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DSB-SC is basically an amplitude modulation wave without the carrier, therefore reducing power waste, giving it a 50% efficiency. This is an increase compared to normal AM transmission (DSB) that has a maximum efficiency of 33.333%, since 2/3 of the power is in the carrier which conveys no useful information and both sidebands containing identical copies of the same information.
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)
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 .
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 ...
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.
Independent sideband (two sidebands containing different signals) C: Vestigial sideband (e.g. NTSC) D: 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 ...
Single-sideband with reduced or variable carrier (R2A, R2B). All CW emission types (not MCW), listed by the FCC (all are one channel): Double-sideband amplitude modulation, no subcarrier (A1A, A1B) Vestigial sideband, no subcarrier (C1A, C1B) Single-sideband modulation with full carrier, no subcarrier (H1A, H1B) Single-sideband with suppressed ...
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.