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Articles de revues sur le sujet « Planar near-field measurement »

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Auteur : Grafiati
Publié le 25 mai 2024

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1

Li, Yong, Jie Ou et Ping Xu. « Errors analysis of planar near-field antenna measurement ». JOURNAL OF ELECTRONIC MEASUREMENT AND INSTRUMENT 24, no 11 (15 décembre 2010) : 987–92. http://dx.doi.org/10.3724/sp.j.1187.2010.00987.

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WANG, NAN, ZHENG-HUI XUE, SHING-MING YANG, BEN-QING GAO et XIAO-WEN XU. « ANTENNA TIME DOMAIN PLANAR NEAR FIELD MEASUREMENT SYSTEM ». International Journal on Wireless & ; Optical Communications 03, no 02 (août 2006) : 127–33. http://dx.doi.org/10.1142/s0219799506000429.

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3

Newell, A. C., et C. F. Stubenrauch. « Effect of random errors in planar near-field measurement ». IEEE Transactions on Antennas and Propagation 36, no 6 (juin 1988) : 769–73. http://dx.doi.org/10.1109/8.1178.

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4

Wittmann, R. C., B. K. Alpert et M. H. Francis. « Nonideal measurement locations in planar near-field antenna metrology ». Computer Standards & ; Interfaces 21, no 2 (juin 1999) : 199. http://dx.doi.org/10.1016/s0920-5489(99)92302-4.

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5

Huang, Shan, Junhao Zheng, Peiyuan Qin, Qiwei Zhan et Xiaoming Chen. « Improved planar near-field measurement based on data assimilation ». Measurement 227 (mars 2024) : 114265. http://dx.doi.org/10.1016/j.measurement.2024.114265.

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6

Yang, Seunggyu, et Kangwook Kim. « One-Port Planar Near-Field Antenna Measurement and Corresponding Scatterer Compensation Method ». Journal of Electromagnetic Engineering and Science 22, no 3 (31 mai 2022) : 344–51. http://dx.doi.org/10.26866/jees.2022.3.r.96.

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A one-port near-field antenna measurement technique with a small wire scatterer is proposed. In the proposed technique, a wire scatterer is scanned with an interval of less than a quarter wavelength, and the measurement is performed at the port of the antenna under test (AUT). A two-dimensional phase unwrapping method is used to remove 180° phase uncertainty. The data obtained in the near-field are transformed to the far-field pattern, and the scattering pattern is compensated for better measurements. The proposed measurement technique was validated by measuring the near-field of an AUT over a planar scanning surface. The far-field radiation pattern obtained using the proposed technique was compared with that obtained from a conventional commercial anechoic chamber. It was observed that they agreed well, especially in the region near the center.
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Sayers, Andrew E., W. Mark Dorsey, Kenneth W. O'Haver et John A. Valenzi. « Planar Near-Field Measurement of Digital Phased Arrays Using Near-Field Scan Plane Reconstruction ». IEEE Transactions on Antennas and Propagation 60, no 6 (juin 2012) : 2711–18. http://dx.doi.org/10.1109/tap.2012.2194666.

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8

D’Agostino, Francesco, Ilaria De Colibus, Flaminio Ferrara, Claudio Gennarelli, Rocco Guerriero et Massimo Migliozzi. « Far-Field Pattern Reconstruction from Near-Field Data Collected via a Nonconventional Plane-Rectangular Scanning : Experimental Testing ». International Journal of Antennas and Propagation 2014 (2014) : 1–9. http://dx.doi.org/10.1155/2014/763687.

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This paper deals with the experimental validation of an efficient near-field-far-field (NF-FF) transformation using the planar wide-mesh scanning (PWMS). Such a nonconventional plane-rectangular scanning technique is so named, since the sample grid is characterized by meshes wider and wider when going away from the center, and makes it possible to lower the number of needed measurements, as well as the time required for the data acquisition when dealing with quasi-planar antennas. It relies on the use of the nonredundant sampling representations of electromagnetic fields which employ an oblate ellipsoid or a surface formed by two circular “bowls” with the same aperture diameter but eventually different bending radii to shape a quasi-planar antenna. A two-dimensional optimal sampling interpolation formula allows the reconstruction of the NF data at any point on the measurement plane and, in particular, at those required by the classical NF-FF transformation with the conventional plane-rectangular scanning. The measurements, performed at the planar NF facility of the antenna characterization laboratories of Selex ES, have confirmed the effectiveness of this innovative scanning also from the experimental viewpoint.
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9

Ponomarev, M. Yu, O. Yu Platonov et V. V. Shubnikov. « Features measurement gain on planar and spherical near-field stands ». Journal of «Almaz – Antey» Air and Space Defence Corporation, no 3 (30 septembre 2015) : 43–47. http://dx.doi.org/10.38013/2542-0542-2015-3-43-47.

