In a synthetic aperture radar (SAR) system, target rotation during the coherent integration time results in a time-varying Doppler frequency shift and a blurred image. Blurred images are not conducive to subsequent information interpretation. This article proposes a complex-valued channel fusion U-shape network (CV-CFUNet) for the 3-D rotation refocusing task of ship targets. The proposed method integrates

Developing intelligent jamming methods to combat the multifunction radar (MFR) has become a vital task in electronic warfare, because the MFR can tune into different working modes according to surrounding environment information. In this article, we present a solution to the limitations of conventional jamming methods, including strong prior knowledge dependence and inaccurate selection strategies

The detection performances of MIMO radar can be improved by waveform diversity technology. The waveform diversity gain depends on the correlation side-lobe level of the orthogonal waveform set. Generally, peak side-lobe level (PSL) and integrated side-lobe level (ISL) are two most important performance metrics of the correlation side-lobe level. Few existing orthogonal waveform set design algorithms

This article first defines a class of estimation problem called simultaneous navigation and characterization (SNAC), which is a superset of simultaneous localization and mapping (SLAM). A SNAC framework is then developed for the Autonomous Nanosatellite Swarming (ANS) mission concept to autonomously navigate about and characterize an asteroid including the asteroid gravity field, rotational motion

Mosaic synthetic aperture radar (SAR) can achieve high resolution and wide swath (HRWS) imaging by steering its antenna beam elaborately. However, its unique time-frequency diagram and radiometric variation challenge the imaging. The conventional methods cannot be applied to mosaic SAR imaging directly. To address these problems, this article takes the imaging geometry into consideration, utilizing

This study is aimed at addressing the event-based state estimation and tracking control problems for a class of nonlinear systems, the output of which is measured by multiple sensors, but the adversary can manipulate nearly half of the measurements simultaneously. First, a sampled-data-based event-triggered strategy is developed to reduce unnecessary data transmissions under sparse sensor attacks,

This work focuses on the attitude control problem for hypersonic morphing vehicles (HMVs) with uncertainties. A span-morphing HMV model is first established with lumped disturbances. Based on fixed-time technique, a disturbance observer with fuzzy logic system (FLS) is proposed to enhance the robustness by estimating the unmodeled dynamics and external disturbances in fixed settling time. The multivariable

Electric sail-based propulsion is an innovative propellant-less propulsion technology that generates continuous thrust through the interaction between an artificial electric field and the solar wind. In an electric sail, the propulsive acceleration is adjusted by controlling the attitude of its normal plane and the coefficient determining the maximum thrust. However, the attitude adjustment speed of

In most of the existing state estimation algorithms for maneuvering target tracking, the formulation of the mode switching process fails to accurately capture the deterministic law that the target mode will persist for a period of time once it turns to be in effect. In this article, two strategies are presented to describe this characteristic. First, a constraint that model switching occurs no more

In this article, the decomposition and retrieval of the chirp modes with dynamic cross, appearance, and/or disappearance in a signal are formulated as a process of tracking time-frequency (TF) trajectories. Analyses show that the amplitude and frequency evolutions of each chirp mode in the signal can be described by polynomial prediction models. When all these evolutions are viewed as state equations

Among the various types of jamming, active deception jamming has similar characteristics to the transmitted signal. The jamming seriously affects the detection and tracking of real targets by radar. In recent years, waveform design has become an effective antijamming method with the maturity of waveform generator technology. However, most antijamming waveforms are only designed to combat a single kind

A semiassisted global navigation satellite systems (GNSS) authentication concept is proposed, with two main advantages. First, it can be implemented in a GNSS without modifications to the signal plan, provided that the GNSS can transmit an encrypted signal and an open signal with unpredictable and verifiable bits regularly. Second, it can work in a receiver for up to several days without any assistance

This article proposes an adaptive fault-tolerant control scheme for an overactuated hybrid vertical take-off and landing canard rotor/wing unmanned aerial vehicle (UAV) to simultaneously compensate actuator faults and model uncertainties without the requirement of fault information and uncertain bounds. The proposed control scheme is constructed with two separate control modules. The high-level control

This article studies the open-loop stability analysis and radial-basis-function-based neural network (RBFNN) control of triangular tethered satellite formation (TTSF) systems, comprised of the in-plane and out-plane dynamics. The dynamical equations of TTSF are nonlinear coupled second-order differential equations (DEs), whose explicit solutions are hard to work out. Therefore, the dynamics of systems

This article proposes a geometric-based method of the ground-point visibility from a satellite or satellite constellation in elliptical orbit considering the J 2 perturbation. First, the field-element equations describing the relationship between the elliptical satellite orbit, field parameters, and ground point are introduced and can be solved semi-analytically. Also, using a 2-D map composed of the

