Amplitudemodulated
Amplitude-modulated, or amplitude-modulated (AM), refers to a method of conveying information by varying the amplitude of a carrier wave in proportion to a modulating signal. In the common case of a sinusoidal carrier, the transmitted waveform can be written as s(t) = A_c [1 + m cos(ω_m t)] cos(ω_c t), where A_c is the carrier amplitude, ω_c is the carrier angular frequency, ω_m is the modulating angular frequency, and m is the modulation index (0 ≤ m ≤ 1 for undistorted modulation).
Principles: The modulating signal controls the envelope of the carrier while the carrier’s frequency and phase
Bandwidth and sidebands: For a single-tone modulating signal, AM creates two sidebands around the carrier with
Types and efficiency: DSB-FC (standard AM with full carrier) retains the carrier, which simplifies envelope detection
Demodulation: Envelope detection uses a diode and RC network to recover the modulating signal; DSB-SC and SSB
Applications and history: AM has a long history in radio broadcasting, aviation communications, and audio transmission.