Identification of Ghost Targets for Automotive Radar in the Presence of Multipath

Colocated multiple-input multiple-output (MIMO) technology has been widely used in automotive radars as it provides accurate angular estimation of the objects with relatively small number of transmitting and receiving antennas. Since the Direction Of Departure (DOD) and the Direction Of Arrival (DOA) of line-of-sight targets coincide, MIMO signal processing allows forming a larger virtual array for angle finding. However, multiple paths impinging the receiver is a major limiting factor, in that radar signals may bounce off obstacles, creating echoes for which the DOD does not equal the DOA. Thus, in complex scenarios with multiple scatterers, the direct paths of the intended targets may be corrupted by indirect paths from other objects, which leads to inaccurate angle estimation or ghost targets. In this paper, we focus on detecting the presence of ghosts due to multipath by regarding it as the problem of deciding between a composite hypothesis, ${\cal H}_0$ say, that the observations only contain an unknown number of direct paths sharing the same (unknown) DOD's and DOA's, and a composite alternative, ${\cal H}_1$ say, that the observations also contain an unknown number of indirect paths, for which DOD's and DOA's do not coincide. We exploit the Generalized Likelihood Ratio Test (GLRT) philosophy to determine the detector structure, wherein the unknown parameters are replaced by carefully designed estimators. The angles of both the active direct paths and of the multi-paths are indeed estimated through a sparsity-enforced Compressed Sensing (CS) approach with Levenberg-Marquardt (LM) optimization to estimate the angular parameters in the continuous domain. An extensive performance analysis is finally offered in order to validate the proposed solution.Comment: 13 pages, 10 figure

MIMO Radar Target Localization and Performance Evaluation under SIRP Clutter

Multiple-input multiple-output (MIMO) radar has become a thriving subject of research during the past decades. In the MIMO radar context, it is sometimes more accurate to model the radar clutter as a non-Gaussian process, more specifically, by using the spherically invariant random process (SIRP) model. In this paper, we focus on the estimation and performance analysis of the angular spacing between two targets for the MIMO radar under the SIRP clutter. First, we propose an iterative maximum likelihood as well as an iterative maximum a posteriori estimator, for the target's spacing parameter estimation in the SIRP clutter context. Then we derive and compare various Cram\'er-Rao-like bounds (CRLBs) for performance assessment. Finally, we address the problem of target resolvability by using the concept of angular resolution limit (ARL), and derive an analytical, closed-form expression of the ARL based on Smith's criterion, between two closely spaced targets in a MIMO radar context under SIRP clutter. For this aim we also obtain the non-matrix, closed-form expressions for each of the CRLBs. Finally, we provide numerical simulations to assess the performance of the proposed algorithms, the validity of the derived ARL expression, and to reveal the ARL's insightful properties.Comment: 34 pages, 12 figure

The Bi-directional Spatial Spectrum for MIMO Radar and Its Applications

<p>Radar systems have long applied electronically-steered phased arrays to discriminate returns in azimuth angle and elevation angle. On receiver arrays, beamforming is performed after reception of the data, allowing for many adaptive array processing algorithms to be employed. However, on transmitter arrays, up until recently pre-determined phase shifts had to applied to each transmitter element before transmission, precluding adaptive transmit array processing schemes. Recent advances in multiple-input multiple-output radar techniques have allowed for transmitter channels to separated after data reception, allowing for virtual non-causal "after-the-fact" transmit beamforming. The ability to discriminate in both direction-of-arrival and direction-of-departure allows for the novel ability to discriminate line-of-sight returns from multipath returns. This works extends the concept of virtual non-causal transmit beamforming to the broader concept of a bi-directional spatial spectrum, and describes application of such a spectrum to applications such as spread-Doppler multipath clutter mitigation in ground-vehicle radar, and calibration of a receiver array of a MIMO system with ground clutter only. Additionally, for this work, a low-power MIMO radar testbed was developed for lab testing of MIMO radar concepts.</p>Dissertatio

Joint Radar and Communication Design: Applications, State-of-the-Art, and the Road Ahead

