scholarly journals Enhancing the Number of Modes in Metasurfaced Reverberation Chambers for Field Uniformity Improvement

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3301 ◽  
Author(s):  
Hengyi Sun ◽  
Changqing Gu ◽  
Zhuo Li ◽  
Qian Xu ◽  
Jiajia Song ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Unit Cell ◽  
Operating Frequency ◽  
Test Volume ◽  
Low Frequencies ◽  
Modal Density ◽  
Resonance Frequencies ◽  
Different Types ◽  
Field Uniformity ◽  
Reverberation Chambers

The use of metasurfaces to increase the number of modes, lower the operating frequency, and improve the field uniformity in reverberation chambers (RCs) is investigated in this paper. The method used to improve the field uniformity and decrease the resonance frequencies is based on increasing the number of modes by using the concept of subwavelength cavities. The resonance frequencies of a RC with metasurface wall are derived and expressed analytically in terms of macroscopic characteristics. Simulation of the reflection phase of the unit cell is then given as a guideline to choose the required microscopic parameters of the designed metasurface. The mode density in such subwavelength RCs is then obtained using a numerical eigenmode solver. Compared to traditional RCs, a much higher modal density is obtained at low frequencies. The standard deviation of the field uniformity in the test volume of the RC corresponding to different types of metasurface walls is finally compared. It is shown that by increasing the number of modes in the RC at the lower band, the operating frequency decreases and the field uniformity of the RC is improved.

scholarly journals Parametric Testing of Metasurface Stirrers for Metasurfaced Reverberation Chambers

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 976
Author(s):  
Hengyi Sun ◽  
Changqing Gu ◽  
Zhuo Li ◽  
Qian Xu ◽  
Mengmeng Wei ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Cross Sections ◽  
Correlation Coefficients ◽  
Random Arrangement ◽  
Different Types ◽  
Unit Cells ◽  
Field Uniformity ◽  
Parametric Testing ◽  
Reverberation Chambers ◽  
Scattering Cross Sections

In this paper, the correlation coefficients and the total scattering cross sections (TSCSs) for different types of metasurfaced stirrers and the traditional metallic stirrer, and the effects on field uniformity when such stirrers are used in reverberation chambers, are analyzed. Three metasurfaced stirrers are considered: A stirrer with two unit cells arranged alternatively (#1), a stirrer with two unit cells arranged in a chessboard-like manner (#2), and a stirrer with two unit cells in random arrangement (#3). From the correlation coefficient and TSCS results obtained in simulations, it follows that metasurfaced stirrer #1 is the best option. Field uniformity analysis of the resulting metasurface reverberation chambers (MRC) equipped with the different stirrers also supports this conclusion.

THE INFLUENCE OF ROOM ACOUSTIC PARAMETERS ON THE PERCEPTION OF ROOM CHARACTERISTICS

Akustika ◽  
2020 ◽  
pp. 28
Author(s):  
Alicja Jasińska ◽  
Maurycy Kin
Keyword(s):  
Standard Deviation ◽  
Subjective Evaluation ◽  
Strength Parameter ◽  
Acoustic Parameters ◽  
Sound Sources ◽  
Different Types

The article presents the possibility of identification of rooms on the basis of binaural perception. Results of subjective evaluation were compared with the values of sound strength, G. A previously unknown sound term was introduced: the strength of spatial impression as the inverse of standard deviation of the results obtained. It turned out that the results presenting the sound strength parameter can be correlated with the subjective evaluation of the spatial impression, which is the size of the room. It can be helpful in the process of room identification, probably due to the reverberation impression in the room. Authors plan to continue the study with more rooms and different types of sound sources.

scholarly journals A Low-Profile HF Meandered Dipole Antenna with a Ferrite-Loaded Artificial Magnetic Conductor

