Compatible Single Sideband

A compatible single-sideband (CSSB) wave is a new type of modulated wave which is compatible with existing AM receivers. Spectrum analysis and measurement indicate that if the CSSB system is applied to a conventional AM broadcast transmitter, a desired-to-undesired sideband ratio of slightly better than 30 db will be achieved under normal modulation conditions. Also described is a beat frequency problem which introduces a special type of undesired sideband component. This component falls extremely close to the carrier and should not be present during the vast majority of program conditions. Thus, the technique meets the requirement of theoretically distortion-free envelope characteristics with a good desired-to-undesired sideband ratio. Measurements are described which show the advantages of the system. It appears that the main advantage of the technique is to reduce co- and adjacent-channel interference effects. CSSB also provides a higher fidelity signal when received by conventional inexpensive broadcast receivers. The on-the-air tests indicated good listener acceptance of the new system. The system also appears to have applications in communications service where cost and size bar the use of conventional sideband techniques. The technique does not suffer from Doppler shift difficulties.