Modeling the noise properties of hybrid frequency synthesizers with automatic compensation of phase noise of DDS

Abstract

Held modeling of noise properties of the three schemes of hybrid frequency synthesizers on the basis of PLL and direct digital synthesizer with automatic compensation of phase noise. Interference suppression of hybrid synthesizers performed by isolating the law of parasitic phase deviation of the output signal of the digital synthesizer and changing the modulating voltage of controlled oscillator of the PLL in accordance with the law of selected phase deviation. The graphs power spectral density of phase noise of individual blocks of hybrid synthesizers are drawn and estimated degree of suppression of phase noise in the output signal of the analyzed devices. Keywords-direct digital synthesizer, hybrid frequency synthesizer, PLL, interference compensation, phase noise spectral densityI.

Analysis of Noise Characteristics of Multichannel Systems of the Formation of Signals of Georadars with Synthesized Aperture

“…An effective method of improving the spectral characteristics of signal formers that contain a DDS is to use the method of automatic compensation for phase distortions (ACPD) [15][16][17][18]. The idea of this method with respect to a DDS is based on the isolation the clock frequency with parasitic phase modulation in the spectrum of the output signal of digital-analog converter with, its comparison with the input clock frequency of the synthesizer (without phase distortions) and the formation of a control signal.…”

“…The main useful effect of the use of the ACPD circuit of the DDS in the hybrid synthesizers is to reduce the level of discrete parasitic spectral components in the output signal spectrum of the device by 10-15 dB. However, the use of this circuit also makes it possible to reduce the level of phase noises [16][17][18] caused by the significant contribution of the Figure 7: Equivalent circuit of the channel for forming signals with the DDS as a reference oscillator of the PLL with all sources of phase noises. DDS which depending on its transmission coefficient and the place of inclusion in the PLL.…”