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

The microstrip antennas matured and improved over the last 25 years. Throughout these years, the limitations, and specifications of the said antennas have been overcome and significantly improved. Known to be lowprofile, suitable for mobile, and lightweight, these microstrip antennas are the focus of this research. In this paper, the researchers designed a microstrip antenna with varying lengths and substrates. They tested the changes and the effects in microstrip antennas of different lengths, along with altering substrates. To verify the differences, the researchers compared the performance parameters maximum gain (dBi), minimum gain (dBi), and S11 graph on each tested length and changed substrate. The rough set theory was used to determine the optimal design via MATLAB. From there, the researchers analyzed the results gathered and drew their respective conclusions. Additionally, they saw and compared each data result to know what antenna has the best performance parameters. From the results, a change in the dimension will result in a decrease in the said performance parameters. Furthermore, the change in substrate thickness also diminishes these changes. [ABSTRACT FROM AUTHOR]

This paper proposes a wearable flexible dual-band antenna that covers the 2.34–2.68 GHz and 4.05–5.26 GHz frequency bands. This antenna employs a novel nested imitation annular solar eclipse structure, where the main radiator is a gradually widening loop, and another loop is coupled inside the radiator. The antenna, with overall dimensions of 40 ∗ 32 ∗ 0.3 mm³, utilizes polyimide as the dielectric material. The gain, efficiency, and cross-polarization of the antenna were tested using a microwave anechoic chamber. The antenna achieves a maximum gain of 6 dBi and a maximum efficiency of 79.6%. We tested the SAR of the antenna at 10 mm from the human body, which was significantly below the international standard of 2.0 W/kg. The flexible antenna presented in this paper exhibits a broad low-frequency bandwidth, enabling coverage of various communication bands such as ISM, WLAN, WIMAX, and Bluetooth. The antenna delivers satisfactory simulation and measurement results while meeting the requirements of minimizing radiation exposure to the human body. [ABSTRACT FROM AUTHOR]

The intrinsic noise of different transformers in the same substation belongs to the same type of noise, which is strongly coherent and difficult to separate, greatly increasing the cost of substation noise assessment and treatment. To solve the problem, the present paper proposes a noise separation technique using the phase conjugation method to separate the intrinsic noise signals of different transformers: firstly, the reconstruction of sound source information is realized by the phase conjugation method based on the measurement and emission of a line array; secondly, the intrinsic noise signals of the sound source are obtained by the equivalent point source method. The error of the separation technique is analyzed by point source simulation, and the optimal arrangement form of the microphone line array is studied. A validation experiment in a semi-anechoic chamber is also carried out, and the results prove that the error of separation technique is less than 2dBA, which is the error tolerance of engineering applications. Finally, a noise separation test of three transformers is performed in a substation using the proposed technique. The results show that the proposed technique is able to realize the intrinsic noise separation of each transformer in the substation, which is of positive significance for substation noise assessment and management. [ABSTRACT FROM AUTHOR]

Emphasizing the importance of acoustic attenuation in maintaining compliance with stringent noise regulations and enhancing workplace safety, this analysis covers theoretical and practical aspects of prediction methods used for the development of sound attenuators for gas-turbine testing stands. This paper presents a preliminary analysis and evaluation of the improvement of the Embleton method for projecting a noise attenuator for industrial applications, especially for gas-turbine test stands. While primarily focusing on the static acoustic behavior of the attenuator, certain considerations were also made regarding flow conditions, Mach number-dependent attenuation, pressure drop, and self-generated noise aspects to provide a comprehensive perspective on applying a suitable evaluation method. The study investigates different calculation methods for the assessment of noise reduction for linear and staggered baffles applied on a scaled reduced model of an attenuator. Thus, the critical parameters and development requirements necessary for effective noise reduction in high-performance gas-turbine testing environments will be evaluated in a downscaled model. Key factors examined include the selection of design parameters and configurations from various topological options (single, double, and triple parallel baffles vs. double and triple staggered baffles). Advanced computational methods, like analytic and finite-element analysis (FEM), are used to predict acoustic performance and evaluate the prediction method. Experimental validation is performed to corroborate the simulation results, ensuring the reliability and efficiency of the attenuator. The results indicate that an improved prediction method led to a better design for a sound-attenuator module, which can significantly reduce noise levels without compromising the operational performance of the gas turbine inside a test cell. [ABSTRACT FROM AUTHOR]

In this paper, the path loss performance of an eight-port Multiple-In-Multiple-Out (MIMO) antenna consisting of four circular slots radiator-based antenna elements is investigated in 3.5–3.75 GHz range for utilisation as an RFID tag and reader antenna. First, the S-parameters between the ports of two proposed MIMO antennas are measured in four channels of spatial diversity; one direct line-of-sight (LOS) and three indirect LOS in an anechoic chamber, each for the horizontal and vertical polarisation schemes at two distances, 5 and 25 cm, and the path losses between the ports of MIMO antennas are evaluated. Then, the path losses between the same MIMO antennas are obtained in a laboratory environment, which are higher by about 5–10 dB than those in the anechoic chamber and so, these losses are more dependent on the antenna position and nearby objects. The tag power sensitivity and the tag (read) range for the presented MIMO antenna are found to be more power level dependent than frequency dependent. The reported results confirm the performance of proposed MIMO antennas for RFID applications in addition to 5 G communications. [ABSTRACT FROM AUTHOR]

Electromagnetic shielding (EMS) clothing is an important product to protect human body from electromagnetic damage, but the change law and influencing factors of its protective effect have not been clarified so far. In this paper, an important phenomenon is found that the shielding effectiveness (SE) value of the EMS clothing is abnormally reduced to 0 or even less than 0 under certain conditions, which is named failure phenomenon. A semi anechoic chamber is selected to build a testing system to carry out the experiments. The occurring rule and mechanism of the failure phenomenon is explored when the emission source parameters and the test positions are different. The projection method is proposed to obtain the equivalent hole and equivalent seam of the clothing. According to the electromagnetic theory, the estimation method of whether the failure phenomenon appears is established. The results show that the failure phenomenon of the EMS clothing is a serious hidden danger to human health, and the parameters of the emission source and test location have an important impact on the generation of the failure phenomenon. Its essence is determined by the distribution and characteristics of the leakage area and the normal area of the clothing area incident by electromagnetic wave. The estimation method of the failure phenomenon and the design principle of the clothing can prevent the occurrence of the failure phenomenon. This paper can provide reference for the design, production, test and evaluation of the EMS clothing and related scientific research, and has great significance for really protection of human health by the EMS clothing. [ABSTRACT FROM AUTHOR]