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Three main method and highlights some features of the measurement of the gain on the near-field stands with flat and spherical surfaces scanning, described their main advantages and disadvantages. The dependence of the final result of the scan parameters and recommendations on their choice. Analyzed the degree of influence on the final outcome of the main factors affecting the accuracy of the gain.
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10

Long, Rui, et Jun Ou Yang. « PLANAR PHASED ARRAY CALIBRATION BASED ON NEAR-FIELD MEASUREMENT SYSTEM ». Progress In Electromagnetics Research C 71 (2017) : 23–31. http://dx.doi.org/10.2528/pierc16112004.

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11

Schmidt, C. H., S. F. Razavi, T. F. Eibert et Y. Rahmat-Samii. « Phaseless spherical near-field antenna measurements for low and medium gain antennas ». Advances in Radio Science 8 (30 septembre 2010) : 43–48. http://dx.doi.org/10.5194/ars-8-43-2010.

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Abstract. The characterisation of antenna radiation patterns by measurements in the near-field and a following near-field far-field transformation require accurate amplitude and phase data. Especially at higher frequencies phase measurements are demanding in terms of instrumentation and measurement accuracy. Phaseless techniques which require amplitude only data on one or more measurement surfaces are therefore of special interest. In this paper a phaseless spherical algorithm based on spherical modal expansion is presented. The algorithm works with amplitude only near-field data measured on two spheres of different radii and is therefore not restricted to certain types of antennas as for planar measurements for example. Simulated as well as measured results of low and medium gain antennas are shown.
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12

Maisto, Maria, Rocco Pierri et Raffaele Solimene. « Near-Field Warping Sampling Scheme for Broad-Side Antenna Characterization ». Electronics 9, no 6 (24 juin 2020) : 1047. http://dx.doi.org/10.3390/electronics9061047.

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In this paper the problem of sampling the field radiated by a planar source observed over a finite planar aperture located in the near-field is addressed. The problem is cast as the determination of the spatial measurement positions which allow us to discretize the radiation problem so that the singular values of the radiation operator are well-approximated. More in detail, thanks to a suitably warping transformation of the observation variables, the kernel function of the relevant operator is approximated by a band-limited function and hence the sampling theorem applied to achieved discretization. It results in the sampling points having to be non-linearity arranged across the measurement aperture and their number can be considerably lowered as compared to more standard sampling approach. It is shown that the proposed sampling scheme works well for measurement apertures that are not too large as compared to the source’s size. As a consequence, the method appears better suited for broad-side large antenna whose radiated field is mainly concentrated in front of the antenna. A numerical analysis is included to check the theoretical findings and to study the trade-off between the field accuracy representation (over the measurement aperture) and the truncation error in the estimated far-field radiation pattern.
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13

Lawler, Blake, Brent Hoffmeister, Ann Viano et Joel Mobley. « Ultrasonic backscatter measurements of cancellous bone in the near field of a planar transducer ». Journal of the Acoustical Society of America 154, no 4_supplement (1 octobre 2023) : A317. http://dx.doi.org/10.1121/10.0023654.

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Ultrasonic backscatter techniques may be used to detect changes in bone caused by osteoporosis and other diseases. Typical measurement locations include peripheral skeletal sites such as the heel, which may place the interrogated region of bone tissue in the acoustic near field of the transducer. The purpose of this study is to investigate how measurements in the near field of a planar transducer affect backscatter parameters used for ultrasonic bone assessment. Ultrasonic measurements were performed in a water tank using a planar 2.25 MHz transducer. Signals were acquired for five transducer-specimen distances: N/4, N/2, 3N/4, N, and 5N/4 where N is the near-field distance, a location that represents the transition from the near field to far field. Three backscatter parameters previously identified as potentially useful for ultrasonic bone assessment purposes were investigated: AIB, FSAB, and FIAB. All three parameters depended on transducer-specimen distance to varying degrees with FSAB exhibiting the greatest dependence on distance. These results suggest that laboratory studies of bone should evaluate the performance of backscatter parameters using clinically relevant transducer-specimen distances including distances where the ultrasonically interrogated region is in the near field of the transducer.
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14

Williams, L. I., Y. Rahmat-Samii et R. G. Yaccarino. « The bi-polar planar near-field measurement technique, part I : implementation and measurement comparisons ». IEEE Transactions on Antennas and Propagation 42, no 2 (1994) : 184–95. http://dx.doi.org/10.1109/8.277212.

