Radar Antenna Research Articles

Applying auxiliary arrays for mainlobe blanking to counter mainlobe repeater jamming

Mainlobe repeater jamming exploits mainlobe gain of radar antenna and signal-processing gain to significantly disrupt the target detection performance of radar. The combination of multiple auxiliary radars to form a distributed array radar improves the radar system’s angle resolution, enabling the realization of traditional spatial jamming cancellation. However, the jamming cancellation method struggle to effectively suppress multiple mainlobe repeater jamming signals when their number exceeds that of auxiliary radars, resulting in pattern distortion and subsequent loss of target energy. To address this issue, the mainlobe blanking method with auxiliary radars is proposed based on the specific characteristics of the jamming signals being distributed in multiple discontinuous peaks at the same angle. This approach leverages the superior angular resolution to accurately differentiate between target and jamming signals based on their distance-angle characteristics. Moreover, specific jamming suppression methods are employed for each jamming signal based on whether it overlaps with the target in the time domain, minimizing the loss of target energy. Furthermore, the proposed method is capable of suppressing jamming even when the target and jamming signals overlap in the time domain, and is not constrained by the number of auxiliary radars available. Simulations and experiments are used to validate the effectiveness and correctness of the proposed method in suppressing mainlobe repeater jamming.

Reliability analysis of GAN based transmit modules for active array antenna of phased array radar

Reliability is one of the most important requirements in our day to day life considering consistency, availability and failure free performance of the product over it’s define mission time. As complexity of the system increases, design for reliable systems is a big challenge. The objective of the reliability prediction analysis is to evaluate the predicted reliability of the active transmit receive modules (TRMs) under specified operating conditions, and to demonstrate that the predicted reliability meets the requirements, also to identify any parts present in the design which leads to higher failure rates. The research shows reliability of generative adversarial network (GAN) based TRMs covering from design to finalization of components as early as practicable in today's short product lifecycles. Using the reliability prediction process, we describe a method for providing design engineers with reliability feedback on their decisions. Using a conventional reliability prediction model, the Telcordia (Bellcore) parts stress prediction model, and some standard rules of thumb, we describe an initial implementation of this technique. It provides systematic identification of likely modes of failure, possible effects of each failure, and the criticality of each failure with regard to reliability, system readiness, mission success, and demand for maintenance/logistic support.

Numerical modeling of wrinkling modulation in tensegrity-membrane structures

Tensegrity-membrane structures are potential to be lightweight gossamer spacecraft (e.g., solar sails, radar antennae, solar module), and the dynamics of deployment has been studied in the past studies where the membranes were usually modeled as a flat panel without wrinkles. However, the attitude control of membrane as well as the flatness are critical to the functionality of gossamer spacecraft. The paper proposes a numerical investigation on the modulation of wrinkling in tensegrity-membrane structures. The kinematic and deformation description is based on the co-rotational finite element method (FEM), while the wrinkling of membrane is modeled by Tension Field Theory (TFT). The numerical method is validated by an illustrative experiment, and then used for a surrogate model-based optimization design, in which clustered actuation is responsible for the attitude control of membrane, while classical actuation accounts for the suppression of wrinkles. An interesting tensegrity-membrane “Sunflower” is presented to show the result of optimization, where “Sunflower” can follow the sunlight angle accurately and freely control the orientation of “corolla” while maintaining its daylighting surface quality. This study provides an effective means for the numerical simulation and optimization design of tensegrity-membrane structures, especially when the attitude and wrinkling of membranes must be considered.

Соотношения для оценки ошибок установки углового положения в матричных имитаторах радиоэлектронной обстановки

Simplified formulas have been obtained to estimate the error in setting the angular position of the apparent center of radiation in a matrix simulator. The approximation of the error function is used for this purpose. It is shown that the well-known formula for calculating the error in simula¬ting radar reflections from point targets, when used to find the statistical characteristics of noise coordinates of distributed targets, requires simplifications. In this case, the error function can be divided into four sections, within which its approximation by polynomials of the first or second degree is allowed. At the same time, the error function has an oblique symmetry, which makes it possible to analyze only two sections, and to extend the results to four. The numerical enumeration method is used as a way to find an optimal division into sections. For the typical shapes of the main lobe of the directional pattern of the radar antenna, the coefficients of the approximating polynomials were obtained by the Nelder–Meade simplex method. It is shown that the use of approximation makes it possible to obtain analytical expressions for the moments of error in setting the angular position of the apparent radiation center. In particular, the relations for finding the mathematical expectation of an error are given.

