Abstract

Direct Digital Synthesis technique is fast evolving and is becoming a key point in the design of advanced communication equipments. The growing interest in the use of such a type of technique is strictly related to the increase of speed and bandwidth in the components and the corresponding achievement of attractive performance in terms of frequency resolution and spectral purity. The increase in the synthesised bandwidth forces the use of very high speed technologies and the use of gallium arsenide devices becomes mandatory to obtain the required performance. The gallium arsenide technology has been playing since many years ago a key role in high-speed analog communication, electronic warfare and analog MMICs but in the recent past has become an astounding weapon also for digital applications. Furthermore processes which combine low-power RF analog and LSI digital functions are now available and they represents a valid alternative to using discrete-components and multichip hybrids for low-power microwave designs. After a brief review of the DDS concept the paper describes the basic design of the Gallium arsenide numerically controlled oscillator which is the key element of the DDS chain. The experimental results are shown with a particular attention to the spectral purity performance and the modulation capability. The trend of the future on-board applications is given with emphasis on the projects in which Alenia Spazio is presently reusing this specific development.