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15

Deguchi, Hiroyuki, Norio Miyahara, Takashi Ebisui, Takashi Katagi, Koryo Miura et Tadashi Takano. « Spacecraft antenna measurement eliminating gravity effect by using planar near-field antenna measurement technique ». Electronics and Communications in Japan (Part II : Electronics) 83, no 3 (mars 2000) : 16–25. http://dx.doi.org/10.1002/(sici)1520-6432(200003)83:3<16 ::aid-ecjb3>3.0.co;2-j.

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16

Schmidt, C. H., et T. F. Eibert. « Near-field to far-field transformation utilising multilevel plane wave representation for planar and quasi-planar measurement contours ». IET Microwaves, Antennas & ; Propagation 4, no 11 (2010) : 1829. http://dx.doi.org/10.1049/iet-map.2009.0076.

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17

Migliore, Marco. « Near Field Antenna Measurement Sampling Strategies : From Linear to Nonlinear Interpolation ». Electronics 7, no 10 (17 octobre 2018) : 257. http://dx.doi.org/10.3390/electronics7100257.

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The aim of this review paper is to discuss some of the advanced sampling techniques proposed in the last decade in the framework of planar near-field measurements, clarifying the theoretical basis of the different techniques, and showing the advantages in terms of number of measurements. Instead of discussing the details of the techniques, the attention is focused on their theoretical bases to give a gentle introduction to the techniques. For each sampling method, examples on a liner array are discussed to clarify the advantages and disadvantages of the method.
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18

Yaccarino, R. G., Y. Rahmat-Samii et L. I. Williams. « The bi-polar planar near-field measurement technique, part II : near-field to far-field transformation and holographic imaging methods ». IEEE Transactions on Antennas and Propagation 42, no 2 (1994) : 196–204. http://dx.doi.org/10.1109/8.277213.

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19

Serhir, Mohammed. « Transient UWB Antenna Near-Field and Far-Field Assessment From Time Domain Planar Near-Field Characterization : Simulation and Measurement Investigations ». IEEE Transactions on Antennas and Propagation 63, no 11 (novembre 2015) : 4868–76. http://dx.doi.org/10.1109/tap.2015.2480404.

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20

Wang, J. J. H. « An examination of the theory and practices of planar near-field measurement ». IEEE Transactions on Antennas and Propagation 36, no 6 (juin 1988) : 746–53. http://dx.doi.org/10.1109/8.1176.

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21

Yaccarino, R. G., L. I. Williams et Y. Rahmat-Samii. « Linear spiral sampling for the bipolar planar near-field antenna measurement technique ». IEEE Transactions on Antennas and Propagation 44, no 7 (juillet 1996) : 1049–51. http://dx.doi.org/10.1109/8.504314.

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22

Rahmat-Samii, Y., L. I. Williams et R. G. Yaccarino. « The UCLA bi-polar planar-near-field antenna-measurement and diagnostics range ». IEEE Antennas and Propagation Magazine 37, no 6 (1995) : 16–35. http://dx.doi.org/10.1109/74.482029.

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23

Bevilacqua, Florindo, Francesco D’Agostino, Flaminio Ferrara, Claudio Gennarelli, Rocco Guerriero, Massimo Migliozzi et Giovanni Riccio. « An Effective Near-Field to Far-Field Transformation with Planar Spiral Scanning for Flat Antennas under Test ». Sensors 23, no 16 (19 août 2023) : 7276. http://dx.doi.org/10.3390/s23167276.

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The goal of this article is to provide numerical and experimental assessments of an effective near-field to far-field transformation (NF–FF T) technique with planar spiral scanning for flat antennas under test (AUTs), which requires a non-redundant, i.e., minimum, number of NF measurements. This technique has its roots in the theory of non-redundant sampling representations of electromagnetic fields and was devised by suitably applying the unified theory of spiral scans for non-volumetric antennas to the case in which the considered AUT is modeled by a circular disk having its radius equal to half of the AUT’s maximum dimension. It makes use of a 2D optimal sampling interpolation (OSI) formula to accurately determine the massive amount of NF data required by the classical plane-rectangular NF–FF T technique from the non-redundant data gathered along the spiral. It must be emphasized that, when considering flat AUTs, the developed transformation allows one to further and significantly save measurement time as compared to that required by the previously developed NF–FF T techniques with planar spiral scans based on a quasi-planar antenna modeling, because the number of turns of the spiral and that of NF data to be acquired depend somewhat on the area of the modeling surface. The reported numerical simulations assess the accuracy of the proposed NF–FF T technique, whereas the experimental tests prove its practical feasibility.
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24

Meyne, Nora, et Arne F. Jacob. « Sectorial substrate-integrated half-mode near-field sensors for biological liquid characterization ». International Journal of Microwave and Wireless Technologies 6, no 3-4 (1 avril 2014) : 305–12. http://dx.doi.org/10.1017/s1759078714000385.

