Showing papers in "IEEE Aerospace and Electronic Systems Magazine in 2016"

Overview of radar waveform diversity

Abstract: Radar waveform diversity has received considerable attention in recent years due to increasing spectral congestion and the burgeoning capabilities of digital waveform generation. The promise of waveform diversity is far greater utilization of available degrees of freedom to enhance sensing performance and to even facilitate new operating modes. This tutorial provides an overview of this very broad topic, from the basic principles upon which it is founded to the myriad different areas being explored in research for practical sensing applications.

Signaling strategies for dual-function radar communications: an overview

Abstract: The last decade witnessed a growing demand on radio frequency that is driven by technological advances benefiting the end consumer but requiring new allocations of frequency bandwidths. Further, higher data rates for faster communications and wireless connections have called for an expanded share of existing frequency allocations. Concerns for spectrum congestion and frequency unavailability have spurred extensive research efforts on spectrum management and efficiency [1]-[4] within the same type of service and have led to cognitive radio [5] and cognitive radar [6]. On the other hand, devising schemes for coexistence among different services have eased the competition for spectrum resources, especially for radar and wireless communication systems [7]-[14]. Both systems have been recently given a common portion of the spectrum by the Federal Communications Commission.

Optimization theory-based radar waveform design for spectrally dense environments

Abstract: The radio frequency (RF) electromagnetic spectrum is a limited natural resource necessary for an ever-growing number of services and systems. It is used in several applications, such as mobile communications, radio and television broadcasting, as well as remote sensing. Together with oil and water, the RF spectrum now represents one of the most important, significant, crucial, and critical commodities due to the huge impact of radio services on society. Both high-quality/high-rate wireless services (4G and 5G) as well as accurate and reliable remote-sensing capabilities (air traffic control (ATC), Earth geophysical monitoring, defense and security applications) call for increased amounts of bandwidth [1], [2]. Besides, basic electromagnetic considerations, such as good foliage penetration [3], low path loss attenuation, and reduced sizes of the devices push some systems to coexist in the same frequency band [4] (for instance VHF and UHF). As a result, the RF spectrum congestion problem has been attracting the interest of many scientists and engineers during the last few years and is currently becoming one of the hot topics in both regulation and research fields [5], [6].

A survey of radar systems for medical applications

Abstract: A survey of radar systems used in the medical field is presented. First, medical applications of radars are described, and some emerging research fields are highlighted. Then, medical radars are analyzed in terms of block diagrams and behavioral equations and some implementations are shown as examples. A section is dedicated to the radiating structures used in these radars. Finally, human safety and environmental impact issues are addressed. The most investigated medical applications of radars are breast tumor diagnostics and remote monitoring of cardiorespiratory activity. New fields of interest are physiological liquid detection, and the monitoring of artery walls and vocal cord movements. Among the various topologies, continuous wave (CW) radars have been proven to yield the highest range resolution that is limited only by the system noise while the resolution of ultra wideband (UWB) and frequency modulated continuous wave (FMCW) radars is also related to the used frequency bandwidth. Concerning the maximum range, UWB radars have the best performance due to their ability to operate in the presence of environmental clutter. As for the radiating structures, planar antennas are preferred for diagnostic applications, due to their small dimensions and good matching when placed in contact with the human body. Radar systems for remote monitoring, instead, are designed by using high gain antennas and taking into account the complex radar cross section (RCS) of the body.

Sense and avoid for unmanned aircraft systems

Abstract: Sense and avoid (SAA) represents one of the main roadblocks to the integration of unmanned aircraft systems (UAS) operations by aviation authorities around the world. This tutorial outlines and reviews the substantial breadth of SAA architectures, technologies, and algorithms. Starting from a discussion about what constitutes a UAS and how it is different than manned aircraft, basic SAA definitions and taxonomies are discussed. The SAA process is dissected into three fundamental tasks, defined as sensing, detecting, and avoiding, which are discussed in detail. The tutorial concludes with a summary of the regulatory and technical issues that continue to challenge the progress on SAA, as a key component of reliable UAS operation in civil aviation authorities (CAAs) around the world.

Recursive Bayesian filtering in circular state spaces

Abstract: To facilitate recursive state estimation in the circular domain based on circular statistics, we introduce a general framework for estimation of a circular state based on different circular distributions. Specifically, we consider the wrapped normal (WN) distribution and the von Mises distribution. We propose an estimation method for circular systems with nonlinear system and measurement functions. This is achieved by relying on efficient deterministic sampling techniques. Furthermore, we show how the calculations can be simplified in a variety of important special cases, such as systems with additive noise, as well as identity system or measurement functions, which are illustrated using an example from aeronautics. We introduce several novel key components, particularly a distribution-free prediction algorithm, a new and superior formula for the multiplication of WN densities, and the ability to deal with nonadditive system noise. All proposed methods are thoroughly evaluated and compared with several state-of-the-art approaches.