2021 ◽  
Vol 11 (5) ◽  
pp. 2237
Author(s):  
Oh Heon Kwon ◽  
Won Bin Park ◽  
Juho Yun ◽  
Hong Jun Lim ◽  
Keum Cheol Hwang
Keyword(s):  
High Frequency ◽  
Dipole Antenna ◽  
Unit Cell ◽  
Operating Frequency ◽  
High Permeability ◽  
Magnetic Conductor ◽  
Artificial Magnetic Conductor ◽  
Low Profile ◽  
Compact Size ◽  
Binary Genetic Algorithm

In this paper, a low-profile HF (high-frequency) meandered dipole antenna with a ferrite-loaded artificial magnetic conductor (AMC) is proposed. To operate in the HF band while retaining a compact size, ferrite with high permeability is applied to the unit cell of the AMC. The operating frequency bandwidth of the designed unit cell of the AMC is 1.89:1 (19–36 MHz). Thereafter, a meandered dipole antenna is designed by implementing a binary genetic algorithm and is combined with the AMC. The overall size of the designed antenna is 0.06×0.06×0.002 λ3 at the lowest operating frequency. The proposed dipole antenna with a ferrite-loaded AMC is fabricated and measured. The measured VSWR bandwidth (<3) covers 20–30 MHz on the HF band. To confirm the performance of the antenna, a reference monopole antenna which operates on the HF band was selected, and the measured receiving power is compared with the result of the proposed antenna with the AMC.

scholarly journals Uncorrelated configurations and field uniformity in reverberation chambers stirred by reconfigurable metasurfaces

2021 ◽  
Vol 118 (14) ◽  
pp. 144101
Author(s):  
J.-B. Gros ◽  
G. Lerosey ◽  
F. Mortessagne ◽  
U. Kuhl ◽  
O. Legrand
Keyword(s):  
Field Uniformity ◽  
Reverberation Chambers

Upgraded Railway Front Searchlight Design Plastic Deformations by its Vibrations with Resonance Frequencies

2016 ◽  
Vol 684 ◽  
pp. 111-119 ◽  
Author(s):  
Stanislav Rafaelevich Abulkhanov ◽  
Dmitrii Sergeevich Goryainov
Keyword(s):  
Natural Frequencies ◽  
Ansys Software ◽  
Software Environment ◽  
Low Frequencies ◽  
Plastic Deformations ◽  
Vibration Resistance ◽  
First Case ◽  
Resonance Frequencies ◽  
The One ◽  
Electric Lamp

Natural frequencies of the four upgraded front searchlight designs were received in ANSYS software environment. In the first case serial front searchlight incandescent electric lamp was replaced by a LED group which was mounted on the one-piece cylinder backing. The second front searchlight design had the backing which was upgraded by a radial ribs and concentric rigidity ferrules. Analyze of the backing deformation character by vibrations with the natural frequencies established a number of design solutions which make it possible to raise front searchlight vibration resistance. By the front searchlight model were established that the natural frequencies of the searchlight with the one-piece backing appertain to the whole range of the train vibrations. Natural frequencies of the backing with perforation, rigidity ferrules, and radial ribs appertain to the low frequencies of the railway locomotive vibrations spectrum. On basis of devised methodology of analyze of the deformation and natural frequencies of the surface carrying a LED group the vibration-proof searchlight design was introduced and researched.

Optimization of spiral-shaped piezoelectric energy harvester using Taguchi method

2017 ◽  
Vol 24 (19) ◽  
pp. 4484-4491 ◽  
Author(s):  
R Tikani ◽  
L Torfenezhad ◽  
M Mousavi ◽  
S Ziaei-Rad
Keyword(s):  
Taguchi Method ◽  
Energy Harvester ◽  
Piezoelectric Materials ◽  
Mechanical Energy ◽  
Experimental Investigations ◽  
Optimum Level ◽  
Low Frequencies ◽  
Piezoelectric Energy ◽  
Resonance Frequencies ◽  
Design Values

Nowadays, environmental energy resources, especially mechanical vibrations, have attracted the attention of researchers to provide energy for low-power electronic circuits. A common method for environmental mechanical energy harvesting involves using piezoelectric materials. In this study, a spiral multimode piezoelectric energy harvester was designed and fabricated. To achieve wide bandwidth in low frequencies (below 15 Hz), the first three resonance frequencies of the beam were designed to be close to each other. To do this, the five lengths of the substrate layer were optimized by the Taguchi method, using an L27 orthogonal array. Each experiment of the Taguchi method was then simulated in ANSYS software. Next, the optimum level of each design variable was obtained. A test rig was then constructed based on the optimum design values and some experimental investigations were conducted. A good correlation was observed between measured and the finite element results.

