Antennas for UWB Applications

“Antennas for UWB Applications” chapter deals with an overview of ultrawideband (UWB) antennas used for different applications. Some fundamental and widely used radiators, such as fat monopole, microstrip-fed and coplanar waveguide (CPW)-fed slot antennas, and tapered end-fire antennas are presented. Selected antenna designs are presented in relation to the UWB applications and their dictating radiation and operation principles. The demonstrated UWB antennas include antennas for handheld devices used for personal area network (PAN) communications; antennas for localization and positioning; UWB antennas for radio-frequency identifications (RFIDs); radar antennas for through-wall imaging, for ground-penetrating radar (GPR), and for breast tumor detection; and more generally, UWB antennas used for sensing. For some of the aforementioned applications, UWB antennas with special characteristics are needed, and they are presented and associated with the relevant applications. These include reconfigurable UWB antennas, metamaterial-loaded UWB antennas, and conformal UWB antennas. The usefulness of these special characteristics in comparison with the claimed advantages is critically evaluated. For the UWB applications presented in the chapter, one type or UWB antenna is recommended

Computational Microwave Imaging Using 3D Printed Conductive Polymer Frequency-Diverse Metasurface Antennas

A frequency-diverse computational imaging system synthesized using three-dimensional (3D) printed frequency-diverse metasurface antennas is demonstrated. The 3D fabrication of the antennas is achieved using a combination of PolyLactic Acid (PLA) polymer material and conductive polymer material (Electrifi), circumventing the requirement for expensive and time-consuming conventional fabrication techniques, such as machine milling, photolithography and laser-etching. Using the 3D printed frequency- diverse metasurface antennas, a composite aperture is designed and simulated for imaging in the K-band frequency regime (17.5-26.5 GHz). The frequency-diverse system is capable of imaging by means of a simple frequency-sweep in an-all electronic manner, avoiding mechanical scanning and active circuit components. Using the synthesized system, microwave imaging of objects is achieved at the diffraction limit. It is also demonstrated that the conductivity of the Electrifi polymer material significantly affects the performance of the 3D printed antennas and therefore is a critical factor governing the fidelity of the reconstructed images.Comment: Original manuscript as submitted to IET Microwaves, Antennas & Propagation (2017). 17 pages, 8 figure

Behind-wall target detection using micro-doppler effects

Abstract: During the last decade technology for seeing through walls and through dense vegetation has interested many researchers. This technology offers excellent opportunities for military and police applications, though applications are not limited to the military and police; they go beyond those applications to where detecting a target behind an obstacle is needed. To be able to disclose the location and velocity of obscured targets, scientists’ resort to electromagnetic wave propagation. Thus, through-the-wall radar (TWR) is technology used to propagate electromagnetic waves towards a target through a wall. Though TWR is a promising technology, it has been reported that TWR imaging (TWRI) poses a range of ambiguities in target characterisation and detection. These ambiguities are related to the thickness and electric properties of walls. It has been reported that the mechanical and electric properties of the wall defocus the target image rendered by the radar. The defocusing problem is the phenomenon of displacing the target away from its true location when the image is rendered. Thus, the operator of the TWR will have a wrong position, not the real position of the target. Defocusing is not the only problem observed while the signal is travelling through the wall. Target classification, wall modelling and others are areas that need investigation...D.Ing. (Electrical and Electronic Engineering

Radio wave imaging using Ultra-Wide Band Spectrum Antennas for Near-Field Applications. Design, Development, and Measurements of Ultra-Wideband Antenna for Microwave Near-Field Imaging Applications by applying Optimisation Algorithms

