Interferometric Radar System including a Photonics-based Architecture for Remote Sensing Applications

This thesis presents the development of different systems for next generation radar transceivers and applications. In particular, three main works are described in the context of radar systems: automotive applications, dual-use radar/communication system and environmental monitoring. The first work regards the use of interferometric radar techniques for automotive applications. This work is the first one that uses interferometric measurements in the context of automotive applications to measure the height of road speed bumps. Currently, this task is usually performed by other types of systems (e.g., video cameras, GPS, Lidar systems). The interferometric techniques can prevail over traditional methods in many ways, specially due to the fact that radar based techniques can provide this kind of obstacle detection even at night or under adverse weather conditions. Here, an interferometric radar system at 24 GHz is used to detect small road objects, in this case speed bumps. Experimental results confirm the effectiveness of the method employed to estimate the bump’s height, and it can be used in the context of driver assistance or even driverless cars in a future. The second work is the implementation of a dual-use radar/communication (rad/comm) system using a photonics-based radar transceiver. Firstly, we introduce the concept of photonics and how it enabled the enhancement of purely electronic radars, resulting in the development the first dual-band photonics-based radar system. Afterwards, the dual-band functionality was tested within the scope of this thesis, for the first time in a dual-use rad/comm scenario. The analysis presents no penalty induced by the coexistence of the two operations, thus proving the effectiveness of the photonic-based transceiver as dual-use simultaneous system. Future radar transceivers are likely to communicate with each other and with the surrounding environment while performing traditional radar tasks. Although multifunctional radar transceivers can be found in the literature, it is the first time that a dual-band photonics-based radar unit is used for a simultaneous transmission and reception of a dual-use radar/comm system. Finally, the third work comprises for the first time the development of a dual-band photonics-based transceiver for environmental monitoring, which is divided in two stages: single and multiple scatterer case. The system performs monitoring of ground displacements, as landslides, based on the principle of differential interferometry, which translates the phase variations into small displacement measures. The combination of several sinusoidal waveforms allows to synthesize a large signal bandwidth, which provides improved range cell resolution. Moreover, the dual-band capability allows to enhance the displacement measure accuracy, due to the possibility of applying the advanced interferometric techniques among the different frequency bands. The system was tested in a single and in a multiple scatterer scenario reaching a sub-mm resolution without correction algorithms, proving the effectiveness of the system for the target applications. The use of two bands also confers an improved robustness to the environmental conditions, and allow to use different system parameters simultaneously. Moreover, it also allows a reduction of SWaP and footprint of the whole system, greatly benefiting future radar transceivers, which will render more information, be more flexible while providing a reduction of dimensions and costs. Although there are three different works apparently uncorrelated, the main scientific novelty lies in the third project, i.e., the use of interferometric techniques using a dual-band photonics-based architecture for environmental monitoring. The idea was to exploit both interferometry and the dual-band capability of the photonics system to show their broad potentiality even in different contexts. For this reason, interferometry has been applied for automotive applications, showing its effectiveness to measure small objects for future driverless cars. On the other hand, the dual-band photonics system has been properly verified in a dual-use radar/comm scenario. Finally, both features are explored in the third project to bring up a new paradigm in the context of remote sensing applications for environmental monitoring, due to its characteristics, i.e. robustness to environmental conditions, combination of multiple bands to make the system more precise, software-defined radio architecture, reduced dimensions and power, etc. For so, it is not only more versatile compared to ground-based interferometric radar systems already present in the literature, but also is a strong candidate for fulfilling the requirements of next generation radar systems.