IR-UWB Detection and Fusion Strategies using Multiple Detector Types

Optimal detection of ultra wideband (UWB) pulses in a UWB transceiver employing multiple detector types is proposed and analyzed in this paper. We propose several fusion techniques for fusing decisions made by individual IR-UWB detectors. We assess the performance of these fusion techniques for commonly used detector types like matched filter, energy detector and amplitude detector. In order to perform this, we derive the detection performance equation for each of the detectors in terms of false alarm rate, shape of the pulse and number of UWB pulses used in the detection and apply these in the fusion algorithms. We show that the performance can be improved approximately by 4 dB in terms of signal to noise ratio (SNR) for perfect detectability of a UWB signal in a practical scenario by fusing the decisions from individual detectors.Comment: Accepted for publishing in IEEE WCNC 201

An efficient ultra-wideband digital transceiver for wireless applications on the field-programmable gate array platform

The ultra-wideband (UWB) technology is a promising short-range communication technology for most wireless applications. The UWB works at higher frequencies and is affected by interferences with the same frequency standards. This manuscript has designed an efficient and low-cost implementation of IEEE 802.15.4a-based UWB-digital transceiver (DTR). The design module contains UWB transmitter (TX), channel, and UWB-receiver (RX) units. Convolutional encoding and modulation units like burst position modulation and binary phase-shift keying modulation are used to construct the UWB-TX. The synchronization and Viterbi decoder units are used to recover the original data bits and are affected by noise in UWB-RX. The UWB-DTR is synthesized using Xilinx ISE® environment with Verilog hardware description language (HDL) and implemented on Artix-7 field-programmable gate array (FPGA). The UWB-DTR utilizes less than 2% (slices and look-up table/LUTs), operates at 268 MHz, and consumes 91 mW of total power on FPGA. The transceiver achieves a 6.86 Mbps data rate, which meets the IEEE 802.15.4a standard. The UWB-DTR module obtains the bit error rate (BER) of 2×10-4 by transmitting 105 data bits. The UWB-DTR module is compared with similar physical layer (PHY) transceivers with improvements in chip area (slices), power, data rate, and BER. 