Cooperative guidance issues with impact time consensus against a maneuvering target are considered in this article. Different from the existing achievements, the expected impact time does not need to be predesigned, which is coordinated by multiple missiles using the neighboring information. First, the impact time consensus command is generated by using the maximum consensus algorithm of time-to-go

Safety-critical navigation applications require that estimation errors be reliably quantified and bounded. This can be challenging for linear dynamic systems if the process noise or measurement errors have uncertain time correlation. In many systems (e.g., in satellite-based or inertial navigation systems), there are sources of time-correlated sensor errors that can be well modeled using Gauss–Markov

We analyze the likelihood distribution for a multipath model in which no target is present, focusing on the peculiarities of the maximum-likelihood probabilistic multi-hypothesis tracker (ML-PMHT) when multiple peaks emerge. We study analytically the case in which peaks are separated and for the general case we propose a numerical algorithm based on sampling. The final distribution is used to compute

Target localization is one of the most important research topics in the field of radar signal processing. In this article, the problem of multitarget enumeration and localization in the distributed multiple-input multiple-output radar with noncoherent processing mode is investigated. We first analyze the theoretical bound of the multitarget localization accuracy under the discrete time signal model

In this article, the problem of wideband radar target detection in a heterogeneous environment is addressed. The wideband radar return of the target with range migration is characterized as a subband model, and the heterogeneous clutter is described with a hierarchical Bayesian model. Both the prior knowledge of the clutter power and the covariance matrix and the dependence of the primary data and

This article investigates the problem of leader–follower cooperative guidance in consideration of false-data injection attacks (FDIAs). Both the leader and the followers are required to reach the target at a desired impact time, while only the leader can receive the impact time command. A fixed-time convergent guidance law is presented for the leader to hit the target with impact time control. A distributed

In this article, we generate accurate global positioning system (GPS) legacy navigation (LNAV) orbital parameters to provide truth satellite positions and satellite clock biases for advanced receiver autonomous integrity monitoring offline monitoring. In our prior work, we proposed an estimator to determine satellite positions and clock biases, and here, we demonstrate the estimator performance using

For synthetic aperture radar (SAR) imaging, the irregular loss of received data and the nonuniformly under sampling yield the SAR azimuth ambiguity (SAA) resulting in the degradation in image quality. To address this issue, the incremental SAR imaging approach based on the estimation of sensing dictionary matrix in the pursuit of sparsity is presented in this article. Several beneficial contributions

For extended object tracking (EOT), a fluctuating number of measurements are generated by a sensor at a time instant. In practice, the measurement number depends on the object extension, sensor resolution, and sensor-to-object geometry. Given the sensor resolution, the number, thus, contains information on the object state and extension. This article proposes a random-matrix approach to EOT utilizing

Distorted sensors could occur randomly and may lead to the breakdown of a sensor array system. In this article, we consider an array model within which a small number of sensors are distorted by unknown sensor gain and phase errors. With such an array model, the problem of joint direction-of-arrival (DOA) estimation and distorted sensor detection is formulated under the framework of low-rank and row-sparse

Existing cross-correlation mitigation algorithms based on the minimum mean square error (MMSE) criterion can effectively suppress multiple access interference (MAI) but suffer from high complexity and modeling grid mismatch. In this work, we propose a cell-straddling robust-fast cross-correlation mitigation (CSR-FCCM) algorithm with two improvements. First, CSR-FCCM combines the 2-D joint iterative

Despite their potential to significantly enhance target detection capability, distributed radar networks, with or without a central coordinator, have not been sufficiently examined. In this article, we propose a generalized likelihood ratio test (GLRT)-based constant false alarm rate (CFAR) detector for distributed detection in a radar network, wherein only neighboring nodes require sharing their GLRT

When tracking maneuvering targets with a nearly constant velocity (NCV) Kalman filter with white noise acceleration, the selection of the process noise variance is complicated by the fact that the process noise errors are modeled as white Gaussian in the Kalman filter, while target maneuvers are deterministic or highly correlated in time. In recent years, the deterministic maneuver index was introduced

In this article, we study the strategy optimization problem of black-box range gate pull-off (RGPO) jamming. In the black-box RGPO jamming, the jammer does not have extensive knowledge about the tracking model of the threat radar, which makes it difficult to accurately estimate the performance of candidate jamming strategies. To address the issue, this article proposes a multimode black-box RGPO jamming

MTRT is an extension of path planning that aims to traverse multiple targets in an unknown environment at the lowest cost. The MTRT is governed by the “multitarget” demand leading to a rather extensive search space and the “real-time” requirement that imposes fast planning. However, the traditional path planning algorithm A* is notoriously inefficient in large spaces. Therefore, spurred by the low

