Wide-band hybrid frequency synthesizer with improved noise performance

This paper considers a hybrid frequency synthesizer based on a direct digital synthesizer (DDS) and phase-locked loop (PLL). The synthesizer operates over a wide frequency range and provides a low level of phase noise due to the use of copies of the spectrum of the fundamental frequency of a direct digital synthesizer - images. The use of images allows to significantly increase the output frequency of DDS. This makes it possible to reduce the division factor of PLL feedback loop and, accordingly, to reduce the phase noise level. The mathematical model of the noise curves of a hybrid synthesizer is obtained and studied. The laboratory model of the hybrid frequency synthesizer was developed and experimentally investigated. The performed studies showed that the experimental noise curves completely coincide with the simulation results.