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Article ISAR Imaging of Drone Swarms at 77 GHz(Tubitak Scientific & Technological Research Council Turkey, 2025) Coruk, Remziye Busra; Kara, Ali; Aydin, ElifThe proliferation of easily available, internet-purchased drones, coupled with the emergence of coordinated drone swarms, poses a significant security threat for airspace. Detecting these swarms is crucial to prevent potential accidents, criminal misuse, and airspace disruptions. This paper proposes a novel inverse synthetic aperture radar (ISAR) imaging technique for high-resolution reconstruction of drone swarms at 77 GHz millimeter wave (mmWave) frequency, offering a valuable tool for military and defense antidrone systems. The key parameters affecting down-range and cross-range resolution (0.05 m), ultimately enabling the generation of detailed ISAR images are discussed. Here, we create diverse scenarios encompassing various swarm formations, sizes, and payload configurations by employing ANSYS simulations. To enhance image quality, different window functions are evaluated, and the Hamming window is selected due to its highest peak signal-to-noise ratio (PSNR) (16.3645) and structural similarity (SSIM) (0.9067) values, ensuring superior noise reduction and structural preservation. The results demonstrate that the effectiveness of high-resolution ISAR imaging in accurately detecting and characterizing drone swarms pave the way for enhanced airspace security measures.Article Citation - WoS: 1Citation - Scopus: 2A Miniaturized Multi-Layer Microstrip Antenna for Linear Wireless Sensor Network Monitoring Systems(Gazi Univ, 2022) Kara, Ali; Aydın, Elif; Benzaghta, Mohamed; Er, Burak; Bilgin, GulsimaThis article presents a sub-GHz ISM band microstrip patch antenna based on the use of multi-layer compact structure, which overcomes the shortcomings of typical microstrip antennas such as low gain and high resonant frequency. The antenna was simulated using an electromagnetic simulator, ANSYS HFSS, and fabricated on two different substrates: RT Duroid 5880 and FR4 epoxy with a compact size of 100 x 100 x 8 mm3 (0.29λ × 0.29λ × 0.02λ). The simulated results of the antenna were then compared with the measured ones, and the two were observed to have a reasonable agreement. The proposed antenna operates in the sub-GHz license-free ISM band (862-875 MHz), with a gain value of 2.92 dB. Two prototypes of the proposed antenna were fabricated and used in a Linear Wireless Sensor Networks (LWSNs) monitoring system. Results show that the proposed antenna is a good candidate for those types of LWSNs systems.Conference Object Citation - Scopus: 2Uav Detection and Ranging With 77-81 Ghz Fmcw Radar(Ieee, 2022) Doganay, Bengisu; Arslan, Mustafa; Demir, Efe Can; Coruk, Remziye Busra; Gokdogan, Bengisu Yalcinkaya; Aydin, ElifIn this study, detection of unmanned aerial vehicles (UAV), determination of radar cross-section (RCS) values, and range estimation were performed using a commercial off-the-shelf (COTS) millimeter-wave Frequency Modulated Continuous Wave (mmWave FMCW) radar system in the 77-81 GHz frequency band. The measurements were carried out in a laboratory environment using a single transceiver antenna without the need for an anechoic chamber. RCS values of different vertically and horizontally positioned UAVs were measured experimentally along the 360 degrees aspect angle, and the simulated results obtained from computational tool were compared with the experimental results. The measurement and simulation results, together with the range estimation, matched with high accuracy.Conference Object Citation - WoS: 2Citation - Scopus: 3Design Considerations for Sub-Ghz Multilayer Microstrip Antenna for Near Ground Communication Links in Rural Areas(Ieee, 2017) Bilgin, Gulsima; Yilmaz, Vadi Su; Aydin, Elif; Kara, Ali; Department of Electrical & Electronics Engineering; Electrical-Electronics EngineeringThis paper presents some preliminary results of design and development of sub-GHz multilayer microstip antenna for use in near ground communication applications. In design stage of the antenna, iterative approach was applied. Firstly, a two layer microstrip antenna design process is presented. Next, the corners of the patch were cut, and