Satellite communication and propagation experiments through the alphasat Q/V band Aldo Paraboni technology demonstration payload

Abstract: Current high-throughput satellite (HTS) systems for broadband distributed user access are designed following two main concepts: ▸ The use of Ka band radio frequency (RF) links both for the forward and for the return link; this choice is due to the congestion of lower frequency bands and to the relatively large bandwidth available in the Ka band. Moreover, the RF technology in the Ka band is mature [1], [2]. ▸ The use of multispot coverage: this technique is largely applied to increase the system throughput through frequency reuse and system reconfigurability [2], [3].

Experiments with cognitive radar

Abstract: The application of cognitive inspired processing to radar is a fast emerging area of research that affects almost all types of radar systems [1]–[13]. Cognition means "knowing" and is the process by which humans and animals know about the world. The cognitive process is extremely complicated and applies equally to "simple" creatures, such as insects, and to humans. Although much is understood about cognition there is much more to be learned [14]– [17]. Despite the need for more research, it is clear that humans and, perhaps more pertinently for radar systems, echolocating mammals, are able to sense and interact with their environment in sophisticated ways that are beyond the capabilities of man-made systems. In the simplest of terms, cognitive radar could be thought of as a system of hardware and software in which the transmit and receive parameters (such as power, pulse length, pulse repetition frequency (PRF), modulation, frequency and polarization) are selected, in real-time, in response to the observed scene to optimize performance for a given application.

Cellular for the skies: exploiting mobile network infrastructure for low altitude air-to-ground communications

Abstract: In this article we presented an overview of UASs for civil applications focusing on the communication component. We identified several available communication technologies for UAVs, their constraints, and also protocols available for implementing the remote operation of the vehicles. As an attractive solution for the A2G communication link for UAVs, we discussed the potential of mobile networks with their fully deployed infrastructures, wide radio coverage, high throughputs, reduced latencies, and large availability of radio modems. We described how a UAS can be implemented in a flexible and modular approach that allows it to rely on one or several wireless (UAVs and GCSs) and wired (GCSs) technologies. Despite the advantages of a system based on cellular and IP networks, there are problems that must be dealt with, namely, possible loss of radio coverage, presence of NAT, delay, jitter, and packet loss. Following the proposed architecture, we implemented an UAS and conducted some flight tests, which showed that the operation of the vehicles in semi-automatic or fully-automatic modes is feasible. It is expected that future enhancements for 4G networks and evolution to 5G will benefit UAV communications even further with lower latencies, higher throughput, and higher reliability.

Detection over sensor networks: a tutorial

Abstract: The applications of sensor networks (SNs) are increasing since they facilitate real-time remote information monitoring and processing. Detection of an event is one of the main tasks of SNs in many applications. Sensors may transmit either raw or processed data to a fusion center (FC), where a final decision is taken. The problems and challenges that exist in detection over SNs and the previously proposed methods to deal with them are reviewed and described in this tutorial.

Feature article: Vision-based UAV collision avoidance with 2D dynamic safety envelope

Abstract: In this article, a vision-only based collision avoidance approach was proposed for SAA of UAVs. The 2D dynamic safety envelope was first generated to capture the threat level of the non-cooperative flying intruder and guide avoidance. Two visual servoing controllers were then designed to separately implement the avoidance and the returning maneuvers. The proposed collision avoidance approach does not require distance information. We demonstrated the effectiveness of the approach through simulations and experiments.

Aggressive congestion control mechanism for space systems

Abstract: The concept of a space system of systems (SoS) is becoming a key consideration in space communication, navigation, and Earth observation. The space SoS is defined as a network of assets on the Earth, in orbit around the Earth, in orbit around solar system bodies and on the surface of solar system bodies that is interconnected and/or interoperated to perform a mission, and/or provide services that cannot be performed by monolithic space systems alone. However, current space information systems are basically operated in a point-to-point pattern between the control center and the spacecrafts, which are only adequate for the individual space missions rather than collaborative missions. In other words, the ground network, space network, and the deep-space network evolve independently and focus on their individual communication regimes. To address these issues, the National Aeronautics and Space Administration (NASA) has developed an integrated space system that integrates the Internet protocols, routers, and interfaces into space networks [3], [4]. The space system, which is also called space Internet, enables large quantities of collaborative operations of those networks. Therefore, the integrated space Internet is essentially an SoS.