Simulation and Design of an UWB Imaging System for Breast Cancer Detection

Breast cancer is the most frequently diagnosed cancer among women. In recent years, the mortality rate due to this disease is greatly decreased thanks to both enormous progress in cancer research, and screening campaigns which have allowed the increase in the number of early diagnoses of the disease. In fact, if the tumor is identied in its early stage, e.g. when it has a diameter of less than one centimeter, the possibility of a cure can reach 93%. However, statistics show that more young aged women are suered breast cancer. The goal of screening exams for early breast cancer detection is to nd cancers before they start to cause symptoms. Regular mass screening of all women at risk is a good option to achieve that. Instead of meeting very high diagnostic standards, it is expected to yield an early warning, not a denitive diagnosis. In the last decades, X-ray mammography is the most ecient screening technique. However, it uses ionizing radiation and, therefore, should not be used for frequent check-ups. Besides, it requires signicant breast compression, which is often painful. In this scenario many alternative technologies were developed to overcome the limitations of mammography. Among these possibilities, Magnetic Resonance Imaging (MRI) is too expensive and time-consuming, Ultrasound is considered to be too operatordependent and low specicity, which are not suitable for mass screening. Microwave imaging techniques, especially Ultra WideBand (UWB) radar imaging, is the most interesting one. The reason of this interest relies on the fact that microwaves are non-ionizing thus permitting frequent examinations. Moreover, it is potentially lowcost and more ecient for young women. Since it has been demonstrated in the literatures that the dielectric constants between cancerous and healthy tissues are quite dierent, the technique consists in illuminating these biological tissues with microwave radiations by one or more antennas and analyzing the re ected signals. An UWB imaging system consists of transmitters, receivers and antennas for the RF part, the transmission channel and of a digital backend imaging unit for processing the received signals. When an UWB pulse strikes the breast, the pulse is re ected due to the dielectric discontinuity in tissues, the bigger the dierence, the bigger the backscatter. The re ected signals are acquired and processed to create the energy maps. This thesis aims to develop an UWB system at high resolution for the detection of carcinoma breast already in its initial phase. To favor the adoption of this method in screening campaigns, it is necessary to replace the expensive and bulky RF instrumentation used so far with ad-hoc designed circuits and systems. In order to realize that, at the very beginning, the overall system environment must be built and veried, which mainly consists of the transmission channel{the breast model and the imaging unit. The used transmission channel data come from MRI of the prone patient. In order to correctly use this numerical model, a simulator was built, which was implemented in Matlab, according to the Finite-Dierence-Time- Domain (FDTD) method. FDTD algorithm solves the electric and magnetic eld both in time and in space, thus, simulates the propagation of electromagnetic waves in the breast model. To better understand the eect of the system non-idealities, two 2D breast models are investigated, one is homogeneous, the other is heterogeneous. Moreover, the modeling takes into account all critical aspects, including stability and medium dispersion. Given the types of tissues under examination, the frequency dependence of tissue dielectric properties is incorporated into wideband FDTD simulations using Debye dispersion parameters. A performed further study is in the implementation of the boundary conditions. The Convolution Perfectly Matched Layer (CPML) is used to implement the absorbing boundaries. The objective of the imaging unit is to obtain an energy map representing the amount of energy re ected from each point of the breast, by recombining the sampled backscattered signals. For this purpose, the study has been carried out on various beamforming in the literature. The basic idea is called as "delay and sum", which is to align the received signals in such a way as to focus a given point in space and then add up all the contributions, so as to obtain a constructive interference at that point if this is a diseased tissue. In this work, Microwave Imaging via Space Time (MIST) Beamforming algorithm is applied, which is based on the above principle and add more elaborations of the signals in order to make the algorithm less sensitive to propagation phenomena in the medium and to the non-idealities of the system. It is divided into two distinct steps: the rst step, called SKin Artifact Removal (SKAR), takes care of removing the contributions from the signal caused by the direct path between the transmitter and receiver, the re ection of skin, as they are orders of magnitude higher compared to the re ections caused by cancers; the second step, which is BEAmForming (BEAF), performs the algorithm of reconstruction by forming a weighted combination of time delayed version of the calibrated re ected signals. As discussed above, more attention must be paid on the implementation of the ad-hoc integration circuits. In this scenario, due to the strict requirements on the RF receiver component, two dierent approaches of the implementation of the RF front-end, Direct Conversion (DC) receiver and Coherent Equivalent Time Sampling (CETS) receiver are compared. They are modeled behaviorally and the eects of various impairments, such as thermal, jitter, and phase noise, as well as phase inaccuracies, non-linearity, ADC quantization noise and distortion, on energy maps and on quantitative metrics such as SCR and SMR are evaluated. Dierential Gaussian pulse is chosen as the exciting source. Results show that DC receiver performs higher sensitivity to phase inaccuracies, which makes it less robust than the CETS receiver. Another advantage of the CETS receiver is that it can work in time domain with UWB pulses, other than in frequency domain with stepped frequency continuous waves like the DC one, which reduces the acquisition time without impacting the performance. Based on the results of the behavioral simulations, low noise amplier (LNA) and Track and Hold Amplier (THA) can be regarded as the most critical parts for the proposed CETS receiver, as well as the UWB antenna. This work therefore focuses on their hardware implementations. The LNA, which shows critical performance limitation at bandwidth and noise gure of receiver, has been developed based on common-gate conguration. And the THA based on Switched Source Follower (SSF) scheme has been presented and improved to obtain high input bandwidth, high sampling rate, high linearity and low power consumption. LNA and THA are implemented in CMOS 130nm technology and the circuit performance evaluation has been taken place separately and together. The small size UWB wide-slot antenna is designed and simulated in HFSS. Finally, in order to evaluate the eect of the implemented transistor level components on system performance, a multi-resolution top-down system methodology is applied. Therfore, the entire ow is analyzed for dierent levels of the RF frontend. Initially the system components are described behaviorally as ideal elements. The main activity consists in the analysis and development of the entire frontend system, observing and complementing each other blocks in a single ow simulation, clear and well-dened in its various interfaces. To achieve that the receiver is modeled and analyzed using VHDL-AMS language block by block, moreover, the impact of quantization, noise, jitter, and non-linearity is also evaluated. At last, the behavioral description of antenna, LNA and THA is replaced with a circuit-level one without changing the rest of the system, which permits a system-level assessment of low-level issues

