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This paper considers the problem of co-existence of collocated multiple-input multiple-output (MIMO) radar and downlink multiple-input single-output (MISO) communication systems, which share the same frequency band. As the interference caused by the communication systems would degrade the accuracy of radar target localization, we formulate the co-design of radar waveform and communication transmit weights by minimizing the Cramér-Rao Bound (CRB) of direction-of-arrival (DOA) estimation, subject to a set of constraints accounting for the worst-case signal-to-noise-plus-interference ratio (SINR), similarity and energy. However, the objective is nonconvex and all variables are coupled together in the SINR constraints, the formulated problem is thus NP-hard. Towards that end, a decentralized block successive upper-bound minimization (D-BSUM) method based on the decomposition theory is developed. More specifically, at each iteration of this algorithm, the radar waveform is obtained with the aid of the alternating direction method of multipliers (ADMM) algorithm, and communication weights are obtained by exploiting the semidefinite programs (SDP). It is also proved that the proposed SDP-based method gives a rank-one solution. Numerical simulations are conducted to evaluate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Frequency-modulated continuous waveform signals are of great interest in automotive radar, perimeter radar, and wide-area surveillance radar applications. For automotive radars and wide-area surveillance radars, which generally utilize high Doppler frequency resolution for target recognition, the important potential target such as a walking person cannot be viewed as a point-like target due to different velocities of the reflection points of a pedestrian. The echoes of such targets have extended Doppler spectrum, and they appear as horizontal lines in the range-Doppler plane, rather than a single point considered in the traditional cases. However, the existing approaches do not make full use of the Doppler-spread characteristic to enhance the detection performance of pedestrians. In this paper, we will show how this characteristic can be used to enhance the detection performance for Doppler-spread targets. The main goal of this paper is pedestrian detection in wide-surveillance radar applications and the proposed approach can also be applied in automotive radar applications. Motivated by the Hough transform, the energies of most Doppler bins corresponding to the target will be accumulated to enhance the detection performance. The questions of how many and which cells should be accumulated in practical applications are discussed in detail. The proposed approach is based on the ordered statistical-constant false alarm rate but tailored to Doppler-spread targets. The detection performance of this algorithm is derived analytically, and verified via practical wide-area surveillance radar signals. [ABSTRACT FROM AUTHOR]

• The different attitudes of the antenna of the conformal array will result in different polarization characteristics of the received signal. Whether this polarization diversity can be used to improve the performance of adaptive detection remains to be studied. • In order to study this issue, in this paper, we take the heterogeneous array, which is a uniform linear array consisting of antennas with different attitudes, as the research object and use the generalized likelihood ratio test to derive an adaptive detection algorithm. • We give the probability of detection and the probability of false alarm of the proposed algorithm in closed form, and the detection performance of the heterogeneous array is compared with the uniform linear array and the uniform linear array consisting of the orthogonal pairs of dipoles. • Through numerical simulations, we analyze the detection ability of the proposed algorithm in various scenarios and verify that the heterogeneous array can improve its detection performance by exploiting the information in the polarization domain. In this paper, to investigate the effect of different antenna attitudes on the problem of polarimetric target detection, we take the heterogeneous array (HA), which is a uniform linear array (ULA) composed of antennas with different attitudes, as the research object, and use the generalized likelihood ratio test (GLRT) criterion to derive an adaptive detection algorithm. Meanwhile, the probability of detection, as well as the probability of false alarm of this algorithm is presented. Through numerical simulations, we analyze the detection ability of the proposed algorithm in various scenarios, and the detection performance of the HA is compared with the ULA and the uniform linear array consisting of the orthogonal pairs of dipoles (ULAP). The simulation results indicate that the HA can improve its detection performance by exploiting the information in the polarization domain, and therefore, the polarimetric target detection ability of the array, which is composed of antennas with different attitudes, is proved. [ABSTRACT FROM AUTHOR]

Designing the radar waveform, which ensures spectral compatibility with the communication systems, is known to be challenging. In addition to having the desirable transmitter efficiency, it is also anticipated to share the good pulse compression property of the reference waveform. In this paper, we investigate the problem of waveform design for multiple-input multiple-output radar with good transmit beampattern under certain practical constraints (e.g., peak to average power ratio and similarity constraints) in coexistence with communication systems. The waveform is designed by minimizing a weighted summation of the beampattern integrated sidelobe-to-mainlobe ratio and waveform energy over the space-frequency bands. Since the resulting problem is NP-hard, two approximated primal-dual algorithms based on the alternating direction method of multipliers algorithm are proposed. Concretely, the proposed algorithms update the primal variable by minimizing the linearized and quadratic approximations of the augmented Lagrangian function of the original problem, respectively. The closed-form solution of each primal variable is provided. Moreover, both the convergence and computational complexities of these two algorithms are discussed. Numerical simulations are provided to demonstrate the effectiveness of the proposed approaches. [ABSTRACT FROM AUTHOR]