Estimation of the spatial resolution of a synthetic aperture radar antenna of the VHF frequency range placed on board an unmanned aerial vehicle along a real flight path

Background. Currently, there is an intensive development of radar systems for remote sensing of the Earth, including those placed on unmanned aerial vehicles. Synthetic aperture radars are an effective means of round-the-clock and all-weather observation of objects on the Earth’s surface. Radars operating in the VHF range allow you to observe hidden and subsurface objects. The need for practical implementation of VHF band radar with synthesizing the aperture on board unmanned aerial vehicles requires additional research on the spatial resolution of radars, taking into account the unstable trajectory of the carrier. Aim. The article considers the analysis of the influence of the flight path and its measurement errors on the quality of the radar image. Methods. The research method provides an analysis of the shape of the radar uncertainty function with the synthesis of an aperture, which was built along a real trajectory using semi-natural mathematical modeling. Results. As a result of the conducted research, it is shown that the quality of radar images is influenced not only by errors in the knowledge of motion parameters, but also by the very nature of the carrier’s movement and the duration of the flight. Conclusion. Based on the results of field tests, it turned out to be possible to analyze these factors and determine the requirements for the UAV navigation system. Thus, the article shows the possibility of quality control of VHF band radar with synthesized aperture placed on board a UAV.

Detection and validation of common noctule bats (Nyctalus noctula) with a pulse radar and acoustic monitoring in the proximity of an onshore wind turbine.

This paper presents the results of bats detected with marine radar and their validation with acoustic detectors in the vicinity of a wind turbine with a hub height of 120 m. Bat detectors are widely used by researchers, even though the common acoustic detectors can cover only a relatively small volume. In contrast, radar technology can overcome this shortcoming by offering a large detection volume, fully covering the rotor-swept areas of modern wind turbines. Our study focused on the common noctule bats (Nyctalus noctula). The measurement setup consisted of a portable X-band pulse radar with a modified radar antenna, a clutter shielding fence, and an acoustic bat detector installed in the wind turbine's nacelle. The radar's detection range was evaluated using an analytical simulation model. We developed a methodology based on a strict set of criteria for selecting suitable radar data, acoustic data and identified bat tracks. By applying this methodology, the study data was limited to time intervals with an average duration of 48 s, which is equal to approximately 20 radar images. For these time intervals, 323 bat tracks were identified. The most common bat speed was extracted to be between 9 and 10 m/s, matching the values found in the literature. Of the 323 identified bat tracks passed within 80 m of the acoustic detector, 32% had the potential to be associated with bat calls due to their timing, directionality, and distance to the acoustic bat detector. The remaining 68% passed within the studied radar detection volume but out of the detection volume of the acoustic bat detector. A comparison of recorded radar echoes with the expected simulated values indicated that the in-flight radar cross-section of recorded common noctule bats was mostly between 1.0 and 5.0 cm2, which is consistent with the values found in the literature for similar sized wildlife.

Research on Tunnel Boring Machine Tunnel Water Disaster Detection and Radar Echo Signal Processing

This study focused on the detection of water inrush in tunnels excavated by full-section hard rock tunnel boring machines (TBMs) and employed ground penetrating radar methods for conducting research on radar signal processing algorithms. The research demonstrates that conventional techniques are inadequate for eliminating the interference of TBM equipment on radar signal propagation. This study employs a radar antenna array method for signal transmission, utilizing a wavelet double-threshold filtering algorithm and wave propagation theory to suppress clutter. These methods exhibit strong signal reception capabilities and are effective in eliminating 13.1% of the direct wave components. The adoption of a novel, efficient radar signal imaging algorithm simplifies the imaging process. Results of verification indicate that the synthetic aperture algorithm, enhanced with cross-correlation calculation, yields the optimal imaging effect. This investigation, which was conducted in conjunction with the construction of a diversion tunnel in a specific region, has confirmed the applicability of the ground penetrating radar method for the detection of water inrush in TBM tunnels by conducting a comparative analysis of the direct wave removal algorithm and the integration of the optimal imaging algorithm. The innovative application of ground penetrating radar within TBM tunnels, along with a targeted technology to mitigate signal interference from metal equipment, has led to the selection of an appropriate algorithm for both signal processing and imaging. This approach offers a novel solution for the detection of water source disasters in TBM tunnels.

Design and Simulation Analysis of Antenna Structure for Active Phased Array Radar

Abstract This article adopts a modular design concept to design an active phased array radar antenna system structure and elaborates on its structural layout design and thermal design content. A finite element model of the antenna structure framework was established, and the rationality of its structural and thermal design was verified through static and thermal simulation analysis.