a vertical wall on all sides of the antenna were introduced. In this way, both the size and resonant freqeuncy can be tuned. Moreover, as an application specific requirement, it is intended to embed this antenna into a metal box in order to protect it from man-made and natural environmental effects. This was also studied, and effects of the embedding ground on the antenna characteristics were examined. It is shown that the designed antenna provides -27dB resturn loss, and 7.3dB peak gain at 915MHz with the dimension of 150x200x13mm. Some preliminary measurements have proven the simulations.Article W-Band RCS Prediction of Small Objects: Comparing Two Widely Used Methods with Experimental Validation(Gazi University, 2025) Kara, Ali; Aydın, Elif; Yardım, Funda Ergün; Sezgin, DenizThis paper compares the accuracy of Shooting and Bouncing Rays and Electric Field Integral Equation methods for Radar Cross Section prediction of small objects at 77-81 GHz band. Existing studies on RCS prediction methods often lack comprehensive comparisons between computational and experimental results, particularly for small objects measured with a 77 GHz radar. This study addresses this gap by presenting an in-depth analysis of both simulation and measurement data. In this work, three targets with varying geometries and materials were measured with a frequency modulated continuous wave radar and simulated using Ansys HFSS and CST Studio Suite. The measurements were performed with a commercial off-the-shelf (COTS) frequency modulated continuous wave radar operating at 77–81 GHz. This study aims to emphasize the importance of considering both efficiency and accuracy when opting for an RCS prediction method. Overall, the outcomes of both methods have largely demonstrated good alignment. It has been noted that, while Shooting and Bouncing Rays method offers promising time-saving advantages, Electric Field Integral Equation method remains a valuable tool for complex geometries where precise results are crucial.Article Citation - WoS: 4Citation - Scopus: 4Genetic Algorithm Approach To Estimate Radar Cross Section of Dielectric Objects(Ieice-inst Electronics information Communications Eng, 2003) Aydin, E; Nakiboglu, KC; Department of Electrical & Electronics EngineeringGenetic algorithm (GA) is a widely used numerical technique to simplify some analytical solutions in electromagnetic theory. Genetic algorithms can be combined with the geometric optics method to tackle electromagnetic scattering problems. This paper presents an extrapolation procedure, which derived, as a first step, a functional representation of the radar cross section (RCS) of three different dielectric objects that was computed via the Mie solution or the method of moments (MOM). An algorithm was employed to fit the scattering characteristics of dielectric objects at high frequencies.Conference Object Citation - WoS: 2Citation - Scopus: 5Low Radar Cross Section Uav Design in X-Band(Ieee, 2022) Unalir, Dizdar; Sezgin, Sila; Yuva, Cansu Sena; Yalcinkaya Gokdogan, Bengisu; Aydin, ElifAs Unmanned Aerial Vehicles (UAVs) have become widespread in defense industry, the radar technology that can detect them has also improved. These improvements cause UAVs to be detected more easily, which limits their effectiveness in military usage. Although the reduction of the radar cross-section (RCS) can provide a solution to this issue, the studies regarding that is insufficient in the literature. In this study, a shaping method is recommended to reduce the RCS of UAVs, and it is shown the method is effective to address the problem. Firstly, using a simulation tool, an UAV model is designed from simple shapes and the model is validated by comparing it with the ones in literature. Secondly, RCS values are measured using vertical and horizontal polarization throughout 360 degrees by incrementing the aspect angle by one degree in X-Band using the CST Studio Suite environment. Then, considering the hardware and aerodynamic requirements as well as limitations of the UAV model, a shaping technique is applied to the body, legs and the hollow parts of the UAV model with parametric simulations. The results show that the recommended shaping technique can provide a significant reduction in the RCS of an UAV.