Timed array antenna system : application to wideband and ultra-wideband beamforming receivers

Antenna array systems have a broad range of applications in radio frequency (RF) and ultra-wideband (UWB) communications to receive/transmit electromagnetic waves from/to the sky. They can enhance the amplitude of the input signals, steer beams electronically, and reject interferences thanks to beamforming technique. In an antenna array beamforming system, delay cells with the tunable capability of delay amount compensate the relative delay of signals received by antennas. In fact, each antenna almost acts individually depending upon time delaying effects on the input signals. As a result, the delay cells are the basic elements of the beamforming systems. For this purpose, novel active true time delay (TTD) cells suitable for RF antenna arrays have been presented in this thesis. These active delay cells are based on 1st- and 2nd-order all-pass filters (APFs) and achieve quite a flat gain and delay within up to 10-GHz frequency range. Various techniques such as phase linearity and delay tunability have been accomplished to improve the design and performance. The 1st-order APF has been designed for a frequency range of 5 GHz, showing desirable frequency responses and linearity which is comparable with the state-of-the-art. This 1st-order APF is able to convert into a 2nd-order APF via adding a grounded capacitor. A compact 2nd-order APF using an active inductor has been also designed and simulated for frequencies up to 10 GHz. The active inductor has been utilized to tune the amount of delay and to reduce the on-chip size of the filter. In order to validate the performance of the delay cells, two UWB four-channel timed array beamforming receivers realized by the active TTD cells have been proposed. Each antenna channel exploits digitally controllable gain and delay on the input signal and demonstrates desirable gain and delay resolutions. The beamforming receivers have been designed for different UWB applications depending on their operating frequency ranges (that is, 3-5 and 3.1-10.6 GHz), and thus they have different system requirements and specifications. All the circuits and topologies presented in this dissertation have been designed in standard 180-nm CMOS technologies, featuring a unity gain frequency ( ft) up to 60 GHz.Els sistemes matricials d’antenes tenen una àmplia gamma d’aplicacions en radiofreqüència (RF) i comunicacions de banda ultraampla (UWB) per rebre i transmetre ones electromagnètics. Poden millorar l’amplitud dels senyals d’entrada rebuts, dirigir els feixos electrònicament i rebutjar les interferències gràcies a la tècnica de formació de feixos (beamforming). En un sistema beamforming de matriu d’antenes, les cèl·lules de retard amb capacitat ajustable del retard, compensen aquest retard relatiu dels senyals rebuts per les diferents antenes. De fet, cada antena gairebé actua individualment depenent dels efectes de retard de temps sobre el senyals d’entrada. Com a resultat, les cel·les de retard són els elements bàsics en el disseny dels actuals sistemes beamforming. Amb aquest propòsit, en aquesta tesi es presenten noves cèl·lules actives de retard en temps real (TTD, true time delay) adequades per a matrius d’antenes de RF. Aquestes cèl·lules de retard actives es basen en cèl·lules de primer i segon ordre passa-tot (APF), i aconsegueixen un guany i un retard força plans, en el rang de freqüència de fins a 10 GHz. Diverses tècniques com ara la linealitat de fase i la sintonització del retard s’han aconseguit per millorar el disseny i el rendiment. La cèl·lula APF de primer ordre s’ha dissenyat per a un rang de freqüències de fins a 5 GHz, mostrant unes respostes freqüencials i linealitat que són comparables amb l’estat de l’art actual. Aquestes cèl·lules APF de primer ordre es poden convertir en un APF de segon ordre afegint un condensador més connectat a massa. També s’ha dissenyat un APF compacte de segon ordre que utilitza una emulació d’inductor actiu per a freqüències de treball de fins a 10 GHz. S’ha utilitzat l'inductor actiu per ajustar la quantitat de retard introduït i reduir les dimensions del filtre al xip. Per validar les prestacions de les cel·les de retard propostes, s’han proposat dos receptors beamforming basats en matrius d’antenes de 4 canals, realitzats por cèl·lules TTD actives. Cada canal d’antena aprofita el guany i el retard controlables digitalment aplicats al senyal d’entrada, i demostra resolucions de guany i retard desitjables. Els receptors beamforming s’han dissenyat per a diferents aplicacions UWB segons els seus rangs de freqüències de funcionament (en aquest cas, 3-5 i 3,1-10,6 GHz) i, per tant, tenen diferents requisits i especificacions de disseny del sistema. Tots els circuits i topologies presentats en aquesta tesi s’han dissenyat en tecnologies CMOS estàndards de 180 nm, amb una freqüència de guany unitari (ft) de fins a 60 GHz.Postprint (published version

