Hand gesture classification using 24 GHz FMCW dual polarised radar

All rights reserved. This paper evaluates the classification performance of a dual polarised on receive, 24 GHz Frequency Modulated Continuous Wave (FMCW) radar system to autonomously identify micro-Doppler signatures of unique hand gestures. We employ an Eigen subspace feature selection technique on the calculated signal subspace in order to classify each gesture. Measurements using the dual polarised radar, permitting simultaneous recording of both the co-pol and cross-pol returns, are evaluated with this processing technique and results are reported herein. Our analysis displays the challenges presented by the high variance in individuals gestures and the limited additional information the cross polarised returns have provided to the classifier. Classification performance comparisons are presented when co, cross and dual polarised data are provided to the classifier. With this technique we achieve autonomous classification performance of up to 84.6% when Eigenvalue derived features are used for classification

Radar UAV and Bird Signature comparisons with Micro-Doppler

This chapter reviews the similarities and differences between micro Unmanned Aerial Vehicles (UAVs), also referred to as drones, and bird targets from the signals they present to radar sensors. With the increasing usage of UAV platforms in both military and civilian applications, the demand for the ability to sense drone locations and discriminate them from background clutter and non-drone targets is becoming a vital requirement. A comparable target in size, speed and Radar Cross Section (RCS) is a bird. These are present almost everywhere that radar systems have to operate and have been detected by radar since the early origin of radar engineering. Due to the similarity in radar signature birds can cause common misclassification between them and the priority drone targets which has been identified as a current key challenge in radar sensing. In this chapter radar bird and drone signature research is initially summarised, then a fundamental model that represents the key contributions from drone rotor blades is introduced and compared to real measurements. Laboratory measurements of quadcopter rotor blade signatures with across 4 linear polarisations are then investigated in order to evaluate the trend of Signal-to-Noise-Ratio (SNR) vs. aspect angle. Next bird signatures from two separate radar systems are shown and compared to drone targets also present in the captures which are of comparable size and RCS. The outputs of all research presented are then summarised in the concluding remarks

Near field sensing and antenna design for wireless body area network

PhD ThesisWireless body area network (WBAN) has emerged in recent years as a special class of wireless sensor network; hence, WBAN inherits the wireless sensor network challenges of interference by passive objects in indoor environments. However, attaching wireless nodes to a person’s body imposes a unique challenge, presented by continuous changes in the working environment, due to the normal activities of the monitored personnel. Basic activities, like sitting on a metallic chair or standing near a metallic door, drastically change the antenna behaviour when the metallic object is within the antenna near field. Although antenna coupling with the human body has been investigated by many recent studies, the coupling of the WBAN node antenna with other objects within the surrounding environment has not been thoroughly studied. To address the problems above, the thesis investigates the state-of-the art of WBAN, eximanes the influence of metallic object near an antenna through experimental studies and proposes antenna design and their applications for near field environments. This thesis philosophy for the previously mentioned challenge is to examine and improve the WBAN interaction with its surrounding by enabling the WBAN node to detect nearby objects based solely on change in antenna measurements. The thesis studies the interference caused by passive objects on WBAN node antenna and extracts relevant features to sense the object presence within the near field, and proposes new design of WBAN antenna suitable for this purpose. The major contributions of this study can be summarised as follows. First, it observes and defines the changes in the return loss of a narrow band antenna when a metallic object is introduced in its near field. Two methods were proposed to detect the object, based on the refelction coefficient and transmission coefficient of an antenna in free space. Then, the thesis introduces a new antenna design that conforms to the WBAN requirements of size, while achieving very low sensitivity to human body. This was achieved through combining two opposite Vivaldi shapes on one PCB and using a metallic sheet to act as a reflector, which minimised the antenna coupling with the human body and reduced the radiation pattern towards the body. Finally, the proposed antennas were tested on several human body parts with nearby metallic objects, to compare the change in antenna s-parameters due to presence of the human body and presence of the metallic object. Based on the measurements, basic statistical indicators and Principal Component Analysis were proposed to detect object presense and estimate its distance. In conclusion, the thesis successfully shows WBAN antenna’s ability to detect nearby metallic objects through a set of proposed indicators and novel antenna design. The thesis is wrapped up by the suggestion to investigate time domain features and modulated signal for future work in WBAN near field sensing