Testing the shielding effectiveness of materials is a key step for many applications, from the industrial to the biomedical field. This task is very relevant for high-sensitivity sensors, whose performance can be greatly affected by electromagnetic fields. However, the available testing procedures often require expensive, bulky, and heavy measurement chambers. In this paper, a cost-effective and reliable measurement procedure for testing the shielding effectiveness of materials is proposed. It exploits a lab-scale anechoic shielded chamber, which is lightweight, compact, and cost-effective if compared to the available commercial solutions. The measurement procedure employs a vector network analyzer to allow an accurate and fast characterization setup. The chamber realization phases and the measurement procedure are described. The shielding capability of the chamber is measured up to 26 GHz, whereas the performance of commercial shielding coatings is tested to demonstrate the measurement's effectiveness. [ABSTRACT FROM AUTHOR]

Since symmetrical geometry makes it easier to arrange pyramid absorbers on anechoic chamber walls compared to wedge absorbers, the goal of this paper is to present an optimal pyramid-shaped absorber which, in addition to the optimal performance in sound absorption, has other advantages such as less thickness, lower material consumption and cost, easier construction, arrangement and maintenance and occupying less space compared to wedges. The COMSOL Multiphysics software was used to simulate the optimized sound absorber by using the genetic algorithm programed in MATLAB software, with the goal of a 100 Hz cut-off frequency. The results show that the optimized chamfered pyramid at the top performs better at sound absorption compared to the complete pyramid and wedge with 18% less thickness. Furthermore, the cut-off frequency decreased to 91 Hz when a gap of up to 15 mm was created between the adjacent absorbers mounted on the surface, which is desirable. [ABSTRACT FROM AUTHOR]

This paper introduces a compact, circularly polarized exponential slot antenna with a rectangular island. The concept of the proposed antenna is similar to that of fractal antennas as it is based on designing an asymmetric slot shape with an increased electrical length within a small area, thanks to the exponential path. The obtained results are as follows. The reflection-coefficient |S11| of the proposed antenna covers the band from 5.5 GHz to 9 GHz. The proposed antenna is circularly polarized with an axial-ratio (AR) bandwidth that extends from 6.87 GHz to 8.9 GHz. It offers simultaneous dual circular polarizations (RHCP and LHCP). The gain of the proposed antenna varies between 4.2 dBic and 5.4 dBic. The efficiency reaches 94%. The size of the antenna is compact making it suitable for CubeSats with limited surface area. The proposed antenna intended application is X-band Earth-Space satellite communication. The proposed antenna can be employed for both the X-band satellite downlink (from 7.25 GHz to 7.75 GHz) and uplink (from 7.9 GHz to 8.4 GHz) frequency bands. Additionally, the antenna can be utilized in military applications, and RFID tag tracking equipment. A prototype of the proposed antenna has been fabricated and then measured using Vector Network Analyzer (VNA) and inside an anechoic chamber. The measurement results of the proposed antenna are in excellent match with the simulated ones. [ABSTRACT FROM AUTHOR]

This paper reports on the design, modeling, and characterization of a multi-resonant, directional, MEMS acoustic sensor. The design builds on previous resonant MEMS sensor designs to broaden the sensor's usable bandwidth while maintaining a high signal-to-noise ratio (SNR). These improvements make the sensor more attractive for detecting and tracking sound sources with acoustic signatures that are broader than discrete tones. In-air sensor characterization was conducted in an anechoic chamber. The sensor was characterized underwater in a semi-anechoic pool and in a standing wave tube. The sensor demonstrated a cosine-like directionality, a maximum acoustic sensitivity of 47.6 V/Pa, and a maximum SNR of 88.6 dB, for 1 Pa sound pressure, over the bandwidth of the sensor circuitry (100 Hz–3 kHz). The presented design represents a significant improvement in sensor performance compared to similar resonant MEMS sensor designs. Increasing the sensitivity of a single-resonator design is typically associated with a decrease in bandwidth. This multi-resonant design overcomes that limitation. [ABSTRACT FROM AUTHOR]

Ever‐increasing bandwidth requirements from various industries drive the need for the ever‐increasing bandwidth of antennas used for testing. Broadband Double‐Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state‐of‐the‐art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial‐to‐ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber‐filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented. [ABSTRACT FROM AUTHOR]

In this study, a flexible multiband fractal antenna mimicking dendrite structure is proposed and designed by combining bionics and fractal theory. The dendritic structure of neurons is extracted and simplified into a simple and clear geometric structure. The initial antenna model is obtained by fractal operation on the geometric structure, and finally, four effective bands are obtained. The antenna is printed on a 50 ∗ 70 ∗ 0.1 mm3 polyimide dielectric board and fed by a coplanar waveguide. This paper discusses the effect of the human body on the performance of the antenna and the robustness of the antenna in the bending regime. The gain, efficiency, and cross-polarization of the antenna were tested using a microwave anechoic chamber. The measured antenna covers 1.37 GHz-1.93 GHz (relative bandwidth 35%), 2.25 GHz-2.51 GHz (relative bandwidth 10.7%), 3.13 GHz-3.81 GHz (relative bandwidth 19.3%), and 4.46 GHz-5.5 GHz (relative bandwidth 21.1%) four operating frequency bands. The maximum gain is 6.05 dBi and the maximum efficiency is 91.05%. The antenna can be used for Bluetooth WLAN (Wireless Local Area Network), 4G (4th Generation Communication System), 5G (5th Generation Mobile Communication System), WiMAX (Worldwide Interoperability for Microwave Access), etc. The test results are in good agreement with the simulation results, which proves that the antenna can meet various wireless communication requirements. [ABSTRACT FROM AUTHOR]

For an aperture synthesis radiometer (ASR), the visibility and the modified brightness temperature (BT) are related to the Fourier transform when the distance between the system and the source is in the far-field region. BT reconstruction can be achieved using G-matrix imaging. However, for ASRs with large array sizes, the far-field condition is not satisfied when performing performance tests in an anechoic chamber due to size limitations. Using far-field imaging methods in near-field conditions can introduce errors in the images and fail to correctly reconstruct the BT. Most of the existing methods deal with visibilities, converting near-field visibilities to far-field visibilities, which are suitable for point sources but not good for extended source correction. In this paper, two near-field imaging methods are proposed based on the near-field distance. These methods enable BT reconstruction in near-field conditions by generating improved resolving matrices: the near-field G-matrix and the F-matrix. These methods do not change the visibility measurements and can effectively image both the point source and the extended source in the near field. Simulations of point sources and extended sources in near-field conditions demonstrate the effectiveness of both methods, with F-matrix imaging outperforming near-field G-matrix imaging. The feasibility of both near-field imaging methods is further validated by carrying out experiments on a 10-element Y-array system. [ABSTRACT FROM AUTHOR]

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

Reverberation chambers (RCs) were recently reported as a low-cost alternative to anechoic chambers (ACs) to perform radar cross-section (RCS) pattern measurements. The method consists of using transmitting and receiving antennas pointing towards a target under test placed on a rotating mast. As a classical RCS characterization, the echo signal is analysed based on two measurements with and without the target in the RC. In the hypothesis of an ideal diffuse field generated in the RC, this signal difference appears as the echo signal hidden in a Gaussian noise. In case of a point-like backscattering target, observing this signal over a given frequency bandwidth allows the identification of the target response as a sinusoidal signal over this bandwidth whose period is related to the antennatarget distance measured from the measurement calibration plane positions. Therefore, the extraction of the magnitude of this sinusoidal signal requires a proper estimation of this distance. Furthermore, a sinusoidal regression processing relies on the approximation of a constant envelope over the selected frequency bandwidth, imposing some restrictions. In this paper, we introduce a two-step method that consists in identifying the most appropriate distance according to the target's orientation before estimating the magnitude of the sinusoidal signal. We highlight the improvement of RCS estimation on a point-like back-scattering target compared to the one-step procedure applied so far. In addition, it is shown that the analysis performed regarding the estimated distance provides a physical insight into the position of the equivalent backscattering point. [ABSTRACT FROM AUTHOR]

The wind profiler radar (WPR) system requires a dual-polarized antenna with multiple low-sidelobe and high-gain beams to facilitate the detection of weak signals reflected by atmospheric turbulence. This paper proposes a dual-polarized continuous transverse stub (CTS) K-band antenna with four reconfigurable beams, which comprises a series-fed CTS array and four 1-to-14 power dividers as line source generators (LSGs) to generate a high-quality quasi-TEM wave. The CTS element incorporates a stepped transition radiation stub design and employs a short cutoff stub on the upper surface of the series-fed parallel plate waveguide (PPW) to achieve optimal impedance matching. The entire antenna is an all-metal structure with remarkably low loss, and low-cost standard fabrication processes are employed for the prototype, which achieves fast reconfigurable four-beam scanning to 15°, with a gain of 31.09 dBi and sidelobe levels below −17.6 dB. Measurement results in an anechoic chamber agree well with simulations, demonstrating the antenna's ease of manufacture, stability, and suitability for wind profile radar applications. [ABSTRACT FROM AUTHOR]

In this paper, we describe the development and design procedure of the new kind of coaxial TEm,1 modes generator based on ring resonator with coupling apertures. The generator enables excitation of subsequent TEm,1 modes in a cylindrical waveguide. The proposed design method allows to obtain high purity TEm,1 modes. The angular mode number can be chosen by replacing the plate with coupling apertures. Structure and parameters of the generator was optimized using CST-Microwave Studio. The mode generator was fabricated and checked on the test bench in an anechoic chamber. The measured field distributions confirm excitation of the desired TEm,1 modes. A good agreement between simulations and measurements is obtained. The presented mode generator, operating in non-rotating TEm,1 modes, is easy to fabricate, and suitable for cold-test experiments of high power components and devices. [ABSTRACT FROM AUTHOR]

Tunable/switchable devices are more and more required in modern communication systems. However, the realization of the tuning requires the presence of active devices, which in turn must be biased. The current paper comes up with a solution for designing and experimentally validating such a switchable Frequency Selective Surface. Two different metallic structures are simulated and measured, having incorporated the same topology control network (CN). In this scenario, the main innovation of this paper is the presence of the feeding part, namely the control network. In this work, the main FSS structure is flanked by three parallel CN microstrip lines and several via holes that allow biasing the active elements, namely PIN diodes. The switchability of the proposed structure is achieved through PIN diodes, whose bias determines the values of the elements in the equivalent circuit. At different biases, the response of the FSS changes accordingly. From all possible values of the bias, the extreme cases when the diodes act as (almost) short- and open-circuits are considered in the submitted manuscript for the sake of brevity. These cases are modeled by the main and cut-slot structures, respectively. The proposed structures have been evaluated using electromagnetic simulation and implemented on an FR4 substrate having a thickness of 1.58 mm. With the periodicity of the square-shaped unit cell of 18 mm edge length, different filtering bands are obtained below 12 GHz. Another novelty that has received very little consideration in the existing literature is the use of a finite array of unit cells instead of an infinite one. And finally, tests in an anechoic chamber have proved that there is a good agreement between practical and simulation results and also demonstrated the proper performance of the devices for wide angular incidence for both TE and TM polarizations. [ABSTRACT FROM AUTHOR]