The emergence of Ultra-wideband (UWB) technology application has yielded tremendous and vital impacts in the field of microwave wireless communications. These applications include military radar imaging, security screening, and tumour detection, especially for early detection of breast cancer. These indicators have stimulated and inspired many researchers to make the best use of this promising technology. UWB technology challenges such as antenna design, the problem of imaging reconstruction techniques, challenges of severe signal attenuation and dispersion in high loss material. Others are lengthy computational time demand and large computer memory requirements are prevalent constraints that need to be tackled especially in a large scale and complex computational electromagnetic analysis. In this regard, it is necessary to find out recently developed optimisation techniques that can provide solutions to these problems. In this thesis, designing, optimisation, development, measurement, and analysis of UWB antennas for near-field microwave imaging applications are considered. This technology emulates the same concept of surface penetrating radar operating in various forms of the UWB spectrum. The initial design of UWB monopole antennas, including T-slots, rectangular slots, and hexagonal slots on a circular radiating patch, was explicitly implemented for medical imaging applications to cover the UWB frequency ranging from 3.1 GHz to 10.6 GHz. Based on this concept, a new bow-tie and Vivaldi UWB antennas were designed for a through-the-wall imaging application. The new antennas were designed to cover a spectrum on a lower frequency ranging from 1 GHz - 4 GHz to ease the high wall losses that will be encountered when using a higher frequency range and to guarantee deeper penetration of the electromagnetic wave. Finally, both simulated and calculated results of the designed, optimised antennas indicate excellent agreement with improved performance in terms of return loss, gain, radiation pattern, and fidelity over the entire UWB frequency. These breakthroughs provided reduced computational time and computer memory requirement for useful, efficient, reliable, and compact sensors for imaging applications, including security and breast cancer detection, thereby saving more lives.Tertiary Education Trust Fund (TET Fund) Supported by the Nigerian Defence Academy (NDA

Radar Imaging in Challenging Scenarios from Smart and Flexible Platforms

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Through-The-Wall Detection Using Ultra Wide Band Frequency Modulated Interrupted Continuous Wave Signals

Through-The-Wall-Detection (TTWD) techniques can improve the situational awareness of police and soldiers, and support first responders in search and rescue operations. A variety of systems for TTWD based on different waveforms have been developed and presented in the literature, e.g. radar systems based on pulses, noise or pseudo-noise waveforms, and frequency modulated continuous wave (FMCW) or stepped frequency continuous wave (SFCW) waveforms. Ultra wide band signals are normally used as they provide suitable resolution to discriminate different targets. A common problem for active radar systems for TTWD is the strong backscattered signal from the air-wall interface. This undesired signal can overshadow the reflections from actual targets, especially those with low radar cross section like human beings, and limit the dynamic range at the receiver, which could be saturated and blocked. Although several techniques have been developed to address this problem, frequency modulated interrupted continuous wave (FMICW) waveforms represent an interesting further approach to wall removal, which can be used as an alternative technique or combined with the existing ones. FMICW waveforms have been used in the past for ionospheric and ocean sensing radar systems, but their application to the wall removal problem in TTWD scenarios is novel. The validation of the effectiveness of the proposed FMICW waveforms as wall removal technique is therefore the primary objective of this thesis, focusing on comparing simulated and experimental results using normal FMCW waveforms and using the proposed FMICW waveforms. Initially, numerical simulations of realistic scenarios for TTWD have been run and FMICW waveforms have been successfully tested for different materials and internal structure of the wall separating the radar system and the targets. Then a radar system capable of generating FMICW waveforms has been designed and built to perform a measurement campaign in environments of the School of Engineering and Computing Sciences, Durham University. These tests aimed at the localization of stationary targets and at the detection of people behind walls. FMICW waveforms prove to be effective in removing/mitigating the undesired return caused by antenna cross-talk and wall reflections, thus enhancing the detection of targets

UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

ANALYSIS AND DESIGN OF ANTENNA PROBES FOR DETECTION / IMAGING APPLICATIONS

Analysis and Design of Antenna Probes for Detection / Imaging Applications Ayman Elboushi, Ph.D. Concordia University. As a result of increasing international terrorist threats, the need for an efficient inspecting tool has become urgent. Not only for seeing through wall applications, but also to be employed as a safe human body scanner at public places such as airports and borders. The usage of microwave and millimeter wave antennas and systems for detection / imaging applications is currently of increasing research interest targeting the enhancement of different security systems. There are many challenges facing researchers in order to develop such systems. One of the challenges is the proper design of a low cost, reduced size and efficient antenna probe to work as a scanning sensor. In this thesis, two different technology choices of antenna probes for the feasibility of constructing detection / imaging systems are investigated. The first one covers the Ultra Wide Band (UWB) range (3.1 GHz to 10.6 GHz), while the second operates over the Millimeter-Wave (MMW) range. In addition to the development of several antenna probes, two detection / imaging systems are demonstrated and showed reasonably accurate detection results. Three different UWB monopole antenna prototypes, with different radiator shapes (circular, crescent and elliptical) have been introduced. These antennas are designed using a standard printed circuit board (PCB) process to work as probing sensors in a proposed UWB detection / imaging system. In order to enhance the resolution and the detection accuracy of the probe, 4-element Balanced Antipodal Vivaldi Antenna (BAVA) array fed by 1-to-4 UWB modified Wilkinson power divider has been developed. Some successful experiments have been conducted using the proposed UWB detection / imaging system combined with the fabricated antenna probes to detect the presence of a gap between two walls made of different material types, to evaluate the gap width and to estimate the size and exact location of a hidden target between the walls. The second research theme of this thesis is to develop small-sized, light-weight and high gain MMW scanning antenna probes. For the realization of such probes, several gain enhancement techniques have been adopted, including hybridization and a multi-element array principle. Several high-gain hybrid antennas have been designed, fabricated and tested. For demonstration purposes, experiments have been carried out for detecting and imaging a small metallic coin under the jeans layer of a three-layer target emulating a human body’s covering layers. A performance comparison between a standard metallic MMW horn and hybrid microstrip patch/conical horn antenna has been made. The proposed reduced size antenna sensor shows increased efficiency compared with the bulky horn antenna. Resolution enhancement of the reconstructed image of the hidden target is implemented using a new triple-antenna MMW sensor. The triple-antenna sensor consists of three adjacent microstrip patch / conical horn antennas separated by 1.5 wavelengths at the center frequency for coupling reduction between these elements. The middle element of the sensor is used for monitoring the time domain back-reflected signal from the target under inspection, while the side elements are used for monitoring the scattered signals. By the aid of a special signal processing algorithm, an enhanced image of the concealed object can be obtained by combining the three readings of each point in the area under study. The proposed system shows a great ability for detecting a hidden target and enhances the reconstructed image resolution

