Achieving sub-Hz frequency resolution in high spectral purity and low power frequency synthesizers

The present paper describes a method to achieve sub-Hz frequency resolution in a microwave frequency synthesizer using commercially available digital PLL components. The key feature of this method is the spectral purity and frequency resolution comparable with the solutions based on direct digital synthesizer chips. The last ones are not used in the described method that allows obtaining the substantial economy in size, cost and power consumption of the system.