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A low-profile and ultra-wideband (UWB) 1-D monopulse antenna based on the tightly coupled dipole linear array (TCDLA) is proposed in this paper. First, a compact UWB monopulse feeding network is discussed. It consists of a UWB monopulse comparator and a pair of miniaturized 1-to-4 power dividers with tapered baluns. Then, a TCDLA element with frequency selective surfaces (FSS) superstrates is designed for radiation. Meanwhile, the feeding network is arranged at the bottom layer to avoid spurious radiation on radiation patterns. Finally, by connecting the feeding network and radiation part, a UWB monopulse antenna prototype is fabricated and measured. The proposed monopulse antenna array achieved an 82.35% (5-12 GHz) shared bandwidth and the isolation is greater than 16 dB. The measured results are in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

This paper proposes a jellyfish search algorithm (JSA)-based offline method to design a DC voltage controller of AC/DC front-end converter (FEC) in a doubly fed induction generator (DFIG)-based wind energy conversion system (WECS). First, a multi-objective tuning problem is formulated using a full-order converter model to achieve maximum utilization of converter parameters in controller design. Next, a normalized mono-objective problem is developed using a utopia-tracking approach to reduce the computational complexity in design. Finally, the mono-objective problem is solved using JSA to enhance the controller performance by obtaining optimal gain values for the controller. A comparative study is performed with other metaheuristic optimization techniques to justify the use of JSA in this application. The results confirm that the accuracy of the JSA-based approach is higher, whereas the execution time of the method is lower than the other methods. Furthermore, to validate the performance of the proposed approach, a DFIG-based WECS is modeled and simulated using OPAL-RT real-time simulator. A grid voltage-oriented vector control is used as the overall control algorithm for the FEC. Unlike the conventional pole-zero cancellation method, the proposed approach provides no voltage overshoot during voltage development. Compared to the published literature, it also ensures 40.65% lesser voltage deviation without any overcurrent, irrespective of wind speed and load variations. [ABSTRACT FROM AUTHOR]

This paper proposes an optimal beamforming strategy for a downlink multi-user multi-input–multi-output (MIMO) dual-function radar communication (DFRC) system with dirty paper coding (DPC) adopted at the transmitter. We aim to achieve the maximum weighted sum rate of communicating users while adhering to a predetermined transmit covariance constraint for radar performance assurance. To make the intended problem trackable, we leverage the equivalence of the weighted sum rate and the weighted minimum mean squared error (MMSE) to reframe the issue and devise a block coordinate descent (BCD) approach to iteratively calculate transmit and receive beamforming solutions. Through this methodology, we demonstrate that the optimal receive beamforming aligns with the traditional MMSE approach, whereas the optimal transmit beamforming design can be cast into a quadratic optimization problem defined on a complex Stiefel manifold. Based on the majorization–minimization (MM) method, an iterative algorithm is then developed to compute the optimal transmit beamforming design by solving a series of orthogonal Procrustes problems (OPPs) that admit closed-form optimal solutions. Numerical findings serve to validate the efficacy of our scheme. It is demonstrated that our approach can achieve at least 73% higher spectral efficiency than the existing methods in a high signal-to-noise ratio (SNR) regime. [ABSTRACT FROM AUTHOR]

The authors present the design, fabrication and testing of a W‐band monopulse antenna. This antenna consists of three main building blocks: an array with 48 × 48 slots, a tapered corporate‐feed network and a comparator. The comparator has four input ports to generate sum and difference patterns in orthogonal cardinal planes for monopulse operation. A novel octuple excitation is adopted for the corporate network to achieve a side lobe level lower than −20 dB for the sum patterns and simultaneously reduce drastically the manufacturing complexity. Diffusion bonding technology is used for fabrication. Twenty‐four etched copper sheets with a thickness of 0.2 mm are stacked to realise the prototype. The total size of the antenna is 40.76×40.76×1.51λ03 $40.76\times 40.76\times 1.51{\lambda }_{0}^{3}$, with λ0 being the wavelength at the centre frequency (94 GHz). The antenna presents an isolation better than 12 dB among the input ports in the 84–100 GHz band. The realised measured gain is 40.7 dBi at 94 GHz. The measured 3‐dB gain bandwidth is 17.4%. The difference patterns at 94.0 GHz present null depths of −24.0, −18.0, −17.5, and −17.4 dB, in the E‐, H‐, 45°‐, and 135°‐planes, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a study to evoke rat cortical functional activities, including hemodynamic and neural tissue signal changes, by monopulse electrical stimulation with a microelectrode array using functional optical coherence tomography (fOCT). Based on the principal component analysis and fuzzy clustering method (PCA-FCM), the hemodynamic response of different size blood vessels in rat cortex are analyzed, showing that the hemodynamic response of the superficial large blood vessels is more concentrated. In the regions of neural tissue where blood vessels are removed, positive significant pixels (the intensity of the pixel for five consecutive frames is greater than the average value plus triple standard deviation) and negative significant pixels (the intensity of the pixel for five consecutive frames is less than the average value minus triple standard deviation) exist, and the averaged intensity signal responds rapidly with an onset time of ~20.8 ms. Furthermore, the hemodynamic response was delayed by ~3.5 s from the neural tissue response. fOCT can provide a label-free, large-scale and depth-resolved map of cortical neurovascular activation, which is a promising technology to monitor cortical small-scale neurovascular activities. [ABSTRACT FROM AUTHOR]