This paper considers the joint design of a multiple-input multiple-output (MIMO) radar with co-located antennas and a MIMO communication system. The degrees of freedom under the designer's control are the waveforms transmitted by the radar transmit array, the filter at the radar array and the code-book employed by the communication system to form its space-time code matrix. Two formulations of the spectrum sharing problem are proposed. First, the design problem is stated as the constrained maximization of the signal-to-interference-plus-noise ratio at the radar receiver, where interference is due to both clutter and the coexistence structure, and the constraints concern both the similarity with a standard radar waveform and the rate achievable by the communication system, on top of those on the transmit energy. The resulting problem is nonconvex, but a reduced-complexity iterative algorithm, based on iterative alternating maximization of three suitably designed subproblems, is proposed and analyzed. In addition, the constrained maximization of the communication rate is also investigated. The convergence of all the devised algorithms is guaranteed. Finally, a thorough performance assessment is presented, aimed at showing the merits of the proposed approach. [ABSTRACT FROM AUTHOR]

To avoid the disadvantage of the traditional over-the-horizon (OTH) radar, which uses only the measurements of ionospheric parameters obtained from an ionosonde to estimate the target parameters, this paper proposes a new multiple-input multiple-output skywave OTH radar, which estimates the ionospheric and target parameters jointly by exploiting the data received by both the ionosonde and the radar receivers. First, we consider the scenario where the prior distribution of ionospheric parameters is unknown, the joint maximum likelihood estimator is developed and the Cramér–Rao bound (CRB) is derived to analyze the estimation performance. Then, the case with known Gaussian ionospheric prior distribution is analyzed, we develop the hybrid maximum likelihood and maximum a posteriori estimator, and the hybrid CRB (HCRB) is derived for analyzing the estimation performance. Finally, we show that the proposed joint estimation approaches lead to better accuracy for the ionospheric and target parameters estimation. We prove that both the CRB and the HCRB vary with the ionosonde measurement error covariance, and the corresponding upper and lower bounds are derived. [ABSTRACT FROM AUTHOR]

In this work, we consider distributed localization of an emitter using a wireless senor network, where each sensor can, respectively, receive the signal transmitted by the emitter, estimate the noise variance and share information with its neighbors. We propose herein a noise-constrained distributed adaptive direct position determination (NCD-ADPD) algorithm by exploiting the a priori knowledge of the noise variance. The NCD-ADPD algorithm turns out to be a variable step-size extension of the recently proposed distributed adaptive direct position determination (D-ADPD) algorithm. Compared with its predecessor, the NCD-ADPD algorithm is endowed with markedly improved localization performance, which is validated by simulation results, at the cost of a slight increase of computational complexity. [ABSTRACT FROM AUTHOR]

In this Letter, the problem of waveform design for MIMO radar with good transmit beampattern performance is investigated. The binary transmit waveforms are designed via minimising the beampattern integrated sidelobe to mainlobe ratio. Since the resulting binary combination optimisation problem is NP‐hard, a generalised likelihood ascent search algorithm is proposed to deal with it. Besides, the effectiveness of the proposed algorithm is demonstrated via simulation results. [ABSTRACT FROM AUTHOR]

To be a qualified engineer, or to pursue further studies in electronics and information engineering, undergraduate students should attempt to broaden their horizons in their professional fields. Particularly important are emerging mathematical theories or tools that produce relevant mathematical formalism for modelling the nature of physical space as simply and compactly as possible. In this article, we illustrate that geometric algebra provides just such a simplified and elegant representation or description of physical space. The basics of geometric algebra are explained and concrete examples in the plane and in 3D space are given. This article also provides two examples where geometric algebra has been found to provide an improved description of coordinate rotations and the Maxwell equations. [ABSTRACT FROM AUTHOR]

The key to successful maneuvering complex extended object tracking (MCEOT) using range extent measurements provided by high resolution sensors lies in accurate and effective modeling of both the extension dynamics and the centroid kinematics. During object maneuvers, the extension dynamics of an object with a complex shape is highly coupled with the centroid kinematics. However, this difficult but important problem is rarely considered and solved explicitly. In view of this, this paper proposes a general approach to modeling a maneuvering complex extended object based on Minkowski sum, so that the coupled turn maneuvers in both the centroid states and extensions can be described accurately. The new model has a concise and unified form, in which the complex extension dynamics can be simply and jointly characterized by multiple simple sub-objects' extension dynamics based on Minkowski sum. The proposed maneuvering model fits range extent measurements very well due to its favorable properties. Based on this model, an MCEOT algorithm dealing with motion and extension maneuvers is also derived. Two different cases of the turn maneuvers with known/unknown turn rates are specifically considered. The proposed algorithm which jointly estimates the kinematic state and the object extension can also be easily implemented. Simulation results demonstrate the effectiveness of the proposed modeling and tracking approaches.