Thermal Design of Tile Type Active Phased Array Radar Antenna

Abstract Based on the structure and heat source distribution characteristics of the tile-type active phased array radar antenna, forced air cooling is adopted for its heat dissipation design. The heat dissipation path and fins of the main heating module of the antenna were designed and calculated, and the reliability of the thermal design was verified through software simulation and thermal testing.

Tracking of invader drone using hybrid unscented Kalman-Continuous Ant Colony Filter (HUK-CACF)

Splendid Unmanned Aerial Vehicle (UAV) applications upshot its enormous use in densely inhabited areas, which is a matter of concern. In such areas, a proper tracking system is required to track an unauthorized/invader drone to ensure safety. With the flexibility of reaching inaccessible places, an Unmanned Aerial Vehicle Mounted Adaptable Radar Antenna Array (UAVMARAA) could be used. In this regard, a Hybrid Unscented Kalman-Continuous Ant Colony Filter (HUK-CACF) is proposed to estimate the position of the invader drone efficiently. Simulation results demonstrate the efficiency and robustness of the proposed filter for tracking system compared to the existing filters in terms of success rate. Further, for various Adaptable Radar Antenna Array (ARAA) patterns such as Uniform Linear Array (ULA), Uniform Rectangular Array (URA), and Uniform Circular Array (UCA), analysis is done for pertaining actual tracking effect for various parameters such as bearing, Doppler shift, ranging, and Radar Cross Section (RCS) by considering wobbling and mutual coupling (MC) effect. The result shows that the proposed filter outperforms in all the scenarios. Among the various ARAA, URA performs better than the other configurations.

High-resolution 2D-DoA sequential algorithm of azimuth and elevation estimation in automotive distributed system of coherent MIMO radars

Objectives. One of the main tasks of radiolocation involves the problem of increasing spatial resolution of the targets in the case of limited aperture of the radar antenna array and short length of time samples (snapshots). Algorithms must be developed to provide high angular resolution and low computational complexity. In order to conform with the existing Advanced Driver Assistance Systems requirements, modern cars are equipped with more than one radar having a common signal processing scheme to improve performance during target detection, positioning, and recognition as compared to a single radar. The present study aims to develop a two-dimensional Direction-of-Arrival algorithm with low computation complexity as part of distributed coherent automotive radar system for cases involving short time samples (snapshots).Methods. A virtual antenna array formation algorithm is formulated according to the two-dimensional Capon method. A proposed modification of two-dimensional Capon algorithm is based on sequentially estimating the directions of arrival for the distributed radar system. The Monte Carlo method is used to compare the effectiveness of the considered algorithms.Results. The 2D-DoA sequential algorithm of azimuth and elevation estimation is proposed. The comparative analysis results for the developed algorithm and classical 2D Capon method based on numerical simulation using Monte Carlo method are presented. The proposed scheme of DoA estimation for coherent signal processing of distributed radars is shown to lead to an improvement of the main considered metrics representing the probability of correctly estimating the number of targets, mean square error, and square error compared to a single radar system. The proposed low-computational algorithm shows the gain in complexity compared to full 2D Capon algorithm.Conclusions. The proposed two-stage algorithm for estimating the directions of arrival of signals in azimuth and elevation planes can be applied to the distributed system of coherent radars with several receiving and transmitting antennas representing multiple input multiple output (MIMO) radars. The algorithm is based on sequentially estimating the directions of arrival, implying estimation in the azimuthal plane at the first stage and estimation in the vertical plane at the second stage. The performance of a coherent radar system with limited antenna array configuration of separate radar is close in characteristics to a high-performance 4D-radar with a large antenna array system.

Design and analysis of K and Ku-band wide-angle polarization-insensitive dual-band perfect metamaterial absorber

This paper presents a polarization-insensitive dual-band metamaterial perfect absorber applied to the Ku and K bands. The proposed dual-band metamaterial absorber (MMA) is a three-layer structure of metal-dielectric-metal. The top metal layer consists of a split circle ring, two intersecting square rings, and a circle ring, the bottom metal layer is made of copper, and the middle dielectric layer is made of FR-4. The simulation results show that the MMA has two absorption peaks at frequencies of 12.06 GHz and 19.07 GHz, with absorption rates of 99.95% and 99.73%, respectively. The MMA exhibits good polarization insensitivity in TE and TM modes. In TE mode, the increase in incident angle significantly broadens the absorption bandwidth. The experimental results verified the dual-band perfect absorption of MMA and the incident angle gain characteristic of TE mode. The proposed dual-band MMA can be applied in related fields such as radar antennas, satellite communication, and sensing.

