FMCW Radar with Enhanced Resolution and Processing Time by Beam Switching

We present the design of a novel K-band radar architecture for short-range target detection. Applications include direction finding systems and automotive radar. The developed system is compact and low cost and employs substrate-integrated-waveguide (SIW) antenna arrays and a $4\times 4$ Butler matrix (BM) beamformer. In particular, the proposed radar transmits a frequency modulated continuous-wave (FMCW) signal at 24 GHz, scanning the horizontal plane by switching the four input ports of the BM in time. Also, in conjunction with a new processing method for the received radar signals, the architecture is able to provide enhanced resolution at reduced computational burden and when compared to more standard single-input multiple-output (SIMO) and multiple-input multiple-output (MIMO) systems. The radar performance has also been measured in an anechoic chamber and results have been analyzed by illuminating and identifying test targets which are 2° apart, while also making comparisons to SIMO and MIMO FMCW radars. Moreover, the proposed radar architecture, by appropriate design, can also be scaled to operate at other microwave and millimeter-wave frequencies, while also providing a computationally efficient multi-channel radar signal processing platform

Quality of service optimization of multimedia traffic in mobile networks

Mobile communication systems have continued to evolve beyond the currently deployed Third Generation (3G) systems with the main goal of providing higher capacity. Systems beyond 3G are expected to cater for a wide variety of services such as speech, data, image transmission, video, as well as multimedia services consisting of a combination of these. With the air interface being the bottleneck in mobile networks, recent enhancing technologies such as the High Speed Downlink Packet Access (HSDPA), incorporate major changes to the radio access segment of 3G Universal Mobile Telecommunications System (UMTS). HSDPA introduces new features such as fast link adaptation mechanisms, fast packet scheduling, and physical layer retransmissions in the base stations, necessitating buffering of data at the air interface which presents a bottleneck to end-to-end communication. Hence, in order to provide end-to-end Quality of Service (QoS) guarantees to multimedia services in wireless networks such as HSDPA, efficient buffer management schemes are required at the air interface. The main objective of this thesis is to propose and evaluate solutions that will address the QoS optimization of multimedia traffic at the radio link interface of HSDPA systems. In the thesis, a novel queuing system known as the Time-Space Priority (TSP) scheme is proposed for multimedia traffic QoS control. TSP provides customized preferential treatment to the constituent flows in the multimedia traffic to suit their diverse QoS requirements. With TSP queuing, the real-time component of the multimedia traffic, being delay sensitive and loss tolerant, is given transmission priority; while the non-real-time component, being loss sensitive and delay tolerant, enjoys space priority. Hence, based on the TSP queuing paradigm, new buffer managementalgorithms are designed for joint QoS control of the diverse components in a multimedia session of the same HSDPA user. In the thesis, a TSP based buffer management algorithm known as the Enhanced Time Space Priority (E-TSP) is proposed for HSDPA. E-TSP incorporates flow control mechanisms to mitigate congestion in the air interface buffer of a user with multimedia session comprising real-time and non-real-time flows. Thus, E-TSP is designed to provide efficient network and radio resource utilization to improve end-to-end multimedia traffic performance. In order to allow real-time optimization of the QoS control between the real-time and non-real-time flows of the HSDPA multimedia session, another TSP based buffer management algorithm known as the Dynamic Time Space Priority (D-TSP) is proposed. D-TSP incorporates dynamic priority switching between the real-time and non-real-time flows. D-TSP is designed to allow optimum QoS trade-off between the flows whilst still guaranteeing the stringent real-time component’s QoS requirements. The thesis presents results of extensive performance studies undertaken via analytical modelling and dynamic network-level HSDPA simulations demonstrating the effectiveness of the proposed TSP queuing system and the TSP based buffer management schemes

Single-cell tracking of therapeutic cells using Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry

Cellular therapy is emerging as a clinically viable strategy in the field of solid organ transplantation, where it is expected to reduce the dependency on conventional immunosuppression. This has produced a demand for highly sensitive methods to monitor the persistence and tissue distribution of administered cells in vivo. However, tracking cells presents significant challenges. In many cases transplanted cells are autologous with the immune system of the transplant recipient, and hence are invisible to typical methods of detection. To enable their differentiation, the cells must be labelled with a suitable, non-toxic and long lifetime label, prior to their administration to patients. In addition, administered cells represent only a small fraction of the recipient’s endogenous cells, which necessitates the use of an extremely sensitive detection method. Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) is an exquisitely sensitive analytical technique, capable of imaging trace elements in complex samples, at high spatial resolution. [Continues.

