The general expression for approximation of power spectral density (SD) of phase noise direct digital synthesizers. The design procedure of factors of SD approximation of phase noise is developed. Calculated SD for integrated DDS from Analog Devices have shown good coincidence with experimental characteristics.Index Terms -DDS, signal synthesis, phase noise, spectral density.
The main features of high-speed digital-to-analog converters designed for direct digital synthesis of radio frequency signals in the UHF and microwave ranges are presented. A block diagram of a digital signal generator based on high-speed DACS is proposed. These DACs are designed to create digital signal generators that work based on the direct digital synthesis method. The main specialized modes of operation of high-speed digital-to-analog converters that allow efficient use of extra components of the spectrum are studied. Images of the main frequency of synthesis occur when the signal is restored from digital to analog form. Special operating modes of high-speed DACS allow you to create broadband and ultra-wideband signals. The use of high-speed digital-to-analog converters in special modes of operation makes it possible to simplify the block diagrams of digital signal generator. The scheme is simplified by reducing the number of cascades of the output frequency multipliers.
The regression model of power spectral density (PSD) of phase noise of direct digital synthesizers (DDS) has been obtained. The refined method of calculating the approximation coefficients of PSD of phase noise has been developed. The calculated PSD of phase noise of integrated Analog Devices' DDS showed a small approximation error compared with the experimental noise curves.
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