Simulation and parameters optimization of hybrid frequency synthesizers for wireless communication systems

Various types of hybrid frequency synthesizers based on the combined use of direct digital synthesis and phase-locked loop are considered in the present paper. Numerical evaluations of the response speed and the stability of hybrid frequency synthesizers, both under standard conditions, and under large disturbances, are obtained. The techniques of hybrid frequency synthesizers' parameters optimization are presented. These techniques allow to provide the maximum response speed and the lowest level of spurious spectral components in wireless communication systems. It was shown that the use of a second or a third order loop filter in the frequency synthesizer instead of a first-order loop filter allows to increase simultaneously the response speed and the attenuation of spurious spectral components in 1.5-2 times. The results of this paper are valid for frequency synthesizers which are used in communication systems of the fourth generation (4G), as well as in other communication systems of UHF, L and S bands.