New broadband, low cost and compact MIMO radar frontends

En esta disertación industrial, se han abordado una variedad de nuevas ideas. En el capítulo 2, se expone una breve introducción a la teoría básica de los radares tipo MIMO, así como también conceptos esenciales como FMCW, TDM o la estimación de ángulos. En el siguiente capítulo, un radar de tipo MIMO es presentado. En el varias tarjetas de circuitos impresos son apiladas, creando de esta forma, una agrupación de antenas de gran ancho de banda bidimensional. Mis trabajo es presentado en este capítulo, así también como las imágenes radar finales. Al final, el incremento de resolución debido a la técnica MIMO se demuestra exitosamente. Una iteración de el prototipo es presentado en el capítulo 4. Este radar sustituye las múltiples tarjetas impresas por una sola, la cual contiene RSPA basadas en cavidades de aire. Este circuito se ha diseñado con dos cadenas de conmutadores independientes, de tal forma que se dos formas de onda podrían ser enviadas de forma simultánea. Por ello, un radar en tiempo real, como por ejemplo un radar OFMD puede ser probado con este hardware. La característica zona vacía de los radares MIMO ha sido ocupada con una segunda funcionalidad. Primero, con antenas espirales para las comunicaciones y después a cámara, la cual mejora la detección, clasificación y el rastreo de objetivos. El capítulo 5 introduce novedosos componentes de RF, de muy ancho de banda e integrables con tarjetas de circuito impreso como un Divisor Wilkinson y una antena impresa en 3D. Estos componentes han sido diseñado, fabricado y medido de forma satisfactoria. El gran ancho de banda objetivo permite a estos componentes operar para múltiples funciones. El capítulo 6 introduce nuevos componentes clave de bajas pérdidas como el acoplador Moreno y la antena de guía de ondas ranurada en una nueva y prometedora tecnología. ESIW reduce las pérdidas de las guías de ondas integradas eliminando el dieléctrico interno. Estos componentes han sido diseñados, fabricados y medidos. Los prototipos producidos son un primer paso antes de un refinamiento final antes de introducir el producto al mercado. Además, se han explorado tecnología más disruptivas para futuros proyectos.In this industrial dissertation, a variety of new and creative ideas has been adressed. In Chapter 2, a brief introduction to an existing MIMO radar theory as well as to the neccessary basic concepts of FMCW, TDM and angle estimation has been given. After that, in Chapter 3 a complete and fully functional MIMO radar has been presented. The sandwich approach enabled to stack PCBs to make up a modular bi-dimensional array of very wideband TSA antennas. My contributions to this radar have been presented in detail as well as the final imaging results, in which the increment of the resolution due to the MIMO technique has succesfully been tested. A next iteration of the portotype has been introduced in Chapter 4. This radar replaces the multiple stacked PCBs by a single one, which is populated with air-cavity-based RSPAs. This PCB has been designed with two independent switch chains, in such a manner that the two different waveforms can be sent simultaneously. Therefore, a real time radar, as for instance OFMD can be tested with this hardware. The characteristic inoccupied space at the center of a bidimentional MIMO array is filled with a second funtionality. Firstly, spiral antennas for communication have been designed, integrated and tested. Secondly, the spiral antennas have been cut off. In the remaining hole, a camara, which improves the detection, clasification and tracking of targets, has been placed. Chapter 5 presents new, very broadband (4-40 GHz) and integrable-with-PCBs RF components as a Wilkinson divider and a 3D printed TEM horn antenna. These components have succesfuly been designed, fabricated and tested. The targeted wide frequency range allows the usage of these components for multiple functions. In Chapter 6 new low losses key components as the Moreno cross-guide coupler and slotted waveguide antenna are presented in a new very promising technology. ESIW reduces the loss of the integrated waveguides (SIW) by removing the inner dielectric, following a very interesting fabrication process. These two components have been, designed, fabricated and measured. On one hand, the produced prototypes are the first step towards further Airbus refinement before introducing a product to the market. On the other hand, some disruptive technologies and components have been explored in order to keep track of the following advances in terms of innovation.En aquesta dissertació industrial, s'han abordat una varietat de noves idees. En el capítol 2, s'exposa una breu introducció a la teoria bàsica dels radars tipus MIMO i conceptes essencials com FMCW, TDM o l'estimació d'angles. En el següent capítol, un radar de tipus MIMO és presentat. Diverses targetes de circuits impresos són apilades, creant d'aquesta manera, una agrupació d'antenes bidimensional de gran ample de banda. El meu treball és presentat en aquest capítol, així també com les imatges radar finals. Al final, l'increment de resolució a causa de la tècnica MIMO es demostra amb èxit. La següent iteració del prototip és presentada al capítol 4. Aquest radar substitueix les múltiples targetes impreses per una sola, la qual conté RSPA basades en cavitats d'aire. Aquest circuit s'ha dissenyat amb dues cadenes de commutadors independents, de tal manera que dues formes d'ona podrien ser enviades de forma simultània. Per això, un radar en temps real, com per exemple un radar OFMD pot ser provat amb aquest radar. La característica zona buida dels radars MIMO ha estat ocupada amb una segona funcionalitat. Primer, amb antenes espirals per a les comunicacions i després per a càmera, la qual millora la detecció, classificació i el rastreig d'objectius. El capítol 5 introdueix nous components de RF, de molt ample de banda i integrables amb targetes de circuit imprès com un Divisor Wilkinson i una antena impresa en 3D. Aquests components han estat dissenyats, fabricats i mesurats de forma satisfactòria. El gran ample de banda objectiu permet a aquests components operar per a múltiples funcions. El capítol 6 introdueix nous components clau de baixes pèrdues com el acoblador Moreno i l'antena de guia d'ones ranurada en una nova i prometedora tecnologia. ESIW redueix les pèrdues de les guies d'ones integrades eliminant el dielèctric intern. Aquests components han estat dissenyats, fabricats i mesurats. Els prototips produïts són un primer pas abans d'un refinament final abans d'introduir el producte al mercat. A més, s'han explorat tecnologia més disruptives per a futurs projectes.Miralles Navarro, E. (2018). New broadband, low cost and compact MIMO radar frontends [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107960TESI

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance