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The design and optimization of laser-Compton x-ray systems based on compact distributed charge accelerator structures can enable micron-scale imaging of disease and the concomitant production of beams of Very High Energy Electrons (VHEEs) capable of producing FLASH-relevant dose rates. The physics of laser-Compton x-ray scattering ensures that the scattered x-rays follow exactly the trajectory of the incident electrons, thus providing a route to image-guided, VHEE FLASH radiotherapy. The keys to a compact architecture capable of producing both laser-Compton x-rays and VHEEs are the use of X-band RF accelerator structures which have been demonstrated to operate with over 100 MeV/m acceleration gradients. The operation of these structures in a distributed charge mode in which each radiofrequency (RF) cycle of the drive RF pulse is filled with a low-charge, high-brightness electron bunch is enabled by the illumination of a high-brightness photogun with a train of UV laser pulses synchronized to the frequency of the underlying accelerator system. The UV pulse trains are created by a patented pulse synthesis approach which utilizes the RF clock of the accelerator to phase and amplitude modulate a narrow band continuous wave (CW) seed laser. In this way it is possible to produce up to 10 μA of average beam current from the accelerator. Such high current from a compact accelerator enables production of sufficient x-rays via laser-Compton scattering for clinical imaging and does so from a machine of "clinical" footprint. At the same time, the production of 1000 or greater individual micro-bunches per RF pulse enables > 10 nC of charge to be produced in a macrobunch of < 100 ns. The design, construction, and test of the 100-MeV class prototype system in Irvine, CA is also presented.

This article presents a flexible four-element antenna for X-band applications. The proposed antenna covers the spectrum ranging from 10.6 to 11.9 GHz, including a significant portion of the X-band. The single antenna element comprises a modified E-shaped radiating patch, which is fed by a unique feeding structure consisting of a 50-Ω feeding strip connected with two rectangular stubs on both sides. All antenna elements are printed on a flexible felt 60 mm × 60 mm × 1 mm (2.12 λ × 2.12 λ × 0.035 λ at 10.6 GHz) substrate. The proposed antenna exhibits circular polarization over the desired bans of operation with an axial ratio (< 3 dB) bandwidth of 1.2 GHz, which is significant for X-band applications. The designed antenna is manufactured and practically tested. Both simulated and measured results agree well with each other, ensuring the optimal performance of the antenna. Moreover, the antenna achieves a maximum gain of up to 8 dBi in the desired band of operation. Further MIMO parameters, including envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and mean effective gain (MEG), are calculated to validate the MIMO performance. Finally, a conformal analysis was carried out to study the robustness of the antenna in various bending scenarios. Results show that the antenna reported in this article is the correct choice for conformal X-band MIMO applications. [ABSTRACT FROM AUTHOR]

The EPFL Spacecraft Team (EST) is working on the Constellation of High-Performance Exospheric Science Satellites (CHESS) mission, which aims to launch a constellation of two CubeSats in 2027. These CubeSats will study the chemical composition of Earth's exosphere using time-of-flight mass spectrometry. To downlink the collected scientific data, the satellites will utilise a custom X-band transceiver, presented in this paper, operating in the amateur frequency range of 10.45 GHz to 10.50 GHz. The proposed transceiver architecture employs Software-Defined Radio (SDR) technology and can be easily adapted for different use cases. This modular approach has the potential to be suitable for future spacecraft missions, such as active debris removal or lifetime extension services, where flexible communication systems are required. • Hybrid SDR architectures enable versatile telecom systems for space missions. • IOD/IOV missions let students follow the entire life cycle of a space project. • Short development/prototyping cycles maximise the lessons learned in student teams. [ABSTRACT FROM AUTHOR]

Abstract This article presents a flexible four-element antenna for X-band applications. The proposed antenna covers the spectrum ranging from 10.6 to 11.9 GHz, including a significant portion of the X-band. The single antenna element comprises a modified E-shaped radiating patch, which is fed by a unique feeding structure consisting of a 50-Ω feeding strip connected with two rectangular stubs on both sides. All antenna elements are printed on a flexible felt 60 mm × 60 mm × 1 mm (2.12 λ × 2.12 λ × 0.035 λ at 10.6 GHz) substrate. The proposed antenna exhibits circular polarization over the desired bans of operation with an axial ratio (

The technique of electromagnetic characterization of materials in free space allows for the measurement of constitutive properties without making contact with the material being measured. Characterization methods in Free Space are naturally suited for Electromagnetic Radiation Absorbing Materials (RAM) but are also important in applications where the material sample to be measured does not undergo major interventions. They consist of evaluating a received signal resulting from a free-space transmission through two horn antennas with beam collimating lenses and a Vector Network Analyzer (VNA). The characteristics of the transmitted signal are modified by a material positioned between the transmitting and receiving antennas. This work presents methods for electromagnetic characterization in Free Space, in the frequency range of 8.2 to 12.4 GHz (X-Band), in a semi-anechoic chamber, seeking the development of measurement processes that present results with repeatability and reliability. The measurements were made with standard and electromagnetic radiation absorbing materials. The measurement technique presented 95% of efficiency. [ABSTRACT FROM AUTHOR]

The design and optimization of laser-Compton x-ray systems based on compact distributed charge accelerator structures can enable micron-scale imaging of disease and the concomitant production of beams of Very High Energy Electrons (VHEEs) capable of producing FLASH-relevant dose rates (∼ 10 Gy in less than 100 ns). The physics of laser-Compton x-ray scattering ensures that the x-rays produced by this process follow exactly the trajectory of the electrons from which the x-rays were produced, thus providing a route to not only compact VHEE radiotherapy but also image-guided, VHEE FLASH radiotherapy. This manuscript will review the compact accelerator architecture considerations that simultaneously optimize the production of laser-Compton x-rays from the collision of energetic laser pulses with high energy electrons and the production of high-bunch-charge VHEEs. The primary keys to this optimization are use of X-band RF accelerator structures which have been demonstrated to operate with over 100 MeV/m acceleration gradients. The operation of these structures in a distributed charge mode in which each radiofrequency (RF) cycle of the drive RF pulse is filled with a low-charge, high-brightness electron bunch is enabled by the illumination of a high-brightness photogun with a train of UV laser pulses synchronized to the frequency of the underlying accelerator system. The UV pulse trains are created by a patented pulse synthesis approach which utilizes the RF clock of the accelerator to phase and amplitude modulate a narrow band continuous wave (CW) seed laser. In this way it is possible to produce up to 10 µA of average beam current from the accelerator. Such high current from a compact accelerator enables production of sufficient x rays via laser-Compton scattering for clinical imaging and does so from a machine of “clinical” footprint. At the same time, the production of 1,000 or greater individual micro-bunches per RF pulse enables > 10 nC of charge to be produced in a macrobunch of < 100 ns. The design, construction, and test of the 100-MeV class prototype system in Irvine, CA is also presented.

