Noise Immunity of Single-Sideband Modulation Signals with a Controlled Carrier Level

Abstract

Single-sideband modulation is actively used in the organization of communication through the ionospheric channel in the decameter range of radio waves. This is due to the fact that transmissions with single-sideband modulation make it possible to minimize the frequency band while maintaining the information transfer rate and at the same time increase the noise immunity of reception in relation to transmissions with amplitude and frequency analog modulation. At the same time, the widespread use of quadrature synthesis technologies has opened up new possibilities for the formation of transmissions with single-sideband modulation without the direct use of filtering procedures. An analysis of the implementation features of the method of quadrature synthesis of signals with single-sideband modulation showed that the introduction of an additional parameter into its procedures will allow you to control the residual level of the carrier wave, and thereby control the noise immunity of the reception. The opened opportunities made it possible to develop a method and a device for generating a single-sideband modulation signal with an adjustable level of the carrier wave that implements it. The technologies of quadrature synthesis of signals of amplitude modulation and single-sideband modulation with the suppressed carrier are considered both at the level of analytical modeling and using a standard quadrature modulator. The necessity of transition to the analytical form of representation of the modulating signal is substantiated. The role and place of the Hilbert converter in the formation of signals with single-sideband modulation are shown. Known technologies for generating single-sideband modulation signals with a stored pilot signal are considered. The possibility of controlling the value of the stored pilot signal at the level of quadrature synthesis procedures is substantiated. An analytical model and, based on it, a structural diagram have been developed that allow one to generate single-sideband modulation signals with an adjustable pilot signal level. The results of analytical modeling are demonstrated. The value of the provided energy gain as a result of regulation by the residual level of the carrier wave is calculated. Approaches to assessing the noise immunity of transmissions with single-sideband modulation are analyzed. An approach is proposed for calculating the bit error probability of SSB transmissions manipulated by discrete oscillations based on the results of energy redistribution between the carrier oscillation and the sideband, determined by the residual pilot signal level. Conclusions and proposals for the practical implementation of the results obtained are formulated.