Development of a Real-time Ultra-wideband See Through Wall Imaging Radar System

Ultra-Wideband (UWB) See-Through-Wall (STW) technology has emerged as a musthave enabling technology by both the military and commercial sectors. As a pioneer in this area, we have led the research in addressing many of the fundamental STW questions. This dissertation is to investigate and resolve a few hurdles in advancing this technology, and produce a realizable high performance STW platform system, which will aid the STW community to find the ultimate answer through experimental and theoretical work. The architectures of a realizable STW imaging system are thoroughly examined and studied. We present both a conceptual system based on RF instruments and a standalone real-time system based on custom design, which utilize reconfigurable design architecture and allows scaling down/up to a desired UWB operating frequency with little difficulty. The systems will serve as a high performance platform for STW study and other related UWB applications. Along the way to a complete STW system, we have developed a simplified transmission line model for wall characteristic prediction; we have developed a scalable synthetic aperture array including both the RF part and the switch control/synchronization part; we have proposed a cost-effective and efficient UWB data acquisition method for real-time STW application based on equivalent-time sampling method. The measurement results reported here include static image formation and tracking moveable targets behind the wall. Even though digital signal processing to generate radar images is not the focus of this research, simple methods for image formation have been implemented and results are very encouraging

A 250-ps integrated ultra-wideband timed array beamforming receiver in 0.18 um CMOS

This paper presents a 4-channel ultra-wideband (UWB) timed array beamforming receiver designed in a standard 0.18-um CMOS technology. The proposed timed array receiver achieves a maximum delay of 250 ps at the maximum beam steering angle of +/-42o with 10.5o (8 steps) steering resolution and 2-cm antenna spacing. Each receiver channel provides gains ranging from 3.6 to -35 dB and less than 8% delay variation for all delay settings over a 3.1-10.6-GHz frequency range, while consuming a maximum of 58 mW power from a 1.8-V supply. The average -1-dB compression point P1dB is -9.9 dBm. The proposed architecture is modeled and simulated by using Virtuoso Cadence.This work has been partially supported by the Spanish Ministerio de Ciencia, Innovacion y Universidades (MICINN)- ´ Agencia Estatal de Investigacion (AEI) and the European ´ Regional Development Funds (FEDER), by project PGC2018- 098946-B-I00.Peer ReviewedPostprint (author's final draft