AbstractCarbon fabric-reinforced polymer (CFRP) composites have replaced most aluminum and ferrous alloys in aerospace construction owing to their attractive high strength-to-weight ratio. CFRPs used in aircraft should have electromagnetic shielding ability in addition to structural properties. Hence, the study of Electromagnetic (EM) wave shielding by hybrid CFRPs is an important topic of research. In this article, we summarize research advancements for enhancing the EM wave shielding of CFRP composites in the X-band frequency range. This study focuses on the manufacturing and performance of carbon-fabric-based composites with metals, metal oxides, and carbon-based fillers. The factors influencing the EM wave shielding ability of the CFRP composites are also discussed. The EM wave shielding of Carbon fibers (CF) was remarkably improved by coating, electroless plating, and synthesizing nanoparticles on the carbon fiber surface. It was found that the carbonious fillers and metal nanofillers such as Nickel (Ni), Iron (Fe), and Silver (Ag)-loaded multilayer CFRP composites showed better absorption modes of EM wave shielding with good structural properties. Owing to the Ag nanowire coating on the CFs, the shielding effectiveness was drastically improved. However, in addition to the type of filler, the structural properties are also influenced by the manufacturing method and type of composite. In the case of laminated composites, the absorption-laminated EM shielding is influenced by the architecture of the plys and the type and number of interplay in the composite construction. In addition, the techniques adopted for the synthesis of nanoparticles and dispersion in composites for effective EM shielding are challenging tasks.

Zinc aluminate (ZnAl2O4) is widely recognized as a ceramic in high demand across various microwave applications. Furthermore, blending dielectric materials with ZnAl2O4 has demonstrated improvements in its dielectric properties, offering promising potential for advancing microstrip patch antenna technology. This paper presents the fabrication and characterization of a sol-gel composite nanoparticle consisting of titanium dioxide (TiO2) and zinc aluminate (ZnAl2O4) for use in a microstrip patch antenna designed for X-band applications. The composite nanoparticle, with a molecular composition of xTiO2(1-x)ZnAl2O4 where x = 8 %, was investigated using X-ray diffraction (XRD), revealing dominant peaks corresponding to ZnAl2O4 and TiO2 with a calculated crystallite size of 16.9 nm. Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), and energy dispersive spectroscopy (EDS) were employed to assess functional groups, morphology, and elemental composition of the nanoparticles. The dielectric properties of the nanoparticles, characterized by a dielectric permittivity of 20.2 and a dielectric loss of 0.19, were measured using an LCR meter. These nanoparticles were utilized to fabricate a prototype patch antenna, exhibiting promising performance in both simulated and measured results. The fabricated patch antenna operated at 8.51/8.49 GHz with a return loss (RL) of − 25.94/−19.97 dB, featuring an enhanced bandwidth of 2.62/2.87 GHz and a voltage standing wave ratio (VSWR) below 2. Additionally, the antenna demonstrated a gain of 2.14, directivity of 3.58, and radiation efficiency of 59.7 %, making it suitable for X-band applications.

• Reconfigurable graphene antenna. • Cognitive radio network. • Innovative solution for X-band satellite communications. • Improvement in satellite communication performance. This study introduces a graphene-based antenna tailored for X-band satellite communication within a cognitive radio network. Leveraging graphene's distinctive traits high conductivity and mechanical flexibility, the antenna design achieves reconfigurability in frequency, polarization, and radiation pattern. This adaptability enables dynamic adjustments to environmental shifts, bolstering the efficiency and dependability of satellite communication. Operating on software-defined radio technology, the cognitive radio system monitors and allocates the available frequency spectrum, allowing real-time adjustments to antenna parameters. Given the widespread usage of the X-band in satellite communications, this antenna proposal stands as an appealing solution for such systems. Its potential applications encompass providing broadband access in remote regions, supporting emergency communication networks, facilitating maritime and aeronautical communications, and enabling self-sustaining wireless networks. The approach involves a novel graphene antenna with slots to facilitate frequency reconfigurability. At 9 GHz, the graphene antenna achieves a gain of 6 dBi, surpassing the 4.3 dBi gain of a copper antenna. By varying the chemical potential of graphene from 0 to 4 eV , we achieved a high gain of 6.4 dBi at 9 GHz and an excellent reflection coefficient of −42 dB at 11.63 GHz. The graphene antenna's improved gain and tuning capabilities surpass traditional materials, showcasing adaptability across diverse frequencies, promising versatility for varied communication needs, and enhancing overall system reliability and effectiveness. [ABSTRACT FROM AUTHOR]

The quality of weather radar affects the reliability and effectiveness of monitoring severe convective weather. Therefore, rigorous calibration and validation are the foundation for the quantitative application of weather radar. Among the available methods, radial velocity validation is of great significance for reducing the false alarm rate in the identification of tornadoes and thunderstorms. Based on the traditional method that utilizes internal and external instrument radar velocity measurements, we propose a weather radar radial velocity validation method that uses RTK UAV to simulate external targets. In addition, according to the characteristics of the UAV application scenarios, we introduce the evaluation parameter of optimal absolute accuracy to supplement the original parametric system. The experimental results show that the evaluation parameter of optimal absolute accuracy can effectively reduce the interference caused by the systematic deviation of the UAV due to the internal and external environment, which can affect the validation results. When the UAV velocity is not greater than 10 m/s, the optimal absolute accuracy of the radial velocity validation is less than 0.05 m/s, which is essentially consistent with the external instruments' measurement results. This method can be effectively applied to the procedural handling of weather radar radial velocity validation. It is significant for ensuring the accuracy and quality of weather radar radial velocity measurements and improving the effectiveness of radar velocity data applications. [ABSTRACT FROM AUTHOR]

Maintaining engine oil quality is critical for industrial machinery and transformers to ensure efficient operation and reduce the risk of failure. This paper presents a novel application of an X-band microwave sensor, using a third-order electroformed iris waveguide filter, for real-time, non-invasive engine oil quality monitoring. By detecting shifts in the dielectric properties of engine oil, the sensor accurately tracks oil degradation as it ages. Unlike traditional methods that require oil extraction and laboratory analysis, this sensor enables continuous, in-situ monitoring, providing immediate feedback without disrupting system operations. Any change in oil quality causes a frequency shift, as variations in its dielectric properties affect the waveguide’s resonance. This shift can be measured in real time, enabling accurate monitoring of oil degradation. Additional measurements were conducted using the coaxial probe technique to analyze the changes in the oil’s electrical behavior during various heating periods. Experimental results demonstrate the sensor’s sensitivity, with measurable frequency shifts of up to 10 MHz observed in the most aged oil samples. These shifts clearly correlate with the oil’s aging process, confirming the sensor’s potential for practical use in predictive maintenance. This system, utilizing an electroformed waveguide, offers a cost-effective and efficient solution for enhancing machinery longevity and optimizing maintenance schedules in industrial applications.

