• Coherent radar
• down-converter
• mode-locked laser (MLL)
• photonic transceiver
• software-defined radio (SDR)
• up-converter
• differential phase estimation
• dual-band radar
• microwave photonics.

This thesis is written in four chapters. In the first chapter, the relevance of this study in our present life and in our environment will be talked about. This system can be used to protect humanity from unforeseen events. In the second chapter, a photonics-based architecture of a multi-band coherent radar system is proposed and validated. The precision and flexibility of photonic technologies are exploited for generating and simultaneously detecting multiple radar signals in an extremely wide frequency range. Moreover, the fully digital approach enables the software-defined radio paradigm, allowing the flexible use of several advanced radar techniques such as waveform diversity or frequency hopping. The proposed architecture is therefore promising for future radar systems that need to adapt to different scenarios for improved situation awareness. The proposed system exploits a single laser unit for the multiband transmitter and receiver sections, reducing the architectural complexity with potential benefits on system dimensions, cost, and reliability. In this chapter, we also detailing the principle of operation of the proposed multi-band coherent radar system, and we describe the implementation of a proof-of-concept dual-band transceiver operating in the X- and S-bands simultaneously and independently. The results from the characterization of the transceiver are presented. The system validation through the coherent detection of moving targets confirms the suitability of the proposed solution, laying the basis for a new paradigm of radar systems.In the third chapter, the coherence phase among carriers generated on different frequency bands by the photonics-based radar is exploited to perform differential phase estimation for enhanced displacement measures. The system employs stepped frequency continuous waves simultaneously in the S- and X-band, measuring the differential phase over a synthetic band up to 7.4GHz. The experimental results demonstrate a precision < 200µm without using correction algorithms. At the middle of this chapter, the same dual-band radar system is used for precise target displacement measures in a multi-target scenario. The radar has been designed for the monitoring and the prevention of possible structural failures of buildings and landslides. There we present a preliminary numerical and experimental evaluation of the displacement accuracy in the case of a multi-target scenario. Our study is focused to understand the impact of multiple scatterers in the target displacement estimation. Simulation results show a typical displacement accuracy <0.2mm for considered distances up to 400m, in presence of five scatterers. These results are confirmed by preliminary experiment outcomes. At the end, we show the manually unwrapping phase with numerical result of a simple experiment with the new SFCW parameter. The fourth chapter is dedicated to conclusion and the next feature on the project.