Sharing of the frequency bands between radar and communication systems has attracted substantial attention, as it can avoid under-utilization of otherwise permanently allocated spectral resources, thus improving efficiency. Further, there is increasing demand for radar and communication systems that share the hardware platform as well as the frequency band, as this not only decongests the spectrum, but also benefits both sensing and signaling operations via the full cooperation between both functionalities. Nevertheless, the success of spectrum and hardware sharing between radar and communication systems critically depends on high-quality joint radar and communication designs. In the first part of this paper, we overview the research progress in the areas of radar-communication coexistence and dual-functional radar-communication (DFRC) systems, with particular emphasis on application scenarios and technical approaches. In the second part, we propose a novel transceiver architecture and frame structure for a DFRC base station (BS) operating in the millimeter wave (mmWave) band, using the hybrid analog-digital (HAD) beamforming technique. We assume that the BS is serving a multi-antenna user equipment (UE) over a mmWave channel, and at the same time it actively detects targets. The targets also play the role of scatterers for the communication signal. In that framework, we propose a novel scheme for joint target search and communication channel estimation, which relies on omni-directional pilot signals generated by the HAD structure. Given a fully-digital communication precoder and a desired radar transmit beampattern, we propose to design the analog and digital precoders under non-convex constant-modulus (CM) and power constraints, such that the BS can formulate narrow beams towards all the targets, while pre-equalizing the impact of the communication channel. Furthermore, we design a HAD receiver that can simultaneously process signals from the UE and echo waves from the targets. By tracking the angular variation of the targets, we show that it is possible to recover the target echoes and mitigate the resulting interference to the UE signals, even when the radar and communication signals share the same signal-to-noise ratio (SNR). The feasibility and efficiency of the proposed approaches in realizing DFRC are verified via numerical simulations. Finally, the paper concludes with an overview of the open problems in the research field of communication and radar spectrum sharing (CRSS)

Analyse d'un système radar intervéhiculaire en onde millimétrique (77 GHZ)

RÉSUMÉ Le nombre de capteurs et des données générées par les véhicules augmentent graduellement et devraient possiblement doubler d’ici 2020. L’avancée assez remarquable des techniques de communications sans fil pousse les recherches au plus haut niveau de la sécurité routière. A cet e˙et, le concept de sécurité routière relevant d’un facteur assez important dans la vaste par-tie des systèmes de transport intelligent, nécessite le déploiement d’infrastructures robustes capables d’implémenter des dispositifs à évitement de collision en circulation routière. Au vu de ce constat, le concept de détection intervéhiculaire par RADAR en ondes millimétrique est celui-là qui répondrait aux exigences des techniques d’évitement de col-lision par le principe de détection d’obstacle et de positionnement. En effet, la détection d’obstacle par RADAR repose sur un élément crustial appelé SER(Surface Equivalente RADAR) 1 qui de par sa valeur peut améliorer ou pas le RSB (SNR) 2 ou du moins les performances du système. Par contre, cette valeur de la SER diffère d’une cible à l’autre ou d’un obstacle à l’autre et ceci dépendamment de sa surface radiante. Dans le cas spécifique de la circulation routière et des usagers de la route, la variation de la SER est fortement liée à la distance de la cible par rapport au RADAR et de l’angle d’incidence des signaux émis. Ceci dit, les faibles variations de distance ou d’angles d’incidence engendrent des grandes variations de la SER ce qui occasionne des pertes importantes de quelques décibels mètre carré des valeurs de la SER. Ces pertes aussi majeures qu’elles soient, dégradent significativement les performances du système.Suite à cette problématique énoncée dans le paragraphe précédent, et dans le but de compenser les variations de la SER, un module de SER a été conçu au laboratoire Poly-Grames de l’école Polytechnique de Montréal.---------- ABSTRACT The number of sensors and data generated by vehicles is gradually increasing and is expected to double by 2020. The remarkable advance of wireless communications techniques is driving research at the highest level of road safety. To this end, the concept of road safety is a fairly important factor in the vast range of intelligent transport systems, requiring the deployment of robusts infrastructures capable of implementing collision avoidance devices in traÿc. In view of this, the concept of inter-vehicular detection by RADAR in millimeter wave is the one that would meet the requirements of collision avoidance techniques by the principle of obstacle detection and positioning. Indeed, the obstacle detection by RADAR is based on a crustial element called RCS (RADAR Cross Section) which by its value can improve or not the SNR (Signal Noise Ratio) or at least the performance of the system. On the other hand, this RCS value differs from one target to another or from one obstacle to another and this depends on its radiant surface. In the specific case of road traÿc and road users, the variation of RCS is strongly related to the distance from the target to RADAR and the angle of incidence of the transmitted signals. The small variations in distance or angles of incidence generate large variations of the RCS, which causes significant losses of a few decibels square meter of the RCS values. These losses as major as they are, significantly degrade the performance of the system. Following this problem stated in the previous paragraph, and in order to compensate for variations in the RCS, a RCS module was designed at Poly-Grames Laboratory of electrical engineering department of Ecole Polytechnique de Montréal. To this end, from the high-lighted RCS designed, the project aims to design and analyze the performance of a RADAR detection system on the following aspects: probability of detection or false alarm in term of SNR and range, optimization of parameters of the RADAR equation, FMCW modulation, estimation of angular position measurements and MSE of angles in the case of ESPRIT algorithms.In response to this design and analysis of the radar system’s performance, the conceptual approach was made at four levels. As a first step, a theoretical analysis of radar binary detection systems was carried out in order to analyze the influence of the parameter attenuation factor (�) commonly represented by the ratio between the distance radar to target (R), the wave-length (�0) and the RCS (˙)