UWB Pulse Radar for Human Imaging and Doppler Detection Applications

We were motivated to develop new technologies capable of identifying human life through walls. Our goal is to pinpoint multiple people at a time, which could pay dividends during military operations, disaster rescue efforts, or assisted-living. Such system requires the combination of two features in one platform: seeing-through wall localization and vital signs Doppler detection. Ultra-wideband (UWB) radar technology has been used due to its distinct advantages, such as ultra-low power, fine imaging resolution, good penetrating through wall characteristics, and high performance in noisy environment. Not only being widely used in imaging systems and ground penetrating detection, UWB radar also targets Doppler sensing, precise positioning and tracking, communications and measurement, and etc. A robust UWB pulse radar prototype has been developed and is presented here. The UWB pulse radar prototype integrates seeing-through imaging and Doppler detection features in one platform. Many challenges existing in implementing such a radar have been addressed extensively in this dissertation. Two Vivaldi antenna arrays have been designed and fabricated to cover 1.5-4.5 GHz and 1.5-10 GHz, respectively. A carrier-based pulse radar transceiver has been implemented to achieve a high dynamic range of 65dB. A 100 GSPS data acquisition module is prototyped using the off-the-shelf field-programmable gate array (FPGA) and analog-to-digital converter (ADC) based on a low cost solution: equivalent time sampling scheme. Ptolemy and transient simulation tools are used to accurately emulate the linear and nonlinear components in the comprehensive simulation platform, incorporated with electromagnetic theory to account for through wall effect and radar scattering. Imaging and Doppler detection examples have been given to demonstrate that such a “Biometrics-at-a-glance” would have a great impact on the security, rescuing, and biomedical applications in the future

Performance evaluation of non-prefiltering vs. time reversal prefiltering in distributed and uncoordinated IR-UWB ad-hoc networks

Time Reversal (TR) is a prefiltering scheme mostly analyzed in the context of centralized and synchronous IR-UWB networks, in order to leverage the trade-off between communication performance and device complexity, in particular in presence of multiuser interference. Several strong assumptions have been typically adopted in the analysis of TR, such as the absence of Inter-Symbol / Inter-Frame Interference (ISI/IFI) and multipath dispersion due to complex signal propagation. This work has the main goal of comparing the performance of TR-based systems with traditional non-prefiltered schemes, in the novel context of a distributed and uncoordinated IR-UWB network, under more realistic assumptions including the presence of ISI/IFI and multipath dispersion. Results show that, lack of power control and imperfect channel knowledge affect the performance of both non-prefiltered and TR systems; in these conditions, TR prefiltering still guarantees a performance improvement in sparse/low-loaded and overloaded network scenarios, while the opposite is true for less extreme scenarios, calling for the developement of an adaptive scheme that enables/disables TR prefiltering depending on network conditions

Feasibility Study of a Mm-Wave Impulse Radio Using Measured Radio Channels

Abstract in Undetermined A millimeter-wave (mm-wave) impulse radio is an attractive alternative to existing high-speed mm- wave radio systems because of the potential for a simpler transceiver architecture. This paper studies the feasibility of a mm-wave impulse radio system for home and office use by considering state-of-the- art transceivers and multiple-input multiple-output measured propagation channels as well as the IEEE 802.15.3c channel model. Our analysis reveals that reliable data transmission is infeasible even in line-of-sight (LOS) scenarios because of a low power level at the Rx if we do not use beamforming. However, introducing 7×7 beamforming at the Tx dramatically improves the coverage beyond 5 m distance in the LOS scenario and up to 5 m in a non- line-of-sight (NLOS) scenario, though the performance varies in the NLOS scenario, depending on the Tx and Rx locations. We propose an adaptive transmit signaling scheme that adjusts the pulse repetition frequency depending on the delay dispersion of the propagation channel in order to avoid intersymbol interference and keep the Rx structure simple. The proposed transmit signaling scheme leads to a pulse transmission rate of 250 Mpulses/s in all measured channels while the rate is lower when the 802.15.3c model is considered because of a more multipath-rich characteristics than our measured channels