This paper focuses on radio resource management (RRM) in multi-user dual-function radar communication (DFRC) systems using orthogonal frequency division multiplexing (OFDM) waveforms. We propose two RRM schemes, one from the perspective of sum rate maximization and the other from the perspective of user fairness maximization. These optimization problems are non-convex due to the presence of mixed integer terms, making them difficult to solve. To address these challenges, we have employed a decomposition approach to transform these two complex problems into separate, more readily solvable ones. In addressing the sum rate maximization problem, we initially introduce a heuristic greedy algorithm to obtain a resource allocation scheme that satisfies radar performance requirements. Subsequently, we utilize a cyclic iterative method along with KKT conditions to solve the sum rate maximization problem for communication users. Concerning the fairness maximization problem for communication users, we similarly employ a heuristic greedy algorithm to obtain a resource allocation scheme that meets radar performance constraints. Then utilize the Lagrangian dual method to solve the multi-user fairness maximization problem for communication users. Our experimental results confirm the effectiveness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

With increasing interest in the W-band, there is growing focus on parabolic reflector antennas that are known for efficiently inducing high-gain radiation characteristics. There is particular focus on parabolic antennas with diverse defocus-fed applications, including monopulse tracking, multi-beam formation using multiple feeds, and aperture-shared antennas for multi-band operation. Thus, a new simplified method is presented in this paper to analyze the radiation characteristics of defocus-fed parabolic antennas. The presented method is based on the discrete division of a parabolic reflector surface and considers only simplified wave propagation theory and the effect of the scalar function pattern from the feeder. Additionally, array theory is exclusively applied for the analysis of radiation characteristics. Therefore, the presented method uses a very simplified formula to calculate the radiation characteristics of a defocused parabolic reflector antenna. The performance of the presented method was evaluated by comparing the results with commercial EM tools. The results of the analysis confirm the applicability of the presented method for the analysis of defocus-fed parabolic antennas. [ABSTRACT FROM AUTHOR]

The purpose of this article is to present the advantages that the use of arc-scanning synthetic aperture radar (Arc-SAR) would provide for accurate location of target to the weapon systems. Arc-SAR systems have an extraordinary capacity of angular discrimination of the targets, this fact make possible they can be used for the precise location of targets by replacing the large antennas required by the monopulse systems, used in this kind of applications, with a small rotating antenna. However, to carry out the real-time location of targets with the current processors a much more complex signal processing is needed. A simulator has been developed in this work, which allows the comparison of the theoretical and experimental results obtained by the classical systems against those obtained with the proposed Arc-SAR system working in the millimeter frequency bands. The results obtained demonstrate the ability of the proposed technique to accurately locate targets. This confirms that the obtained precisions allow the use the presented system in some important applications as Sense & Avoid (S&A) and weapon-pointing systems. Finally, possible applications of these techniques are described, especially useful is onboard sensors, because of the small size and weight of the antenna needed to implement an Arc-SAR system. [ABSTRACT FROM AUTHOR]

When radar receivers adopt digital channelization, it is prone to generating a cross-channel split signal, the rabbit ear effect, and a transition band repeated signal, leading to errors in radar signal sorting or identification. The pulse-splitting model and detection method proposed in this paper can model split pulses and identify them in radar pulse streams, facilitating the merging of split pulses to enhance sorting and identification performance. Firstly, the mechanism of splitting pulse generation is deeply analyzed, and the splitting site theory is proposed. Then, the split pulse signal model and the split pulse number statistical model based on geometric distribution are constructed, which are used to guide the construction of simulation data of split pulse flow with different characteristics. Furthermore, a time-domain convergence degree (TCD) index is proposed to characterize the pulse split phenomenon. At the same time, in order to avoid a large number of threshold searching problems in pulse-splitting detection, an empirical formula for the pulse-splitting detection threshold based on the TCD is given to quickly determine whether there is a pulse train split problem. The selected measured radar pulse stream is verified to follow a geometric distribution at a significance level of 0.05. The proposed method achieved a detection accuracy of at least 99.55% on the simulation dataset and at least 95.68% on the experimental dataset, validating the rationality of pulse-splitting modeling and the effectiveness of the detection method. [ABSTRACT FROM AUTHOR]

A new scheme has been proposed for mitigating noise contamination in the guidance signal (line of sight rate) of a strapdown active electronically scanned array (AESA) seeker which occurs due to the coarse resolution of the beam shifter. An earlier work has been reviewed and its shortcomings, which include difficulty of implementation and sensitivity to the gain of the monopulse angle measurement subsystem, have been discussed. The above shortcomings of the earlier work have been eliminated in the proposed scheme where a signal is tapped from an accessible point and passes through an additional path in the signal processing loop of the strapdown seeker. Using the proposed scheme, the impulsive noise due to the finite resolution of the beam shifter (and bit transition spikes) can be completely eliminated in the nominal condition for any arbitrary transfer functions of the seeker blocks, without adversely affecting the bandwidth/speed of response of the extracted line of sight rate signal. The scheme also has reasonable performance under off-nominal conditions. Efficacy of the proposed scheme has been demonstrated quantitatively with examples of nominal and off-nominal conditions. [ABSTRACT FROM AUTHOR]

Offboard active decoys (OADs) can effectively jam monopulse radars. However, for missiles approaching from a particular direction and distance, the OAD should be placed at a specific location, posing high requirements for timing and deployment. To improve the response speed and jamming effect, a cluster of OADs based on an unmanned surface vehicle (USV) is proposed. The formation of the cluster determines the effectiveness of jamming. First, based on the mechanism of OAD jamming, critical conditions are identified, and a method for assessing the jamming effect is proposed. Then, for the optimization of the cluster formation, a mathematical model is built, and a multi-tribe adaptive particle swarm optimization algorithm based on mutation strategy and Metropolis criterion (3M-APSO) is designed. Finally, the formation optimization problem is solved and analyzed using the 3M-APSO algorithm under specific scenarios. The results show that the improved algorithm has a faster convergence rate and superior performance as compared to the standard Adaptive-PSO algorithm. Compared with a single OAD, the optimal formation of USV-OAD cluster effectively fills the blind area and maximizes the use of jamming resources. [ABSTRACT FROM AUTHOR]

Monostatic rapid single-view radar imaging technology is a technique that employs single incidence angle and single frequency point information to implement rapid monostatic radar imaging within a small angular field. Owing to its analytical expression, this technique can substitute the traditional frequency-angle- scanning imaging in a small angular range, facilitating the rapid generation of highly realistic radar imaging data slices for complex targets and environments. This technology has been significantly applied in scatter hotspot diagnostics and target recognition. In order to achieve the windowing effect equivalent to that of frequency-angle-scanning imaging, and to enhance the scattering feature of monostatic imaging while controlling sidelobes, this paper derives analytic windowed imaging formulas for monostatic radar. It then obtains analytical expressions for various typical monostatic windowing rapid radar imaging scenarios. This enables the monostatic rapid imaging technology to maintain high efficiency in its analytical expressions while achieving the windowing effect equivalent to traditional imaging. The validity and correctness of the analytical formula and software implementation have been confirmed through 1D, 2D, and 3D imaging verifications. This technology can provide a vast amount of training data for modern radars. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Distinguishing multiple targets in the same resolution cell is an important and challenging task in the forward-looking imaging process of monopulse radar. Although Doppler processing can improve the recognition performance for multiple targets at high squint angles, the precise estimation of Doppler frequency remains challenging under conditions with unknown target numbers and energy leakage from strong point targets. To address these issues, this paper proposes a Fast Iterative Interpolated Beamforming (FIIB) algorithm with model order estimation and single snapshot processing for monopulse forward-looking imaging, which combines information theory to unbiasedly estimate the number of targets and Doppler frequencies. The simulation results show the superiority of the proposed FIIB algorithm over the Chirp-Z Transform (CZT) algorithm for estimating target numbers and Doppler frequencies within the same resolution cell in the presence of multiple point targets. In addition, the proposed FIIB algorithm can accurately estimate point targets beyond a ±5° azimuth angle in monopulse angle measurement tasks. Real-data experiments also reveal that FIIB-based monopulse forward-looking imaging has high focusing capability and imaging contrast and can effectively suppress background clutter.

The evolution in wireless radio communication systems has fueled the development of array antenna designs toward the direction of inventive, economical, and outcome-driven solutions. This article explored unorthodox techniques for designing array antennas for multiple radiation pattern synthesis by eradicating the required attenuators and phase shifters. An economical alternate design model is proposed with “Time-modulated” antennas capable of scanning and steering the beam electronically. “Time” is employed as a four-dimensional antenna parameter, and hence, the “Time-modulated” antennas are referred to as four-dimensional (4D) antennas. The idea is conceptualized by controlling high-speed switches attached to the antennas in a periodic way to produce the desirable excitation and phase tapering. So, the requirement of costly phase shifters and attenuators is eliminated. This work expanded the idea of “Time-modulation” for synthesizing multiple radiating beams such as monopulse, scanned beams, and shaped beams for multifunction radar systems. An appropriate switch sequence is designed to produce a concurrent sum-difference pattern for monopulse radars. Simultaneous scanning patterns and shaped flat-top patterns are also proposed for multifunction radars. To achieve the goals, two sets of 4D linear arrays are designed and the modulation parameters switch ON time and periods are optimized with a quasi-Newton memetic GA (Genetic algorithm). All the optimal outcomes are reported and also compared with other counterpart outcomes to show the efficacies of the “Time-modulation” concept for the said applications. [ABSTRACT FROM AUTHOR]

Let k ≥ 2. A generalization of the well-known Pell sequence is the k-Pell sequence whose first k terms are 0,..., 0, 1 and each term afterwards is given by the linear recurrence p n (k) = 2 P n − 1 (k) + P n − 2 (k) + ⋯ + P n − k (k) . The goal of this paper is to show that 11, 33, 55, 88 and 99 are all repdigits expressible as sum or difference of two k-Pell. The proof of our main theorem uses lower bounds for linear forms in logarithms of algebraic numbers and a modified version of Baker-Davenport reduction method (due to Dujella and Pethő). This extends a result of Bravo and Herrera [Repdigits in generalized Pell sequences, Arch. Math. (Brno) 56(4) (2020), 249–262]. [ABSTRACT FROM AUTHOR]

The notion of the weighted core inverse in a ring with involution was introduced recently [Mosić et al. Comm. Algebra, 2018; 46(6); 2332–2345]. In this paper, we explore new characterizations of the weighted core inverse of sum and the difference between two weighted core invertible elements in a ring with involution under different conditions. Further, we discuss reverse order and mixed-type reverse order laws for the weighted core invertible elements in a ring. [ABSTRACT FROM AUTHOR]

The use of radio frequency (RF) communications and radar signals with multiarray antennas is increasing. The array antennas used in these applications should be sophisticatedly matched in terms of the phase and amplitude for beam steering. In particular, phase and amplitude matching are the core techniques of cross-eye jamming that is known to cause angle deception in radars and missiles with monopulse sensors, resulting in wavefront distortion. In this study, to improve the beam steering performance of typical transceivers with phased array antennas and generate large angle errors in systems with monopulse sensors, a novel architecture to precisely match the phases and amplitudes of multichannel transceiver array antennas in the dual-frequency band is proposed, and the performance is verified using the fabricated device. [ABSTRACT FROM AUTHOR]

Recent multi-domain processing methods have demonstrated promising performance for monaural speech enhancement tasks. However, few of them explain why they behave better over single-domain approaches. As an attempt to fill this gap, this paper presents a complementary single-channel speech enhancement network (CompNet) that demonstrates promising denoising capabilities and provides a unique perspective to understand the improvements introduced by multi-domain processing. Specifically, the noisy speech is initially enhanced through a time-domain network. However, despite the waveform can be feasibly recovered, the distribution of the time–frequency bins may still be partly different from the target spectrum when we reconsider the problem in the frequency domain. To solve this problem, we design a dedicated dual-path network as a post-processing module to independently filter the magnitude and refine the phase. This further drives the estimated spectrum to closely approximate the target spectrum in the time–frequency domain. We conduct extensive experiments with the WSJ0-SI84 and VoiceBank + Demand datasets. Objective test results show that the performance of the proposed system is highly competitive with existing systems. [ABSTRACT FROM AUTHOR]

The heart is an important organ that maintains human life activities, and its movement reflects its health status. Utilizing electromagnetic waves as a sensing tool, radar sensors enable noncontact measurement of cardiac motion, offering advantages over conventional contact-based methods in terms of comfort, hygiene, and efficiency. In this study, the high-precision displacement detection algorithm of radar is applied to measure cardiac motion. Experimental is conducted using a single out-channel frequency modulated continuous wave (FMCW) radar operating in the ISM frequency band with a center frequency of 24 GHz and a bandwidth of 150 MHz. Since the detection signal is influenced by both respiratory and heartbeat movements, it is necessary to eliminate the respiratory signal from the measurement signal. Firstly, the harmonic composition of the respiratory signal is analyzed, and a method is proposed to calculate the parameters of the respiratory waveform by comparing the respiratory waveform coverage area with the area of the circumscribed rectangle. This allows for determining the number of respiratory harmonics, assisting in determining whether respiratory harmonics overlap with the frequency range of the heartbeat signal. Subsequently, a more accurate cardiac motion waveform is extracted. A reference basis is provided for extracting cardiac health information from radar measurement waveforms by analyzing the corresponding relationship between certain extreme points of the waveform and characteristic positions of the electrocardiogram (ECG) signal. This is achieved by eliminating the fundamental frequency component of the heartbeat waveform to emphasize other spectral components present in the heartbeat signal and comparing the heartbeat waveform, the heartbeat waveform with the fundamental frequency removed, and the heartbeat velocity waveform with synchronized ECG signals. [ABSTRACT FROM AUTHOR]

In this paper, a novel concept of a three-dimensional full metal system including a Dual-Mode Converter (DMC) network integrated with a high-gain Conical Horn Antenna (CHA) is presented. This system is designed for 5G millimeter wave applications requiring monopulse operation at K-band ( 37.5 – 39   GHz ). The DMC integrates two mode converters. They excite either the  T E 11 c i r  or the  T E 01 c i r  modes of the circular waveguide of the CHA. The input of the mode converters is the  T E 10 r e c  mode of two independent WR-28 standard rectangular waveguide ports. By integrating the DMC with the CHA, the whole system, called a Dual-Mode Conical Horn Antenna (DM-CHA), is formed, radiating the sum (Σ) and difference (Δ) patterns associated to the monopulse operation. To adequately prevent the propagation of higher order modes and mode mutual coupling, this integration procedure is carefully designed and fabricated. To prove the performance of the design, the DMC network was fabricated using subtractive manufacturing by Computer Numerical Control (CNC) technology. The CHA was fabricated using additive manufacturing by Direct Metal Laser Sintering (DLMS) technology. Finally, the simulation and measurement results were exhaustively compared, including return loss, isolation, radiation pattern, and gain of the full DM-CHA structure. It is noteworthy that this system provided up to  ± 11 °  per beam in the angular of arrival detection to support the high data rate operation for 5G satellite communications in the millimeter-wave band. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the jamming effectiveness evaluation against monopulse radar when using a non-coherent blinking jamming model at regular intervals based on three aircraft flight trajectories. To begin, the formation trajectory is solved under various aircraft attitudes to provide the radar cross section model for three-aircraft formation flying. Following that, the jamming angle tracking error model for three-aircraft formation flying is built and coupled with the features of monopulse radar angle tracking. The effective decoy angle and other criteria are used to measure the variance in jamming performance and the efficacy of formation flying radar jamming under varying jamming power and jamming gain. Finally, using the jamming effectiveness assessment criterion, the jamming effectiveness of formation flight is calculated. The findings demonstrate that the three-aircraft formation based on time transformation jamming model can successfully induce the monopulse radar angular tracking error, enhance it to 1.54 times, and stabilize the jamming effectiveness at 0.84, and it also has a relatively good jamming effect under straight flight trajectory and circular flight trajectory. Our jamming strategy will contribute to the design of electronic countermeasures, of which the findings of this research have practical significance for the application of new jamming styles. [ABSTRACT FROM AUTHOR]

A one-dimensional mono-pulse microstrip antenna plays an important role in target detection, tracking, recognition and imaging. However, feeding and coupling are the main reasons for the large size of the mono-pulse antenna, which is not conducive to miniaturization and integration. A miniaturized mono-pulse antenna is proposed to reduce the size and improve the integration in antenna design. The proposed antenna has a more compact size and good isolation, with a well-maintained radiation pattern and zero depth. The antenna unit size is 0.19 λ0 × 0.19 λ0 × 0.006 λ0. The overall antenna size is 78 mm × 78 mm × 1.48 mm (0.63 λ0 × 0.63 λ0 × 0.0012 λ0). In this communication, a general decoupling feeding network for two-element microstrip array antennas is also designed. Experiment validations confirm that the operating frequency of the designed antenna system is at 2.45 GHz with a gain of 5.54 dBi. The return loss of the sum and difference ports is 16.14 dB and 15.2 dB, respectively. The isolation of the ports is 36.6 dB. The proposed miniaturized mono-pulse antenna is approximately 64% smaller in size compared to previous versions. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tolerance of reconfigurable monopulse linear arrays on the uncertainties of the excitation amplitudes is analyzed with a method based on the rules of the interval arithmetic (IA) and analytic bounds for the sum and the difference power patterns are computed. Thanks to the reliability and the computational efficiency of such an IA-based formulation in deriving conservative and narrow pattern bounds, which include all possible pattern deviations, an innovative strategy is proposed for the worst-case performance analysis when dealing with tolerances on different parts of the beam forming network. Representative numerical examples both validate the formulation at hand and prove the effectiveness of the arising worst-case tool. [ABSTRACT FROM AUTHOR]

We propose a new approach to the mask‐constrained power synthesis of reconfigurable circular‐ring array antennas for monopulse radar applications. By resorting to Orbital Angular Momentum vortex beams, and without increasing either the complexity of the beam forming network or the signal processing times with respect to the state‐of‐art solutions, the proposed method allows improving the precision pointing with respect to usual techniques. The overall synthesis is cast as a Convex Programming optimization problem aimed at reducing as much as possible the number of control points of the array, and it is tested in relevant application scenarios. Plain Language Summary: A new antenna‐design method is presented in order to enhance the target localization accuracy of monopulse radars. The synthesis procedure is cast as a Convex Programming problem in the case of reconfigurable circular arrays. Key Points: Phase‐only reconfigurable circular‐ring arrays can be exploited as effective monopulse antennasOrbital Angular Momentum vortex beams increase precision pointingConvex Programming can maximize performance of reconfigurable arrays [ABSTRACT FROM AUTHOR]

In this paper, a sidelobe recognition method using boresight error and quadrant signal difference for a monopulse array is proposed. A conventional sidelobe recognition method compares the difference between the sum and delta channels. This method works well for the azimuth and elevation planes. However, the method is prone to many errors in the diagonal region of the two-dimensional plane. To overcome this problem, a method to calculate the deviation of the boresight error difference with different frequency combinations and a threshold to identify the sidelobe is proposed, and the method is validated to significantly reduce the error region. If a four-quadrant signal can be extracted separately, the signal deviation can be calculated and compared with the threshold, and the error region can be further reduced. The effects of each margin and bandwidth on the recognition performance are analyzed, and a slot array antenna is simulated to assess the method's effectiveness. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multiple input multiple output with frequency diversity array (FDA-MIMO) radar has unique advantages in mainlobe deception jamming suppression and target location. However, if the training sample contains the target signal, it will lead to poor jamming suppression performance and large target measurement error. To deal with the problem, a method of coarse target location in the time domain is proposed based on the cumulative sampling analysis. Taking full advantages of the strongest correlation characteristic between the expected steering vector and the true target, the feature vector and feature value corresponding to the true target are found after feature decomposition. The time domain location of the target is roughly estimated during the cumulative sampling analysis from near to far. Then, a pure jamming training sample can be obtained by avoiding the location. Noise subspace projection algorithm is used to measure the angle and range of the target while suppressing mainlobe jamming. The simulation results show that the proposed method can roughly estimate the target location in the time domain when the mainlobe deception jamming completely covers the target. Compared with conventional methods, the performance of jamming suppression and target localization error are closer to the performance of ideal sampling. [ABSTRACT FROM AUTHOR]

This paper presents a method based on the support vector regression (SVR) model and grey wolf optimizer (GWO) algorithm to efficiently predict the monostatic radar cross-section (mono-RCS) of complex objects over a wide angular range and frequency band. Using only a small-size of the mono-RCS data as the training set to construct the SVR model, the proposed method can predict accurate mono-RCS of complex objects under arbitrary incident angle over the entire three-dimensional space. In addition, the wideband prediction capability of the method is significantly enhanced by incorporating the meta-heuristic algorithm GWO. Numerical experiments verify the efficiency and accuracy of the proposed SVR-GWO model over a wide frequency band [ABSTRACT FROM AUTHOR]

The accuracy of radar emitter signal sorting nowadays deteriorates due to the high flexibility and complexity of modern radar pulse streams and the density of crowded electromagnetic environment. In modern radar signal sorting based on pulse repetition interval, conventional methods usually fail to achieve acceptable accuracy and lack stable performance for two main reasons: (1) Conventional methods require a large number of pulses in the stream, which is not practical in many applications. (2) These methods are sensitive to pulse loss and random noise pulses. These two reasons are the main problem that is addressed in this paper. Our proposed model is a machine learning architecture called Unified Residual Recurrent Neural Network (URRNN). In this architecture, residual neural network and recurrent neural network are combined and modified to alleviate the forementioned shortcomings of traditional approaches and enhance the model performance in both classification and deinterleaving tasks. This aim is achieved due to the fact that URRNN extracts both spatial and temporal features, which means more information about processed stream that is exploited to enhance model performance. Three different architectural combinations of URRNN, which show high accuracy and reasonable processing time, are built and trained. The structural and functional description are provided for each architecture. Simulation demonstrates high accuracy and reliable performance of the proposed methods in different circumstances. The results are compared with the results obtained by other conventional machine learning techniques. [ABSTRACT FROM AUTHOR]

In radar, an extended target or structure is perceived as a collection of multiple point scatterers. For tracking radar, determining the weighted mean (or centroid) angle of these unresolved scatterers is crucial. Our study demonstrates that the monopulse angle estimate corresponds to the weighted circular mean of the angles of multiple scatterers, as supported by both analytical and simulation results. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although many multiplexed arrays of a superconducting nanowire single-photon detector (SNSPD) have been reported, it is still a major challenge to develop pixel-level readout arrays with high efficiency, parallel detection, and fast processing for real-time imaging. Here, we report a SNSPD array with inductor-shaping pulses for approaching the pixel-level readout. Optimized inductors are introduced to shape the output pulses of each pixel, and the response pulses of all pixels are synthesized in a series-connected structure. Then, the on/off states of all pixels can be encoded to the widths, amplitudes, and areas of the output pulses by the single-channel readout. This proposal is verified by a 4-pixel SNSPD array and a 16-pixel SNSPD array. It shows that the array not only inherits the features of the single-pixel SNSPD, such as photosensitive area, filling factor, quantum efficiency, and dark count rate, but also implements parallel operation of all pixels, which is always confused in traditional multiplexed SNSPD arrays. At the same time, the single-channel readout simplifies the system, and the serial digital signal converted from the shaped pulse enabled an easy and fast readout process, paving the way for high performance and real-time imaging. [ABSTRACT FROM AUTHOR]

The development of novel and innovative phased array designs toward affordable and performance‐oriented solutions has become the dire need of modern‐age wireless communication technologies. This paper proposed an unconventional method to design phased array antennas by eliminating the need of phase shifters. A cost‐effective alternative is presented by using "time‐modulation" based arrays capable of beam steering and electronic scanning. Controlling the high‐speed absorptive switches connected with each radiating elements in a periodic manner to generate the desired amplitude and phase tapering is the main purpose of these time‐domain arrays. So, the need for expensive phase shifters and erroneous attenuators can be avoided. This article explored the idea of "time‐modulation" to design innovative and efficient phased arrays for monopulse and multifunction radar systems. Suitable switching sequences are designed to produce simultaneous sum‐difference radiation patterns for monopulse tracking radars, and simultaneous scanned beam patterns for multifunction radars. To achieve the desired objectives, time‐modulated linear arrays of 10, 20, and 30 elements are proposed with appropriate switching sequences. The parameters of the arrays such as switch‐ON instants, switch‐ON periods, and switch‐OFF instants are controlled by employing the crow search optimization (CSO) algorithm. Representative results for both the applications are elaborated and compared with recently published counterpart designs to present the potentialities of the proposed concept for electronic steering and beam scanning applications. [ABSTRACT FROM AUTHOR]

Purpose: The aero-engine array electrostatic monitoring technology (AEMT) can provide more and more accurate information about the direct product of the fault, and it is a novel condition monitoring technology that is expected to solve the problem of high false alarm rate of traditional electrostatic monitoring technology. However, aliasing of the array electrostatic signals often occurs, which will greatly affect the accuracy of the information identified by using the electrostatic sensor array. The purpose of this paper is to propose special solutions to the above problems. Design/methodology/approach: In this paper, a method for de-aliasing of array electrostatic signals based on compressive sensing principle is proposed by taking advantage of the sparsity of the distribution of multiple pulse signals that originally constitute aliased signals in the time domain. Findings: The proposed method is verified by finite element simulation experiments. The simulation experiments show that the proposed method can recover the original pulse signal with an accuracy of 96.0%; when the number of pulse signals does not exceed 5, the proposed method can recover the pulse peak with an average absolute error of less than 5.5%; and the recovered aliased signal time-domain waveform is very similar to the original aliased signal time-domain waveform, indicating that the proposed method is accurate. Originality/value: The proposed method is one of the key technologies of AEMT. [ABSTRACT FROM AUTHOR]