Efficient method of estimating Direction of Arrival (DOA) in communications systems.

Masters Degree. University of KwaZulu- Natal, Durban.In wireless communications systems, estimation of Direction of Arrival (DOA) has been used both for military and commercial purposes. The signal whose DOA is being estimated, could be a signal that has been reflected from a moving or stationary object, or a signal that has been generated from unwanted or illegal transmitter. When combined with estimating time of arrival, it is also possible to pinpoint the location of a target in space. Localization in space can also be achieved by estimating DOA using two receiving nodes with capability of estimating DOA. The beamforming pattern in smart antenna system is adjusted to emphasize the desired signal and to minimize the interference signal. Therefore, DOA estimation algorithms are critical for estimating the Angle of Arrival (AOA) and beamforming in smart antennas. This dissertation investigates the performance, angular accuracy and resolution of the Minimum Variance Distortionless Response (MVDR), Multiple Signal Classification (MUSIC) and our proposed method Advanced Multiple Signal Classification (A-MUSIC) as DOA algorithms on both Non-Uniform Array (NLA) and Uniform Linear Array (ULA). DOA is critical in antenna design for emphasizing the desired signal and minimizing interference. The scarcity of radio spectrum has fuelled the migration of communication networks to higher frequencies. This has resulted into radio propagation challenges due to the adverse environmental elements otherwise unexperienced at lower frequencies. In rainfall-impacted environments, DOA estimation is greatly affected by signal attenuation and scattering at the higher frequencies. Therefore, new DOA algorithms cognisant of these factors need to be developed and the performance of the existing algorithms quantified. This work investigates the performance of the Conventional Minimum Variance Distortion-less Look (MVDL), Subspace DOA Estimation Methods of Multiple Signal Classification (MUSIC) and the developed hybrid DOA algorithm on a weather impacted wireless channel. The performance of the proposed Advanced-MUSIC (A-MUSIC) algorithm is compared to the conventional DOA estimation algorithms of Minimum Variance Distortionless Response (MVDR) and the Multiple Signal Classification (MUSIC) algorithms for both NLA and ULA antenna arrays. The developed simulation results show that A-MUSIC shows superior performance compared to the two other algorithms in terms of Signal Noise Ratio (SNR) and the number of antenna elements. The results show performance degradation in a rainfall impacted communication network with the developed algorithm showing better performance degradation

Air Force Institute of Technology Research Report 2015

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems Engineering and Management, Operational Sciences, Mathematics, Statistics and Engineering Physics

Air Force Institute of Technology Research Report 2015

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems Engineering and Management, Operational Sciences, Mathematics, Statistics and Engineering Physics