“A l’alta fantasia qui mancò possa;
ma già volgeva il mio disio e ’l velle,
sì come rota ch’igualmente è mossa,
l’Amor che move il sole e l’altre stelle.”
La Divina Commedia
Paradiso, CANTO XXXIII, versetti 142–145
“Here force failed my high fantasy; but my
desire and will were moved already – like
a wheel revolving uniformly – by
the Love that moves the sun and the other stars.”
(Par. XXXIII, 142–145)
[Dante’s conclusion of The Divine Comedy. Canto XXXIII, Paradiso]
If ever there were an engineering book which deals with topics close to the functioning of the human brain, it is that on cognitive radar (CR).We say so because the preceptor of the brain follows modeling an environment and estimating its state, which is then followed by the executive for acting on the environment; this kind of scenario is beautifully made for CR, often referred to as the “Visual Radar” borrowed from the “Visual Brain.” In this context, it is noteworthy that in the IEEE International Radar Conference, 1990, Cognition was the first to be called the Visual Radar. What is important, however, is how to build a CR system to be successful; the answer to this profound question follows the four principles of cognition: the perception–action cycle (PAC), memory, attention, and intelligence; such a scenario reminds us of the engineering paradigm: divide and conquer. Out of these four principles, the most important is the PAC, on which the other principles build. It is therefore not surprising that the chapters in the book address the concepts of the PAC.
To this end, the chapters of this book are arranged as follows:
- How cognitive is radars today? This is the main question addressed in Chapter 1. The introduction of the radar management computer in modern phased-arrays radar provides a clue to the answer, whereby the quest to achieve increase of Cognition requires that the radar architecture and related functions are more aligned with architecture of the brain. A sequence of interlaced technology S curves, fitted by an exponential curve, illustrate the evolution of radar technology and system architecture through time. CRs of new generation are discussed that comply with the new operational requirements—always present in developing an industrial product—and exploit the enabling technologies available from today’s wide commercial developments.
- Chapter 2, entitled CR embodies the four principles of cognition, the essence of which is to address the PAC, memory, attention, and intelligence; the chapter illustrates how the CR tracks an object falling in space.
- Chapter 3 discusses the concept of cognitive constant false alarm rate (CFAR) detection providing a real data analysis to support it. The general scheme of a cognitive CFAR processor based on the interaction with endogenous and exogenous information sources is presented and its performance is analyzed in comparison with some classic radar architectures showing the potential benefits that cognition can provide.
- In Chapter 4, cognitive procedures are proposed to devise radar waveforms that exhibit desirable spectral features (ensuring coexistence with overlaid wireless networks) and optimize radar detection performance. It is supposed that the radar system has the ability to predict the behavior of surrounding licensed radiators, for instance using a radio environmental map (REM). The techniques consider as a prime example the signal to interference plus noise ratio (SINR) and optimize the transmitted radar waveform constraining the amount of interference energy on crowded/reserved frequency bands.
- Chapter 5 addresses cognitive joint design of the transmit radar waveform and receive Doppler filter bank in the presence of a reverberating environment for a search radar. In particular, to account for an unknown target Doppler shift, the worst case SINR at the output of the filter bank is considered as the figure of merit to optimize. By doing so, the effectiveness of the cognitive architecture is investigated and the potential performance benefits are highlighted.
- Chapter 6 discusses two underpinning principles of cognitive control, namely, learning and planning. After the mathematical formalization of the learning process in cognitive control, the proposed cognitive control learning algorithm is shown to be a special case of the celebrated Bellman’s dynamic programing, proving its convergence and optimality.
- Chapter 7 is devoted to the design of a tracker exploiting cognition at multiple levels (waveform diversity, validation ellipse size selection, confirmation parameters setting, etc.). Environmental maps and characteristics of the targets, available in the environmental database or learnt from the feedback channel, are used to gain improved performance in the tracking of multiple targets via measurements provided by a ship-borne radar operating in a littoral environment.
- Chapter 8 is focused on a typical example of cognition more in intimacy with the radar functions: “Anticipative Target Tracking” where the radar exploits some a-priori and contextual knowledge to improve the prediction and filtering of target tracks. This is certainly a noticeable selling point for CR systems. Anticipative target tracking is not a new concept. A paper dated 2002 describes the tracking of airborne targets occasionally hidden in the blind Doppler region. Another paper dated 2011 tackles the tracking of move–stop–move of many surface entities such as people and vehicles. The chapter reviews these and other application and real examples. Then it develops a new target tracking for docking, predator–prey, etc. applications. The task of intercepting a target and/or rendezvous is an important technical challenge that occurs in many defense operations as well as in civilian applications like robotics, simultaneous localization and map and similar. Here, the tracking filter develops both input platform guidance for docking and it refines step-by-step the radar radiated waveform to help improve either the relative track between the predator or the prey or the platform and the docking point. Cognition naturally blends with “on-the-fly” waveform update. In doing this, we try to mimic nature. In fact, bats during the search, detection, approach and capture phases shape the radiated nonlinear chirp to improve the range and Doppler measurements of their prey. A new tracking scheme is conceived and its working principle is suitably illustrated and tested with simulation study cases.
- Chapter 9 is devoted to the presentation of some miscellanea applications which could significantly benefit by the use of cognition. The first part is devoted to the presentation of the multiple input multiple output (MIMO) radar transmit beampattern design process which can highly take advantage of the cognitive paradigm. The second part of the chapter is focused on the electronic warfare (EW) domain. Finally, the last part concerns the domain of synthetic aperture radar (SAR) signal processing.
- Chapter 10 reconsiders arguments already mentioned in the previous chapters adding some new topics with the purpose of gaining application examples for CR thus moving from theories to suitable practice. “Intelligence” has been mentioned, as a capability of CR but a definition and a theory are not yet available today. An attempt to shed some light on the path to follow from information to intelligence theory is anyway sketched. Furthermore, the powerfulness of networks is surveyed, inspired by brain connectivity, social behavior, and so pervasive for modeling and processing almost everything. Controllability and complexity of a network is discussed and numerical examples are presented for few notional network topologies. Collective behavior, mimicked from nature (e.g., swarms), can be exploited in some practical applications for signal and data processing for CR and network of CRs. Exciting recent research and discoveries in neuroscience are offered to the attention of the reader from the specialized scientific literature. Potential applications to CR are also conjectured. The controversial discovery of memristor, the missing fourth element of circuits, is recollected together with its postulated role in the modeling of synapses and axons of brain. The potential cybersecurity issues, related to a radar network, are reviewed also from the CR vantage point, and suitable mitigation capabilities are argued. As usual for each chapter, conclusions, and references are provided.
As a final remark, the book is characterized by a uniform notation used within all the chapters which is reported at the end of this foreword.
Dear readers, your criticisms and comments are most welcome.
Please enjoy reading the book.
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