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Two compact resonant near-field sensors are introduced for the characterization of aqueous solutions at 5 GHz. They are based on folded substrate-integrate circular half-mode resonators with a planar sensing tip. Owing to the planar design, the sensor is simple and cheap to manufacture, and a sample can be easily coupled to the resonator from the top. The operating principle of the sensor is explained and verified by both simulation and measurement. The radiation of the sensors is quantified by means of a quality factor analysis. Finally, a previously introduced calibration method based on the perturbation theory is applied to the sensors and its accuracy is improved by choosing more suitable reference materials.
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Cicchetti, Renato, Francesco D’Agostino, Flaminio Ferrara, Claudio Gennarelli, Rocco Guerriero et Massimo Migliozzi. « Near-Field to Far-Field Transformation Techniques with Spiral Scannings : A Comprehensive Review ». International Journal of Antennas and Propagation 2014 (2014) : 1–13. http://dx.doi.org/10.1155/2014/143084.

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An overview of the near-field-far-field (NF-FF) transformation techniques with innovative spiral scannings, useful to derive the radiation patterns of the antennas commonly employed in the modern wireless communication systems, is provided in this paper. The theoretical background and the development of a unified theory of the spiral scannings for quasi-spherical and nonspherical antennas are described, and an optimal sampling interpolation expansion to evaluate the probe response on a quite arbitrary rotational surface from a nonredundant number of its samples, collected along a proper spiral wrapping it, is presented. This unified theory can be applied to spirals wrapping the conventional scanning surfaces and makes it possible to accurately reconstruct the NF data required by the NF-FF transformation employing the corresponding classical scanning. A remarkable reduction of the measurement time is so achieved, due to the use of continuous and synchronized movements of the positioning systems and to the reduced number of needed NF measurements. Some numerical and experimental results relevant to the spherical spiral scanning case when dealing with quasi-planar and electrically long antennas are shown.
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26

Cano-Fácila, Francisco José, Sergey Pivnenko et Manuel Sierra-Castañer. « Reduction of Truncation Errors in Planar, Cylindrical, and Partial Spherical Near-Field Antenna Measurements ». International Journal of Antennas and Propagation 2012 (2012) : 1–19. http://dx.doi.org/10.1155/2012/438727.

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A method to reduce truncation errors in near-field antenna measurements is presented. The method is based on the Gerchberg-Papoulis iterative algorithm used to extrapolate band-limited functions and it is able to extend the valid region of the calculated far-field pattern up to the whole forward hemisphere. The extension of the valid region is achieved by the iterative application of a transformation between two different domains. After each transformation, a filtering process that is based on known information at each domain is applied. The first domain is the spectral domain in which the plane wave spectrum (PWS) is reliable only within a known region. The second domain is the field distribution over the antenna under test (AUT) plane in which the desired field is assumed to be concentrated on the antenna aperture. The method can be applied to any scanning geometry, but in this paper, only the planar, cylindrical, and partial spherical near-field measurements are considered. Several simulation and measurement examples are presented to verify the effectiveness of the method.
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27

Cho, Yong-Heui. « Planar near-field antenna measurement method based on symplectic relation and reaction concept ». International Journal of Contents 6, no 2 (28 juin 2010) : 6–9. http://dx.doi.org/10.5392/ijoc.2010.6.2.006.

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28

Chujo, W., T. Ito, Y. Hori et T. Teshirogi. « Surface accuracy measurement of a deployable mesh reflector by planar near-field scanning ». IEEE Transactions on Antennas and Propagation 36, no 6 (juin 1988) : 879–83. http://dx.doi.org/10.1109/8.1191.

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Park, Se-Ho, Geon-Ho Jang, Young-Hun Seo, Hong-Sik Keum et Sung-Il Bang. « High-Speed Antenna Measurement System Using Multi-Probe Array Technique for 5G Applications ». Electronics 11, no 21 (24 octobre 2022) : 3435. http://dx.doi.org/10.3390/electronics11213435.