Space transportation system and associated payloads: Glossary, acronyms, and abbreviations

A collection of some of the acronyms and abbreviations now in everyday use in the shuttle world is presented. It is a combination of lists that were prepared at Marshall Space Flight Center and Kennedy and Johnson Space Centers, places where intensive shuttle activities are being carried out. This list is intended as a guide or reference and should not be considered to have the status and sanction of a dictionary

Space Transportation System and associated payloads: Glossary, acronyms, and abbreviations

A collection of acronyms now in everyday use in the Shuttle world are listed. It is a combination of lists that were prepared at the Kennedy and Johnson Space Centers and by the Air Force

Antenna array design for retrodirective wireless power transmission and radar

This thesis presents antenna array design and the integration of microwave circuit systems for retrodirective wireless power transmission and radar. Wireless power transmission (WPT) and automotive radar are emerging topics which have attracted a lot of interest in the past few years. The development of these systems usually brings high associated costs if competitive performance is required. The first part of the thesis is concerned with the development of a new retrodirective antenna array (RDA) system for WPT which uses sub-arrays in transmit to save costs, however, losing tracking in one plane. Nevertheless, depending on the application, the proposed system might be an alternative solution to existing approaches as similar performances are achieved, but at generally a lower cost for the proposed RDA design as compared to the conventional solution. The proposed system has been designed to work in the ISM band (2.5 GHz for receiving and 2.4 GHz for transmitting) which exhibits an 80◦ 3-dB half-power beamwidth for the monostatic pattern. Additionally, it has been demonstrated that the system is able to work in the near-field region, being able to achieve wireless charging of a handeld electronic device at a 50 cm distance. The power for the beacon signal sent by the device to be charged by the system (for tracking purposes) is 6.6 dBm, whereas the received RF power from the RDA is in excess of 27 dBm, which means that the device is receiving a hundred times the power sent for battery charging. On the other hand, the second part of the thesis relates to the development of two important elements within a frequency-modulated-continuous-wave (FMCW) auto motive radar working at 24 GHz: a substrate integrated waveguide (SIW) butler matrix antenna array as the transmitter and a new post-processing technique called Pwr+. These two in combination bring some interesting advantages in terms of angular resolution improvements when compared to conventional single-input-multiple output (SIMO) radars. For example, the proposed system is able to distinguish two targets which are 2 degrees apart as well as a higher field-of-view (FOV) thanks to the beamforming network that generates 4 individual beams covering a wide FOV. The newly developed radar system is also comparable to multiple-input-multiple output (MIMO) radars but with the added value of having a shorter processing time, which for automotive radar applications is a crucial characteristic to be minimized, and could, therefore, avoid potential road accidents. It should also be mentioned that this thesis was supported by the Samsung Advanced Institute of Technology

Impact of biopolymer matrices on relaxometric properties of MRI contrast agents and their application to Nanotechnology