Accurate estimation of forest aboveground biomass (AGB) is crucial for research on terrestrial carbon cycling and global climate change. In this study, we introduce an improved approach for estimating forest AGB combining P-band and X-band interferometric synthetic aperture radar (InSAR) data. Forest AGB was estimated by combining unbiased forest height and volume backscatter intensity. For forest height, a multilayer model and subaperture decomposition technology were used to remove the penetration bias of the X-band and reduce the effects of forest scatterers on the extraction of a pure understory terrain phase based on P-band, respectively. For volume backscatter intensity, a ground cancellation algorithm based on P-band InSAR was used to eliminate ground scattering contributions unrelated to forest AGB. The proposed method was validated using airborne P-band InSAR data and spaceborne X-band InSAR data gathered over the study area on the Saihanba Forest Farm in Hebei, China. The unbiased forest height and volume backscatter intensity had stronger correlations with forest AGB than estimates derived from unimproved features. The proposed method returned high-precision estimates of forest AGB with an accuracy of 83.73%, an improvement of 8.80% over an estimate derived from unoptimized features. Additionally, AGB estimates combined with forest height and backscatter intensity were greater than those based on a single feature, with the contribution of the former is greater than that of the latter.

In this paper, we propose a dual-band shared-aperture antenna composed of array elements with high electromagnetic (EM) transparency. To increase EM transparency, the antenna consists of an optimized substrate with low effective permittivity by combining thin dielectric sheets and air-gap layers. To further improve the EM transparency, thin dual-loop radiators with optimized widths and lengths are adopted for the S-band element, and an E-shaped patch antenna is employed for an X-band element. This configuration minimize the pattern distortion in the X-band elements while enhancing antenna bandwidths. In addition, a calibration layer comprising four monopole probes and microstrip transmission lines is included for monitoring the phase and amplitude errors of each element. To verify the feasibility, the proposed antenna is fabricated to measure antenna characteristics, such as reflection coefficients, beam steering performance, and mutual coupling in a full anechoic chamber. The fractional bandwidths of the antenna in the S- and X-bands are 16.4% and 26.8%, respectively. The array gains at the bore-sight are 16.0 dBi in the S-band and 24.0 dBi in the X-band.

In this paper, two composites ZrB₂/Al₂O₃ and FeSiAl/Al₂O₃ were characterized using the Transmission/Reflection characterization technique. The volume contents of ZrB₂ and FeSiAl inclusions in these composites vary between 0 and 15%. The results obtained indicate that the percentage of the inclusions in the composites effectively improves the dielectric property. The comparison of the effect of ZrB₂ and FeSiAl inclusions on the dielectric properties of these composites confirms that reinforcing these composites with FeSiAl particles results in better dielectric properties. Furthermore, these results indicate that the dielectric property of the two composites studied decreases progressively with increasing frequency in the X band. This frequency dependence of the dielectric property of the composites studied is very important and shows that the composites studied are good candidates for microwave absorption applications in the X-band and for antenna design. Additionally, a comparison between the numerical results obtained in this work and the experimental results published in the literature reveals a close agreement, validating the reliability of the study's findings.

In this study, we fabricated a coplanar waveguide using a novel graphene-silver nanowire composite structure (GNCS) on a polyethylene terephthalate (PET) substrate and then investigated its radio frequency (RF) characteristics. According to the measured results, the coplanar waveguide employing GNCS exhibited a substantially lower loss of transmission line than conventional waveguides. Furthermore, compared to the conventional graphene-based coplanar waveguide, the proposed structure allowed for lower skin depth and higher conductivity, resulting from the high electric conductivity of the silver nanowire. In addition, repetitive bending tests, which were performed to investigate the electric stability of the graphene-silver nanowire, showed that the coplanar waveguide employing GNCS offered substantially better electrical stability than the conventional graphene-based coplanar waveguide. These results indicate that the graphene-silver nanowire structure is a promising candidate for application in flexible wireless communication systems. Notably, this is also the first study to investigate the RF performance and electrical stability of a graphene-silver nanowire/PET structure.

The manufacturing of active RF devices like klystrons is dominated by expensive and time-consuming cycles of machining and brazing. In this article, we characterize the RF properties of X-band klystron cavities and an integrated circuit manufactured with a novel additive manufacturing process. Parts are 3D printed in 316 L stainless steel with direct metal laser sintering, electroplated in copper, and brazed in one simple braze cycle. Stand-alone test cavities and integrated circuit cavities were measured throughout the manufacturing process. The un-tuned cavity frequency varies by less than 5% of the intended frequency, and Q factors reach above 1200. A tuning study was performed, and unoptimized tuning pins achieved a tuning range of 138 MHz without compromising Q. Klystron system performance was simulated with as-built cavity parameters and realistic tuning. Together, these results show promise that this process can be used to cheaply and quickly manufacture a new generation of highly integrated high power vacuum devices. [ABSTRACT FROM AUTHOR]

This paper will propose an innovative compact, lowcost, low-profile inverted U-shaped patch antenna with a single and dual band-notched ultra-wideband (UWB) with split ring resonators (SRRs). To achieve our main goal based on the reduction of electromagnetic interference in narrowband communications (WLAN, WiMAX, and satellite), four-element rectangular split-ring resonators (SRRs) array are placed nearby the feedline to create notch band at approximately 5.15-5.35 and 5.725-5.85 GHz. The SRRs antenna's measured data indicate a directivity of 8.52 dBi, a gain of 7.18 dBi, a reflection coefficient of -27 dB, and an efficiency of 84.3%. The realized prototype, including the SRRs and CSRRs structures, were carried out using a PCB prototyping machine. Reflection coefficient measurement is obtained using a vector network analyzer (VNA) PNA-X from Agilent Technologies. The measured values of the proposed antenna, with 50 x 38 x 1.6 mm3 in total and constructed on a FR4 substrate with permittivity of er = 4.3, loss tand = 0.0024 and substrate thickness of h = 1.6 mm, correlate well with the simulated values. The proposed antenna, compared with other published work, is a good candidate to operate in WLAN, X-band. [ABSTRACT FROM AUTHOR]

