Wideband Multiple-input Multiple-output Radar Research Articles

Cognitive Sparse Imaging Method for MIMO Radar under Wideband Interference

Target three-dimensional (3D) high-resolution imaging via multiple-input multiple-output (MIMO) radar may suffer from a heavy sampling burden and complicated radio frequency interferences. Considering a collocated two-dimensional wideband MIMO radar under dynamic wideband interference (WBI), this paper proposes a cognitive method to achieve a 3D high-resolution target image with a reduced sampling cost. Firstly, based on the known knowledge of the target and WBI, provided by previous measurements, optimal sparse sampling in the 3D signal domain is conducted to reduce the number of sub-pulses and transceiving antennas by solving an optimization problem. Then, the detection and removal of the interfered signal components are conducted to provide the WBI information for following measurements and the interference-free signal cube for the target imaging process. Finally, by using the tensor-based smoothed L0 algorithm, the 3D high-resolution image of the target is obtained, providing the target information for the next measurement. Based on these three steps, a cognitive sparse imaging loop is formed for MIMO radar under WBI situations. The simulation and experiment results demonstrate the effectiveness and advantage of the proposed methods.

Fractional Ambiguity Function for the Generalized Wideband MIMO Radar

In this article, we define an ambiguity function (AF) for the generalized wideband multiple-input multiple-output (MIMO) radar, wherein the AF combines the signal processing in the fractional Fourier domain with all the functions of conventional AFs. We name it as the fractional AF for the wideband MIMO radar. In order to obtain the AF, we start from introducing the fractional order that relates to fractional signal processing into the matched-filter exploited by the AF, based on which we then derive the explicit expression of the AF. We provide explanations and implications of the fractional AF, and also derive its simplifications in terms of the case of slow-moving targets in far field. Moreover, we derive corresponding properties for the fractional AF, and meanwhile, we conduct analysis on the computational complexity of the AF. On the basis of the AF definition as well as its simplifications, we establish relationships of our proposed fractional AF to conventional AF forms. We show that our defined fractional AF can serve as a generalized AF form since conventional AFs are special cases of it. Our simulations show that the proper selection of fractional-orders can enable low sidelobe levels of the fractional AF for wideband MIMO radar.

Waveform Design Based ECCM Scheme Against Interrupted Sampling Repeater Jamming for Wideband MIMO Radar in Multiple Targets Scenario

In this paper, we propose a waveform design based electronic counter-countermeasures (ECCM) scheme against interrupted sampling repeater jamming (ISRJ) for wideband multiple-input multiple-output (MIMO) radar. The ECCM scheme includes two steps: ISRJ parameters estimation and ISRJ signal suppression. The ISRJ signal interpretations based on time-frequency (TF) domain and Doppler domain are proposed respectively. Based on the Doppler interpretation, a waveform with thumbtack ambiguity function and a corresponding multiple Doppler channels processing structure are proposed to obtain ISRJ parameters. According to the TF interpretation and the known ISRJ parameters, a waveform with desired TF distribution and a corresponding frequency filter processing strategy are proposed to suppress ISRJ signal. The proposed ECCM scheme can be directly used in phased-array mode without waveform optimization. Considering the multiple targets scenario, the simultaneous multiple beams technology in MIMO radar is preferred. Therefore, a constant modulus waveform design method is proposed to match the desired transmit beampattern and TF distribution. Besides, in order to further suppress the sidelobe output of ISRJ signal, an extended version of the proposed ECCM scheme in the slow-time dimension is proposed. Finally, the numerical simulations are provided to demonstrate the effectiveness of the proposed ECCM scheme in multiple targets scenario.

Three‐dimensional decoupling imaging method for wideband two‐dimensional multiple‐input‐multiple‐output radar

Wideband two-dimensional multiple input multiple output (MIMO) radar can be used for target three-dimensional (3-D) imaging. As the echo of wideband MIMO radar is derived from both time and spatial sampling, the time-frequency coupling is contained, resulting in imaging defocussing. To solve this problem, a time-frequency decoupling algorithm based on matrix enhancement and matrix pencil (MEMP) is proposed to achieve high-resolution 3-D imaging. By combining the enhanced matrix constructed via MEMP with the modern spectral estimation theory, the time-frequency coupling term is regarded as a space rotation factor and is eliminated in the process of target position estimation. Simulation results show that the proposed algorithm can reduce the negative influence of time-frequency coupling and improve the imaging accuracy of wideband two-dimensional MIMO radar.