Blinking jamming is an active self-screening technique performed by at least two aircraft to tackle monopulse radars and all complexity related thereto. Nowadays, the technique can be performed with digital radiofrequency memories (DRFMs), which are cumbersome, complex, expensive, need a dedicated compartment and antenna, and introduce spurs in the signals. In this paper, we propose an alternative to the implementation of blinking jamming with DRFMs, namely with reconfigurable metasurfaces. By covering the aircraft parts that most contribute to the radar cross-section (RCS), reconfigurable metasurfaces can interchangeably absorb or amplify impinging waves, making the aircraft 'blink' from the radar perspective. To validate the feasibility, simulations accounting for realistic phenomena are conducted. It is seen that, if the aircraft RCS can be varied in a ratio of 10:1, either with absorptive or power-amplifying metasurfaces, a performance similar to that of the DRFM is achieved. Furthermore, a ratio of 2:1 is sufficient to make the radar antenna system movements exceed the angular range of the formation. We also anticipate our work to be a starting point for completely new ways of countering radars, e.g., with countless small drones performing passive or active stand-off blinking jamming. [ABSTRACT FROM AUTHOR]

The results of determination of the peak power of monopulses of YAG:Nd3+ laser emission by two methods are presented. It is shown that the most reliable data can be obtained by the procedure from GOST and by the often used method when recording the time form of the monopulse of radiation using an FK-15 coaxial photocell. An often used technique using the measured value of the monopulse duration by the level of 0.5 of the amplitude value, when recording the time shape using an LFD-2 avalanche photodiode overestimates the value of the peak power of the monopulse compared to a reliable one by 12%. [ABSTRACT FROM AUTHOR]

Distributed radar systems promise to significantly enhance target localization by virtue of the superiority of multi-view observations from widely separated radars, compared to their monostatic counterparts. Nevertheless, when the radar number is limited, performing target localization bears the brunt of the parameter identifiability requirement that the parameter number must be no less than the number of independent measurements. In this way, the canonical two-stage target localization method, as well as its developments, is no longer appropriate for direct application. Hence, in this paper, we propose a novel target localization method using time-difference-of-arrival (TDOA) measurements with the minimum number of radars under platform position uncertainties. The referred distributed system is a bistatic multi-receiver system, where the primary signal is transmitted by a geostationary Earth orbit (GEO) satellite while receivers are equipped on several unmanned aerial vehicles (UAVs). In the first stage, the reference range from the reference radar to the target is estimated by a quadratic function, and then the weighted least squares (WLS) solution of the target location is updated by substituting the range estimate back into it. In the second stage, we invoke the Taylor series approximation to further refine the target localization obtained by the first stage. It can be foreseen that the developed method is beneficial for scenarios with a limited number of radars, including engineering projects such as fire control, surveillance, and guidance, to support high-accuracy target localization. The simulation results show the superiority of the localization performance of the proposed method over other existing methods. [ABSTRACT FROM AUTHOR]

Some monopulse radars on a ship require an altitude value of the radar relative to the sea level with error levels of several tens of centimeters (cm). In conventional methods, it is difficult to frequently measure the radar altitude relative to the sea level, which changes according to ship conditions, while maintaining error levels of several tens of centimeters. In this study, a monopulse radar irradiates a radar beam, measures the distance from the radar to the sea surface at the beam irradiation position, and presents a method for precisely measuring the radar altitude by considering the radar mounting error. The proposed method can be operated whenever necessary in a radar operating environment. We analyzed and verified the performance of the proposed method using simulations. [ABSTRACT FROM AUTHOR]

The problem of processing the results of radar measurements of the parameters of motion of a target under conditions of perturbations due to aircraft maneuvers is examined. In order to adapt to the perturbations of measurement procedures, the method of invariant immersion has been modified. The use of the modified method in the case of a linear observation equation results in the widespread form of the discrete measurement procedure, derived in this article as a special case of a modified equation of invariant immersion. Based on statistical modeling of the digital processing of the results of radar measurements of the movement parameters of a maneuvering target, performance indicators of radar stations were calculated — the averaged absolute and relative measurement errors of the motion parameters, the wiring ratio, and the duration of path breaks. The analysis of specific indicators confirmed the enhanced performance of using the measurement procedures of radar stations in informational-measurement procedures, synthesized using acceleration models in the form of white noise and the Singer acceleration model. Enhancement of the performance was due to the inclusion of the coefficient of adaptation in the structure of the modified equations of invariant immersion. The proposed measurement procedures based on the modified method of invariant immersion were compared with the Kalman measurement procedures, synthesized using specified acceleration models. Calculations of the performance indicators confirm the reliability of the results obtained, since the well-known fact of an increase in the error of measurement of the height of an aircraft by monopulse radar stations near the surface is demonstrated. The results of the study will be useful in the development of adaptive measurement procedures for information-measurement systems operating under conditions of perturbations of measurement processes, such as for survey locators. [ABSTRACT FROM AUTHOR]

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Typical monopulse radar cannot detect the angle of two closely‐spaced targets in one resolution cell. The authors propose a closed‐form technique to estimate the angle of two unresolved targets by using a single snapshot of four radar receiver channels. In this work, phase comparison and amplitude comparison problems for monopulse radar are resolved. The monopulse radar angle estimation system has been enhanced using the diagonal difference channel. Using a single pulse, this technique can accurately determine the angle and amplitude of the deceptive decoy and the real target. If both targets have the same direction, the proposed scheme cannot detect them; therefore, to estimate the angle of such targets, we used an additional antenna. The effectiveness of the proposed method is validated by comparing the exact solutions and simulations. [ABSTRACT FROM AUTHOR]