The civil navigation message (CNAV) of the global navigation satellite system (GNSS) is transmitted in an open channel without authentication and integrity protection mechanism. Therefore, the CNAV is facing the threat of interception and tampering, and it is vulnerable to spoofing attacks. To guarantee the authenticity and integrity of CNAV, we propose a cryptographic antispoofing scheme of CNAV in

A restricted Bayes approach is proposed for linear estimation of a scalar random parameter based on a scalar observation under uncertainty regarding the correlation between the parameter and the observation. In particular, the optimal linear estimator that minimizes the average mean-squared error (MSE) is derived under a constraint on the worst-case MSE by considering possible values of the correlation

This article looks into the topic of distributed formation control for a group of quadrotors that are vulnerable to denial-of-service (DoS) attacks. By preventing information interaction between adjacent quadrotors, the DoS attacks, which happen independently on individual communication channels, disrupt the formation mission. A decomposition-combination control framework is devised for the formation

In order to simulate highly realistic scenarios for modern radar sensors, like traffic scenarios, radar target simulators require the capability to generate targets in all four radar dimensions, which are range, radial velocity, azimuth, and elevation angle. To generate targets with angular information, coherent direction-of-arrival (DoA) simulation allows a highly accurate and flexible angular simulation

This article investigates the problem of specific emitter identification (SEI), i.e., radar emitter fingerprint or individual emitter identification, which first measures the emitter-specific differences caused by radar's nonlinearities, e.g., mixer, power amplifiers, transmitter, and then makes a decision. In this article, the SEI problem is considered in the single-modal, dual-modal, and multimodal

The next generation of synthetic aperture radar (SAR) systems will need transmit and receive analog signals over a wide frequency range with large bandwidth to fulfil the increasing demands. Since the performance of the digital microwave component is deteriorated at increasing frequency, radio frequency (RF) front-end with the capability of frequency conversion is needed for frequency beyond a few

Infrared small target detection techniques remain a challenging task due to the complex background. To overcome this problem, by exploring context information, this research presents a data-driven approach called attention-guided pyramid context network (AGPCNet). Specifically, we design attention-guided context block and perceive pixel correlations within and between patches at specific scales via

We derive several parametric detectors for the case of a ground-based distributed multiple-input multiple-output radar system with colocated transmitters and receivers. The proposed detectors are based on exact and approximate generalized likelihood ratio tests. For the transmit–receive paths, which start and end at the same node, we incorporate the constraint of spectral symmetry, meaning that the

In this article, we address the problem of the range-Doppler map evaluation in continuous wave radar exploiting orthogonal frequency division multiplexing (OFDM) signals. This stage is usually implemented by resorting to a suboptimal batches algorithm and a typical choice is to fragment the signal in batches with length equal to the OFDM symbol length and to apply at each batch an appropriate range

Reliable wireless coverage in drone corridors is critical to enable a connected, safe, and secure airspace. To support beyond-visual-line-of-sight operations of aerial vehicles in a drone corridor, cellular base stations (BSs) can serve as a convenient infrastructure as they are widely deployed to provide seamless wireless coverage. However, antennas in the existing cellular networks are downtilted

A unified optimal guidance scheme is presented in this article for both midcourse and terminal phases combined. It minimizes the total deceleration resulting in enhanced range and/or higher impact velocity, while satisfying the terminal constraints on impact angle and miss distance. State-dependent terms are included in the cost function of the recently proposed generalized quasi-spectral-model predictive

This article devises a fixed-time distributed adaptive formation control algorithm under the event-triggered framework to guarantee the expected formation pattern for multiple quadrotor unmanned aerial vehicles (QUAVs) with full-state constraints. The multiple QUAVs subject to full-state constraints are transformed into the ones that are free from any constraints via a time-varying nonlinear transformation

In this article, a flocking control strategy combining with artificial potential field is developed for collision-free trajectory tracking of satellite cluster with multiple disturbances and communication delay. Considering the link constraints of each satellite, a degree-constrained spanning tree is adopted as the communication topology. Furthermore, a topology optimization method based on the Prim

This article proposes a cognitive frequency diversity array (FDA) multiple-input multiple-output (MIMO) (FDA-MIMO) radar network (CFDA-MIMON) target discrimination and tracking algorithm under main-lobe deceptive trajectory interference. This algorithm can be divided into two stages: search-discrimination-initialization and cognitive target tracking. The first stage mainly uses the distribution characteristics

Harmonic radar is a special radar system that has been widely used in insect tracking, search and rescue, and electronic equipment detection in recent years due to its excellent anti-clutter capability. However, in complex close-range scenarios, harmonic radar still suffers from nonlinear clutter interferences, which will cause a large number of clutter false alarms and seriously affect the performance