Wideband MIMO Radar Transmit Beampattern Synthesis via Majorization–Minimization

We consider the design of constant-modulus waveforms for wideband multiple-input multiple-output radar. The aim is to match a desired transmit beampattern. To tackle the non-convex design problem, we develop an iterative algorithm, which is based on cyclic optimization and majorization–minimization. We prove that the sequence of the objective values of the proposed algorithm has guaranteed convergence. Moreover, we can obtain closed-form solutions for the associated optimization problems at every iteration. Furthermore, the proposed method can be implemented without matrix inversion and hence is computationally efficient. Simulation results demonstrate that the performance of the proposed algorithm is better than existing methods.

Wideband multiple‐input multiple‐output radar waveform design with low peak‐to‐average ratio constraint

Multiple-input multiple-output (MIMO) radar systems allow array antennas to transmit different waveforms and enable flexible transmit beampattern synthesis. Most existing transmit beampattern synthesis methods focus on narrowband MIMO radar system configurations. In this study, the authors propose a novel technique to design transmit waveforms for wideband MIMO radar systems. This technique is based on the optimisation of the cross-spectral density matrix and achieves a low peak-to-average power ratio as desired in practical radar systems. Simulation results are provided to verify the low PAR waveform design capability corresponding to arbitrary beampatterns.

Wideband MIMO Radar Waveform Design for Multiple Target Imaging

This paper focuses on the design of wideband multiple-input multiple-output (MIMO) radar waveform and its application to multi-target imaging. In a multiple targets scenario, the imaging performances are affected by the transmit beampattern and the power spectral density (PSD) illuminating on targets. Taking into account these factors, we have established an unconstrained optimization model based on jointly minimizing the matching errors of the beampattern and PSDs. To solve the large-scale optimization problem, a conjugate gradient-based wideband MIMO waveform design method is proposed. For the purpose of improving the computational efficiency, the Chirp-Z transform is employed in evaluating the discrete frequency spectrum. Numerical results show that the proposed method can approximately realize the desired multibeam and PSDs. By utilizing a sparse representation method, the designed waveform with randomly distributed PSDs can be applied to multi-target imaging.

Robust transceiver design for wideband MIMO radar utilizing a subarray antenna structure

In this paper, we investigate the possibility to suppress interference in wideband multiple-input multiple-output radar. The idea is to employ tunable filters at the transmitter and the receiver sides, and to derive filter coefficients that result in optimal transmitted signals from a system performance point of view, for a given radar scenario. The system performance is measured in signal-to-interference-and-noise ratio (SINR) at the receiver output, from which the filter properties are derived. The focus is to suppress active jamming interference, and especially deceptive jamming interference. We discuss two ways to derive the transmit and the receive filters. Each procedure utilizes two different power constraints related to the transmit filters. To incorporate imperfections in the given scenario, a robust extension to the design problem is proposed. Two different robust methods are evaluated: one that utilizes a Taylor series expansion of the SINR, and one that exploits a worst-case SINR maximization. Numerical validation illustrates the possibility to suppress interference without actually forming a spatial null in the direction towards interference, and the necessity to design transmit filters that are robust to uncertainties in the given scenario.

High-Resolution Imaging Using a Wideband MIMO Radar System With Two Distributed Arrays

Imaging a fast maneuvering target has been an active research area in past decades. Usually, an array antenna with multiple elements is implemented to avoid the motion compensations involved in the inverse synthetic aperture radar (ISAR) imaging. Nevertheless, there is a price dilemma due to the high level of hardware complexity compared to complex algorithm implemented in the ISAR imaging system with only one antenna. In this paper, a wideband multiple-input multiple-output (MIMO) radar system with two distributed arrays is proposed to reduce the hardware complexity of the system. Furthermore, the system model, the equivalent array production method and the imaging procedure are presented. As compared with the classical real aperture radar (RAR) imaging system, there is a very important contribution in our method that the lower hardware complexity can be involved in the imaging system since many additive virtual array elements can be obtained. Numerical simulations are provided for testing our system and imaging method.