This paper proposed a plasmonic absorbing structure suitable for super high frequency. The plasmon absorbing structure is a periodic square cavity structure; the bottom of the cavity is a metal plate, the wall of the cavity is a polyester plate, and metal frames loaded with lumped resistors are printed on both sides of the polyester plate. The transmission characteristics of the absorbing structure are studied using the finite difference time domain method. The results show that the plasmon resonance characteristics can be effectively improved by loading the lumped resistance reasonably. The absorption rate of the absorbing structure is over 80% in the 4.3–21.5 GHz frequency band, and in the 4.3–7.7 GHz and 14.2–21.5 GHz frequency bands, the absorption rate is around 90%. Under different polarization modes, it is less sensitive to the incident angle. The transmission response of the absorbing structure is measured in a microwave anechoic chamber, and the measurement results agree well with the simulation results. After replacing the metal bottom plate of the absorber with a metal cavity, the radar cross-section of the cavity is reduced by 99.45% at 10 GHz. It proves that the designed and fabricated absorbing structure has the broadband absorbing ability, high angular stability, and broad application prospects. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a slotted printed rectangular monopole antenna (SPRMA) is proposed that covers the entire UWB (ultra‐wideband) except for WiMAX and WLAN (802.11/a‐n). In the first stage, a rectangular monopole antenna is designed, which covers the entire UWB frequency. Then, a T‐slot is inserted in the radiating patch to have the rejection of the band containing WiMAX and WLAN (802.11/a‐n). The notch characteristics of the proposed antenna are observed from 3.0 to 3.65 GHz and 4.5 to 6.65 GHz respectively. Measured peak gain of 3.28 dBi has been observed at 4.25 GHz frequency. To show the validation of antenna, mathematical analysis using circuit theory has been also given in the paper. The prototype has been also tested inside the anechoic chamber to give the validation in real‐time environment. Several other reported antenna structures have also the same notch band in UWB with different notching methods. The proposed structure's radiation properties are compared with other reported structures proving the compactness of the proposed structure. [ABSTRACT FROM AUTHOR]

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

Digital coding metasurfaces composed of subwavelength meta-atoms can flexibly control electromagnetic waves to achieve holography, which has great potential in millimeter-wave imaging systems and data storage. In this paper, we propose a 3-bit reflective digital coding metasurface. The incident linearly polarized waves can be transformed into cross-polarized components with distinct phase responses by adjusting the rotational and open angles of the coding elements. The 3-bit phase performance can be retained over a wide bandwidth from 12 to 18 GHz by simultaneously changing the rotational and open angles. Based on the proposed broadband metasurface, broadband holography is successfully demonstrated with the optimization of a modified Gerchberg–Saxton algorithm. As a proof of concept, five schemes with different holograms integrating the letters "S," "E," "U," "X," and "Z" are simulated from 12 to 18 GHz. Good simulation results validate the performance of the proposed broadband holography, showing a relative bandwidth of 40%. Two prototypes superposing the holograms of letters "U" and "X" are fabricated and measured in a near-field microwave anechoic chamber. The experimental results corroborate well with simulated results, further supporting the demonstration. We believe that the proposed broadband holography based on the digital coding metasurface paves a way to wideband applications for microwave imaging, information processing, and holographic data storage. [ABSTRACT FROM AUTHOR]

This paper proposes and experimentally evaluates, a reconfigurable intelligent surface (RIS) control system for multiple users using stereo camera images. The aim is to enable fast and fair received signal strength (RSS) beamforming for multiple users. In the proposed system, a stereo camera is mounted on top of the RIS. Human bodies are recognized from the obtained images. Subsequently, the beam directions and the phase of the RIS are calculated for the estimated positions. The stereo camera‐based scheme enables fast beamforming because channel state information estimation is omitted. Moreover, identical RSS beamforming is enabled by calculating the weighted sums of the RIS phases for multiple users utilizing distance and angle information of users from the RIS obtained using the stereo camera. Experiments are conducted in an anechoic chamber using RIS operating at 28 GHz. The efficacy of the RIS control system using stereo camera images and its ability to increase the RSS fairly for multiple users is validated via simulations and experiments. [ABSTRACT FROM AUTHOR]

In this paper, we will discuss a calibration algorithm for a digital antenna array that diagnoses its real performance. It can be applied at such stages of the antenna system life cycle as design, tuning, and especially maintenance. A calibration implementation using a scalar method for a multi-beam digital antenna array is proposed and investigated. On-the-fly calibration ensures a continuous improvement in beam pointing accuracy by reducing internal errors in the receiving (transmitting) channels. The purpose of the study is to experimentally examine the capabilities of digital beamforming to increase the angle-of-arrival estimation accuracy. A simulation model of the receiving antenna was created in an anechoic chamber with a planar antenna positioner. The possibility of precise estimation of the direction of arrival using the digital beamforming with electronic scanning was demonstrated. The proposed simulation model made it possible to observe the convergence of the antenna array calibration process using the proposed method for various errors in the signal paths, as well as different signal-to-noise ratios. It has been proven that even under adverse conditions early in the calibration algorithm, the phase error detection converges with high accuracy, and its value decreases uniformly even to the fractions of an angular degree. [ABSTRACT FROM AUTHOR]

This paper introduces the new design of a choke loaded horn antenna, at 89.75 GHz for metrology of the large paneled reflector antenna using the Fresnel field based radio holography technique. The proposed choke loaded horn antenna offers the f cutwise extremely stable phase center (< 2 µm), which is required to obtain < 5 µm surface accuracy during holographic measurement. The design of choke loaded horn antenna has been presented along with its simulation performance and tolerance analysis. The antenna has been developed using a simple computer numerical control (CNC) milling process and characterized in the anechoic chamber. The measured and simulated results are also compared, and a good match has been achieved between the measured and simulated performances of the horn antenna. [ABSTRACT FROM AUTHOR]

The demand for vehicular antennas increases in tandem with the need for multiple features in automobiles. The development of optically transparent antenna (OTA) has made it possible to deploy antennas on delicate surfaces such as glass. Earlier studies on OTA demonstrated its viability using materials such as transparent conducting oxides (TCO) and conductive polymers. A tri-band OTA is proposed in this paper for vehicular applications. The antenna operates at 1.8 GHz, 2.4 GHz and 3.39–12 GHz bands, covering automotive/wireless applications such as GSM, Bluetooth, Wi-Fi, vehicular communication and electronic toll collection. The proposed OTA is developed on soda lime glass, and the material TCO is used for the radiator and the ground plane. The antenna prototype is tested on windshield and in an anechoic chamber, the gain and efficiency are found to be greater than 1 dBi and 80%, respectively. Furthermore, a machine learning technique for vehicle classification is proposed, which could help in electronic toll collection, automatic vehicle identifier, and parking management applications. The presented algorithm achieves 80% classification accuracy with a minimum window size. [ABSTRACT FROM AUTHOR]