The role of antennas in wireless communication is critical for enabling efficient signal transmission and reception across various frequency bands, including those associated with IoT (Internet of Things), X-band, S-band, and RFID (radio-frequency identification) systems. This paper presents a small quadruple-band antenna with 25 × 40 × 1.5 mm3 dimensions designed for diverse wireless applications. It is adept at operating in the S-band (2.2 GHz), wireless local area network (WLAN) (5.7 GHz), microwave RFID frequency band (5.8 GHz), and X-band (7.7 GHz and 8.3 GHz). While the majority of existing research focuses on antennas covering two or three bands, our work stands out by achieving quad-band operation in the proposed antenna design. This antenna is constructed on a semiflexible Rogers RT5880 substrate, making it well-suited for wearable applications. Computer Simulation Technology (CST) Microwave studio (2019) simulation package software is chosen for design and analysis. The antenna design features a comb-shaped radiating structure, where each "tooth" is responsible for resonating at a distinct frequency with an appropriate bandwidth. The antenna retains stability in both free space and on-body wearability scenarios. It achieves a low specific absorption rate (SAR), meeting wearable criteria with SAR values below 1.6 W/Kg for all resonating frequencies. The proposed antenna demonstrates suitable radiation efficiency, reaching a maximum of 82.6% and a peak gain of 6.3 dBi. It exhibits a bidirectional pattern in the elevation plane and omnidirectional behavior in the azimuth plane. The antenna finds applications across multiple frequencies and shows close agreement between simulated and measured results, validating its effectiveness. [ABSTRACT FROM AUTHOR]

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Remote sensing of the Earth is now widely used in various fields. One of the challenges of remote sensing is the creation of inexpensive satellite systems operating in polar circular orbits. These systems require the development of a receptiontransmission system that allows tens of gigabits of video information to be transmitted to an earth receiving station within ten minutes. That is, there is a need to create a communication system that provides high speed data transmission from small satellites weighing up to 50 kg. Objective. The aim of the work is to study the features of digital signal formation in modern satellite communication lines and to develop a communication system with a high data transfer rate (usually 300 Mbit/s), which can be applied to small Earth Observation satellites. Method. Proposed concept for building a high-speed data transmitter from a remote sensing earth satellite using commercially available off-the-shelf technology. Calculations of the power flow density created at the input of the receiving earth station were performed to find out the possible power of the on-board transmitter. Results. A diagram of a communication system based on the DVB-S standard using the technology of commercially available off-the-shelf products has been developed. The high-speed data transmitter is implemented on a Xilinx® Zynq Ultrascale+ ™ MPSoC FPGA microchip, which is located on an Enclustra Mercury XU8 module with a high-performance dual 16-bit AD9174 DAC. The on-board transmitter with a power of up to 2 W meets the requirements of the ITU Radio Regulations for the power flux density on the surface of the Earth, which is created by the radiation of the space station EESS in the range 8025–8400 MHz. It is shown that the energy reserve of the communication line of 3 dB is achieved for various commands for coding and modulation changes with an increase in the elevation angle, which allows to increase the speed of information transmission. Conclusions. An original receiving-transmitting system was developed for use in small satellites for remote sensing of the Earth. It is shown that the function of adaptive modeling of ACM of the DVB-S standard allows you to automatically change the transmission parameters in real time depending on the changing conditions of the channel, providing opportunities for more flexible and effective data transmission in various conditions, which will allow to increase the volumes of information transmitted by communication session. The proposed system operates in the X-band and is built using commercially available off-the-shelf products. An antenna with double circular polarization is used as the emitter. Two physical channels represent two polarization modes: right circular polarization and left circular polarization, each of which has three frequency channels. [ABSTRACT FROM AUTHOR]

This study presents an original parallel connected hybrid microstrip-substrate integrated waveguide (PCHM-SIW) bandstop filter. A low-pass filter implemented on a microstrip structure and a SIW-based high-pass filter are connected in parallel to each other. In this way, the aim is to obtain a bandstop filter in the novel hybrid design. The parallel connected hybrid microstrip-substrate integrated waveguide (PCHM-SIW) bandstop filter is synthesised, simulated, and produced. The effects of connecting filters in parallel are discussed. It is seen from the results of CST Studio Suite simulation that PCHM-SIW bandstop filter has a bandwidth of 2.85 GHz and a center frequency of 4.26 GHz. The frequency change rate of the center frequency between simulation and measurement is 7.02 % where it is just 3.76 % for the deviation in bandwidth. The results of the simulation and those of the measurement are close to each other. These results converge to ideal analytical results.

A compact single-layer, polarization-insensitive, and angularly stable frequency selective surface (FSS) based multi-stop band filter is reported for shielding three useful frequency bands covering 1.82–2.86 GHz Industrial, scientific, and medical (ISM), 3.52–4.06 GHz Worldwide Interoperability for Microwave Access (WiMAX), and 7.42–8.72 GHz (satellite downlink), centered at 2.4 GHz, 3.6 GHz, and 8.1 GHz, respectively. The proposed unit cell (15 mm × 15 mm) contains four equal-sized square-headed dumbbell (SHD) shaped resonators surrounded by two square ring resonators. The outer and inner square rings offer the first and second stop bands, while the SHD resonators provide the third stop band. A highly polarization-insensitive response is realized owing to the four-fold symmetry in the proposed structure. The unique arrangements of the SHD resonators help to realize higher angular stability under transverse electric (TE), transverse magnetic (TM), and diagonally polarized incident electromagnetic (EM) waves for incidence angles up to 80°, 80°, and 70°, respectively. A detailed analysis in terms of equivalent circuit and parametric variation is carried out to illustrate the higher to lower frequency band ratio. A prototype is fabricated and tested through a proper measurement setup to validate its performance, and it shows good agreement with the simulated results. The proposed FSS unit cell offers better angular stability under diagonally polarised incident waves, attenuation level, minimum higher to lower frequency band ratio, good fractional bandwidth, and compactness. So the designed multi-stopband FSS can be considered a potential candidate for shielding EM radiation across the useful bands

This paper presents the design and development of a mini-compact Wilkinson Power Divider (WPD) operating at 9.3 GHz, with a wide bandwidth of 200 MHz, for the Man-Pack Surveillance Radar (MPSR) application. The design of the WPD was carried out using Advanced Design System (ADS) software with a microstrip feeding technique. The substrate material used in this design was Duroid Roger 5880, which has a thickness (h) of 1.575 mm, dielectric constant (εr) of 2.20, and loss tangent (tan δ) of 0.0009. A WPD was designed, developed, and measured. The simulation results obtained included return loss (S11) -37.50 dB, (S22) -26.59 dB, (S33) -26.09 dB, insertion loss (S21) -3.61 dB and (S31) - 2.55 dB, and isolation (S32) -12.89 dB. Overall, the simulation result parameters worked at a frequency of 9.3 GHz. Furthermore, when the WPD measurement produces a measured return loss of (S11) -28.69 dB, (S22) -28.5 dB, (S33) -29.95 dB, insertion loss (S21) -6.61 dB, and (S31) -7.55 dB, and isolation (S32) -21.89 dB. The dimensions resulting from the realization were 20.5 mm x 20 mm.

Introduction. Conventional contact measurements of hydrographic parameters frequently fail to provide the necessary accuracy of data in the field of water area monitoring. This problem can be solved using coherent radars enabling direct measurements of surface current velocities.Aim. To establish the accuracy of surface current velocities measured by a Doppler radar using drifter data.Materials and methods. In June 2022, coastal operational oceanography studies were conducted at the hydrophysical test site of the Institute of Oceanology of the Russian Academy of Sciences in the Black Sea near Gelendzhik. Measurements were carried out using a coherent X-band radar installed on the Ashamba research vessel simultaneously with drifter experiments using Lagrangian drifters of the near-surface layer with an underwater 0.5 m sail. Coordinates were transmitted via mobile communication. The drifter data on the current velocity and direction were used to verify radar measurements. Measurements were taken onboard of the research vessel at a low speed and different distances from the shore, near the drifters. The tracks of the vessel and drifters were recorded simultaneously. Processing of the radar data involved obtaining Doppler spectra of signals to estimate the dynamic processes on the sea surface, including the current velocity.Results. Radial components of the near-surface current velocity were calculated. Then, the current velocity values obtained based on the drifter and radar data were compared.Conclusion. The present work makes a contribution to the advancement of methods for measuring surface currents from the board of a moving ship by Doppler radars. The obtained results confirm the suitability of the radar hardware and software and signal processing algorithms for measuring currents. The radar measurement data were found agree well with drifter data in the velocity range from 15 cm/s.

This research presents a concept, for an elliptical ring patch microstrip antenna (ERPA) which was created tested and produced Employing types of materials, with varying permittivity values. The antenna is meant for X band use. In this study the substrates employed are FR4 (Design (1)) and RT5880 (Design (2)) having permittivity values of 4.4 and 2.2 respectively and thicknesses of 1.6 mm and 1.575 mm. The ERPA design includes four rings, with holes of different sizes. The Ansoft HFSS, a high-frequency structure simulator, is utilized to model the antenna design, which is crucial for optimizing the design and accurately predicting its performance. Moreover, simulation tools were integral in optimizing antenna characteristics before physical testing. Curiously, there is a significant consensus over the comparative outcomes. The research primarily examines key characteristics, including radiation pattern gain, return loss, and input impedance, which have been shown to fall below acceptable thresholds. The results show that relative permittivity and difference in the thickness of the substrate materials have a substantial impact on both bandwidth and gain. The analysis of efficiency showed the superior efficiency of 85.70% by RT-5880 in contrast to 69.96% efficiency gained via FR-4 substrate. The bandwidth of both proposed antennas is greater than 2 GHz which is 2.420 GHz and 3500 GHz for Design (1) and Design (2) respectively. The gain 3 is observed in both the Designs 1 and 2. The higher bandwidth and gain makes RT5880 substrate more efficient, and provide better design for X- band applications. Maintaining the X-band frequency range the proposed antenna design can be applied to wide range of applications.

Precise knowledge of the antenna pointing direction is a key facet to ensure the accuracy of observations from scanning weather radars. The sun is an often-used reference point to aid accurate alignment of weather radar systems and is particularly useful when observed as interference during normal scanning operations. In this study, we combine two online solar interference approaches to determine the pointing accuracy of an X-band mobile weather radar system deployed for 26 months in northern England (54.517°N, 3.615°W). During the deployment, several shifts in the tilt of the radar system are diagnosed between site visits. One extended period of time (>11 months) is shown to have a changing tilt that is independent of human intervention. To verify the corrections derived from this combined approach, quantitative precipitation estimates (QPEs) from the radar system are compared to surface observations: an approach that takes advantage of the variations in the magnitude of partial beam blockage corrections required due to tilting of the radar system close to mountainous terrain. The observed improvements in QPE performance after correction support the use of the derived tilt corrections for further applications using the corrected dataset. Finally, recommendations for future deployments are made, with particular focus on higher latitudes where solar interference spikes show more seasonality than those at mid-latitudes. [ABSTRACT FROM AUTHOR]

Beam scanning devices in the X-band allow spatial reorientation of the beam, but this poses challenges for material and device design. To meet such challenges, the development of microwave dielectric materials and the design of special structures are crucial. Here, the microwave dielectric properties of Ca 5 Mn 4 V 6- x Nb x O 24 (x = 0.00–0.08) ceramics are systematically investigated by using first-principles calculations and microstructural analysis. The ceramic has the best microwave dielectric properties (ε r = 10.92 ± 0.14, Q × f = 50032 ± 1795 GHz (@10.52 GHz), τ f = −59.58 ± 3.81 ppm/°C) when x = 0.04 and T = 875 °C. As a concept demonstration for device applications, a frequency-controlled beam scanning device in the X-band is designed by using this ceramic and copper electrode. This device has a beam scanning space of 3.248° (from 27.143° to 32.371°) in the frequency range of 10–11 GHz while maintaining high reflectivity (≥0.6). This function is verified by simulation results for far-field amplitude and far-field phase. This work contributes to the application of microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

This paper presents a dual-band bandpass filter (BPF) operating at 9.5 GHz and 11 GHz using a substrate integrated waveguide (SIW) technology. The filter was designed on the diplexer structure to enable the flexible control of the spacing of two passbands. By carefully designing the input/output cavities, spacing between two passbands can be adjusted freely. In addition, thanks to the design of each branch cavity, performance of each band is able to tune easily. The filter was designed on a cost-effective RO4003C substrate and simulated using a CST Microwave Studio 2019 simulator based on the time-domain analysis. The simulated insertion losses at 9.5 GHz and 11 GHz are 2.0 and 1.9 dB, respectively whereas the return losses at these two center frequencies are -15.7 dB and 32.8 dB, respectively. The fractional bandwidth of 1-dB insertion loss is 3.7 % and 3.6 % at the two passbands. The total size of the filter is just 2.4 x 3.5 mm² . The proposed filter aims at using for next-generation wireless communications such as satellite communication, 5G, 6G and beyond. [ABSTRACT FROM AUTHOR]

This study presents an original parallel connected hybrid microstrip-substrate integrated waveguide (PCHMSIW) bandstop filter. A low-pass filter implemented on a microstrip structure and a SIW-based high-pass filter are connected in parallel to each other. In this way, the aim is to obtain a bandstop filter in the novel hybrid design. The parallel connected hybrid microstrip-substrate integrated waveguide (PCHM-SIW) bandstop filter is synthesised, simulated, and produced. The effects of connecting filters in parallel are discussed. It is seen from the results of CST Studio Suite simulation that PCHM-SIW bandstop filter has a bandwidth of 2.85 GHz and a center frequency of 4.26 GHz. The frequency change rate of the center frequency between simulation and measurement is 7.02 % where it is just 3.76 % for the deviation in bandwidth. The results of the simulation and those of the measurement are close to each other. These results converge to ideal analytical results. [ABSTRACT FROM AUTHOR]