Magnetic Resonance Imaging (MRI) represents the first-line diagnostic imaging modality for numerous indications. It is a clinically well-established, non-invasive technique providing three dimensional whole body anatomical and functional imaging. It takes advantage of the magnetic properties of water protons present in the body and their tissue-dependent behaviour. High magnetic fields (1.5 T and above) are clinically favoured because of their higher signal-to-noise ratio, capability for MR spectroscopy, and other forms of functional MRI, high speed imaging, and high resolution imaging. Signal intensity in MRI is related to the relaxation rate of in vivo water protons and can be enhanced by the administration of a contrast agent (CA) prior to scanning. These CAs utilize paramagnetic metal ions and enhance the contrast in an MR image by positively influencing the relaxation rates of water protons in the immediate surroundings of the tissue in which they localize. Among different CAs, Gadolinium contrast medium is used in up to 30% of MRI scans and the most clinically-used MRI. However, Gadolinium (Gd), like most of the clinically-used CAs, is characterized by a relaxivity well below its theoretical limit, lacks in tissue specificity and, in addition, it causes heavy allergic effects and serious nephrotoxicity. In this framework, Port et al. have reported that the rigidification of MRI CAs, obtained through covalent or non-covalent binding to macromolecules, could be favourable to an increase in relaxivity of the metal-chelate. Later, Decuzzi et al. have proved that it is possible to modify through the geometrical confinement the magnetic properties of MRI CAs by controlling their characteristic correlation times without the chemical modification of the chelate structure. Furthermore, Courant et al. have highlighted the capability of combined hydrogels to boost the relaxivity of Gd-based CAs. Despite several experimental studies addressed in this field, a comprehensive knowledge of the mechanisms involved in the relaxation enhancement due to the entrapment of CAs in polymer-based architectures is still missing. In particular, the role played by the water at the interface between polymer chains and MRI CAs has not been fully investigated and could lead to the availability of tailored models that accurately describe these novel complex systems. In this work, we aim to demonstrate that a more in-depth knowledge about the interference between macromolecules and MRI CAs and an understanding of their physicochemical properties can significantly to impact in the design strategies of the nanostructures and, consequently, to overcome the limitations of clinically used MRI CAs, particularly linked to the low relaxivity. In this perspective, it is of primary importance to study the main phenomena involved in the formation of polymer matrices and how their properties can influence the relaxivity of MRI CAs. For this reason, we proposed a general strategy based on formation of nanostructures for boosting the efficacy of commercial Gd-based CAs by using FDA approved biopolymers, providing also tissue specificity and reduced nephrotoxicity. Indeed, we want to take advantage not only by the use of nanotechnologies for enhanced MRI but only by their capability to reach a specific target and to accumulate only in the site of interest. The implemented strategy has consisted in the control of the relaxometric properties by tuning the water dynamics, the physicochemical interactions and, therefore, the polymer conformation. Effectively, we primary investigated, in bulk, the impact of hydrogel solutions on the relaxometric properties of commercial CAs, highlighting the key role of hydrogel structural parameters (mesh size and crosslink density) in the relaxation enhancement. In this part, chemical and thermodynamic interactions involved in the complexation between biopolymers and CAs have been investigated through Isothermal Titration Calorimetry. Furthermore, characterizations of water dynamics and mobility and measurement of the relaxometric properties in hydrogel solutions containing CAs have been carried out by NMR and Time-Domain relaxometer. The main outputs were summarized in a concept called Hydrodenticity and defined as the equilibrium between the water osmotic pressure, the elastodynamic forces of the polymer chains and the hydration degree of the CA which is able to increase the relaxivity of the CA itself. Indeed, hydrogel nanostructures made of hydrophilic polymer chains held together by chemical or physical crosslinking, have the ability to swell in water, forming elastic gels that retain a large quantity of fluid in their mesh-like structures. The presence of hydrophilic polymer interfaces and the control of water behaviour in hydrogels play a fundamental role in the relaxation enhancement of the Gadolinium-based CAs by influencing the characteristic correlation times defined by the theory of Solomon and Bloembergen. Then, starting from the acquired knowledge, we moved to observe the role of Hydrodenticity in the design of biopolymer nanostructures for enhanced MRI. For the nanostructures’ synthesis, we used two different processing techniques: (1) High Pressure Homogenization; (2) Microfluidic Flow Focusing. These techniques were selected because of their ability to control process parameters enabling the tuning of the interaction between the biopolymers and the CA. Indeed, by easily adjusting concentrations, pressure of the Homogenizer and/or flow rates of the Microfluidic platform, we can modulate the crosslinking degree of the nanostructures and tune their hydrophilicity, size, shape and surface charge, impacting on the relaxometric properties. These approaches allow us to load MRI CAs into functional nanostructures and obtain nanocarries with tunable relaxometric properties. The powerful aspect and the novelty of our approach lies in the definition of Hydrodenticity and in its application to several architectures, biopolymers, lipids and mixture of them., preserving the main properties of nanoparticles for drug delivery. As future perspective, the nanostructures can also be engineered to carry more than one agent, accumulate in specific tissues or to act as probes for simultaneous diagnosis and therapy (theranostic or multimodal imaging agents), thereby facilitating targeted treatments and precision medicine

NASA Tech Briefs, May 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences