On the Use of Passive Reflecting Surfaces and Compressive Sensing Techniques for Detecting Security Threats at Standoff Distances

This work presents a new radar system concept, capable of detecting explosive related threats at standoff distances. The system consists of a two-dimensional aperture of randomly distributed transmitting/receiving antenna elements and a set of passive reflecting surfaces (PRS) positioned in the vicinity of the target. The PRS act as a mirror that enhances the field of view of the radar system, thus increasing its resolution. A 3D imaging algorithm, based on novel compressive sensing techniques, is used in this work. This system configuration provides a resolution of 7.1 mm in cross-range and 25 mm in range, when the target is at 10 m range, and the radar works at 60 GHz center frequency and has 6 GHz bandwidth

Millimeter wave imaging : a historical review

The SPIE Passive and Active Millimeter Wave Imaging conference has provided an annual focus and forum for practitioners in the field of millimeter wave imaging for the past two decades. To celebrate the conference's twentieth anniversary we present a historical review of the evolution of millimeter wave imaging over the past twenty years. Advances in device technology play a fundamental role in imaging capability whilst system architectures have also evolved. Imaging phenomenology continues to be a crucial topic underpinning the deployment of millimeter wave imaging in diverse applications such as security, remote sensing, non-destructive testing and synthetic vision.Publisher PD

Microwave imaging for security applications

Microwave imaging technologies have been widely researched in the biomedical field where they rely on the imaging of dielectric properties of tissues. Healthy and malignant tissue have different dielectric properties in the microwave frequency region, therefore, the dielectric properties of a human body’s tissues are generally different from other contraband materials. Consequently, dielectric data analysis techniques using microwave signals can be used to distinguish between different types of materials that could be hidden in the human body, such as explosives or drugs. Other concerns raised about these particular imaging systems were how to build them cost effectively, with less radiation emissions, and to overcome the disadvantages of X-ray imaging systems. The key challenge in security applications using microwave imaging is the image reconstruction methods adopted in order to gain a clear image of illuminated objects inside the human body or underneath clothing. This thesis will discuss in detail how microwave tomography scanning could overcome the challenge of imaging objects concealed in the human body, and prove the concept of imaging inside a human body using image reconstruction algorithms such as Radon transformation image reconstruction. Also, this thesis presents subspace based TR-MUSIC algorithms for point targets and extended targets. The algorithm is based on the collection of the dominant response matrix reflected by targets at the transducers in homogenous backgrounds, and uses the MUSIC function to image it. Lumerical FDTD solution is used to model the transducers and the objects to process its response matrix data in Matlab. Clear images of metal dielectric properties have been clearly detected. Security management understanding in airports is also discussed to use new scanning technologies such as microwave imaging in the future.The main contribution of this reseach is that microwave was proved to be able to image and detect illegal objects embedded or implanted inside human body

Indoor Full-Body Security Screening: Radiometric Microwave Imaging Phenomenology and Polarimetric Scene Simulation

The paper discusses the scene simulation of radiometric imagers and its use to illustrate the phenomenology of full-body screening of people for weapons and threats concealed under clothing. The aperture synthesis technique is introduced as this offers benefits of wide field-of-views and large depths-of-fields in a system that is potentially conformally deployable in the confined spaces of building entrances and at airport departure lounges. The technique offers a non-invasive, non-cooperative screening capability to scrutinize all human body surfaces for illegal items. However, for indoor operation, the realization of this capability is challenging due to the low radiation temperature contrasts in imagery. The contrast is quantified using a polarimetric radiometric layer model of the clothed human subject concealing threats. A radiation frequency of 20 GHz was chosen for the simulation as system component costs here are relatively low and the attainable half-wavelength spatial resolution of 7.5 mm is sufficient for screening. The contrasts against the human body of the threat materials of metal, zirconia ceramic, carbon fiber, nitrogen-based energetic materials, yellow beeswax, and water were calculated to be ≤7 K. Furthermore, the model indicates how some threats frequency modulate the radiation temperatures by ~ ±1 K. These results are confirmed by experiments using a radiometer measuring left-hand circularly polarized radiation. It is also shown using scene simulation how circularly polarized radiation has benefits for reducing false alarms and how threat objects appear in canyon regions of the body, such as between the legs and in the armpits

Study on THz Imaging System for Concealed Threats Detection.

PhD ThesisMany research groups have conducted studies on Terahertz technology for various applications in the last decades. THz imaging for personnel screening is one prospective application due in part to its superior performance compared with imaging microwave bands. Because of the demand for the accurate detection, it is desirable to devise a high-performance THz imaging system for concealed threats detection. Therefore, this thesis presents my research on the low-cost THz imaging system for security detection. The key contributions of this research lie in investigating the linear sparse periodic array (SPA) THz imaging system for concealed threats detection, improving the traditional reconstruction algorithm of Generalized Synthetic Aperture Focusing Technique (GSAFT) to suppress the ghost images and applying the compressive sensing technique into the proposed SPA-THz imaging system to reduce the sampling data but maintain the image quality. The first part of the work is to investigate the linear sparse periodic array (SPA) and its configuration with large element spacing in simulation, deriving the design guideline for such a SPA THz imaging system. Meanwhile, the improved GSAFT reconstruction algorithm and multi-pass interferometric synthetic aperture imaging technique have been proposed to suppress the ghost image and improve the image quality, respectively. Secondly, the compressive sensing technique has been investigated to reduce the sampling data. Therefore, we have proposed the corresponding discrete CS SPA-THz reconstruction model and verified it in simulation. Finally, we have devised a simplified experimental set-up to assess the practical imaging performance, verifying the proposed SPA-THz imaging system. The set-up only uses 1 Tx and 1 Rx scanning on two separate tracks to effectively realize the proposed imaging system. The reconstructed images by the GSAFT and CS approaches with the measured data have both shown good consistency with the simulated results, respectively. And the multi-pass interferometric synthetic aperture imaging has been experimentally proved effective in improving image SNR and contras

Development of techniques and technology for full polarimetric radar applied to concealed weapons detection

One of the biggest threats to modern society is the increasing use by criminals and terrorists of concealed weapons and person born improvised explosive devices (PBIED). Current highly mature security screening technologies using x-ray and metal detectors have limited deployment scenarios based on health and safety issues and operational range, respectively. Given that most clothing is greater than 90% transmissive in the microwave region, this spectral band is ideal for screening people for concealed threats. However, due to diffraction, imagery to screen subjects is limited due to the small number of pixels. In this regime, the exploitation of microwave polarimetry from the field of remote sensing has particular benefits, as it extracts maximum information content from a single pixel. The work presented in this thesis has assembled a full polarimetric frequency stepped radar from a vector network analyser (VNA), a linear orthogonal mode transducer (OMT) of the turnstile type and a conical corrugated horn antenna. The system’s characterisation by antenna pattern measurements, the measuring of canonical targets of the plane, dihedral, dipole and helical reflectors showed the system to be capable of making localised Sinclair matrix measurements of targets at ranges of two to three metres. The work presents a calibration procedure comprising the VNA’s internal calibration and an external calibration to compensate for dispersion and cross-polar leakage of system components. Static target measurements (canonical and various surrogate items) were analysed, using range gating for clutter rejection. Calibrated Sinclair parameter measurements compared with those from simple simulations, all software being programmed in Matlab. Measurements of moving targets revealed the phenomenon of speckle, this introducing rapid changes in the Sinclair Parameters. Data analysis performed using the coherency matrix and the Cloude/Pottier decomposition minimised the effects of speckle in the processed data. Measurements show movement from particularly rough surfaces increased the parameter of the Cloude/Pottier entropy, the level of this being directly linked to the degree of speckle. Application of the Huynen polarisation fork technique (a type of decomposition) has proved to aid the identification of static and moving targets. A detailed analysis of iii the Huynen fork responses is made of the human torso on its own, weapons on their own and then weapons positioned against the human torso. Responses of nondangerous objects such as keys and a smartphone are additionally presented

Late time response analysis in UWB radar for concealed weapon detection : feasibility study

Remote detection of body-worn concealed weapons or explosives (CWE) is a field of ongoing research. In this Thesis the feasibility of CWE detection by using the UWB radar is explored. The CWE detection is based on the analysis of the Late Time Response (LTR) of the human which has been illuminated by the UWB signal. A specific set of LTR parameters characterizes the target signature. Therefore the existence of a CWE attached on the human body will influence the LTR characteristics and give the composite object i.e. human-CWE a different signature than the simple object i.e. human. The CWE detection methodology is verified by theoretical analysis, modelling and extensive laboratory experimentation. Investigation of the way the LTR parameters are influenced by the existence of the CWE signifies the differences of the LTR signature between the human and human-CWE. So the resolution of the differences in the LTR of a human with and without a CWE as the main objective of the research, are presented in the Thesis. The results verify that CWE detection with the use of LTR is feasible under the experimental conditions presented. Furthermore consideration of all possible detection scenarios is out of the scope of this Thesis.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

1995 BRAC Commission

Data Call - Naval Command, Control and Ocean Surveillance Center, Research Development Test Evaluation Division - San Diego, CA. Data Call #5. Box 186, L-118

Air Traffic Management Abbreviation Compendium

As in all fields of work, an unmanageable number of abbreviations are used today in aviation for terms, definitions, commands, standards and technical descriptions. This applies in general to the areas of aeronautical communication, navigation and surveillance, cockpit and air traffic control working positions, passenger and cargo transport, and all other areas of flight planning, organization and guidance. In addition, many abbreviations are used more than once or have different meanings in different languages. In order to obtain an overview of the most common abbreviations used in air traffic management, organizations like EUROCONTROL, FAA, DWD and DLR have published lists of abbreviations in the past, which have also been enclosed in this document. In addition, abbreviations from some larger international projects related to aviation have been included to provide users with a directory as complete as possible. This means that the second edition of the Air Traffic Management Abbreviation Compendium includes now around 16,500 abbreviations and acronyms from the field of aviation