A dual-port multiple-input multiple-output (MIMO) filtenna with minimal sizes of 80 × 45 mm2 is set up in this study. Each element in this MIMO filtenna is positioned orthogonally to the one next to it to improve isolation. For the MIMO element to achieve high-frequency selectivity and compact size, a frequency-reconfigurable filtenna that was created by fusing a band-pass filter and a monopole radiator was used. The suggested filtenna can switch between its C-band and X-band operating states with ease. On build the filtenna circuit, a band-pass filter based on defective microstrip structure is inserted to a circular monopole radiator. The developed filtenna operates in the C-band frequency range of 6.5–8 GHz and the X-band frequency range of 8–12 GHz. It is possible to use the X-band operating state for communication in a cognitive radio environment. Used as a decoupling structure, metamaterial structures can increase isolation to more than 40 dB across the bandwidth. The suggested MIMO filtenna system has an envelope correlation coefficient of 2.4e−6, a peak gain of 6 dBi, and an impedance bandwidth of 7.4–7.75 GHz. The MIMO filtenna is constructed and measured, and the findings of the measurement and simulation are in good agreement. [ABSTRACT FROM AUTHOR]

In this study, spinel Ni 0.5 Zn 0.5 Fe 2 O 4 doped with transition metal ions as well as rare-earth ions Ni 0.4 Zn 0.4 M′ 0.2 Fe 2 O 4 (M′ = Cu, Dy, Gd and Lu) and M″ 0.5 Zn 0.5 Fe 2 O 4 (M″ = Ni, Mn and Co) are developed using the sol-gel auto-combustion route, and the role of substitution on electromagnetic properties is investigated. The powder X-ray diffraction accompanied by Rietveld refinement signifies a single-phase spinel ferrite that belongs to Fd- 3 m space group for all the compositions. Rietveld refinement confirms that doped Cu2+, Dy3+, Gd3+ and Lu3+ ions are at random distribution between spinel tetrahedral and spinel octahedral sites against their preferential occupancy. The saturation magnetisation (M S) of Ni 0.5 Zn 0.5 Fe 2 O 4 (M S = 50.5 emu/g) increased with partial doping showing M S = 60.08 emu/g for transition-metal doped Ni 0.4 Zn 0.4 Cu 0.2 Fe 2 O 4 and M S = 109.7 emu/g for rare-earth doped Ni 0.4 Zn 0.4 Dy 0.2 Fe 2 O 4 , which was the highest among all the doped compositions. Doping enhances the dielectric permittivity of Ni 0.5 Zn 0.5 Fe 2 O 4 from 4.2 to 6.5 for Ni 0.4 Zn 0.4 Cu 0.2 Fe 2 O 4 and 7.7 for Ni 0.4 Zn 0.4 Dy 0.2 Fe 2 O 4. Further, the reflection coefficient (R L) of all the doped compositions of Ni 0.4 Zn 0.4 M′ 0.2 Fe 2 O 4 (M′ = Cu, Dy, Gd and Lu) was less than −8 dB (85% absorption) throughout the frequency band of 8–12 GHz with an optimum material thickness of 3.5 mm. Transition metal ion doped Ni 0.4 Zn 0.4 Cu 0.2 Fe 2 O 4 resulted in further improvement of its absorption characteristics of the incident EM waves with reflection coefficient (R L) less than −10 dB (between 84.15% and 90%) between 10 and 12 GHz at a material thickness of 3.5 mm in the X-band frequency range. [ABSTRACT FROM AUTHOR]

Variation in canopy water content (CWC) that can be detected from microwave remote sensing of vegetation optical depth (VOD) has been proposed as an important measure of vegetation water stress. However, the contribution of leaf surface water (LWs ), arising from dew formation and rainfall interception, to CWC is largely unknown, particularly in tropical forests and other high-humidity ecosystems. We compared VOD data from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) and CWC predicted by a plant hydrodynamics model at four tropical sites in Brazil spanning a rainfall gradient. We assessed how LWs influenced the relationship between VOD and CWC. The analysis indicates that while CWC is strongly correlated with VOD (R2  = 0.62 across all sites), LWs accounts for 61-76% of the diurnal variation in CWC despite being < 10% of CWC. Ignoring LWs weakens the near-linear relationship between CWC and VOD and reduces the consistency in diurnal variation. The contribution of LWs to CWC variation, however, decreases at longer, seasonal to inter-annual, time scales. Our results demonstrate that diurnal patterns of dew formation and rainfall interception can be an important driver of diurnal variation in CWC and VOD over tropical ecosystems and therefore should be accounted for when inferring plant diurnal water stress from VOD measurements.

A porous 3D cross-linked conductive network pierced by multi-wall carbon nanotubes (MWCNTs) was successfully designed from zeolitic imidazolate framework-8 (ZIF-8). Zn@NPC@MWCNTs composites were tailored by the facile regulating the mass ratios and thermal annealing treatment. Due to the combination of less eddy current loss and dielectric loss together with multiple reflection attenuation caused by a unique structure. With a 10 wt% filler loading, the Zn@NPC@MWCNTs composites carbonized at 800 °C show two high reflection loss (RL) values with different thicknesses. An RL value is −53.18 dB with 4.09 mm thickness in the C-Band (4–8 GHz), and a minimum RL can reach −74.83 dB (10.8 GHz) with a matching thickness of 2.749 mm. The effective absorption bandwidth is 4 GHz (from 8 to 12 GHz, RL ≤ −10 dB), which just covers the full X-band. Low cost and easy preparation can also provide advantages to develop MOF-based materials as effective EMW absorbents.

A compact single-layer, polarization-insensitive, and angularly stable frequency selective surface (FSS) based multi-stop band filter is reported for shielding three useful frequency bands covering 1.82-2.86 GHz Industrial, scientific, and medical (ISM), 3.52-4.06 GHz Worldwide Interoperability for Microwave Access (WiMAX), and 7.42-8.72 GHz (satellite downlink), centered at 2.4 GHz, 3.6 GHz, and 8.1 GHz, respectively. The proposed unit cell (15 mm x 15 mm) contains four equal-sized square-headed dumbbell (SHD) shaped resonators surrounded by two square ring resonators. The outer and inner square rings offer the first and second stop bands, while the SHD resonators provide the third stop band. A highly polarization-insensitive response is realized owing to the four-fold symmetry in the proposed structure. The unique arrangements of the SHD resonators help to realize higher angular stability under transverse electric (TE), transverse magnetic (TM), and diagonally polarized incident electromagnetic (EM) waves for incidence angles up to 80°, 80°, and 70°, respectively. A detailed analysis in terms of equivalent circuit and parametric variation is carried out to illustrate the higher to lower frequency band ratio. A prototype is fabricated and tested through a proper measurement setup to validate its performance, and it shows good agreement with the simulated results. The proposed FSS unit cell offers better angular stability under diagonally polarised incident waves, attenuation level, minimum higher to lower frequency band ratio, good fractional bandwidth, and compactness. So the designed multi-stopband FSS can be considered a potential candidate for shielding EM radiation across the useful bands. [ABSTRACT FROM AUTHOR]

