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This article is devoted to the application of the method of automatic phase distortion compensation of direct digital synthesizers (DDSs) to improve the spectral characteristics of signal generators of radio transmitters of unmanned aerial vehicles (UAVs) operating as part of flying ad-hoc networks (FANET) in "smart cities". A block diagram of a universal signal generator for UAV radio transmitters is considered, based on the use of a quadrature modulator and obtaining a carrier oscillation from a reference one using a frequency multiplier based on a phase-locked loop (PLL) and information quadrature components using a DDS. It is shown that one of the key requirements for signal generators of UAV radio transmitters is the spectral purity of the synthesized signals. It is noted that the proposed version of the device has insufficient spectral purity due to the presence of a DDS in the generator, because its output signal spectrum contains a noise component and a set of discrete spectral components of a significant level. It was found that known methods of improving the spectral characteristics are not efficient enough; therefore it was suggested to use the principle of automatic compensation of phase distortion. A block diagram of generating control signals was proposed for its implementation, and analysis of normalized amplitudefrequency characteristics of the proposed scheme was shown.

Application of Phase Distortion Autocompensation to Improve the Spectral Characteristics of Signal Generators of UAV Radio Transmitters