This paper proposes the experimental demonstration of an anapole-based cylindrical electromagnetic cloaking scheme. An anapole state is excited by arranging around a cylindrical metallic target vertical split-ring resonators, forming an equivalent surface admittance boundary condition able to suppress the scattering. Using Mie formalism and multipole scattering theory, we identify the actual reason behind the cloaking operation, characterizing the anapole condition by the scattering contributions from toroidal and electric dipole moments. Numerical results are verified using full-wave simulation softwares and subsequently validated with back-scattering measurements inside an anechoic chamber. [ABSTRACT FROM AUTHOR]

As UWB technology develops and devices become smaller, miniaturization techniques for an array antenna system are required. In addition, more in-depth research is needed for UWB direction-finding techniques using channel impulse response (CIR) data. This paper proposes an ultra-wideband (UWB) antenna using a single-radiator multiple-port (SRMP) design for the direction-finding systems of smart devices. The proposed SRMP antenna was designed using a single tripod-shaped patch that can replace the array system. The tripod-shaped radiator was optimized using the edge shape design function to improve its broadband and mutual coupling characteristics. For performance verification, the proposed antenna was fabricated, and the reflection coefficient, mutual coupling, and radiation patterns were measured in a fully anechoic chamber. The proposed antenna has an operating frequency band of 6.1 GHz (from 5.8 GHz to 11.9 GHz) for port 1 and a measured mutual coupling of −14.8 dB at 8 GHz. The SRMP antenna has measured maximum gains of 3.5 dBi for port 1 and 2.9 dBi for port 2. To examine the direction-finding performance, the fabricated antenna was connected to a circuit module with a DW3000 chip, which is widely employed in commercial mobile UWB systems. The direction of arrival (DoA) results using the measured CIR data show root-mean-square (RMS) errors of 1.57° and 4.58° at distances of 30 cm and 60 cm. [ABSTRACT FROM AUTHOR]

The paper presents a dualband and compact antipodal Vivaldi antenna (AVA) array by using a dielectric lens (DL) and corrugations for 5G applications. The proposed novel antenna provides very high efficiency and it alleviates beam titling very effectively. Its efficiency is in the range of 95.93%–97.52% whereas the H plane beam titling is ± 1 ° over most of the frequency range. The antenna frequency response is improved by incorporating corrugations which results in the antenna miniaturization. The designed AVA array size is 2.86 × 3.58 × 0.06 λ g 3 (for lower guided frequency). The proposed dualband antenna operates from 24.17 GHz to 29.37 GHz and 30.76 GHz to 40.58 GHz. These frequency bands cover 28 GHz and 38 GHz bands of 5G communications. Next, the front-to-back ratio is improved significantly which further results in the gain enhancement. Also, the grooves in the feeding network minimize reverse power reflections. The radiation pattern is stable and it shows that the designed antenna is a directional antenna. The antenna is designed, simulated, and tested by using a network analyzer and anechoic chamber. The testing and simulated results indicate that the proposed AVA array is the best candidate to integrate it in 5G devices. [ABSTRACT FROM AUTHOR]

Radars in the W-band are being integrated into car bumpers for functionalities such as adaptive cruise control, collision avoidance, or lane-keeping. These Advanced Driving Assistance Systems (ADAS) enhance traffic security in coordination with Intelligent Transport Systems (ITS). This paper analyzes the attenuation effect that car bumpers cause on the signals passing through them. Using the free-space transmission technique inside an anechoic chamber, we measured the attenuation caused by car bumper samples with different material compositions. The results show level drops lower than 1.25 dB in all the samples analyzed. The signal attenuation triggered by the bumpers decreases with the frequency, with differences ranging from 0.55 dB to 0.86 dB when comparing the end frequencies within the radar band. Among the analyzed bumper samples, those with a thicker varnish layer or with talc in the composition seem to attenuate more. We also provide an estimation of the measurement uncertainty for the validation of the obtained results. Uncertainty analysis yields values below 0.21 dB with a 95% coverage interval in the measured frequency band. When comparing the measured value with its uncertainty, i.e., the relative uncertainty, the lower the frequency in the measured band, the more accurate the measurements seem to be. [ABSTRACT FROM AUTHOR]

The paper presents a proof-of-concept of a millimeter-wave identification system based on Van Atta array tags in the 60 GHz band. For interrogation of the tags, a vector network analyzer and a measurement transceiver were employed in alternative test configurations. The design, fabrication and measurements of co- and cross-polarized Van Atta arrays are presented in the paper. They can be treated as simple chipless RFID tags with frequency-response-based identification. Tags with various resonance frequencies are designed by scaling an optimized base model. The designed 57–67 GHz co-polarized and cross-polarized tags have small dimensions of approximately 23 mm × 21 mm and 40 mm × 25 mm, and they exhibit radar cross-section (RCS) levels of −16 dBsm and −21 dBsm, respectively. Owing to the retrodirective properties of Van Atta arrays, the RCS can be maintained at a high level within a broad range of angles of incidence. The system was validated in an anechoic chamber where the spectral responses of all the manufactured tags can be clearly distinguished from the environment, enabling their identification. Tests in a reflective environment were also performed, and they have shown that only the cross-polarized tags could be detected and identified in the presence of reflections from the tags' surroundings. [ABSTRACT FROM AUTHOR]

The radiated immunity of passenger cars and commercial vehicles is validated using electromagnetic interference from off-vehicle radiation sources in an anechoic chamber according to the procedure in ISO 11451-2. Common electrical or electronic vehicle systems, including dual flash, monitors, and entertainment systems, must be validated using a standardized immunity evaluation procedure. However, Automated Driver Assistance System (ADAS) functions often lack verification in complex electromagnetic fields, which might create potential risk due to electromagnetic compatibility problems. For example, radar and camera sensors based on autonomous emergency braking (AEB), adaptive cruise control (ACC), or lane departure warning (LDW) functions may be ineffective in the real world if subjected to electromagnetic interference. This paper presents a new methodology to evaluate vehicle immunity performance based on the main ADAS functions. A target simulator and a virtual driving environment are designed to trigger AEB, ACC, and LDW functions in an anechoic chamber. Moreover, the vehicle In-the-Loop (VHIL) conception is also applied by acquiring and analyzing key ADAS-related signals. The reliability of ADAS functions at the whole-vehicle level can be evaluated and improved using standardized external radiation sources. [ABSTRACT FROM AUTHOR]

