Single-sideband with suppressed carrier (e.g. Shortwave utility and amateur stations) K: Pulse-amplitude modulation: L: Pulse-width modulation (e.g. as used by WWVB) M ...
FM broadcasting is a method of radio broadcasting that uses frequency modulation (FM) of the radio broadcast carrier wave. Invented in 1933 by American engineer Edwin Armstrong , wide-band FM is used worldwide to transmit high-fidelity sound over broadcast radio . [ 1 ]
The goal of keying is to transmit a digital signal over an analog channel. The name derives from the Morse code key used for telegraph signaling. Modulation is the general technique of shaping a signal to convey information. When a digital message has to be represented as an analog waveform, the technique and term keying (or digital modulation ...
Morse code is called the original digital mode. Radio telegraphy, designed for machine-to-machine communication is the direct on / off keying of a continuous wave carrier by Morse code symbols, often called amplitude-shift keying or ASK, may be considered to be an amplitude modulated mode of communications, and is rightfully considered the first digital data mode.