Nowadays, satellites equipped with synthetic aperture radars (SARs) find use in a plethora of applications that are essential for realising the green transition of the world: from forest and sea-level monitoring to biomass estimation, passing through homeland security and disaster prevention and mitigation. In addition, SAR satellites represent an enabling technology at the basis of several disciplines in Earth and Planetary sciences.
A SAR system essentially consists of two parts: the reflector and the active phased array. The last one is an array of antenna elements, where the relative phase of each element is properly controlled by a phase shifter to steer the radiation pattern in the desired direction (i.e., the main lobe), whereas the radiation is minimised in the undesired directions (i.e., the side lobes).

In the last twenty years, Digital Beamforming Synthetic Aperture Radar (DBSAR) Systems are gradually superseding their analogue version. It is not surprising that the evolution for these systems is very similar to what we saw in the past concerning microwave instrumentation. Among different examples, the most suitable one is probably represented by the spectrum analyser. Starting from a fully analogue swept-tuned architecture, its first digital version saw the Analog-to-Digital Converters (ADC) cascaded to the video filter at the end of the acquisition channel, whereas nowadays, its progeny, the so-called vector signal analyser, has the ADC just after the Intermediate Frequency (IF) filter, featuring an analysis bandwidth of 1-GHz, which enables the complete analysis of modern radar and communication signals based on complex wideband modulations. The described development was driven by the availability of increasingly performing ADCs at a lower cost. In SAR systems the tendency is exactly the same: to move the digital interface towards the antenna, replacing analogue hardware. The main difference between the two scenarios is that SAR systems are composed of hundreds or thousands front-end modules, which define the radar performance in terms of spatial resolution and coverage, and for each one is required a digital acquisition board.

The aim of the present project is to study and empirically demonstrate the feasibility of an X-band DBSAR for spaceborne applications, taking advantage of the disruptive capabilities of Gallium Nitride (GaN) electronics at microwave frequencies.