DISARMA - DIgital Synthetic Aperture Radars to MAintain National Excellence in Space Applications

Abstract:

In the last twenty years, as will be deeply discussed in the state-of-the-art section, 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. Moreover, it should be pointed out that, since SAR front-end modules are used not only for receiving but also for transmitting microwave signals, in a fully digital architecture, it is necessary to consider both Digital-to-Analog (DAC) and ADC. However, as we will see, digital beamforming on-receive-only systems are also common in literature. The digital innovation shows disruptive advantages in terms of flexibility and reconfigurability. In fact, the beamforming is entirely realised by means of digital signal processing (DSP), which means that the system can be reconfigured by software. The scope 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. The research units involved in the present project have an internationally recognized know-how in terms of characterization and modelling of electron devices and circuit design at microwave frequencies. Moreover, to reach such a challenging target, an industrial advisory board (IAB) is also established. The IAB will be composed by members belonging to the following companies:

- Thales Alenia Space, which has 40 years of heritage in worldwide radar missions.

- Anteverta-mw, which manufactured the first large-signal vector network analyser ensuring 1-GHz modulation bandwidth analysis.

- MEC srl, which has designed many microwave circuits in GaN technology for SAR applications.