In this paper, a coplanar waveguide (CPW) fed slot antenna using fractal shaped isosceles trapezoidal corrugations is designed and presented for Ultra-Wideband (UWB) applications. The proposed antenna is formed by a regular hexagonal patch fed through a CPW feed line and radiates amidst a notched wide hexagonal slot. The edge of the wide slot is shaped by a fractal structure that is formed by five trapezoidal notches. The antenna is printed on RO4350B substrate having a compact size of 0.305λ0 × 0.313λ0 × 0.012λ0 at 2.35 GHz. Good agreement is registered between the experimental results of the fabricated prototype and the calculated ones. By using an Agilent 8722ES vector network analyzer, the fabricated prototype confirms that the antenna has an excellent matching impedance over the bandwidth 2.35-10.65 GHz (127%) which covers the entire UWB band. Furthermore, good radiation performances are measured in an anechoic chamber. Consistent radiation patterns with a reasonable peak gain are measured over the entire working bandwidth. Therefore, the designed structure may be worthy considered for different wireless communications systems. [ABSTRACT FROM AUTHOR]

This paper takes as its catalyst a series of live art events that took place between London and Manchester in 2019. Thinking in conversation with Erin Manning’s propositions for “minor movements” and the Duchampian “infrathin”, we explore the potential for live art to temporarily suspend the thresholds of perceptibility and permissibility in the public realm. We argue that artful techniques of improvisation carry the potential to suspend capitalistic orderings of time by temporarily confounding the perceived barriers between art and life. Drawing together anarchival traces of improvised movement, sound, image, and thought, the paper is composed of vignettes that sketch the infrathin variations of a “pedagogy of suspensions” as elaborated through live art events in a public park, a moving train, a university gymnasium, and an anechoic sound chamber. [ABSTRACT FROM AUTHOR]

Immersive and spatial sound reproduction has been widely studied using loudspeaker arrays. However, flat-panel loudspeakers that utilize thin flat panels with force actuators are a promising alternative to traditional coaxial loudspeakers for practical applications, with benefits in low-visual profiles and diffuse radiation. Literature has addressed the sound quality and applications of flat-panel loudspeakers in three-dimensional sound reproduction, such as wave field synthesis and sound zones. This paper revisits the spatial sound perception of flat-panel loudspeakers, specifically the localization mismatch between the perceived and desired sound directions when using amplitude panning. Subjective tests in an anechoic chamber with 24 subjects result in the mean azimuth direction mismatch within ±6.0° and the mean elevation mismatch within ±10.0°. The experimental results show that the virtual source created by amplitude panning over a flat-panel loudspeaker still achieves spatial localization accuracy close to that of a real sound source, despite not using complex algorithms or acoustic transfer function information. The findings of this study establish a benchmark for virtual source localization in spatial sound reproduction using flat-panel loudspeakers, which can serve as a starting point for future research and optimization of algorithms. [ABSTRACT FROM AUTHOR]

This paper explores a novel metamaterial-inspired low-scattering electric quadrupole antenna in the microwave regime. The metasurface unit cell used here is the well-known stacked dogbone doublet which is conventionally used to get electric and magnetic resonances under plane wave illumination. An offset in the position of the upper dogbone metallization results in the excitation of the higher-order high-Q electric quadrupole resonance having insignificant scattering in comparison with the fundamental resonances. This unit cell is hence used as the base element of an antenna and electric quadrupole resonance is excited using direct probe feed while the fundamental electric and magnetic resonances are suppressed. The fabricated antenna shows a 2:1 VSWR bandwidth of 4% and a measured radiation efficiency of 42% around resonance. The experimental studies are conducted inside an anechoic chamber using a vector network analyzer, computational studies are performed using the full-wave CST Microwave Studio and these results are validated using the multipole scattering theory. [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]

The present paper describes a test campaign performed to investigate the noise footprint emitted by a helicopter in an idealised urban context, reproducing the approach to an elevated helipad. The test campaign was performed in Politecnico di Milano's anechoic chamber and was finalised to investigate the effects produced only by helicopter noise. The set up consisted of a two-blade main rotor helicopter model and an aluminium rectangular prism model reproducing the landing building. Ground observer perceptions were recorded by means of a surface microphone and a realistic landing trajectory was approximated as a succession of fixed point measurements. Collected data were analysed through acoustic spectra and sound maps. Spectra were used to comprehend physical phenomena, such as reflection, diffraction and shielding, and to analyse the different contributions of helicopter noise. A sound map analysis enabled us to obtain a global perspective of the involved phenomena and to understand th extent to which people close to a building are stressed by a helicopter approaching an elevated urban helipad. Moreover, the experimental database, obtained over a free geometry, can be considered a useful tool for the validation of aeroacoustic solvers with different levels of fidelity. [ABSTRACT FROM AUTHOR]

In this paper, a slotted‐circle patch metasurface that can efficiently absorb electromagnetic (EM) waves in three different bands is proposed. Based on the fundamental resonance of a single circular patch, EM resonances are generated making slits in the circular patch leading to multi‐band operation. Simulation results show that the proposed structure can absorb signals in three different bands, namely at 8.10, 15.39, and 19.7 GHz with absorption peaks of 99.8%, 99.7%, and 99.8%, and absorption bandwidths of 132, 181, and 90 MHz, respectively. The absorption mechanism is discussed on the basis of the single‐layer effective medium model and the analysis of surface current and electric field distributions. Furthermore, the experimental results show good agreement with the numerical simulations, with an average absorption greater than 99%. The 2‐mm thick absorber is electrically thin, corresponding to ∼λ/18 at its lowest operating frequency. Compared to other published designs, the proposed absorber has a single resonator with simple geometry, but operates in multiband. Therefore, it can be used in many applications such as anechoic chambers, scattering control, photodetectors, microbolometers, and solar cells. The proposed metasurface absorber can be used for microwave energy harvesting as well as sensor and radar cross‐section reduction applications. Key Points: The metamaterial concept was used to synthesize the structure proposed in this studyMulti‐band absorption characteristics using a single resonator were observed in the X, Ku, and K bandsThe proposed metasurface is ultra‐thin (∼λ/18), which makes it suitable for applications such as energy harvesting and radar cross‐section reduction [ABSTRACT FROM AUTHOR]

