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Double-sideband suppressed-carrier transmission (DSB-SC) is transmission in which frequencies produced by amplitude modulation (AM) are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level, ideally being completely suppressed. [1] In the DSB-SC modulation, unlike in AM, the ...
The term DSB reduced-carrier normally implies enough carrier remains in the transmission to enable a receiver circuit to regenerate a strong carrier or at least synchronise a phase-locked loop but there are forms where the carrier is removed completely, producing double sideband with suppressed carrier (DSB-SC). Suppressed carrier systems ...
In the Armstrong method, the audio signal and the radio frequency carrier signal are applied to the balanced modulator to generate a double sideband suppressed carrier signal. The phase of this output signal is then shifted 90 degrees with respect to the original carrier. The balanced modulator output can either lead or lag the carrier's phase.
Reduced-carrier transmission is an amplitude modulation (AM) transmission in which the carrier signal level is reduced to reduce wasted electrical power. Suppressed-carrier transmission is a special case in which the carrier level is reduced below that required for demodulation by a normal receiver .
A Costas loop is a phase-locked loop (PLL) based circuit which is used for carrier frequency recovery from suppressed-carrier modulation signals (e.g. double-sideband suppressed carrier signals) and phase modulation signals (e.g. BPSK, QPSK). It was invented by John P. Costas at General Electric in the 1950s.
Double-sideband reduced carrier transmission (DSB-RC): transmission in which (a) the frequencies produced by amplitude modulation are symmetrically spaced above and below the carrier and (b) the carrier level is reduced for transmission at a fixed level below that which is provided to the modulator.
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: Pulse-position modulation: N: Unmodulated carrier (steady, single-frequency signal) P: Sequence of pulses ...
The first such analog modulating waveforms applied to radio carriers were human voice signals picked up by microphone sensors and applied to the carrier waveforms. The resulting analog voice modes are known today as: Amplitude modulation (AM) Double-sideband suppressed carrier (DSB-SC) Independent sideband (ISB) Single sideband (SSB)