Structure and Optimisation of Liquid Crystal based Phase Shifter for Millimetre-wave Applications

The delivery of tunable millimetre-wave components at 60GHz is of research and development interests with the advent of 5G era. Among applications such as high-data-rate wireless communications, high-precision automotive radars and hand-gesture sensing, variable phase shifters are vital components for antenna arrays to steer an electromagnetic beam without mechanical movement. However, present microwave technology has limited scope in meeting more and more stringent requirements in wavefront phase control and device performance for those cutting-edge applications in the millimetre-wavelength range. Although some existing microwave switchable techniques (such as RF MEMS and solid-state p-i-n diodes) can offer ultra-fast speed for phase modulation, their binary beam-steering nature is resolution-limited and thereby degrades the beam-scanning performance. In response to this, continuously-tunable phase shifting can be realised by using tunable dielectric materials such as ferroelectric BST and liquid crystals (LCs). BST thin films can offer relatively fast switching and modest tunability. However, the increased dielectric loss beyond 10GHz impedes their implementation for higher frequency applications. By comparison, liquid crystals (LCs) have drawn attention in recent years because of their continuous tunability as well as low losses especially at millimetre-wavebands. The principle of shifting the phase continuously is based on the shape anisotropy of LC molecules for variable polarizabilities and hence tunable dielectric constants, which allows wave speed to be controlled with ease by a low-frequency field of only up to 10V. However, LC-based tunable delay lines are not well established in the frequency regime of 60GHz-90GHz because of the limited status of LC microwave technology in which most of the LC based devices have been designed for below 40GHz. It is the aim of this PhD research to bridge the gap and address future societal needs based on our group’s focus and experience in developing cutting-edge LC-based agile microwave components. In this work, a liquid crystal (LC) based 0-180˚continuously-variable phase shifter is developed with insertion loss less than -4.4dB and return loss below -15dB across a wide spectrum from 54GHz to 67GHz. The device is driven by a 0-10V AC bias and structured in a novel enclosed coplanar waveguide (ECPW) including an enclosed ground plate in the design, which significantly reduces the instability due to floating effects of the transmission line. This structure screens out interference and stray modes, allowing resonance-free quasi-TEM wave propagation up to 90GHz. The tunable ECPW is optimised by competing spatial volume distribution of the millimetre-wave signal occupying lossy tunable dielectrics versus low-loss but non-tunable dielectrics and minimising the total of dielectric volumetric loss and metal surface loss for a fixed phase-tuning range. A variety of influences affecting the actual device performance are studied, experimented and optimised. Fabricated prototypes exhibit wideband low-loss performance and 0-π continuous tuning with low power consumptions and high linearity compared with the state-of-the-arts. Potentially, the ECPW-fed phased antenna array will be incorporated with advanced beam-forming algorithms to develop compact beam-steering systems of improved performances and targeted for ultra-high-data-rate wireless communications, inter-satellite communications, current road safety improvement, futuristic autonomous driving, and other smart devices such as the hand-gesture recognition

Advanced signal processing solutions for ATR and spectrum sharing in distributed radar systems

