A comparison of single-sideband, suppressed-carrier and double-sideband, full-carrier amplitude modulation

by Edward Bedrosian, William Sollfrey

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The spectral economy of single-sideband, suppressed-carrier modulation (SSB) in comparison with conventional amplitude modulation (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 wave forms. Even in the transmission of analog signals, such as speech or music, undesirable peaks can be encountered. In this paper, SSB and AM signals are analyzed using a wave form 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. The paper shows 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 9#dB higher than it is for AM for modulating signals ranging in shape from a sine wave to a spike.

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