Recursive direct digital synthesizer of complex broadband frequency-modulated signals

The major trends of the development of radiolocation, navigation and communication systems are: the application of higher frequencies and the transition to the use of complex signals for the creation of new advanced radio engineering systems with high resolution and noise immunity. Direct digital synthesizers (DDS), developed on the basis of the direct digital synthesis method, have unique technical characteristics and allow improving the parameters of radio engineering systems considerably.The article considers problems of increasing the linearity of the frequency change law of direct digital synthesizers due to the application of recursive principles of the formation of complex broadband frequency modulated signals. Electrical block diagrams of recursive and nonrecursive DDS allowing forming FM signals in a wide band of frequencies are presented. A recursive direct digital synthesizer allows achieving the high linearity of the frequency change law with the considerable capacity reduction of a phase accumulator (phase calculator) in comparison with the nonrecursive DDS.