Cognitive radars in spectrally dense environments

Abstract: Radar technology has been evolving towards higher resolution, high-precision detection instruments with an ever-increasing list of functionalities. One of the areas, which have very good potential for combining the benefits of these developments, is multifunction radar systems. These systems perform multiple functions simultaneously, including surveillance, tracking, confirmation of false alarm, backscanning, clutter, and interference cancellation, which are traditionally performed by dedicated individual radars. With the introduction of these new radar requirements, future radar systems will need to work with wider frequency bands than traditional radar systems.

Feature article: Reconfigurable S-band patch antenna system for cubesat satellites

Abstract: Small satellites are revolutionizing the space industry [1]. In particular, nanosatellites are very attractive because they enable access to space with a significant reduction of costs for satellite industries, and a shorter development time with respect to large satellites [2], [3]. Moreover, thanks to modern technologies, relatively complex missions can be planned for Earth observation [4], remote sensing [5], communication technology experiments [6], hardware validation and other scientific missions, as well as educational purposes [7]-[10].

Coherent radar detection in Compound-Gaussian clutter: Clairvoyant detectors

Abstract: This paper provides a historical and tutorial overview of coherent radar target detection in compound-Gaussian clutter and offers some new perspectives and avenues of research in this challenging area. It begins with a brief introduction that motivates the need to develop statistical models of non-Gaussian clutter and then reviews some of the physical ideas that led to modeling multivariate radar clutter statistics by the compound-Gaussian model. With this starting point, the paper then reviews a series of ideas that have been developed to describe clairvoyant detectors in such clutter. The term “clairvoyant” refers to the assumption that the properties of the clutter are assumed to be known. In a practical scenario, this assumption does not hold and adaptive techniques are needed to estimate clutter properties and implement the detector. Such techniques are guided however by the appropriate clairvoyant detector structures and hence it is proper to start by studying these detectors. As part of this review, the paper offers new ways of looking at this problem that suggest new research topics. This review is limited to the problem of clairvoyant detection in which the relevant properties of the clutter are assumed to be known. Adaptive detection in compound- Gaussian clutter will be the topic of a subsequent tutorial that the authors are preparing.

Feature article: Robust Aerial Object Tracking from an Airborne platform

Abstract: While the average remaining time to collision of about 20 s is quite promising, there are also a couple of scenarios where it drops below 10 s. The main issue there is generally the low contrast between the terrain as background and the approaching traffic aircraft—a result of the exceptional dynamic range if the sun is close to the camera FOV and shady terrain is visible at the same time. These situations could certainly be improved by using a higher bit depth instead of the 8-bit used for the scenarios presented here.

A survey of correlated waveform design for multifunction software radar

Abstract: To change the transmit beam pattern, single antenna radar requires a change of antenna while multiple antenna array radar, such as phased-array, require amplitude/phase tapers, which are hardware components. Therefore, there is a genuine demand that the parameters of future radar systems be controlled through a software without changing any hardware or using amplitude/phase tapers. It is well known that the parameters of an antenna array radar can be controlled by transmitting suitable correlated waveforms. This approach provides more degree-of-freedom and if constant-envelope (CE) or low peak-to-average power ratio (PAPR) correlated waveforms are used, it allows us to control the parameters of the radar without changing any hardware. Therefore, this approach can be considered as a step towards a software radar. The aim of this article is to provide a survey of recent techniques used to design CE and low PAPR correlated waveforms and discuss the benefits and drawbacks of each.

Feature article: onboard visual sense and avoid system for small aircraft

Abstract: The sense and avoid (SAA) capability is a key issue in the integration of Unmanned Aircraft Systems (UAS) into the common airspace [1]. Besides the lack of a regulatory framework in most countries, some technological challenges are still not resolved which holds back routine UAS applications. Most UAS or Remotely Piloted Aircraft Systems (RPAS) have no SAA capability. The separation for these aircrafts must be done solely by the Air Traffic Control (ATC) which is not cost effective. Furthermore, in the case of a lost link, there should be some kind of collision avoidance capability onboard; otherwise, if we want to maintain the current safety level of the air traffic system, a single unmanned airplane would block a significant sector of the airspace.