Global navigation satellite system has been widely used for navigation and positioning in many areas, from professional applications to the mass market. However, in the real-time kinematic positioning, the ambiguities usually cannot be fixed in natural and urban canyon environments due to the high occlusion, strong reflection, and frequent maneuvering. In this article, the best integer equivariant

The maximum surveillance of a target which is holding course is considered, wherein an observer vehicle aims to maximize the time that a faster target remains within a fixed-range of the observer. This entails two coupled phases: 1) approach phase and 2) observation phase. In the approach phase, the observer strives to make contact with the faster target, such that in the observation phase, the observer

Due to the large sizes of synthetic aperture radar (SAR) images, traditional deep learning-based ship detection methods usually utilize the sliding window preprocessing strategy to obtain the small-sized subimages. However, there are amounts of background clutter areas without ships in SAR images. Thus, traditional sliding window-based methods may generate numerous subimages without ships, which can

In this article, the spacecraft attitude takeover control (ATC) problem with limited communication and the unavailable angular velocity using cellular satellites is addressed. First, a dynamic uniform quantizer (DUQ) is proposed to quantize unit quaternion between sensor cellular satellites and controller cellular satellite. Second, an adaptive fuzzy observer is proposed to estimate the unavailable

Space-air-ground integrated vehicular networks (SAGIVN) have been widely envisioned as a promising network architecture for sixth-generation to support the Internet of Vehicles (IoV). In SAGIVN, free-space optics (FSO)-based, high altitude platform relay-assisted low Earth orbit (LEO) satellite systems have recently attracted research efforts worldwide. Critical challenges in designing and implementing

Signal propagation speed may not be available in practical localization scenarios. This article addresses both the moving and stationary source localization problems by using frequency measurements when the signal propagation speed is unavailable. The task is fulfilled by exploiting the Doppler frequency shift coming from the relative motion between the source and a network of mobile sensors. Owing

This article proposes a real-time capable tropospheric delay model for terrestrial radio navigation systems used for aviation. Its functional scope ranges from elevation angles below the local horizon to zenith. Flight experiments were carried out to quantify the improvement in service coverage achieved for measurements close to and below the local horizon, with aircraft distances in the order of 250

Due to the increasing number of aerial radars and joint communication/sensing technologies, interference from uncoordinated radars will limit the target detection and ranging performance in the future. In this article, we investigate the interference behavior in an aerial radar network for sensing ground targets. We consider that the radars mounted on unmanned aerial vehicles (UAVs) that fly at a certain

In this article, the nonzero-sum pursuit-evasion (PE) game control problem is studied for a class of linear spacecraft control systems subject to the complete information case and incomplete information case. The incomplete information includes the cost functions and the control inputs. In practical confrontation situations, due to the incomplete information constraints, it is impossible for the pursuer

The actual performance of a task-assignment method of unmanned aerial vehicles (UAVs) shows a considerable dependence on the path planning process coupled with it; however, this topic has been rarely studied in the existing literature. This article considers the problem of maximizing the task-assignment reward of a fleet of heterogeneous UAVs for a dynamic reconnaissance and confirmation task under

Approximate analytical solutions for the ascent trajectory of a solid-fuel launch vehicle are derived. To the best of the authors’ knowledge, the solutions are the ones achieving the highest accuracy in ascent-trajectory prediction under the condition of high angle-of-attack (AOA) maneuvers, where the magnitude of AOA can even be greater than 60° at high altitudes. As the first step of deriving the

Recently, deep unfolded networks have been widely utilized in direction of arrival (DOA) estimation due to the reduced computational complexity and improved estimation accuracy. However, few consider the nested array for off-grid DOA estimation, where the estimated DOAs are not on the prespecified grids. In this article, we propose a deep unfolded FOCal underdetermined system solver network and a deep

Defensive formation of the pursuers is critical to the result of the two pursuers and one evader differential games. This article focuses on the horizontal defensive formation as well as the orthogonal defensive formation for the end game of homing missile interception, in which the payoff function is the minimal terminal miss of the pursuers. In particular, in the horizontal formation, it is proved

Autonomous emergency landing capability of fixed-wing aircraft is essential for opening airspace for civil unmanned aviation. This article proposes a goal-oriented control scheme to exploit wind information for the benefit of forced landing. Different from general disturbances in a classic control system, a favorable wind would help aircraft to glide to a selected landing site more easily so increase

This study focuses on a Doppler frequency search strategy for signal acquisition in direct-sequence spread spectrum (DSSS) systems. According to DSSS signal accumulation energy vibration characteristics, the whole 2-D search region can be divided into the non-vicinity region, the transition region, and the vicinity region. If only one search strategy is used for the whole region, it is difficult to