Radar is a powerful tool for detecting and tracking airborne targets such as aircraft and missiles by day and night. Nowadays, it is seen as a genuine solution to the problem of target recognition. Recent events showed that cooperative means of identification such as the IFF transponders carried by most aircraft are not entirely reliable and can be switched off by terrorists. For this reason, it is important that target identification be obtained through measurements and reconnaissance based on non-cooperative techniques. In practice, recognition is achieved by comparing the electromagnetic sig nature of a target to a set of others previously collected and stored in a library. Such signatures generally represent the targets reflectivity as a function of space. A common representation is known as one-dimensional high-resolution range-profile (HRRP) and can be described as the projection of the reflectivity along the direction of propagation of the wave. When the measured signature matches a template, the target is identified. The main drawback of this technique is that signatures greatly vary with aspect-angle so that measurements must be made for many angles and in three dimensions. This implies a potentially large cost as large datasets must be created, stored and processed. Besides, any modification of the target structure may yield incorrect classification results. Instead, other processing techniques exist that rely on recent mathematical algorithms. These techniques can be used to extract target features directly from the radar data. Because of the direct relation with target geometry, these feature-based methods seem to be suitable candidates for reducing the need of large databases. However, their performances and their domains of validity are not known. This is especially true when it comes to real targets for at least three reasons. First, the performance of the methods varies with the signal-to-noise ratio. Second, man-made targets arc often more complex than just a set of independent theoretical point-like scatterers. Third, these targets are made up of a large number of scattering elements so that mathematical assumptions are not met. In conclusion, the physical correctness of the computational models are questionable. This thesis investigates the processing techniques that can be used for non-cooperative target recognition. It demonstrates that the scattering-centre extraction is not suitable for the model-based approach. In contrast, it shows that the technique can be used with the feature-based approach. In particular, it investigates the recognition when achieved directly in the z-domain and proposes a novel algorithm that exploits the information al ready in the database for identifying the signal features that corresponds to physical scatterers on the target. Experiments involving real targets show that the technique can enhance the classification performance and therefore could be used for non-cooperative target recognition.

To obtain adequately narrow beams, high frequency radars (HF) commonly employ long receiving arrays since they must be large in comparison with the transmission wavelengths. In such radars the overall system beamwidth can be reduced for a given size of the receiving array, by transmitting signals sequentially from a small number of sector coverage antennas, suitably positioned relative to the array. A comprehensive study of this technique applied to the frequency modulated continuous wave radars (FMCW) is presented, and the bearing- Doppler ambiguities arising from the use of sequential transmission have been investigated. The practical usefulness of the technique has been verified experimentally by measuring the overall system beam patterns both before and after the application of a dual transmission scheme. The experimental procedure required an active transponder capable of simulating a target of large echoing area, a special beam forming network capable of slewing the receiving beam in small steps, and a dual transmission switching unit. The design and development of these items of test equipment are discussed. Radar signal processing using the double Fourier transformation with subsequent phase correction has been proposed, and the recorded experimental data was processed according to these techniques. The measured beam patterns have been presented for single and dual transmission schemes. In addition to the beam narrowing studies a family of slow rise of sensitivity sequences (SRS) have been developed which could improve FMCW radar operation in a monostatic mode, also a new and compact shaping and switching signal generator has been designed and developed.

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In recent years, several emerging technologies in modern radar system design are attracting the attention of radar researchers and practitioners alike, noteworthy among which are multiple-input multiple-output (MIMO), ultra wideband (UWB) and joint communication-radar technologies. This thesis, in particular focuses upon a cognitive approach to design these modern radars. In the existing literature, these technologies have been implemented on a traditional platform in which the transmitter and receiver subsystems are discrete and do not exchange vital radar scene information. Although such radar architectures benefit from these mentioned technological advances, their performance remains sub-optimal due to the lack of exchange of dynamic radar scene information between the subsystems. Consequently, such systems are not capable to adapt their operational parameters “on the fly”, which is in accordance with the dynamic radar environment. This thesis explores the research gap of evaluating cognitive mechanisms, which could enable modern radars to adapt their operational parameters like waveform, power and spectrum by continually learning about the radar scene through constant interactions with the environment and exchanging this information between the radar transmitter and receiver. The cognitive feedback between the receiver and transmitter subsystems is the facilitator of intelligence for this type of architecture. In this thesis, the cognitive architecture is fused together with modern radar systems like MIMO, UWB and joint communication-radar designs to achieve significant performance improvement in terms of target parameter extraction. Specifically, in the context of MIMO radar, a novel cognitive waveform optimization approach has been developed which facilitates enhanced target signature extraction. In terms of UWB radar system design, a novel cognitive illumination and target tracking algorithm for target parameter extraction in indoor scenarios has been developed. A cognitive system architecture and waveform design algorithm has been proposed for joint communication-radar systems. This thesis also explores the development of cognitive dynamic systems that allows the fusion of cognitive radar and cognitive radio paradigms for optimal resources allocation in wireless networks. In summary, the thesis provides a theoretical framework for implementing cognitive mechanisms in modern radar system design. Through such a novel approach, intelligent illumination strategies could be devised, which enable the adaptation of radar operational modes in accordance with the target scene variations in real time. This leads to the development of radar systems which are better aware of their surroundings and are able to quickly adapt to the target scene variations in real time.

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This thesis for a PhD by Publication attempts to demonstrate the author’s contribution towards the development of terrestrial satellite radar interferometry (InSAR) for geohazard applications between 1995 and 2016. The author’s role is shown by reference to six peer-reviewed articles, and five ‘documents of influence’ that demonstrate key pieces of work that helped progress the application of InSAR technology. The work included ranged from the first InSAR-related contract to be funded by ESA, through the introduction of InSAR into the CEO’s Disaster Management Support project that influenced both the Space Charter for Major Disasters and the Global Monitoring for Environment and Security programme, to the widespread exploitation and standardisation of InSAR seen in the Terrafirma and FP7 PanGeo projects. The author’s contributions have resulted in a wider-spread InSAR awareness and expertise, direct support to the European Space Agency’s flagship application of the time, the inclusion of InSAR within Copernicus services, and support to the mission-design of Sentinel-1a/b.

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