Embroidery Leaf Shape Dipole Antenna Performances and Characterisation

2017 ◽  
Vol 7 (3) ◽  
pp. 1467
Author(s):  
N. J. Ramly ◽  
M. K. A. Rahim ◽  
N. A. Samsuri ◽  
H. A. Majid
Keyword(s):  
Return Loss ◽  
Leaf Shape ◽  
Dipole Antenna ◽  
Antenna Design ◽  
Operating Frequency ◽  
Ism Band ◽  
Textile Antenna ◽  
Different Types

In this paper, leaf shape textile antenna in ISM band has been chosen to study. The operating frequency of the dipole antenna is 2.45GHz. The effect of conductive threads with three different types of sewing has been analysed. The first type of sewing leaf shape dipole antenna is to stitch around itself and embroidered into a fleece fabric with circular follow by vertical and horizontal stitch respectively. From measured return loss, the antenna with circular stitch shows better performances with optimum resonances compared with the two types of stitching. The measured results confirm that the circular stitch is more suitable for leaf shape dipole antenna design. Thus it can be concluded that different stitch gives different results for leaf shape dipole antenna.

Extracting Maximum Power in the Presence of Internal Inductance of Electromagnetic Energy Harvesting Systems

2020 ◽  
Author(s):  
Yamini Sharma ◽  
Lei Zuo
Keyword(s):  
Energy Harvesting ◽  
Electromagnetic Energy ◽  
Maximum Power ◽  
Operating Frequency ◽  
Frequency Range ◽  
Low Frequencies ◽  
Internal Inductance ◽  
Piezoelectric Energy ◽  
Operating Frequency Range ◽  
Electromagnetic Energy Harvesting

Abstract In this paper, the effect of internal inductance of electromagnetic generators in the field of energy harvesting is discussed. Electromagnetic energy harvesters are typically operated at low frequencies. This results in the generator internal inductor impedance being significantly less than the generator internal resistance. However, at high frequencies, this inductance can no longer be ignored. Therefore, to maximize the harvested power, the internal inductance must be considered while designing the power electronics. This paper presents two methods to tackle this issue. The first method involves making use of a discrete capacitor which is able to reduce the inductance effect not just at resonant frequency but for the entire operating frequency range. The second method makes use of a concept similar to synchronized switching harvesting on inductors (SSHI) in piezoelectric energy harvesting. A capacitor and switch are added in the electromagnetic energy harvesting circuit to reduce the generator internal inductance effect. This method not only provides the benefit of performing well in the entire operating frequency range but also eliminates the need for precise maximum power tracking techniques, which further helps in reducing the circuit losses. Simulation results show a maximum power output increase of 56%.

Design of a Hybrid Acoustic Device Based on Proof-Mass Actuators

2012 ◽  
Author(s):  
Francesco Braghin ◽  
Francesco Castelli-Dezza ◽  
Simone Cinquemani ◽  
Ferruccio Resta
Keyword(s):  
High Performance ◽  
Proof Mass ◽  
Supporting Surface ◽  
Low Frequencies ◽  
High Frequencies ◽  
Sound Reproduction ◽  
Different Types ◽  
Magnetostrictive Actuator ◽  
Acoustic Device

The paper deals with the design of a device for sound reproduction to be fixed to a supporting surface. The device is made up of two different types of acoustic actuators based on different technologies that allow good sound reproduction in the range of frequencies from 20Hz to 20kHz. The generation of sound at high frequencies is demanded to a magnetostrictive actuator, while a more traditional magnetodynamics actuator is used to generate sound at low frequencies. The coupling between these two actuators leads to a device having small overall dimensions and high performance.

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