Two-dimensional angular parameter estimation for noncircular incoherently distributed sources based on an L-shaped array

In this paper, a two-stage reduced-rank estimator is proposed for two-dimensional (2D) direction estimation of incoherently distributed (ID) noncircular sources, including their center directions of arrival (DOAs) and angular spreads, based on an L-shaped array. Firstly, based on the first-order Taylor series approximation, a noncircularity-based extended generalized array manifold (GAM) model is established. Then, the 2D center DOAs of incident ID signals are obtained separately with the noncircularity-based generalized shift-invariance property of the array manifold and the reduced-rank principle. The pairing of the two center DOAs is completed by searching for the minimum value of a cost function. Secondly, the 2D angular spreads can be obtained in closed-form solution from the central moments of the angular distribution. The proposed estimator achieves higher accuracy in angle estimation that manages more sources and shows promising results in the general scenario, where different sources possess different angular distributions. Furthermore, the approximate noncircular stochastic Cramer-Rao bound (CRB) of the concerned problem is derived as a benchmark. Numerical analysis proves that the proposed algorithm achieves better estimation performance in both 2D center DOAs and 2D angular spreads than an existing estimator

5G Positioning and Mapping with Diffuse Multipath

5G mmWave communication is useful for positioning due to the geometric connection between the propagation channel and the propagation environment. Channel estimation methods can exploit the resulting sparsity to estimate parameters(delay and angles) of each propagation path, which in turn can be exploited for positioning and mapping. When paths exhibit significant spread in either angle or delay, these methods breakdown or lead to significant biases. We present a novel tensor-based method for channel estimation that allows estimation of mmWave channel parameters in a non-parametric form. The method is able to accurately estimate the channel, even in the absence of a specular component. This in turn enables positioning and mapping using only diffuse multipath. Simulation results are provided to demonstrate the efficacy of the proposed approach

Anti-Jam GPS Controlled Reception Pattern Antennas for Man-Portable Applications

Military GPS receivers provide crucial information to soldiers in the field, however, the performance of these devices is degraded by in band RF interference, making GPS susceptible to jamming. Anti-jam techniques for aircraft and vehicular platforms have been developed, but at present there is no system for dismounted soldiers. There is a need for an anti-jam system which meets the demands of a dismounted soldier and conforms to the size, weight, and power requirements of a portable device. A controlled reception pattern antenna, or CRPA, is a potential solution for jammer mitigation. These devices work by steering reception pattern nulls toward the jammer direction, reducing the jammer power which reaches the GPS receiver. Prior CRPA realizations have been designed for use on vehicular and aircraft applications, however, these platforms do not suffer from the same limitations as a man-portable CRPA. Three considerations which are more pertinent for man-portable designs than prior work are (i) distributed antenna element positions and orientations dynamically change during use changing the reception pattern characteristics, (ii) the user is lower to the ground and moves through the environment meaning that multipath propagation can have a greater effect on CRPA performance, and (iii) the size weight and power constraints for a portable system limit the number of antenna elements reducing the degrees of freedom that can be used for cancellation. To address these challenges, a framework for man-portable CRPA modeling is presented. This includes development of efficient modeling methods which enable investigations into element perturbations to address the dynamic orientation problem. These and other methods are presented in Chapter 3, along with a discussion of the relative strengths and weaknesses of each. Additionally, a mixed scattering channel model is applied to the CRPA reception patterns, combining diffuse and specular reflection in Chapter 4. Discussion of this model centers around the eigenvalues of the signal covariance matrix and the effect of coherence between multipath components. Following this, Chapter 5 examines the performance of polarimetric CRPAs and space-time adaptive processing for man-portable CRPAs with limited degrees of freedom

Remote Sensing of the Oceans

This book covers different topics in the framework of remote sensing of the oceans. Latest research advancements and brand-new studies are presented that address the exploitation of remote sensing instruments and simulation tools to improve the understanding of ocean processes and enable cutting-edge applications with the aim of preserving the ocean environment and supporting the blue economy. Hence, this book provides a reference framework for state-of-the-art remote sensing methods that deal with the generation of added-value products and the geophysical information retrieval in related fields, including: Oil spill detection and discrimination; Analysis of tropical cyclones and sea echoes; Shoreline and aquaculture area extraction; Monitoring coastal marine litter and moving vessels; Processing of SAR, HF radar and UAV measurements

Multimodal eye\u27s optical quality (MEOQ)

This document summarizes the work done during the implementation of the Multimodal Eye\u27s Optical Quality (MEOQ) system, a measurement device that integrates a double-pass (DP) instrument and a Hartmann-Shack (HS) sensor. The system has been used to quantify scattering in the human eye. Moreover, the configurable properties of the system have been used to explore a method for reducing speckle in systems that rely on reflections of light in the ocular fundus

Recent Progress in Optical Fiber Research

This book presents a comprehensive account of the recent progress in optical fiber research. It consists of four sections with 20 chapters covering the topics of nonlinear and polarisation effects in optical fibers, photonic crystal fibers and new applications for optical fibers. Section 1 reviews nonlinear effects in optical fibers in terms of theoretical analysis, experiments and applications. Section 2 presents polarization mode dispersion, chromatic dispersion and polarization dependent losses in optical fibers, fiber birefringence effects and spun fibers. Section 3 and 4 cover the topics of photonic crystal fibers and a new trend of optical fiber applications. Edited by three scientists with wide knowledge and experience in the field of fiber optics and photonics, the book brings together leading academics and practitioners in a comprehensive and incisive treatment of the subject. This is an essential point of reference for researchers working and teaching in optical fiber technologies, and for industrial users who need to be aware of current developments in optical fiber research areas