Comparison of Single-Sideband, Suppressed-Carrier and Double-Sideband, Full-Carrier Amplitude Modulation

摘要

The spectral economy of SSB (single-sideband, suppressed-carrier modulation) in comparison with conventional AM has long been recognized. However, the use of SSB, particularly for data transmission, has been limited by the large peak envelope excursions caused by pulse-like waveforms. Even in the transmission of analog signals, such as speech or music, undesirable peaks can be encountered. SSB and AM signals are analyzed using a waveform that can be varied in shape from a spike through a sine wave to a square wave by varying a parameter. The average sideband powers and the peak envelope powers are then calculated and compared. It is shown that the ratio of average sideband power to peak envelope power for AM is more favorable than that for SSB for squarish modulating signals. However, the ratio for SSB is about 9dB higher than it is for AM for modulating signals ranging in shape from a sine wave to a spike.