This paper proposes a planar wideband microstrip feedline to a slot-line-based patch antenna for high-frequency pattern diversity applications. The antenna consists of two adjacent rectangular patches separated by the ground slots, with a directive patch slot along the edge of the substrate. A compact common feedline-to-slot configuration is used to miniaturize the antenna. The antenna is designed in stages, starting with an in-phase feedline, followed by a slot line structure, with two radiating patches on top and a director on the side. This creates radiation diversity with directive radiation patterns. The antenna was fabricated and analyzed inside a far-field anechoic chamber. The experimental results validate the return loss, gain, and radiation performance. The measured results of the antenna within a frequency range of 8.5 to 11 GHz show good agreement with the simulation. The antenna has a maximum gain of 9.2 dBi and has the potential to be beneficial for beam steering and X-band applications due to its low profile, broad bandwidth, high gain, and good directivity. [ABSTRACT FROM AUTHOR]

Artificially designed anisotropic materials are gaining momentum in the microwave region to cater for various wideband applications such as 5G communication, microwave imaging, etc. In this work, a metasurface-based single-layer reflective cross-polarization rotator with 90% polarization conversion has been demonstrated. The proposed structure has been examined for both transverse electric (TE) and transverse magnetic (TM) wave incidences, and the physical mechanism has been thoroughly examined using the surface current distribution. The metasurface structure has been fabricated and measured in a compact range anechoic chamber. The simulation and measurement results show a polarization conversion ratio (PCR) of above 0.9 from 6.07 GHz to 13.77 GHz. Additionally, the generalized sheet transition condition (GSTC) has been used to calculate the structure's effective electric and magnetic surface susceptibility. The proposed metasurface can be used for monostatic radar cross-section reduction, low scattering antennae, and as an antenna polarization converter. [ABSTRACT FROM AUTHOR]

A monopole antenna with dual (linear/circular) polarization reconfigurability for X-band applications is presented in this paper. The antenna consists of a bent arm cross-shaped (BACS) slot created on the inverted triangular staircase fractal (ITSF) shaped patch. Two PIN diodes are embedded on the opposite side of the horizontal arm of the BACS slot for electronic switching between two different polarization states. By varying the biasing conditions of PIN diodes, the measured antenna’s 3 dB axial ratio (AR) operational band for left-hand circular polarization (LHCP) is observed from 9.88 GHz to 11.06 GHz, whereas linear polarization (LP) is achieved from 7.95 GHz to 12.64 GHz. The measured peak gain of the antenna is 5.71 dBi, whereas the average peak gain is obtained as 4.97 dBi. The size of the antenna is $1.57\mathrm {\lambda }_{\mathrm {g}}\times 1.25\mathrm {\lambda }_{\mathrm {g}}$ where, $\mathrm {\lambda }_{\mathrm {g}}$ is guided wavelength at the lowest cutoff frequency, 7.95 GHz. The proposed monopole antenna’s progressive design steps, an equivalent lumped circuit model analysis, and a comparative study between electromagnetic (EM) simulation and measured results are carried out to validate the antenna’s performance.

A dual-functionality printed dipole array antenna is proposed in this study with a fan-beam property. An integrated balun structure cooperation with the dipole arms creates a resonance in the X-band for the antenna. Adding Single-Ring Split-Ring Resonator (SR-SRR) next to the feed line allows another resonance in the C-band. This way, a dual-band dipole array antenna with identical radiation properties is accomplished. Considering the distance between the two resonances of the antenna, the main contribution of this work is the similar radiation pattern in the two frequency bands of the antenna. According to the experimental results, the introduced antenna can cover the frequency band of 4.52-5.83 GHz for C-band applications (such as; satellite communication and microwave relay) and 9.08-9.66 GHz for X-band applications (such as; weather mapping and detecting and long-range tracking radar) with peak gains of 9.05 dBi and 11.30 dBi respectively and similar fan-beam radiation patterns in two frequency bands.

The proposed paper presents a flexible antenna that is capable of operating in several frequency bands, namely 2.45 GHz, 5.8 GHz, and 8 GHz. The first two frequency bands are frequently utilized in industrial, scientific, and medical (ISM) as well as wireless local area network (WLAN) applications, whereas the third frequency band is associated with X-band applications. The antenna, with dimensions of 52 mm × 40 mm (0.79 λ × 0.61 λ), was designed using a 1.8 mm thick flexible kapton polyimide substrate with a permittivity of 3.5. Using CST Studio Suite, full-wave electromagnetic simulations were conducted, and the proposed design achieved a reflection coefficient below −10 dB for the intended frequency bands. Additionally, the proposed antenna achieves an efficiency value of up to 83% and appropriate values of gain in the desired frequency bands. In order to quantify the specific absorption rate (SAR), simulations were conducted by mounting the proposed antenna on a three-layered phantom. The SAR1g values recorded for the frequency bands of 2.45 GHz, 5.8 GHz, and 8 GHz were 0.34, 1.45, and 1.57 W/Kg respectively. These SAR values were observed to be significantly lower than the 1.6 W/Kg threshold set by the Federal Communication Commission (FCC). Moreover, the performance of the antenna was evaluated by simulating various deformation tests. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) systems are one of the best resources to gather information in polar environments, but the detection and monitoring of sea ice types and icebergs using them is still a challenge. Limitations using single-frequency images in sea ice characterization are well known, and using different SAR bands has been revealed to be useful. In this paper, we present the quantitative results of an intercomparison experiment conducted by the Argentine Naval Hydrographic Service (SHN) using X-, C-, and L-bands from COSMO-SkyMed, Sentinel-1, and SAOCOM satellites, respectively. The aim of the experiment was to evaluate SAOCOM for its use on SHN products. There were 25 images with different SAR parameters that were analyzed, incorporating the diversity in the information that everyday Ice Services attend to. Particularly, iceberg detections, fast first-year ice, and belts and strips were studied in the Antarctic Sound, the surroundings of Marambio Island, and Erebus and Terror Gulf. The results show that the HV polarization channel of the L-band provides useful information for iceberg detection and fast first-year ice surface feature recognition and is a promising frequency for the study of strip identification under windy sea conditions and snow accumulation on first-year ice.

The quality of weather radar affects the reliability and effectiveness of monitoring severe convective weather. Therefore, rigorous calibration and validation are the foundation for the quantitative application of weather radar. Among the available methods, radial velocity validation is of great significance for reducing the false alarm rate in the identification of tornadoes and thunderstorms. Based on the traditional method that utilizes internal and external instrument radar velocity measurements, we propose a weather radar radial velocity validation method that uses RTK UAV to simulate external targets. In addition, according to the characteristics of the UAV application scenarios, we introduce the evaluation parameter of optimal absolute accuracy to supplement the original parametric system. The experimental results show that the evaluation parameter of optimal absolute accuracy can effectively reduce the interference caused by the systematic deviation of the UAV due to the internal and external environment, which can affect the validation results. When the UAV velocity is not greater than 10 m/s, the optimal absolute accuracy of the radial velocity validation is less than 0.05 m/s, which is essentially consistent with the external instruments’ measurement results. This method can be effectively applied to the procedural handling of weather radar radial velocity validation. It is significant for ensuring the accuracy and quality of weather radar radial velocity measurements and improving the effectiveness of radar velocity data applications.