Previously held under moratorium from 11 September 2017 until 16 February 2022This Thesis presents advanced signal processing solutions for Automatic Target Recognition (ATR) operations and for spectrum sharing in distributed radar systems. Two Synthetic Aperture Radar (SAR) ATR algorithms are described for full- and single-polarimetric images, and tested on the GOTCHA and the MSTAR datasets. The first one exploits the Krogager polarimetric decomposition in order to enhance peculiar scattering mechanisms from manmade targets, used in combination with the pseudo-Zernike image moments. The second algorithm employs the Krawtchouk image moments, that, being discrete defined, provide better representations of targets’ details. The proposed image moments based framework can be extended to the availability of several images from multiple sensors through the implementation of a simple fusion rule. A model-based micro-Doppler algorithm is developed for the identification of helicopters. The approach relies on the proposed sparse representation of the signal scattered from the helicopter’s rotor and received by the radar. Such a sparse representation is obtained through the application of a greedy sparse recovery framework, with the goal of estimating the number, the length and the rotation speed of the blades, parameters that are peculiar for each helicopter’s model. The algorithm is extended to deal with the identification of multiple helicopters flying in formation that cannot be resolved in another domain. Moreover, a fusion rule is presented to integrate the results of the identification performed from several sensors in a distributed radar system. Tests performed both on simulated signals and on real signals acquired from a scale model of a helicopter, confirm the validity of the algorithm. Finally, a waveform design framework for joint radar-communication systems is presented. The waveform is composed by quasi-orthogonal chirp sub-carriers generated through the Fractional Fourier Transform (FrFT), with the aim of preserving the radar performance of a typical Linear Frequency Modulated (LFM) pulse while embedding data to be sent to a cooperative system. Techniques aimed at optimise the design parameters and mitigate the Inter-Carrier Interference (ICI) caused by the quasiorthogonality of the chirp sub-carriers are also described. The FrFT based waveform is extensively tested and compared with Orthogonal Frequency Division Multiplexing (OFDM) and LFM waveforms, in order to assess both its radar and communication performance.This Thesis presents advanced signal processing solutions for Automatic Target Recognition (ATR) operations and for spectrum sharing in distributed radar systems. Two Synthetic Aperture Radar (SAR) ATR algorithms are described for full- and single-polarimetric images, and tested on the GOTCHA and the MSTAR datasets. The first one exploits the Krogager polarimetric decomposition in order to enhance peculiar scattering mechanisms from manmade targets, used in combination with the pseudo-Zernike image moments. The second algorithm employs the Krawtchouk image moments, that, being discrete defined, provide better representations of targets’ details. The proposed image moments based framework can be extended to the availability of several images from multiple sensors through the implementation of a simple fusion rule. A model-based micro-Doppler algorithm is developed for the identification of helicopters. The approach relies on the proposed sparse representation of the signal scattered from the helicopter’s rotor and received by the radar. Such a sparse representation is obtained through the application of a greedy sparse recovery framework, with the goal of estimating the number, the length and the rotation speed of the blades, parameters that are peculiar for each helicopter’s model. The algorithm is extended to deal with the identification of multiple helicopters flying in formation that cannot be resolved in another domain. Moreover, a fusion rule is presented to integrate the results of the identification performed from several sensors in a distributed radar system. Tests performed both on simulated signals and on real signals acquired from a scale model of a helicopter, confirm the validity of the algorithm. Finally, a waveform design framework for joint radar-communication systems is presented. The waveform is composed by quasi-orthogonal chirp sub-carriers generated through the Fractional Fourier Transform (FrFT), with the aim of preserving the radar performance of a typical Linear Frequency Modulated (LFM) pulse while embedding data to be sent to a cooperative system. Techniques aimed at optimise the design parameters and mitigate the Inter-Carrier Interference (ICI) caused by the quasiorthogonality of the chirp sub-carriers are also described. The FrFT based waveform is extensively tested and compared with Orthogonal Frequency Division Multiplexing (OFDM) and LFM waveforms, in order to assess both its radar and communication performance

ATHENA Research Book, Volume 2

ATHENA European University is an association of nine higher education institutions with the mission of promoting excellence in research and innovation by enabling international cooperation. The acronym ATHENA stands for Association of Advanced Technologies in Higher Education. Partner institutions are from France, Germany, Greece, Italy, Lithuania, Portugal and Slovenia: University of Orléans, University of Siegen, Hellenic Mediterranean University, Niccolò Cusano University, Vilnius Gediminas Technical University, Polytechnic Institute of Porto and University of Maribor. In 2022, two institutions joined the alliance: the Maria Curie-Skłodowska University from Poland and the University of Vigo from Spain. Also in 2022, an institution from Austria joined the alliance as an associate member: Carinthia University of Applied Sciences. This research book presents a selection of the research activities of ATHENA University's partners. It contains an overview of the research activities of individual members, a selection of the most important bibliographic works of members, peer-reviewed student theses, a descriptive list of ATHENA lectures and reports from individual working sections of the ATHENA project. The ATHENA Research Book provides a platform that encourages collaborative and interdisciplinary research projects by advanced and early career researchers