Mesut Kartal

This paper aims to design and fabricate a circularly polarized MIMO antenna with opposite rotating senses and use a new decoupling element to improve the isolation between the antenna ports. The proposed design includes two pairs of crossed-dipoles fed by two branch-line couplers to accomplish a dual-sense CP MIMO antenna. The elements used in this design are printed dipole antennas with balun feeding. As a validation, an antenna prototype is fabricated and measured. The experimental results show that operating bandwidths of the antenna are 32.98 % (1.95–2.72 GHz) and 29.17 % (2.02–2.71 GHz) with |S11| < 10 dB for Port-R and Port-L respectively, with axial ratio bandwidth of 1.97–2.51 GHz at the two ports. Furthermore, measured results approve that by employing the decoupling component, at least 15.2 dB isolation between the ports with an ECC value of less than 0.0037 in the operating …

In this study, a jammer localization method with high accuracy and low-complexity features is proposed to protect 5G networks from malicious jammer attacks. To satisfy both features, the proposed method has a hybrid structure that activates the range-free and range-based localization approaches. Prior to localization, the jamming signal disturbing user equipment (UE) receivers is detected by observing the error vector magnitude (EVM) metric. Then, in the range-free stage, which is the first stage of our localization method, contours are drawn on the map using EVM data obtained from the UEs. When the UE density around the jammer's location is sufficiently high, accurate localization can be achieved quickly with these contours without the need for a second operation step. Otherwise, the contours provide a coarse position of the jammer and the second stage, which is the range-based stage, is activated to improve …

In this paper, a hybrid sensor composed of a frequency selective surface (FSS) and microstrip patch antenna is investigated numerically for non-invasive glucose sensing in the microwave region. The sensing method relies on detecting changes in the dielectric constant of the sample under test (SUT) in response to variations in the concentration of glucose-deionized water solutions. The SUT consists of the area between the microstrip patch antenna and FSS. Four glucose-deionized water solutions (i.e., 72 mg/dL, 216 mg/dL, 330 mg/dL, and 600 mg/dL) are tested in the SUT. The dielectric properties of the solutions are determined using the Debye model. For the sensitivity analyses, the return losses of the proposed sensor and the dependence of the resonance frequencies on the volume percentage of glucose in glucose-deionized water solutions have been noted. When the glucose-deionized water …

A new target-refocusing technique based-on re-centering phase computation of previously recorded moving target raw data is implemented to the Spotlight SAR data in order to obtain refocused moving targets. The technique is tested on the integrated simulated data; background real spotlight SAR Raw data with the synthetically generated data domes of civilian moving targets. First Polar format Algorithm is applied to detect and estimate the speed of ground-moving targets on the integrated raw data. At the next step, re-organize the integrated raw data by selecting and arranging target focusing center with a new technique based on re-centering phase computation to each moving target speed. At the third step re-organize the raw data by re-centering the phase computation to each moving target location. Finally, Polar Format Algorithm is applied to each reorganized raw data to obtain highly focused moving targets individually

This article presents the designs and analyses of a co-planar ultra-wideband monopole antenna using graphene as a conductive patch. A graphene-based film (GBF) is used as the radiating conductive layer of the antenna, and a Polydimethylsiloxane (PDMS) is used as a substrate. Since both layers are flexible, they are very suitable for use in wearable technologies. In this study, two basic antenna structures are studied. The design-1 antenna covers 3-11 GHz bandwidth. The simulated antenna efficiency is obtained as 72% at 10 GHz. The antenna size is 30 mm× 23.2 mm. The second designed antenna (design-2), stands out with its optimizations, is designed in a smaller size, high gain and wide band features. The size of the second antenna has been reduced to 28 mm× 21 mm. Although the conductive graphene layer of the antenna was replaced with a higher conductivity, the substrate material remained the same. In the second antenna design, 3.3-30 GHz ultra-bandwidth and 83% efficiency at 25 GHz have been achieved. In addition, new antenna designs with different conductor and substrate properties on the second antenna design are proposed in this study. The effect of antenna bending was also examined and comparative analyses of the obtained results were made in terms of properties such as efficiency, gain, and radiation pattern. In addition to the use of flexible materials in both the substrate and the conductive layer of the designed antennas, their smaller dimensions, broadband structures and high efficiencies allow these antennas to be used as good candidates in wearable technologies.

This paper addresses the escalating threat of malicious jamming in next-generation communication systems, propelled by their continuous advancement in speed, latency, and connectivity. Recognizing the imperative for communication security, we propose an efficient jamming detection method with distinct innovations and contributions. Motivated by the growing sophistication of jamming techniques, we advocate the adoption of the error vector magnitude (EVM) metric, measured in IQ symbols, deviating from traditional received signal strength and bit error rate-based measurements. Our method achieves enhanced jamming detection sensitivity, surpassing existing approaches. Furthermore, it introduces low complexity, ensuring resource-effective detection. Crucially, our approach provides vital jammer frequency information, enhancing counteraction capabilities against jamming attacks. It demonstrates stable results against varying system parameters, such as modulation type and code rate, thereby contributing to adaptability. Emphasizing practicality, the method seamlessly integrates into 5G and LTE systems without imposing additional overhead. Versatility is demonstrated through successful operations in diverse scenarios that are run by extended simulation conditions. Theoretical analysis substantiates these advantages, reinforcing the validity of our methodology. The study’s success is further validated through laboratory experiments, providing empirical evidence of its effectiveness. The proposed method represents a significant step toward fortifying next-generation communication systems against evolving jamming threats.

Herein, NiFe2O4 doped Cu was synthesized using a mixed-oxide method to investigate its potential for creating composites with high microwave shielding effectiveness. The compound NiFe2−xCuxO4 was synthesized with x values of 0.1, 0.3 and 0.5, respectively. After sintering at 1250 °C for 4 h, single-phase Ni ferrite was formed. To analyze the phase composition and the structure of the synthesized compound, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were employed. The study's findings showed that NiFe2−xCuxO4 did not exhibit a second phase. To create composites with high microwave shielding effectiveness, polyaniline-NiFe2O4:Cu composites were fabricated using a hot-pressing technique, with compositions of NiFe1.9Cu0.1O3.95, NiFe1.7Cu0.3O3.85 and NiFe1.5Cu0.5O3.75 with the aniline, The weight ratios of Cu-added nickel ferrite and aniline were …

This dataset consists of signatures of human vital signs that are recorded by ultrawideband radar and lidar sensors. The data acquisition scene considers the human posture models(supine/lateral/facedown), different radar antenna angles towards the human, various set of distances and operational radar characteristics (bandwidth selection/mean power). The raw data files of lidar&radar and processed data files are presented separately in the data repository. The lidar sensor is chosen as a reference sensor. There are 432 data records, and each data scene's trial number is eight. There is a homogeneous wooden table to mimic clutter while forming a dataset. Thus, this dataset covers applications of search and rescue operations, sleep monitoring, and ambient assisted living (AAL) applications.