Dual-Polarization Conversion and Coding Metasurface for Wideband Radar Cross-Section Reduction

Modern stealth application systems require integrated meta-devices to operate effectively and have gained significant attention recently. This research paper proposes a 1-bit coding metasurface (CM) design. The fundamental component of the proposed CM is integrated to convert linearly polarized incoming electromagnetic waves into their orthogonal counterpart within frequency bands of 12.37–13.03 GHz and 18.96–32.37 GHz, achieving a polarization conversion ratio exceeding 99%. Furthermore, it enables linear-to-circular polarization conversion from 11.80 to 12.29, 13.17 to 18.44, and 33.33 to 40.35 GHz. A second element is produced by rotating a fundamental component by 90°, introducing a phase difference of π (pi) between them. Both elements are arranged in an array using a random aperiodic coding sequence to create a 1-bit CM for reducing the radar cross-section (RCS). The planar structure achieved over 10 dB RCS reduction for polarized waves in the frequency bands of 13.1–13.8 GHz and 20.4–30.9 GHz. A prototype was fabricated and tested, with the experimental results showing a good agreement with the simulated outcomes. The proposed design holds potential applications in radar systems, reflector antennas, stealth technologies, and satellite communication.

An Improved OMP Algorithm for Enhancing the Anti-Interference Performance of Array Antennas.

The demand for precise positioning in noisy environments has propelled the development of research on array antenna radar systems. Although the orthogonal matching pursuit (OMP) algorithm demonstrates superior performance in signal reconstruction, its application efficacy in noisy settings faces challenges. Consequently, this paper introduces an innovative OMP algorithm, DTM_OMP_ICA (a dual-threshold mask OMP algorithm based on independent component analysis), which optimizes the OMP signal reconstruction framework by utilizing two different observation bases in conjunction with independent component analysis (ICA). By implementing a mean mask strategy, it effectively denoises signals received by array antennas in noisy environments. Simulation results reveal that compared to traditional OMP algorithms, the DTM_OMP_ICA algorithm shows significant advantages in noise suppression capability and algorithm stability. Under optimal conditions, this algorithm achieves a noise suppression rate of up to 96.8%, with its stability also reaching as high as 99%. Furthermore, DTM_OMP_ICA surpasses traditional denoising algorithms in practical denoising applications, proving its effectiveness in reconstructing array antenna signals in noisy settings. This presents an efficient method for accurately reconstructing array antenna signals against a noisy backdrop.

Accurate Localization of Intruder Drone by UAV Mounted Adaptable Radar Antenna in Restricted Areas

Accurate Localization of Intruder Drone by UAV Mounted Adaptable Radar Antenna in Restricted Areas

Radar antenna scanning type identification based on the fusion of multiple temporal features

Identifying the antenna scanning type (AST) of radar signal aims to deeply analyze the parameters of radar waveform and accurately judge the AST of the radar signal. Traditional methods rely heavily on domain priors and expert experience to set classification thresholds, which introduces human errors. Moreover, the generalization and anti-noise interference abilities are relatively weak, and it is difficult to deal with complex battlefield environments. The model based on the convolutional neural network (CNN) is limited by the receptive field of the convolution kernel, which makes the model unable to make full use of the global information of the signal. To fully exploit the global timing characteristics of radar signals, we propose a radar AST recognition method based on the fusion of multiple temporal features. Specifically, for the time series characteristics of the radar antenna scanning signal, a 1D CNN branch is first built to extract its short time series features. Given the limited receptive field of the convolutional network and the inability to fully consider the overall characteristics of the radar signal, we propose a transformer network branch to extract the global timing features fully. The recognition of radar AST based on multi-time series feature fusion can fully model the local and global sequence attributes, thereby improving the cognitive recognition ability of radar signals. Our method attains state-of-the-art results based on experimental findings.