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In this article, a high-speed antenna measurement system using multi-probe array technique for 5G application is suggested. The spherical near-field scan measurement system for millimeter wave frequency band (3 GHz–40 GHz) and the multi-probe array rotation method is adopted to improve the antenna measurement speed. The proposed measurement RF system consists of the 14 multi-probe array (28 channel with dual-polarization), switch matrix, downconverters, amplifiers/attenuators, digitizers, and signal generators, and is compared to the conventional planar near-field scan antenna measurement system. The measurement speed performance can be improved significantly and the 3D beam pattern of the AUT can be achieved. The designed system was verified through comparison with a verified far-field measurement system. In addition, to increase the measurement efficiency, an effective sampling technique was proposed and verified.
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Bucci, O. M., et M. D. Migliore. « Strategy to avoid truncation error in planar and cylindrical near-field antenna measurement setups ». Electronics Letters 39, no 10 (2003) : 765. http://dx.doi.org/10.1049/el:20030507.

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31

Peng, Huo, Wu Jianhua, Wang Zhengpeng et Li Zhiping. « Digital Holographic Reconstruction and Filtering Method for Antenna Planar Near-Field Phase-Less Measurement ». IEEE Antennas and Wireless Propagation Letters 16 (2017) : 2927–30. http://dx.doi.org/10.1109/lawp.2017.2752898.

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Pfeifer, T., T. Löffler, H. G. Roskos, H. Kurz, M. Singer et E. M. Biebl. « Electro-optic measurement of the electric near-field distribution of 7 GHz planar resonator ». Electronics Letters 32, no 14 (1996) : 1305. http://dx.doi.org/10.1049/el:19960881.

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33

Käläntär, K., Tomonori Tashiro, Toshihiro Toyota et Yasuki Yamauchi. « 64‐2 : Metrology of Non‐Planar Light Sources Using Near‐Field Goniometric Measurement Method ». SID Symposium Digest of Technical Papers 51, no 1 (août 2020) : 953–56. http://dx.doi.org/10.1002/sdtp.14029.

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34

González-Blanco, Pilar, et Manuel Sierra-Castañer. « Analysis of time filtering techniques for echo reduction in antenna measurements ». International Journal of Microwave and Wireless Technologies 9, no 7 (22 août 2017) : 1387–95. http://dx.doi.org/10.1017/s1759078717000873.

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This paper presents a review of filtering methods to eliminate echo in antenna measurements. Two different methods, fast Fourier transform and Matrix Pencil, are explained, compared, and simulated in a planar near field where other effects, such as aliasing, can and will be present if the simulation is not appropriately made and the parameters are not carefully chosen. Finally both methods are applied to real measurements of a dipole in a Microwave Vision Group multiprobe system and of a horn in a single-cut measurement. Other effects, such as window shift, may appear depending on the geometry of the system where the measurement is taken. These effects must be taken into consideration and carefully corrected.
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Rinas, D., et S. Frei. « Two methods for transmission line simulation model creation based on time domain measurements ». Advances in Radio Science 9 (29 juillet 2011) : 117–21. http://dx.doi.org/10.5194/ars-9-117-2011.

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Abstract. The emission from transmission lines plays an important role in the electromagnetic compatibility of automotive electronic systems. In a frequency range below 200 MHz radiation from cables is often the dominant emission factor. In higher frequency ranges radiation from PCBs and their housing becomes more relevant. Main sources for this emission are the conducting traces. The established field measurement methods according CISPR 25 for evaluation of emissions suffer from the need to use large anechoic chambers. Furthermore measurement data can not be used for simulation model creation in order to compute the overall fields radiated from a car. In this paper a method to determine the far-fields and a simulation model of radiating transmission lines, esp. cable bundles and conducting traces on planar structures, is proposed. The method measures the electromagnetic near-field above the test object. Measurements are done in time domain in order to get phase information and to reduce measurement time. On the basis of near-field data equivalent source identification can be done. Considering correlations between sources along each conductive structure in model creation process, the model accuracy increases and computational costs can be reduced.
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36

Omi, Shuntaro, Toru Uno, Takuji Arima, Yujiro Kushiyama et Takao Fujii. « Planar scanning measurement of monostatic/bistatic RCS by near-field far-field transformation based on fast multipole method ». IEICE Communications Express 4, no 9 (2015) : 282–86. http://dx.doi.org/10.1587/comex.4.282.

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Körner, Georg, Daniel Oppelt, Julian Adametz et Martin Vossiek. « Calibration of MIMO Fully Polarimetric Imaging Radar Systems with Passive Targets ». Frequenz 73, no 11-12 (26 novembre 2019) : 389–98. http://dx.doi.org/10.1515/freq-2019-0154.

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Abstract The performance of polarimetric imaging radar systems depends greatly on how well they are calibrated. The complexity of the calibration procedure scales with the number of send and receive antennas, i. e. the size of the antenna array. This article proposes a practical and effective approach for calibrating a polarimetric near field MIMO imaging radar using only two simple passive targets. The calibration requires four measurement steps: An empty space measurement for suppressing direct mutual coupling between the channels. An offset short calibration with the specular reflection of a planar metal plate for the co-polarized channels. Two measurements with a dihedral reflector inclined at different angles for the cross-polarized calibration.
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38

Gregson, S. F., A. C. Newell et G. E. Hindman. « Examination of Far-Field Mathematical Absorber Reflection Suppression through Computational Electromagnetic Simulation ». International Journal of Antennas and Propagation 2012 (2012) : 1–10. http://dx.doi.org/10.1155/2012/623268.

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The mathematical absorber reflection suppression (MARS) technique has been used to identify and then suppress the effects of spurious scattering within spherical, cylindrical, and planar near-field antenna measurement systems, compact antenna test ranges (CATRs), and far-field measurement facilities for some time now. The recent development of a general-purpose three-dimensional computational electromagnetic model of a spherical antenna test system has enabled the MARS measurement and postprocessing technique to be further investigated. This paper provides an overview of the far-field MARS technique and presents an introduction to the computational electromagnetic range model. Preliminary results of computational electromagnetic range simulations that replicate typical MARS measurement configurations are presented and discussed which, for the first time, confirm through simulation many of the observations that have previously been noted using purely empirical techniques.
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Wang, Shiquan. « Far-Field Performances Prediction of High Frequency Projectors Using Secondary Source Array Method ». Journal of Computational Acoustics 25, no 02 (2 novembre 2016) : 1750002. http://dx.doi.org/10.1142/s0218396x17500023.

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This paper investigates the prediction of the far-field performances of high frequency projectors using the second source array method (SSAM). The far-field parameters can be calculated accurately using the complex acoustic pressure data of two very close parallel planes which lie in the near-field region of the projector. The paper simulates the feasibility of predicting the far-field parameters such as transmitting voltage response and the far-field directivity pattern. The predicting results are compared with that calculated using boundary element method (BEM). It shows very good agreement between the two methods. A planar high frequency projector is measured using the near-field method. In order to verify the predicting results, the far-field measurement is performed for the same projector. The comparison of the results shows that the near-field method is capable to precisely predict the far-field parameters of the projector.
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Avetissian, V. H. « Scanner With Transmission Line for Conventional Planar Antenna Near-Field Measurement in the Short Millimeter Waveband ». IEEE Transactions on Antennas and Propagation 52, no 9 (septembre 2004) : 2500–2503. http://dx.doi.org/10.1109/tap.2004.834069.

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41

Yu, Xin, Yun Shen, Guohong Dai, Liner Zou, Tailin Zhang et Xiaohua Deng. « Phase-Controlled Planar Metalenses for High-Resolution Terahertz Focusing ». Photonics 8, no 5 (26 avril 2021) : 143. http://dx.doi.org/10.3390/photonics8050143.

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We experimentally demonstrate that high-resolution terahertz focusing can be realized in planar metalenses, which consist of arrays of different V-shaped antenna units on a silicon substrate. Numerical results show that a larger numerical aperture of metalenses can provide smaller full width at half maximum of field distribution, leading to higher spatial resolution. The measurement of fabricated metalenses samples was performed by a terahertz near-field imaging system, and experimental results agree well with the numerical prediction. Especially for 1.1 THz incident light, when the numerical aperture increases from 0.79 to 0.95, the full width at half maximum correspondingly decreases from 343 μm to 206 μm, offering an improvement of spatial resolution.
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42

Cheng, Wei, Shengming Han, Chao Song, Zelin Nie, Xuefeng Chen, Peng Zhang et Jinglei Ni. « A combined sound field reconstruction method for large cylindrical surfaces using non-conformal plane measurement ». Measurement Science and Technology 33, no 1 (29 octobre 2021) : 015009. http://dx.doi.org/10.1088/1361-6501/ac2f53.

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Abstract In practical acoustic measurement for large cylindrical surfaces, it is difficult to keep conformal and coaxial between the holographic surface and the reconstruction surface. To overcome this problem, a combined sound field reconstruction method using non-conformal plane measurement is proposed in this paper. Based on the sound pressure measured on the holographic plane, the combined method first reconstructs the sound field on the cylindrical conformal surface using statistically optimal planar near-field acoustic holography, and then reconstructs the sound field on the cylindrical reconstruction surface using statistically optimal cylindrical near-field acoustic holography. And a least square optimization method is proposed to determine the optimal position of the conformal surface. In addition, to overcome ill-posed problems, an error reduction method combining truncated singular value decomposition and Tikhonov regularization is proposed. Finally, the proposed method is applied to a test bed, and the accuracy and robustness of the sound field reconstruction for large cylindrical surfaces are obviously improved, which can provide reliable evidences for noise monitoring and control of mechanical systems.
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Li, Jian-Kun, Hong-Zhang Wang, Jie-Yin Zhang, Yuan-Jun Song, Zheng-Shan Guo, Cheng-Gang Yang, Xi Lin, Jian-Jun Zhang, Jian-Hao Chen et Tian Pei. « Quantum capacitance properties of the holes in planar germanium ». Applied Physics Letters 122, no 6 (6 février 2023) : 063102. http://dx.doi.org/10.1063/5.0137292.

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Quantum capacitance of two-dimensional (2D) systems contains useful physical information. Here, we report a high sensitivity quantum capacitance measurement with an improved radio frequency superheterodyne bridge technique for probing the electronic characteristic of Ge/SiGe 2D hole gas (2DHG) at low temperatures and under a perpendicular magnetic field B⊥. At low fields, a rapid decrease in quantum capacitance following [Formula: see text] dependence is observed, indicating an abrupt change in chemical potential near the gate boundary at high frequencies; at high fields, a series of capacitance oscillations are observed due to the Landau quantization and Zeeman splitting of the Ge/SiGe 2DHG, where gate-dependent effective [Formula: see text] factor under B⊥ is extracted. These results represent implementation of the high-precision capacitance measurement for exploring the physical properties of Ge/SiGe 2DHG.
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44

Kazemi, Fatemeh, Farahnaz Mohanna et Javad Ahmadi-Shokouh. « Detection of biological abnormalities using a near-field microwave microscope ». International Journal of Microwave and Wireless Technologies 10, no 8 (21 mai 2018) : 933–41. http://dx.doi.org/10.1017/s1759078718000752.

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Microwave and millimeter-wave reflectometry is one of the potential techniques for the diagnosis and detection of biological abnormalities, such as subcutaneous masses or cancerous tumors in human body. In this paper, a high-quality microwave sensor based on planar misrostrip resonator is designed, fabricated, and successfully tested with different kinds of biological samples. The proposed sensor has unique properties such as small size, simple fabrication, non-contact with a sample, excellent de-coupling from surroundings, and high microwave power is directly coupled into the tissue. Two experiments are performed for the detection of visible and hidden “lipoma” (fat masses), and minimum size of “lipoma” that is diagnosed by the sensor is obtained as well. In this regard, a two-dimensional image of hidden “lipomas” with amplitude contrast about 30 dB and frequency shifts contrast about 60 MHz at aλ/10 (at 13.5 GHz) stand-off distance is provided. Finally, a measurement scenario for the detection of skin cancer based on the artificial model using different layers of raw chicken with different water content is described. Results show that the proposed microscope is easy to fabricate and provide a low-cost solution for fast and accurate skin cancer detection.
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Lee, In-Gon, Young-Joon Yoon, Kwang-Sik Choi et Ic-Pyo Hong. « Design of an Optical Transparent Absorber and Defect Diagnostics Analysis Based on Near-Field Measurement ». Sensors 21, no 9 (28 avril 2021) : 3076. http://dx.doi.org/10.3390/s21093076.

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To reduce the electromagnetic wave interference caused by cavity resonance or electromagnetic wave leakage, herein, an optical transparent radar absorbing structure (RAS) was designed using transparent conductive oxides (TCOs) with a high optical transmittance and electrical conductivity, and a procedure was proposed for detecting possible defects in the fabrication and operation and for assessing the influence of the defects on the electromagnetic performance. To detect locally occurring defects in planar and three-dimensional absorbing structures, a measurement system based on an open-ended near-field antenna capable of producing small beam spots at a close distance was constructed. Moreover, the reflection characteristics of the transparent RAS were derived from a simplified multiple reflection equation, and the derived results were compared with the analysis results of an equivalent circuit model to predict the surface resistance of the TCO coating layer, based on which the presence of defects could be confirmed. By using the experimental results, the predicted surface resistance results of the coating layer and the results measured using a non-contact sheet resistance meter were compared and were found to correspond, thereby confirming the effectiveness of the proposed defect detection method.
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Xia, Shengli, Sujuan Huang, Cheng Yan, Ning Ma et Tingyun Wang. « Refractive index profile measurement of planar optical waveguides based on the near-field technique and digital holography ». Optical Fiber Technology 72 (septembre 2022) : 102991. http://dx.doi.org/10.1016/j.yofte.2022.102991.

