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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 .
Most amateur digital modes are transmitted by inserting audio into the microphone input of a radio and using an analog scheme, such as amplitude modulation (AM), frequency modulation (FM), or single-sideband modulation (SSB). Amateur teleprinting over radio (AMTOR) D-STAR (Digital Data) a high speed (128 kbit/s), data-only mode.
A constellation diagram is a representation of a signal modulated by a digital modulation scheme such as quadrature amplitude modulation or phase-shift keying. [1] It displays the signal as a two-dimensional xy-plane scatter diagram in the complex plane at symbol sampling instants.
fc is the carrier frequency, fm is the maximum modulation frequency. In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, that are the result of the modulation process. The sidebands carry the information transmitted by the radio signal.
A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. Amplitude modulation produces an output signal the bandwidth of which is twice the maximum frequency of the original baseband signal. Single-sideband modulation avoids this bandwidth increase, and the power wasted on a carrier, at the cost of ...
Pulse-amplitude modulation: L: Pulse-width modulation (e.g. as used by WWVB) M: Pulse-position modulation: N: Unmodulated carrier (steady, single-frequency signal) P: Sequence of pulses without modulation Q: Sequence of pulses, with phase or frequency modulation in each pulse R: Single-sideband with reduced or variable carrier: V
A linear time-invariant system cannot produce intermodulation. If the input of a linear time-invariant system is a signal of a single frequency, then the output is a signal of the same frequency; only the amplitude and phase can differ from the input signal.
The modulation index (or modulation depth) of a modulation scheme describes by how much the modulated variable of the carrier signal varies around its unmodulated level. It is defined differently in each modulation scheme. Amplitude modulation index; Frequency modulation index; Phase modulation index