Context is due to the need to analyze the electromagnetic accessibility of terrestrial radio radiation sources at long distances, which is typical for the operation of a spacecraft of radio technical intelligence with a passive synthesis of the antenna aperture. Objective is to calculate the probability indicators of detecting the fact of signal emission of ground-based radar stations using radio-technical intelligence installed on a space carrier. Method. Analytical calculation of the correct detection probability of the signal of the radio radiation sources by the spacecraft of radio technical intelligence based on the determination of the signal-to-noise ratio at the input of the detection device. The analysis of the technical characteristics of the group of ground radars made it possible to calculate the probability of correct detection only for the virtual radar, which generates the minimum number of pulses with the minimum energy during reconnaissance among all the analyzed radars. Results. The fulfillment of the conditions of electromagnetic accessibility is checked and the correct detection probability of the signals of modern radar stations by the space radio-technical intelligence system with a passive synthesis of the antenna aperture was calculated. Conclusion. Proposed use of the correct detection probability of the signal as the resulting indicator of electromagnetic accessibility of the radio radiation source. In the example radar stations of the air defense proved, that the proposed parameters of the space radio technical intelligence system with a passive synthesis of the antenna aperture provide the values of the correct detection probability of the signal, which are quite acceptable for modern monitoring systems. [ABSTRACT FROM AUTHOR]

With the rapid development of sensor technology and artificial intelligence, the video gesture recognition technology under the background of big data makes human‐computer interaction more natural and flexible, bringing richer interactive experience to teaching, on‐board control, electronic games, etc. In order to perform robust recognition under the conditions of illumination change, background clutter, rapid movement, partial occlusion, an algorithm based on multi‐level feature fusion of two‐stream convolutional neural network is proposed, which includes three main steps. Firstly, the Kinect sensor obtains RGB‐D images to establish a gesture database. At the same time, data enhancement is performed on training and test sets. Then, a model of multi‐level feature fusion of two‐stream convolutional neural network is established and trained. Experiments result show that the proposed network model can robustly track and recognize gestures, and compared with the single‐channel model, the average detection accuracy is improved by 1.08%, and mean average precision (mAP) is improved by 3.56%. The average recognition rate of gestures under occlusion and different light intensity was 93.98%. Finally, in the ASL dataset, LaRED dataset, and 1‐miohand dataset, recognition accuracy shows satisfactory performances compared to the other method. [ABSTRACT FROM AUTHOR]

Presented in this paper is a conceptual design by computer simulation of a monopulse reflector antenna with dual-circularly polarized sum patterns and linearly polarized azimuth and elevation difference patterns, which can be called a semi-dual polarized antenna. The proposed antenna consists of a five-element monopulse feed and a prime-focus parabolic reflector. The novelty of the proposed antenna is a monopulse feed consisting of a dual-circularly polarized square waveguide sum channel radiator and linearly polarized rectangular waveguide azimuth and elevation difference channel radiators. The separation of dual circular polarization is realized by a septum polarizer. The difference pattern is obtained by feeding two rectangular waveguides in opposite directions using a coaxial probe. The proposed monopulse feed geometry requires only two power combiners for a monopulse comparator network while providing dual-polarized performance comparable to the full dual-polarized sum and difference channel monopulse scheme. The concept of the proposed antenna is shown in a conceptual design by computer simulation. The monopulse feed is designed first, and then combined with a parabolic reflector. The designed monopulse reflector antenna operates at 14.5–16.0 GHz, and shows excellent sum and difference pattern characteristics: 36.1–36.7 dBc sum channel directivity with 0.65 dB boresight axial ratio and 32.6–32.9 dBi difference channel directivity with 1.56–1.66° crossover angle. [ABSTRACT FROM AUTHOR]

This paper presents a new millimeter-wave monopulse dielectric resonator (DR) filtering antenna (filtenna) array based on substrate-integrated waveguide (SIW) technology. The monopulse comparator realized by a square dual-mode (TE102 and TE201) SIW feed cavity uses diagonal irises, of which couplings between the feed and next-stage cavities lead to almost identical filter responses for the sum and difference channels with compact size and a planar single-substrate structure. Both dielectric resonator antennas (DRAs) adopting HEM133 mode for enhanced directivity are implemented with two filters based on SIW. The DR acts as the last resonator and the radiator in the filtenna. The prototype is designed at the Ka-band with a center frequency of 27.65 GHz and an operation bandwidth of 700 MHz. The measurement shows a 15-dB fractional bandwidth of 2.36%, a gain of 10.84 dBi for the sum channel, and a null depth of -15.6 dB for the difference channel. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, we study an end-to-end implementation of a Prime + Probe covert channel on the CVA6 RISC-V processor implemented on a FPGA target and running a Linux OS. We develop the building blocks of the covert channel and provide a detailed view of its behavior and effectiveness. We propose a realistic scenario for extracting information of an AES-128 encryption algorithm implementation. Throughout this work, we discuss the challenges brought by the presence of a running OS while carrying out a micro architectural covert channel. This includes the effects of having other running processes, unwanted cache evictions and the OS' timing behavior. We also propose an analysis of the relationship between the data cache's characteristics and the developed covert channel's capacity to extract information. According to the results of our experimentations, we present guidelines on how to build and configure a micro architectural covert channel resilient cache in a mono-core mono-thread scenario. [ABSTRACT FROM AUTHOR]