An advanced sense and collision avoidance strategy for unmanned aerial vehicles in landing phase

Abstract: Unmanned Aerial Vehicles (UAVs) become promising in different civilian and military applications due to their lower cost and greater flexibility in comparison to manned aircraft. However, the growing diversity of flight makes UAVs vulnerable to mid-air collisions. To ensure the safety for manned aircraft, human pilots are responsible for detecting intruders in airspace and performing appropriate maneuvers to avoid collisions [1]. Unlike manned aircraft with human pilots involved, UAVs must be equipped with Sense and Avoid (SAA) systems to guarantee the flight safety [2]. Thus, SAA systems play an important role in merging UAVs into the National Airspace System. As illustrated in Figure 1, an SAA scheme is composed of four units, which are sensing, conflict detection, collision avoidance, and flight controller, respectively.

Feature article: A survey on two-stage decision schemes for point-like targets in Gaussian interference

Abstract: In recent years, the design of so-called tunable detectors has raised significant interest in the radar community. The class of tunable detectors has been shown to be an effective means to attack detection of mainlobe targets or rejection of coherent repeater interferers in the presence of clutter and/or possible noise-like in-terferers. Tunable detectors allow adjustment of the rate at which the probability of detection Pd decreases as the received signal departs from the nominal one. In this case, a mismatch between the nominal and the actual steering vector is present. We refer to the capability of rejecting or detecting signals as directivity. Existing architectures can be classified according to their directivity as follows [1]: ▸ Robust decision schemes provide good detection performance in the presence of echoes containing signal components not aligned with the nominal (transmitted) signal (as shown in Figure 1, where target returns lie on a direction that is not aligned with the antenna beam boresight). ▸ Selective decision schemes are capable of rejecting signals whose signature is unlikely to correspond to the signal of interest to avoid false alarms.

Sense and avoid technology developments at Queensland University of Technology

Abstract: In recent years, the avoidance strategies have become progressively more complex, yet better aligned to pilot see and avoid behaviour. Significant advances have also allowed the system to be characterised by two mutual exclusive thresholds, one for making avoidance decisions and the other for determining when to stop avoidance behaviour. The importance of this is that existing performance evaluation techniques, used to asses systems, such as TCAS, can be leveraged to simultaneously optimise system parameters, determine performance limits, and visualise design trade-offs. The evaluation framework also follows on naturally from the techniques utilising receiver operating curves used to asses the detection performance using similar techniques.

Geometry of complex data

Abstract: Geometric algebra has been called a “unified language for mathematics and physics.” Sometimes known as Clifford algebra, it is based on the notion of an invertible product of vectors that captures the geometric relationship between two vectors, i.e., their relative magnitudes and the angle between them. This seemingly simple concept leads to a rich system of algebra and calculus that encompasses the diverse areas of complex numbers, quaternions, vectors, tensors, spinors, and differential forms. This tutorial provides a basic introduction to geometric algebra and presents formulations of known electrical engineering and signal processing concepts to illustrate some inherent advantages of geometric algebra for formulating and solving problems involving vectors. Being introductory, the goal of the tutorial is to introduce this emerging area that, although old as a mathematics discipline, has only recently started to garner significant attention in engineering communities. Geometric algebra should give another potentially powerful tool for pursuing research in any area that uses vectors.

Atmosphere effects on sonar sensor model for UAS applications

Abstract: The use of Unmanned Aerial System (UAS) applications is growing in both civilian and military fields. Fully autonomous UAS applications are useful to a variety of disciplines; for example, they can provide structural damage inspections in critical or dangerous areas (e.g. the L'Aquila earthquake in Italy, or Hurricane Ike in Galveston, Texas, USA). However, in some conditions, such as urban or low altitude operations, the Global Navigation Satellite System (GNSS) receiver antenna is prone to losing the line-of-sight from the satellite, making GNSS unable to deliver high quality positon information. This is quite dangerous for closed-loop control systems during the landing phase. In these cases, an ultrasonic sensor may be very useful for altitude control during the vehicle landing.

The disappearance of MH370 and the search operations — The role of technology and emerging research challenges

Abstract: The passenger aircraft is a wonderful revolution in the history of human transportation. It has greatly contributed to enhanced international trade, tourism, employment options, education, political relations, and so on. While flying is an amazing experience, it always imparts a level of mental unrest in the passengers until they are safely landed. Flight disasters have been a matter of serious concern not only for the governments and the aviation industry but also for the scientific research community. Detailed accounts of the various airline disasters to date are well documented [1], and a brief history of flight disappearance is provided by Yu [2]. This article focuses on the mysterious vanishing of MH370, which has sparked widespread debates and has opened doors for diverse scientific explorations.