Recent research shows that a directional quiet zone from near to far field can be created with a near-field microphone array. However, there is no systematic theoretical analysis of this error-sensing strategy. In this paper, an analytical model of the angular spectrum of point sources in the free field is proposed, based on which the near-field error-sensing strategy for active directivity noise control can be quantitively analyzed. It is found that the noise reduction in the far field is determined by the angular spectrum estimation error of both the primary and secondary sources. The impacts of the error microphone array configuration, sound source position, and target direction on the estimation error of angular spectrum are investigated. Finally, experiments were conducted in the anechoic chamber to validate the impact of the location of the secondary source. [ABSTRACT FROM AUTHOR]

The indoor acoustic environment is very important for auditory learning, and the completion of various auditory learning tasks cannot be separated from auditory sustained attention. Noise and reverberation time (RT) are the two most common acoustic indicators that affect attention. Based on this, experiments on auditory sustained attention under two factors of noise masking and reverberation effect alone were conducted in an anechoic chamber and a reverberation chamber, respectively. In addition, nine kinds of RT and signal-to-noise ratios (SNR) (3 RT × 3 SNRs) were also designed and implemented in the paper, and the impact of RT and noise on the perception of auditory sustained attention was analyzed through the above three experimental scenarios. The experimental results show the following: (1) noise type has no significant effect on auditory sustained attention performance, and SNR has a significant effect on omission errors (OEs), commission errors (CEs), and mean reaction time (MRT). All three decline with the increase in SNR; when SNR reaches a certain level, it tends to stabilize, and according to the experimental results, good auditory sustained attention SNR needs at least 18 dB; (2) The effect of RT on auditory sustained attention perception has significant differences. As RT increases, the number of inattentive OE increases, the number of impulses CE increases, and the response time becomes longer; (3) SNR has a significant negative impact on college students' auditory sustained attention performance, while RT has a less negative effect compared to SNR; (4) The functional relationships between auditory sustained attention performance and SNR and RT in three scenarios were obtained, which can be used to predict inattentive OE, impulse, and MRT in noisy and reverberant environments. This study is the first attempt to explore the influence of noise and RT on the auditory sustained attention of Chinese university students, providing theoretical support for the acoustic design of indoor learning environments, and the findings can fill the gap of the lack of basic experimental data in the current standards of the indoor acoustic environment in China. [ABSTRACT FROM AUTHOR]

In this paper, we propose a miniaturized 2.5-dimensional (2.5D) frequency selective surface (FSS) structure with high angular stability. A novel closed-loop FSS is formed by combining the Jerusalem cross (JC) structure with the conventional rectangular closed loop using vias. This approach further enhances the coupling performance of the FSS and thus achieves miniaturized design. The unit cell size of the proposed FSS is 0.019λ0 × 0.019λ0 at the resonant frequency, and the metal is printed on a dielectric substrate with a thickness of 0.003λ0. The proposed FSS has a resonant frequency of 850 MHz and exhibits band-stop characteristics. It is insensitive to the incident angle with a good operating performance in both the TE and TM wave modes. Therefore, it can be well used as an electromagnetic shield for the GSM 850 band. In order to facilitate the rapid analysis and design of the FSS, the equivalent circuit model is further analyzed and established, and values of the corresponding lumped components are derived. In addition, a prototype FSS is fabricated using printed circuit board technology and is tested in a microwave anechoic chamber. The full-wave analysis simulation, equivalent circuit model simulation, and practical measurement results reflect a high level of consistency. [ABSTRACT FROM AUTHOR]

The anechoic chamber can shield the interference of external electromagnetic waves, so that the measurement activities are not affected by the external electromagnetic environment, at the same time, it can suppress the internal electromagnetic multipath reflection interference, and construct a pure electromagnetic measurement environment that can absorb almost all to waves. Most anechoic chambers have relatively single test functions and can only serve one or two test requirements. According to the functional requirements, a multifunctional composite test anechoic chamber is designed and constructed in this paper, and the structure and performance design method of anechoic chamber is given based on practical experience. The anechoic chamber is equipped with near-field, far-field, RCS, Beidou navigation simulation, complex electromagnetic environment simulation and other functions. It provides various testing conditions for each research team in the unit, and has achieved good scientific research and social service effects. [ABSTRACT FROM AUTHOR]

Purpose: Antenna miniaturization, multiband operation and wider operational bandwidth are vital to achieve optimal design for modern wireless communication devices. Using fractal geometries is recognized as one of the most promising solutions to attain these characteristics. The purpose of this paper is to present a unique structure of patch antenna using hybrid fractal technique to enhance the performance characteristics for various wireless applications and to achieve better miniaturization. Design/methodology/approach: In this paper, the authors propose a novel hybrid fractal antenna by combining Koch and Minkowski (K-M) fractal geometries. A microstrip patch antenna (MPA) operating at 1.8 GHz is incorporated with a novel K-M hybrid fractal geometry. The proposed fractal antenna is designed and simulated in CST Microwave studio and compared with existing Koch fractal geometry. The prototype for the third iteration of the K-M fractal antenna is then fabricated on FR-4 substrate and tested through vector network analyzer for operating band/voltage standing wave ratio. Findings: The third iteration of the proposed K-M fractal geometry results in achieving a 20% size reduction as compared to an ordinary MPA for the same resonant frequency with impedance bandwidth of 16.25 MHz and a directional gain of 6.48 dB, respectively. The operating frequency of MPA also lowers down to 1.44 GHz. Originality/value: Further testing for the radiation patterns in an anechoic chamber shows good agreement to those of simulated results. [ABSTRACT FROM AUTHOR]

• Microwave techniques used as a dual-purpose tool for: i) the elimination of moisture and ii) the moisture infiltration measurement in a monument's masonry. • Important pieces of cultural heritage architecture or art could be treated with non-destructive microwave techniques for moisture elimination and assessment. • Measurement of electrical permittivity for the extraction of volumetric water content in tuff bricks. • Electrical characterisation with a vector network analyser for measuring the phase shift of scattering parameters and calculating electrical permittivity. • A complete two-step methodology for controllable moisture elimination. In this paper, we present our experimental methodology, which was developed to assess and eliminate the excess moisture levels in the masonry of a Roman archeological monument, namely the Mensa Ponderaria of Tivoli, which is an important landmark dating back to the first century A.D. The need to keep interventions to a minimum were crucial factors for choosing microwave techniques as a non-destructive method for removal and moisture infiltration measurements in the walls. We used a microwave generator connected to a horn antenna to increase the temperature locally at the point of treatment and achieve the elimination of moisture. Additionally, to quantify the amount of eliminated water, we used a free space transmission measurement by two patch micro-strip fed antennas with a resonance at 2.62 GHz connected to a vector network analyser (VNA). S-parameters were measured at a frequency range 2–3 GHz. The phase shift method was used to extract the effective dielectric permittivity by the phase of the transmission S 21 parameter. In the final step, we derived the volumetric water content of the wall θ (%) based on the dielectric permittivity of the wall material (tuff). Measurements were performed at several points of the masonry, which were previously treated with microwaves or remained without treatment for comparison. We report an average of 139 gr in water extraction from the treated areas of the masonry with the mild treatment protocol we used, with the possibility of further increase with longer or higher-power drying cycles. [ABSTRACT FROM AUTHOR]

