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Multi-input-multi-output (MIMO) radar can fundamentally improve radar performance by using diversity technique. A group of specially designed signals, which usually are orthogonal, are required to be transmitted for MIMO radar obt...
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Multi-input-multi-output (MIMO) radar can fundamentally improve radar performance by using diversity technique. A group of specially designed signals, which usually are orthogonal, are required to be transmitted for MIMO radar obtaining excellent diversity performance. Although some well orthogonal codes have been provided, they are mostly Doppler sensitive, and their side-lobes level also need to be improved. In this study, the poly-phase codes model is presented and the optimisation problem is then analysed. An adaptive clonal selection algorithm is proposed to numerically optimise such poly-phase coded orthogonal signals. To obtain low level of aperiodic autocorrelation side lobe and cross correlation as well as good Doppler shift tolerance, sustainable Doppler shifts are introduced into the optimisation course. Numerical simulation results show the superior correlation and Doppler tolerance performances comparing with some well known codes.
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The increasing interest on spectrum resources causes various efforts on developing smart and compact solutions as joint radar-communication (JRC) systems. A JRC system can offer cost-effective solution with concurrent operation, a...
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The increasing interest on spectrum resources causes various efforts on developing smart and compact solutions as joint radar-communication (JRC) systems. A JRC system can offer cost-effective solution with concurrent operation, as target sensing via radar processing and establishing communication links. JRC capability has been proposed over the years for different types of MIMO radars. However, a JRC capable monostatic coherent MIMO radar system is yet to be developed. These radars offer several advantages as fully coherent signal processing and coherent transmit beamforming which provides beampatterns to minimize probability of intercept. In this paper, two new waveform generation techniques suitable for JRC operation without disturbing transmit beamforming requirements and waveform orthogonality condition in space and time domain are proposed for monostatic coherent MIMO radars. Then, new communication methods are introduced for phase coded monostatic coherent MIMO radars. First method uses chirp-wise information encoding inside the radar pulse as intra-pulse communications. Second rotates the phase of a specific waveform on radiated symbols to a specific direction and the last method applies a small amount of progressive phase shift to the radar waveforms emitted from the antennas to create relative phase modulation between selected radar waveforms. Then, the performance of the proposed communication techniques are investigated in terms of bit error rate (BER) and generated waveforms are examined according to the orthogonality and transmit beamforming requirements. (C) 2018 Elsevier B.V. All rights reserved.
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The gain and phase calibration of monostatic multiple-input multiple-output (MIMO) radars with partly calibrated arrays is addressed and a clutter-based orthogonal projection (OP) method is introduced. When the transmitter and rec...
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The gain and phase calibration of monostatic multiple-input multiple-output (MIMO) radars with partly calibrated arrays is addressed and a clutter-based orthogonal projection (OP) method is introduced. When the transmitter and receiver of a monostatic MIMO radar are both uniform linear arrays with the same array spacing, a non-zero OP matrix for the joint transmit-receive array steering vectors can be found. The clutter output power projected on the OP matrix is zero if array is perfectly calibrated. Hence, the transmitter gain and phase can be calibrated by minimizing clutter projection output power for a well-calibrated receiver subarray. Subsequently, the unknown receiver gain and phase errors can be estimated with a similar projection method. Numerical simulation results confirm the effectiveness of the proposed method. (C) 2019 Elsevier B.V. All rights reserved.
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Transmit sequence design plays a significant role in multiple-input multiple-output (MIMO) radar to suppress correlation function side-lobe levels. This paper investigates two practical constraints, namely, constant envelope const...
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Transmit sequence design plays a significant role in multiple-input multiple-output (MIMO) radar to suppress correlation function side-lobe levels. This paper investigates two practical constraints, namely, constant envelope constraint to reduce the effect of nonlinear amplifiers, and low side-lobe levels to reduce the effect of interference among various transmitting sequences. To facilitate this, new Legendre sequences (L-seq) are designed that uses Legendre orthogonal polynomial (LOP). Superiority of the proposed L-seq is proven for peak side-lobe level (PSL) and cross-correlation level (CCL) performance parameters. Further, the signal cross-interference in MIMO radar is minimized by generating orthogonal L-seq. The impact of designed L-seq on the delay-Doppler plane is observed using the ambiguity function (AF). Simulation results show that the proposed L-seq has a constant envelope and suppressed side-lobe levels compared to the existing popular methods.
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Distributed multi-input multi-output (MIMO) radar with non-orthogonal waveforms has become a critical problem because waveform orthogonality may be lost as waveforms experience distinct delays and Doppler across different transmit...
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Distributed multi-input multi-output (MIMO) radar with non-orthogonal waveforms has become a critical problem because waveform orthogonality may be lost as waveforms experience distinct delays and Doppler across different transmit-receive propagation paths. In such cases, the widely used matched filter (MF) cannot perfectly separate the waveforms, and it outputs the filtered echo of the desired waveform (auto term) as well as multiple undesired waveform residuals (cross terms). In this paper, a transmit delay compensation scheme is proposed by employing a set of transmit delay compensation variables to control the cross terms so that they can be utilized to enhance target detection. Specifically, the probability of detection is maximized by optimizing the delay parameters. To solve the resulting nonconvex problem, an optimum solution based on multi-dimensional search and a computationally efficient suboptimal method are proposed. Simulation results show that the proposed delay compensation approach can substantially improve the target detection performance.
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During the last decade, spectrum sharing between different wireless technologies has been suggested as a promising solution to the spectrum scarcity problem. However, with the increasing growth of mobile devices and data rate hung...
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During the last decade, spectrum sharing between different wireless technologies has been suggested as a promising solution to the spectrum scarcity problem. However, with the increasing growth of mobile devices and data rate hungry applications, it becomes a necessity to find more innovative spectrum sharing solutions. This paper proposes a novel three-phases non-orthogonal multiple access (NOMA)-based spectrum sharing strategy between multi-user MIMO (MU-MIMO) communication (comm) systems and collocated MIMO radars. The proposed strategy exploits a win-win relationship between the MIMO radar and MIMO comm systems. The MIMO radar wins the improvement of its performance in terms of probability of detection through the delegation of its transmission to the base-station (BS) that has better channels with the targets. On the other hand, the comm system improves its sum-rate throughput and outage performance through sharing the spectrum originally assigned to the radar. The proposed cooperative spectrum sharing strategy is examined in terms of sum-rate throughput and outage probability for the comm system, and the probability of detection for the MIMO radar. Simulation results are presented to illustrate that the proposed spectrum sharing strategy outperforms the state-of-the-art approaches to spectrum sharing between the MIMO radar and MIMO comm systems. (C) 2018 Elsevier Inc. All rights reserved.
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Digital modulations such as orthogonal frequency-division multiplexing (OFDM) have received increasing interest for radar. However, the required fast analog-to-digital (AD) and digital-to-analog (DA) converters providing the neces...
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Digital modulations such as orthogonal frequency-division multiplexing (OFDM) have received increasing interest for radar. However, the required fast analog-to-digital (AD) and digital-to-analog (DA) converters providing the necessary bandwidth have not been feasible for automotive applications so far. In this paper, the first highly integrated, fully coherent OFDM radar capable of multiple-input multiple-output (MIMO) and stepped-carrier OFDM for automotive applications is presented. The stepped-carrier OFDM approach is adopted to reduce AD/DA requirements using an analog local oscillator (LO) frequency step generator. The capability to generate frequency steps with a duration of a few microseconds required for automotive applications is demonstrated. Calibration steps that are required with the new architecture are discussed and measurements are done to validate the functionality of the system. Also, possibilities for adaptive reconfiguration of the radar sensor in the presence of ambiguities are demonstrated.
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The orthogonal waveform design and good hardware realization of multiple-input-multiple-output (MIMO) radar have always been important research topics. The orthogonal frequency division multiplexing (OFDM) chirp waveform has recei...
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The orthogonal waveform design and good hardware realization of multiple-input-multiple-output (MIMO) radar have always been important research topics. The orthogonal frequency division multiplexing (OFDM) chirp waveform has received more attention because of its large time-bandwidth product, constant modulus, no range-Doppler coupling, good orthogonality, and good Doppler tolerance. Dechirp technique can reduce the amount of raw sampled data very well in near-field miniature lightweight MIMO radar detection and synthetic aperture radar (SAR) imaging. However, most of the current waveform analysis methods are based on matched filtering (MF). In this letter, an ambiguity function (AF) based on the dechirp signal processing approach to analyze the waveform performance is proposed, called dechirp ambiguity function (DAF). The pulse compression performance of the waveform itself and the level of mutual interference between the waveforms are described from the perspective of DAF. Numerical results validate reliability and effectiveness of the DAF.
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This article describes the design and implementation of intrapulse polyphase codes for a weather radar system. Algorithms to generate codes with good correlation properties are discussed. Thereafter, a new design framework is desc...
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This article describes the design and implementation of intrapulse polyphase codes for a weather radar system. Algorithms to generate codes with good correlation properties are discussed. Thereafter, a new design framework is described, which optimizes the polyphase code and corresponding mismatched filter, using a cost/error function, especially for weather radars. It establishes the performance of these intrapulse techniques with specific application toward second trip removal. The developed code is implemented on NASA D3R, which is a dual-frequency, dual-polarization, Doppler weather radar system.
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The Hybrid MIMO Phased Array Radar (HMPAR) is a notional concept for a multisensor radar architecture that combines elements of traditional phased-array radar with the emerging technology of multiple-input multiple output (MIMO) ...
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The Hybrid MIMO Phased Array Radar (HMPAR) is a notional concept for a multisensor radar architecture that combines elements of traditional phased-array radar with the emerging technology of multiple-input multiple output (MIMO) radar. A HMPAR comprises a large number, $MP$, of T/R elements, organized into $M$ subarrays of $P$ elements each. Within each subarray, passive element-level phase shifting is used to steer transmit and receive beams in some desired fashion. Each of the $M$ subarrays are in turn driven by independently amplified phase-coded signals which could be quasi-orthogonal, phase-coherent, or partially correlated. Such a radar system could be used in an airborne platform for concurrent search, detect, and track missions. This paper considers various signaling strategies which could be employed in the notional HMPAR architecture to achieve various objectives quantified by transmit beampatterns and space–time ambiguity functions. First, we propose a method to generate multiple correlated signals for uniform linear and rectangular arrays that achieve arbitrary rectangular transmit beampatterns in one and two dimensions, while maintaining desirable temporal properties. Examples of the range of transmit beampatterns possible with this technique are illustrated for an array of $MP=900$ elements, arranged using different values of $M$ and $P$. Then the space–time, or MIMO, ambiguity function that is appropriate for the HMPAR radar system is derived. Examples of ambiguity funct-
ions for our signals using a one-dimensional HMPAR architecture are given, demonstrating that one can achieve phased-array-like resolution on receive, for arbitrary transmit beampatterns.
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