Radar near-field sensing using metasurface for biomedical applications

Metasurfaces, promising technology exemplified by their precise manipulation of incident wave properties and exquisite control over electromagnetic field propagation, offer unparalleled benefits when integrated into radar systems, providing higher resolution and increased sensitivity. Here, we introduce a metasurface-enhanced millimeter-wave radar system for advanced near-field bio-sensing, underscoring its adaptability to the skin-device interface, and heightened diagnostic precision in non-invasive healthcare monitoring. The low-profile planar metasurface, featuring a phase-synthesized array for near-field impedance matching, integrates with radar antennas to concentrate absorbed power density within the skin medium while simultaneously improving the received power level, thereby enhancing sensor signal-to-noise ratio. Measurement verification employs a phantom with material properties resembling human skin within the radar frequency range of 58 to 63 GHz. Results demonstrate a notable increase of over 11 dB in near-field Poynting power density within the phantom model, while radar signal processing analysis indicates a commensurate improvement in signal-to-noise ratio, thus facilitating enhanced sensing in biomedical applications.

A Multiband and Multifunctional Metasurface for Linear and Circular Polarization Conversion in Reflection Modes

Multifunctional integrated meta-devices are the demand of modern communication systems and are given a lot of attention nowadays. Most of the research has focused on either cross-polarization conversion (CPC) or linear-to-circular (LP–CP) conversion. However, simultaneously realizing multiple bands with good conversion efficiency remains crucial. This paper proposes a multiband and multifunctional dual reflective polarization converter surface capable of converting a linearly polarized (LP) wave into a circularly polarized (CP) wave, in frequency bands of 12.29–12.63 GHz, 16.08–24.16 GHz, 27.82–32.21 GHz, 33.75–38.74 GHz, and 39.70–39.79 GHz, with 3 dB axial ratio bandwidths of 2.7%, 40.15%, 14.6%, 13.76%, and 0.2%, respectively. Moreover, the converter is capable of achieving CPC with a polarization conversion ratio (PCR) that exceeds 95%, within the frequency ranges of 13.10–14.72 GHz, 25.43–26.00, 32.46–32.56 GHz, and 39.14–39.59 GHz. In addition, to identify the fundamental cause of the CPC and LP–CP conversion, a comprehensive theoretical investigation is provided. Furthermore, the surface current distribution patterns at different frequencies are investigated to analyze the conversion phenomena. A sample prototype consisting of 20 × 20 unit cells was fabricated and measured, verifying our design and the simulated results. The proposed structure has potential applications in satellite communications, radar, stealth technologies, and reflector antennas.

Radar nonlinear multi-target tracking method with parallel PHD filter

Since probability hypothesis density (PHD) filters do not need explicit data association, they have recently been widely used in radar multi-target tracking (MTT). However, in existing PHD filters, sampling times are generally considered the same for all targets. Due to the limitation of antenna beam width in radar applications, the same sampling time for all targets will lead to a mismatch between the predicted data and measurement data, reducing the accuracy of radar MTT. In order to eliminate the estimation error with less computational cost, a radar nonlinear multi-target tracking method with a parallel PHD filter is proposed in this article. The measurement area is divided into several subspaces according to the beam width of the radar antenna, and the PHD of all subspaces is calculated in parallel. Then, multi-feature information in radar echo assists tracking and improves real-time performance. Experimental results in various scenarios illustrate that the proposed method can eliminate the estimation errors introduced by sampling time diversity at the cost of less computation cost, especially in cluttered environments.

Increasing the probing depth of pulsed GPR by reducing the antenna impedance

At the present time, dipole antennas with resistively loaded vibrators are widely used in pulsed georadar. The main property of such antennas is the emission of an electromagnetic wave into the subsurface medium with rapid attenuation of the ultra-wideband pulse to the end of the vibrators without reflection. When the total resistance of the vibrator decreases below 200 Ohms, parasitic self-oscillations appear in this antenna, limiting the increase in power supplied to the antenna. Development of a dipole antenna for subsurface ground penetrating radar with the ability to reduce the antenna impedance below 200 Ohms to increase the radiated power and increase the depth of ground penetrating radar. The design of a dipole antenna with several resistively loaded vibrators connected in parallel is proposed. The total resistance of a single vibrator is selected based on the stability requirements to prevent parasitic self-oscillations, but the impedance of the dipole antenna decreases in proportion to the number of connected vibrators. A dipole antenna with five dipoles connected and arranged parallel to each other has a gain 10 dB higher compared to a dipole with a single resistively loaded dipole. Compared to a plate antenna 3 meters long and 25 cm wide, a five-vibrator dipole antenna of the same length has a gain of 3.3 dB higher. Another advantage of the proposed antenna is its higher resolution. At the same time, insulated vibrators made of flexible conductors allow twisting to reduce the overall diameter of the dipole antenna, which allows its use in difficult engineering and geological conditions. Experiments with three-meter dipole antennas showed an increase in sounding depth in the Moscow region from 14 to 20 meters.