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Budka, T. P., S. D. Waclawik et G. M. Rebeiz. « A coaxial 0.5-18 GHz near electric field measurement system for planar microwave circuits using integrated probes ». IEEE Transactions on Microwave Theory and Techniques 44, no 12 (1996) : 2174–84. http://dx.doi.org/10.1109/22.556445.

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SU, L. K., D. B. HELMER et C. J. BROWNELL. « Quantitative planar imaging of turbulent buoyant jet mixing ». Journal of Fluid Mechanics 643 (9 décembre 2009) : 59–95. http://dx.doi.org/10.1017/s0022112009991856.

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Planar Rayleigh scattering provides quantitative mixing measurements in the developing region of axisymmetric turbulent helium jets issuing into air. The measurements focus on the relatively near field, in which the jets are primarily momentum driven. The imaging parameters are specified to ensure high spatial resolution. The mean jet fluid concentration fields attain self-similarity within the measurement region, though the forms of the mole fraction profiles indicate a reduction in turbulent transport at the jet outer boundary, arising from the reduced jet fluid density. Nevertheless, jet-like scaling pertains for the concentration fields. Mass fraction fluctuations on the jet centreline attain the expected asymptotic value of ≈23% of the centreline mass fraction values. The scalar dissipation rates, however, show an axial decay rate that is slower than theoretical predictions. The two-dimensional extent of the measurements also allows spatial filtering similar to that inherent in large-eddy simulations (LESs). The results confirm that fluctuation levels and scalar dissipation rates determined for the filtered fields are reduced as the effective resolution is reduced, but while the fluctuation profiles for the filtered fields are similar for the different filter sizes, the forms of the scalar dissipation profiles are highly dependent on filter size. These latter results in particular are of a form that will be useful for grid-dependent assessments of LES results.
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49

D’Agostino, Francesco, Flaminio Ferrara, Claudio Gennarelli, Rocco Guerriero et Massimo Migliozzi. « A Spherical Near-to-far-Field Transformation Using a Non-Redundant Voltage Representation Optimized for Non-Centered Mounted Quasi-Planar Antennas ». Electronics 9, no 6 (5 juin 2020) : 944. http://dx.doi.org/10.3390/electronics9060944.

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This research falls in the antenna measurements related topic, and deals with the problem occurring in the classical spherical near-to-far-field (NTFF) transformation, when it becomes unpractical to mount the antenna under test (AUT) with its center at the center of the scanning sphere. This issue reflects in a growth of the number of near-field (NF) samples to be acquired, since this number depends on the radius of the minimum sphere, which contains the antenna, and is centered at the scanning sphere center. The non-redundant sampling representations of the electromagnetic field are conveniently exploited, to develop an effective spherical NTFF transformation for non-centered AUTs with quasi-planar geometry, requiring a minimum amount of NF samples, and nearly the same as that for a centered mounting of the AUT. Then, the NF data needed to perform the classical NTFF transformation are determined in efficient way from the acquired non-redundant NF samples by employing an accurate 2-D sampling interpolation scheme. Thus, it is possible to significantly save measurement time. Some simulation and laboratory results are reported to show the effectiveness of the developed technique, which takes into account a non-centered AUT mounting.
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Zhang, Zhenyang, et Hongwei Ma. « Particle Image Velocimetry (PIV) Investigation of Blade and Purge Flow Impacts on Inter-Stage Flow Field in a Research Turbine ». Energies 12, no 7 (1 avril 2019) : 1240. http://dx.doi.org/10.3390/en12071240.

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Flow field in the inter-stage is of great importance to jet engine turbine performance and efficiency. Investigation of flow fields is limited by the complex geometrical structure. Traditional measurement techniques, such as hot wire, pressure probe and laser Doppler velocimetry (LDV) can hardly obtain a planar information of the flow field simultaneously. To overcome this difficulty, an instantaneous planar velocimetry technique, the particle image velocimetry (PIV) technique is widely employed. However, there is no publication that studied the detailed flow field by PIV in a turbine inter-stage with the consideration of the influence of rotor blade and purge flow. This paper presents a quasi-three dimensional perspective of flow field between inlet guide vane (IGV) and rotor blade in a research turbine inter-stage by using a 2D PIV system. Coherent structures in the flow field are extracted by the proper orthogonal decomposition (POD) method. Time-averaged results show the ellipsoid structures caused by secondary flow in the inter-stage. Rotor blade influence to axial and radial flow is evaluated by time-averaged data and the first order POD mode. Egress of purge flow (9.4% of main annulus flow rate) leads to a domain with 60% axial velocity loss near hub and a growth over three times in radial velocity. POD analysis of purge flow shows detailed flow migration in the whole measurement plane.
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