Editing Single-sideband modulation (section)

== Controlled-envelope single-sideband modulation ([[CESSB]]) ==

The generation of standard SSB modulation results in large envelope overshoots well above the average envelope level for a sinusoidal tone (even when the audio signal is peak-limited). The standard SSB envelope peaks are due to truncation of the spectrum and nonlinear phase distortion from the approximation errors of the practical implementation of the required Hilbert transform. It was recently shown that suitable overshoot compensation (so-called [[controlled-envelope single-sideband modulation]] or [[CESSB]]) achieves about 3.8&nbsp;dB of peak reduction for speech transmission. This results in an effective average power increase of about 140%.<ref>{{cite web|url=http://www.arrl.org/files/file/QEX_Next_Issue/2014/Nov-Dec_2014/Hershberger_QEX_11_14.pdf|title=Controlled Envelope Single Sideband|publisher=www.arrl.org|date=2014-11-01|access-date=2017-01-15}} by David L. Hershberger, W9GR, QEX, issue Nov./Dec. 2014, pp. 3–13.</ref>
Although the generation of the CESSB signal can be integrated into the SSB modulator, it is feasible to separate the generation of the CESSB signal (e.g. in form of an external speech preprocessor) from a standard SSB radio. This requires that the standard SSB radio's modulator be linear-phase and have a sufficient bandwidth to pass the CESSB signal. If a standard SSB modulator meets these requirements, then the envelope control by the CESSB process is preserved.<ref>{{cite web|url=http://www.arrl.org/files/file/QEX_Next_Issue/2016/January_February_2016/Hershberger_QEX_1_16.pdf|title=External Processing for Controlled Envelope Single Sideband|publisher=www.arrl.org|date=2016-01-01|access-date=2017-01-15}} by David L. Hershberger, W9GR, QEX, issue Jan./Feb. 2016, pp. 9–12.</ref>