The manufacturing of active RF devices like klystrons is dominated by expensive and time-consuming cycles of machining and brazing. In this article, we characterize the RF properties of X-band klystron cavities and an integrated circuit manufactured with a novel additive manufacturing process. Parts are 3D printed in 316 L stainless steel with direct metal laser sintering, electroplated in copper, and brazed in one simple braze cycle. Stand-alone test cavities and integrated circuit cavities were measured throughout the manufacturing process. The un-tuned cavity frequency varies by less than 5% of the intended frequency, and Q factors reach above 1200. A tuning study was performed, and unoptimized tuning pins achieved a tuning range of 138 MHz without compromising Q. Klystron system performance was simulated with as-built cavity parameters and realistic tuning. Together, these results show promise that this process can be used to cheaply and quickly manufacture a new generation of highly integrated high power vacuum devices.

The paper considers the possibilities of 3D printing technology for the manufacture of X-band waveguide photonic crystals. The photonic crystals for an EIA WR-90 standard rectangular waveguide with a cross section of 22,86 10,16 mm2 in the X-band were designed and manufactured. Numerical modeling of the reflection characteristics of photonic crystals of several designs in the OpenEMS software package was carried out. Based on the simulation results, the best types of the structures were selected, which were manufactured using the physical modeling technique by the fusion method of PETG plastic. Experimental study of the manufactured layouts and comparison of the experimental data with the numerical simulation data were performed. The best types of manufactured models of waveguide photonic crystals showed transmittance and reflection drop in the corresponding frequency bands of the order of 1520 dB, which is acceptable for technical applications. The numerical modeling results are in good agreement with experiments, thus indicating the high efficiency and good control of the topology and dimensions of the manufactured photonic crystals structural elements in the used type of 3D printing technology.

Herein, the PMMA/MWCNT/Ag hybrid composite films are prepared by solvent casting method to be used in an electrical application. The AC conductivity and dielectric characteristics have been investigated at room temperature. The electrical conductivity of the hybrid composite reaches a percolation critical concentration of 2.14×10-4 S/cm by Ag doping. For all PMMA/MWCNT/Ag hybrid composites, the frequency-dependent dielectric constant decreases as the frequency area widens. As the concentrations of MWCNT and Ag increase, the AC conductivity exhibits an increasing trend. The MWCNT and Ag content was found to significantly affect the SE of the given composites. A high electromagnetic (EM) shielding efficiency (SE) was achieved between 8.2 and 12.4 GHz (X-band). The highest EM attenuation of 18 dB at 12 GHz was achieved using 0.5 wt% MWCNT and Ag. The thermal analysis of the formed PMMA/MWCNT/Ag hybrid composites showed that exothermic reactions with the greatest weight loss took place between 200°C and 300°C. FESEM show that PMMA/MWCNT/Ag hybrid composites had uniform dispersion of the carbon nano tube and silver particles within the PMMA matrix .

ABSTRAK Jalan kelas IIIC memiliki struktur yang lebih sempit dan biasanya dibangun didekat permukiman penduduk untuk penggunaan pejalan kaki. Selain pejalan kaki, kendaraan motor roda dua juga dapat mempergunakaan jalan tersebut. Permasalahan mulai timbul saat kendaaraan bermotor memiliki kecepatan yang cukup tinggi sehingga membahayakan pengguna jalan lainnya khususnya pedestrian. Untuk mengatasi hal tersebut, pada penelitian ini dilakukan pengembangan X-band speed detector berbasis efek pergeseran doppler untuk kendaraan motor roda dua di jalan kelas IIIC. Detektor yang dibangun mengimplementasikan sensor HB100 dengan frekuensi 10 GHz Adapun efek pergeseran doppler diproses menggunakan Arduino. Parameter yang dijadikan perhitungan diantaranya kecepatan, pergeseran doppler, dan jarak detektor. Hasil pengujian menunjukan bahwa sistem berhasil memiliki akurasi diatas 95% (atau error

In this dissemination, a glueless compact dual port dielectric resonator antenna (DRA) is proposed for X-band applications. A prototype has been fabricated with RT Duroid substrate and Eccostock ( ϵ r = 10)-made DRA. The ring shaped DRA is excited by aperture coupled feeds maintaining symmetry between both the ports. Four cylindrical copper rods with four strips have been used to fix the DRA on the substrate and provide additional mechanical stability. Eight copper strips are used to provide impedance matching and impedance bandwidth (IBW) widening. The measured IBW of dual port DRA is 10.5% (8.05–8.95 GHz) and maximum gain of radiator is 6.2 dBi. The proposed antenna becomes compact when the net volume of DRA is approximately 3.5 cm 3 and the volume of the substrate is 2.88 cm 3 , with a surface area of 36 cm 2 and operating in X-band, which finds applications in satellite communication, weather radar, synthetic aperture radar, and telemetry tracking and control. [ABSTRACT FROM AUTHOR]

A low-profile single-ridge waveguide magic-T is proposed as a combination of two T-junctions at an X band. A slot coupling technique is used to reduce the component dimensions in the E-plane, thus leading to a low profile. The device can assume two configurations by arranging the sum and difference ports in the same or opposite direction, an attractive feature in the design of beamforming networks with complex routing. A magic-T prototype is fabricated using laser powder bed fusion additive manufacturing techniques. Good agreement between simulations and measurements is found. [ABSTRACT FROM AUTHOR]

In this article, a 4 × 4 miniaturized UWB-MIMO antenna with reduced isolation is designed and analyzed using a unique methodology known as characteristic mode analysis. To minimize the antenna's physical size and to improve the isolation, an arrangement of four symmetrical radiating elements is positioned orthogonally. The antenna dimension is 40 mm × 40 mm (0.42λ0 × 0.42λ0) (λ0 is the wavelength at first lower frequency), which is printed on FR-4 material with a width of 1.6 mm and ε r   = 4.3. A square-shaped defected ground framework was placed on the ground to improve the isolation. Etching square-shaped slots on the ground plane achieved the return losses S11 < −10 dB and isolation 26 dB in the entire operating band 3.2 GHz–12.44 GHz (UWB (3.1–10.6 GHz) and X-band (8 GHz–12 GHz) spectrum and achieved good isolation bandwidth of 118.15%. The outcomes of estimated and observed values are examined for MIMO inclusion factors such as DG, ECC, CCL, and MEG. The antenna's performances, including radiation efficiency and gain, are remarkable for this antenna design. The designed antenna is successfully tested in a cutting-edge laboratory. The measured outcomes are quite similar to the modeled outcomes. This antenna is ideal for WLAN and Wi-Max applications. [ABSTRACT FROM AUTHOR]