An autonomous quadrotor avoiding a helicopter in low-altitude flights

Abstract: Recent advances in sensing and computing technology has made unmanned aerial vehicles/systems (UAV/UAS) low cost but still increasingly capable of executing complex missions in challenging environments. They have gained popularity in a vast range of civilian applications, including search and rescue, disaster relief, and filming. Recently, the Federal Aviation Administration (FAA) has issued the Notice of Proposed Rulemaking (NPRM) on UAS certifications [1], indicating that a large number of UAS will be present in the National Airspace System (NAS) in the near future. The NASA UTM project is an effort on enabling low-altitude UAS flights [2]. Big value envisaged by Amazon Prime Air [3] happens only when the drone is able to fly itself tens of miles from the distribution center to people’s homes autonomously. One prerequisite for such flights is collision avoidance. Our research aims at drones that travel in class G airspace. This article is an exploration of the drone collision avoidance problem in urban areas. The main contribution is a safety control framework that enables a UAS to perform collision avoidance with manned aircraft during autonomous navigation.

Feature article: Experimental analysis of onboard non-cooperative sense and avoid solutions based on radar, optical sensors, and data fusion

Abstract: This article summarized processing approaches and presented an experimental analysis of the levels of situational awareness relevant to different sensing architectures for non-cooperative sense and avoid, based on standalone radar, standalone EO, and radar/EO data fusion, respectively.

Three-axis sun sensor for attitude determination

Abstract: The field of attitude determination sensors is mature. The different sensor technologies have been known for decades, and existing product lines are available for all types of sensors. Table 1 shows existing attitude determination sensor technologies [1], [2].

AULOS: Finmeccanica family of passive sensors

Abstract: The name comes from an Ancient Greek wind instrument because AULOS is a passive radar family system developed by SELEX Sistemi Integrati (now Finmeccanica) that exploits electromagnetic energy already present in the environment such as FM frequency radio and DVB-T (digital video broadcast - terrestrial) emissions, and is completely environmentally friendly. The new green system is the result of many years of R&D, some undertaken in concert with the Terrestrial Armaments Department [1], [2], [3], [4]. It is a technologically advanced family of sensors developed entirely on the basis of a "soft radar" approach, involving signal sampling directly at carrier frequency using COTS (commercial off the shelf) devices for signal reception and digital processing. The resulting biband family offers great flexibility for potential use in a variety of operating conditions, along with enhanced target monitoring distance and position estimate performance.

Statistical approach to the operational testing of space fence

Abstract: The United States is acquiring a new terrestrial space-directed radar system to detect, track, and catalog space objects, including the growing population of space debris (“space junk”). The new system will consist of two S-band (2- to 4-GHz) phased-array radar sites, located at Kwajalein in the Marshall Islands and one other location to be determined. The radars will autonomously perform cued and uncued surveillance, as well as cued searches for objects in low- and medium-Earth orbits and higher. Space Fence will provide object tracking and radar characterization data to the U.S. Air Force Joint Space Operations Center (JSpOC) to support Satellite Catalog (SATCAT) maintenance and other space situational awareness needs [1].

Instrumentation of the basic finner reference projectile for attitude measurements at supersonic velocities

Abstract: Attitude measurements of reference projectiles are required in order to validate numerical aerodynamic simulations as well as dedicated numerical tools for the aerodynamic coefficient determination, based on a 6 degrees of freedom (DoF) data reduction. In this context we recently performed firing campaigns with a well-known reference projectile called “basic finner” (BF) [1], [2]. In comparison to the previous work [1], [2] in which shadow graphs were taken in firing tunnels, the BF is now instrumented with onboard attitude sensors and free-flight data is transmitted in real time to a receiving station. Telemetry for projectiles has been an issue for a long time [3], and progress has been made continuously throughout the years, with wider bandwidth and higher frequencies [4]–[14] in specialized centers of many countries (mainly, but not exclusively by the Army Research Laboratory (ARL) in the USA, and the French-German Research Institute of Saint- Louis (ISL) in France). D-fuze [10] is a patented measurement system integrating attitude sensors, acquisition electronics, and transmitter in a fuze (NATO-compatible shape), for large caliber projectiles and firing ranges; many U.S. development programs benefited from this advance in technology during the last decade. In [11], a miniaturized electronic of diameter 18 mm was used onboard a kinetic projectile in combination with specific equipment dedicated to telemetry reception.