The Compatibility Problem in Single-Sideband Transmission

Under the assumption of simultaneous amplitude and phase modulation of a carrier, a study is made of the relations that must hold between the envelope and the phase of a single-sideband wave. In particular, it is shown that absolute compatibility with standard AM receivers employing a linear envelope detector cannot possibly be achieved with the spectral economy of conventional single sideband. On the other hand, if one conveys the message function in the square of the envelope rather than in the envelope itself, it is shown that a phase function can be found for which the hybrid wave occupies a spectral width equal to that of a conventional single-sideband (SSB) system. Distortionless detection is achieved with a square-law envelope detector. The operations required to generate this square-law SSB signal are described in detail.