Aims: In this paper, a wire mesh-assisted ventilation acoustic metamaterial (MVAM) is presented for efficient noise suppression and ensuring ventilation and heat exchange. Method: The analytical models of ventilated acoustic metamaterial (VAM) and MVAM in the absence of flow conditions were established based on the wave expansion method and Green's function. The complex frequency planes and transmission coefficients of each resonant part (RP) were obtained, and the bandwidth and the effects of wire mesh on the transmission coefficients were analyzed. The results were compared with numerical models based on the finite element method, which showed excellent agreement. Four RPs were arranged in an artificial array to create VAM and MVAM configurations. Subsequently, the sound transmission losses for both VAM and MVAM were obtained, and experiments were carried out with the quadrupole two-loading method to verify the accuracy of the analytical and numerical models. When considering the effect of the grazing flow, a numerical model of acoustic-flow field coupling was established. The transfer impedance and the flow field distribution at different flow velocities were calculated and analyzed, and the influence law of different flow states on acoustic performance was revealed. Finally, experiments were carried out on the effect of MVAM at a grazing velocity of Ma = 0.01 utilizing a Norsonic acoustic imager. The results show that MVAM can attenuate noise under a certain grazing velocity, which verified the reliability. Results: In the absence of flow, the metal wire mesh caused a slight increase in the transmission coefficient of a single RP. Therefore, under this condition, the metal wire mesh harms noise attenuation. The bandwidth of a single RP is negatively correlated with its distance to the center of the duct. By analyzing the results for the VAM and MVAM models in the absence of flow, the wire mesh makes the STL, which still maintains four distinct peaks, decrease overall. The accuracy of the analytical and numerical calculation results was verified experimentally by the quadrupole dual-load method. By the analysis of the coupled acoustic-flow field model, the perturbation of the grazing flow on the sound field and the effect mechanism of the wire mesh are revealed. With the increase in the grazing flow velocity, the mode of the flow field is changed, which suppresses the influence of the pressure perturbation generated by the vortex on the acoustic field. The MVAM can effectively reduce the pressure loss along the path caused by the structure. The experiments on noise reduction performance under the influence of grazing flow in an anechoic chamber were conducted, and MVAM can achieve efficient noise attenuation was verified, ensuring its reliability. Conclusions: The analytical and numerical models of the relevant configurations are developed. The acoustic performances of VAM and MVAM in the absence of flow and grazing flow conditions are analyzed and compared, and the accuracy of the calculation results is verified by experiments, which proves that MVAM can effectively control the duct noise under the influence of grazing flow and reduce the pressure loss. [ABSTRACT FROM AUTHOR]

The paper presents a novel miniaturized (1.2 λ0 × 0.5 λ0 × 0.026 λ0) frequency reconfigurable travelling wave antenna (TWA) operating at 8–12 GHz band. The antenna uses PIN diodes arranged in a novel configuration to produce frequency reconfigurability and operates at single frequency bands of 8.5, 9, 9.35, 9.9, 10.45 and 11 GHz with an average bandwidth of 1 GHz based on different switch configurations. The proposed antenna demonstrates an efficiency>80% for the operating frequency in different stations while maintaining a stable average gain of 8.5 dBi. The antenna's compact nature and high gain make it suitable for several applications within modern satellite communication devices and radar systems. The proposed antenna is designed and tested for its conformality using CST Microwave-Studio. The proposed design is further verified with a fabricated prototype measured in an anechoic chamber, agreeing well with the simulated results. [ABSTRACT FROM AUTHOR]

With the development of modern industrial technology, it is an essential problem to calculate the noise reduction performance of the flexible partition walls. The sound insulation measurement model is modeled by the Spectral geometry method (SGM). Compared with the traditional ones, it is a method with higher calculation accuracy and faster convergence speed. The displacement of the panel and the sound pressure field inside the rooms are expressed as Fourier series with additional items. In order to simulate the real measurement environment, the sound source room and the receiving room are set as a reverberation chamber and an anechoic chamber with impedance boundaries, respectively. The coupling relationship is established by the Hamilton's principle. Then the natural frequencies and the sound pressure level are compared with those derived by the finite element method (FEM). The results show that the analytical method has good accuracy and convergence. Moreover, the sound transmission loss (STL) of the partition could be obtained by the sound pressure method. Considering there is no accurate method for measuring the STL, this paper studies some factors affecting the sound insulation performance of the model by the parametric analysis method, such as the thickness of the panel, the length of the receiving room, the impedance of the receiving room and the parameters of medium. [ABSTRACT FROM AUTHOR]

In this paper, an antenna design method operating at 3.5 GHz for 5G system is presented to improve its performance. The antenna is designed using fractal geometry combined with an imperfectly structured ground plane. In which, the radiation surface has the form of a Minkowski island fractal geometry, and the removed part of the ground is a complementary split ring resonator unit cell. In this design, the substrate material is FR4-epoxy microwave laminates with dielectric constant ϵ = 4.4, loss tangent (tan δ) of 0.02, and h = 1.6 mm thickness used to design the antennas. HFSS software is used in the simulation with the feeding method with a microstrip line. The proposed antenna has a significant performance increase compared to the original microstrip antenna such as reduced about 56% reduction in total size, enhanced 207% bandwidth, increased peak gain to 4.66 dB, and improved radiated efficiency to 89.3%. The physical model of the antenna has been fabricated and measured to verify the correctness of the design. [ABSTRACT FROM AUTHOR]