The development of radar has been one of the most successful direct applications of physics ever attempted, and then implemented and applied at large scale. Certain watchwords of radar engineering have underpinned many of the developments of the past 80 years and remain potential avenues for improvement. For example, 'Narrow beams are good', 'Fast detection is good', 'Agility is good', and 'Clutter is bad'. All these statements of merit are true. The underlying principles for all these statements are the laws of physics, and they provide support for current radar designs. However, each of these statements is really a design choice, rather than their necessary consequence. This book shows that under the physical laws and with modern data processing, staring radar offers a new direction of travel. The process of detection and tracking can be updated through persistent signal discovery and target analysis, without losses in sensitivity, and while delivering detailed information on target dynamics and classification. The first part of the book introduces various forms of staring radar, which include the earliest and simplest forms of electromagnetic surveillance and its users. The next step is to summarise the physical laws under which all radar operates, and the requirements that these systems need or will need to meet to fulfil a range of applications. We are then able to be specific about the technology needed to implement staring radar.
Inspec keywords: remote sensing by radar; plasma flow; radar detection; search radar; radar imaging
Other keywords: search radar detection; plasma flow; remote sensing; radar imaging; holographic staring radar
Subjects: Signal detection; Radar equipment, systems and applications; Optical, image and video signal processing; General electrical engineering topics
Radar, the use of radio signals non-cooperatively to determine the presence and trajectory of air and marine craft, grew out of an urgent need for long-range threat warning. It has since become a customary feature of airports, ships, military aircraft and ground operations, and more recently of cars on public roads. During World War II, radar both exploited and drove the development of radio systems and electronics, playing a major role in several theatres of war. Its earliest forms were ground-based, massive, static structures that were soon to be replaced by more compact systems capable of both search and tracking functions.
In this chapter the roles and requirements for surveillance radar are briefly reviewed in order to provide the background against which applications particularly suited to a ground-based staring radar configuration can be introduced. Most modern surveillance radar systems carry out multiple tasks such as detection, tracking and, sometimes, target classification. Examples include civil and military Air Traffic Management (ATM), maritime surveillance and military air-defence radar.
This chapter aims to outline how radar signals, scattered by objects of interest within a VoR, communicate descriptive information about those objects, their positions and motions, and how they can be analysed and understood remotely. We have set out the physical laws governing the function of radar, and introduced the premise that for objects large enough to scatter EM waves of a given wavelength, and for radars with sufficient power and resolution, solutions can be found for all such objects.
Staring radar is finding a raft of applications, sometimes in areas of traditional radar operation and sometimes as a reaction to environmental changes and new target types. Here, we consider just a sample of current and emerging applications that fit well with the attributes of staring radar, and the challenges and requirements they impose.
The discussion of staring radar will benefit from identifying a small number of examples of HSR configurations. Without limiting the discussion to these examples, they will provide a simple way of referring to specifics, and a basis for comparing approaches. This chapter provides reference points with which the relationship between physics and the engineering of HSR can be explored.
This chapter describes the range of signals that can be expected at the aperture and its constituent receiving array, and methods by which the presence of targets may be captured and other influences including clutter, noise, phase noise, multipath and interference may influence the process. Staring radar is process-intensive, and the necessary capacity will only be manageable provided that it can use extensive parallel computing capacity efficiently. It will then support surveillance requirements that include classification and discrimination between different targets and behaviours. The ATC example is used to investigate a high level of processing demand.
This book relies on the robustness of the electromagnetic uniqueness theorem. It presents opportunities that might stress practicality; in particular most functions of a staring surveillance radar will depend on substantial computing resources that require the capacity and speed of several still-advancing technologies. To assure surveillance functions under challenging target conditions that will test the resilience of these theories and methods, we shall consider what methods can work, what capacity will be needed for the performance of staring radar in reality and whether that is likely to be affordable.
The evidence indicates that continual, regular observations, made available by staring radar, offer benefits in signal quality and surveillance capability. The next step is to explore what is to be gained by further continuing coherent observations. This chapter focuses on extended observation of targets known to be of interest, and their potential for deeper analysis, including target dynamics and suppression of repetitive clutter.
This chapter provides, in some detail, the physical basis on which HSR satellite returns are identifiable and how the information they convey can be decoded and describes why that information provides for their suppression. For radar practitioners whose constant and justified focus is on minimising false alarms, satellites generated by scanning radar are anathema, but are relatively rare. For HSR they occur more frequently, but persistent, coherent observation makes them identifiable as features of propagation in the CVoR whose origin can be found, and the effects suppressed.
This chapter is an enquiry into constructive spectrum re-use within a wide-area air surveillance network, under conditions where congestion, re-assignment or sharing of the radio spectrum with other services might threaten aspects of performance. The primary issues in this more speculative chapter are as follows: spectrum demands for operation, mutual interference of surveillance radars, operation, target identity and measurement, resilience to external interference.
This book has addressed the possibility that a logjam has arisen in radar development not because the radar is insufficiently agile, but because the resulting short dwell times restrict the scanned information to a small fraction of what can be encoded in continually scattered and observed target returns. In this book, we have aimed to establish expectations of performance under a finite set of conditions ranging from normal to challenging, based on applying the EM uniqueness theorem through a series of propagation models. In summary, the results suggest that substantial advances in radar surveillance depend on the recognition that continuity in measurement is more important than agility and speed of detection, and that staring, persistent and coherent radar can enable otherwise inaccessible surveillance capabilities.