Journal articles: 'Near-Field Radiation Pattern'

1

Shankpal, Preetham, Varun Arur, Govind Kadambi, and James Shuttleworth. "A Generalized Approach for Computation of Near Field Radiation Pattern of an Antenna." International Journal of Antennas and Propagation 2014 (2014): 1–18. http://dx.doi.org/10.1155/2014/958148.

Full text

Abstract:

A generalized procedure in the form of an analytical formulation for the determination of radiation pattern of an antenna at any arbitrary distance which covers the near field as well as far field is presented in this paper. With the prior knowledge of either the current or field distribution on the radiating aperture, the proposed near field analysis is generic and can be applied for wide variety of antenna elements. The underlying principle of the generalized procedure is tantamount to considering the radiating aperture as an array of point electric and magnetic dipoles. The validity and novelty of the proposed new approach have been substantiated considering an open ended circular cylindrical waveguide and a conical horn as case studies and treating the far field as a special case of near field with pertinent distance criterion. The effect of change in the distance of observation ranging from reactive near field to far field on the radiation patterns of these antennas has also been discussed. The simulation studies reveal that the depicted normalized phase patterns of both the circular waveguide and conical horn follow the changes in the profile of the corresponding amplitude patterns.

APA, Harvard, Vancouver, ISO, and other styles

2

Aho-Mantila, L., F. Subba, M. Bernert, D. P. Coster, S. Wiesen, M. Wischmeier, X. Bonnin, et al. "Predictions of radiation pattern and in–out asymmetries in the DEMO scrape-off layer using fluid neutrals." Nuclear Fusion 62, no. 5 (March 2, 2022): 056015. http://dx.doi.org/10.1088/1741-4326/ac4d62.

Full text

Abstract:

Abstract Strongly radiating and detached high-power discharges in present-day full-metal tokamaks have a characteristic radiation pattern involving condensation of radiation near the X-point, with significant radiative losses above the X-point. In contrast, Demonstration Fusion Power Plant (DEMO) divertor exhaust scoping studies using reduced physics models, including a fluid description for the neutrals, place the strongest radiation fronts in the divertor legs, near the separatrix. The present contribution studies sensitivity of the radiation pattern corresponding to maximal divertor impurity radiation to those physics models that are typically neglected in the simulations due to their computational expense: cross-field drifts, complex impurity models and kinetic neutrals. Model benchmarking is carried out in comparison to L-mode discharges, which are shown to feature both divertor and X-point radiation. The simulated plasma conditions with maximal divertor radiation have in–out asymmetries in the divertor legs and at the divertor entrance, and the asymmetries and the radiation patterns are observed to be sensitive to both cross-field drift effects and the neutral model. DEMO simulations, carried out using SOLPS-ITER, show an impact of cross-field drifts on the divertor asymmetries, but the impact is not large enough to move the radiation front from the divertor legs to regions above the X-point.

APA, Harvard, Vancouver, ISO, and other styles

3

Isernia, T., G. Leone, and R. Pierri. "Radiation pattern evaluation from near-field intensities on planes." IEEE Transactions on Antennas and Propagation 44, no. 5 (May 1996): 701. http://dx.doi.org/10.1109/8.496257.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Peña-Ruiz, S., J. Sosa-Pedroza, F. Martinez-Zuñiga, A. Rodríguez-Sánchez, E. Garduño-Nolasco, and And M. Enciso-Aguilar. "Near field analysis and field transformation applied to a parabolic profile at 5GHz." Revista Mexicana de Física 65, no. 3 (May 7, 2019): 268. http://dx.doi.org/10.31349/revmexfis.65.268.

Full text

Abstract:

We proposed a method of analysis and field transformation is applied to a 1.5 m diameter parabolic reflector at a frequency of 5 GHz, an antenna of these dimensions requires at least a 75 m region to obtain its radiation pattern, and this represents a problem, here arises the necessity to make field transformations like the one presented in this work. Near field is modeled by means of Finite Difference Time Domain Method (FDTD) and current distribution is obtained using the discrete Pocklington equation. Radiation pattern is calculated applying the array factor for parabolic profiles. Results are compared with those obtained by CST Microwave Studio with a very good agreement.

APA, Harvard, Vancouver, ISO, and other styles

5

Calazans, T., H. D. Griffiths, A. L. Cullen, D. E. N. Davies, and R. Benjamin. "Antenna radiation pattern measurement using a near-field wire scattering technique." IEE Proceedings - Microwaves, Antennas and Propagation 145, no. 3 (1998): 263. http://dx.doi.org/10.1049/ip-map:19981775.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Stangl, N. "MF AM antenna radiation pattern verification method by near field measurements." IEEE Transactions on Broadcasting 47, no. 3 (2001): 285–91. http://dx.doi.org/10.1109/11.969377.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Herschmann, R., and O. Büchel. "Radiation characteristics of a coaxial waveguide with eccentric inner conductor for application in hyperthermia and microwave reflex therapy." Advances in Radio Science 5 (June 13, 2007): 189–95. http://dx.doi.org/10.5194/ars-5-189-2007.

Full text

Abstract:

Abstract. This paper examines the radiation characteristics of a contact emitter conceived for application in hyperthermia and microwave reflex therapy. It is important to analyse the distribution of power density in the near field area, as the radiator's therapeutic sphere of activity is localized here. The contact emitter is a coaxial radiator with an eccentric course of the inner conductor. According to Huygens principle, a theoretical view of the near field radiation characteristics is made by determining the equivalent current densities in the emitter aperture. It is shown that by an eccentric shift of the inner conductor, an almost isotropic near field radiation pattern and power density can be achieved. For this, the electromagnetic field in the emitter aperture is determined by using a Bipolar coordinate system. This calculation considers only the fundamental TEM mode of the contact emitter. Besides the theoretical results near and far fields are simulated using the programme system Ansoft HFSS.

APA, Harvard, Vancouver, ISO, and other styles

8

Shum, S. M., and K. M. Luk. "An efficient FDTD near-to-far-field transformation for radiation pattern calculation." Microwave and Optical Technology Letters 20, no. 2 (January 20, 1999): 129–31. http://dx.doi.org/10.1002/(sici)1098-2760(19990120)20:2<129::aid-mop14>3.0.co;2-c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Huang, Quan, Yuxin Wu, Yan Gao, Wenxiao Fang, Zhiqiang Yi, Yun Huang, Guoguang Lu, and Kaiwei Wang. "An EMI radiation grouping approach based on spectral cluster in near filed scanning for assessment." IOP Conference Series: Materials Science and Engineering 1207, no. 1 (November 1, 2021): 012018. http://dx.doi.org/10.1088/1757-899x/1207/1/012018.

Full text

Abstract:

Abstract With the ever-increasing operating frequency in integrated circuit, it is very essentialto assess the radiation used to help the IC designer. Based on the similarity of electromagnetic patterns obtained from the radiation of ICs and their nonlinear edge, we develop a post-processing technique to group the electromagnetic patterns. A near field scanning is performed to obtain and extract the electromagnetic pattern that is used to validate the technique. Experiment results show that it can accurately group the electromagnetic patterns by which radiation assessment can be performed.

APA, Harvard, Vancouver, ISO, and other styles

10

Maisto, Maria Antonia, Giovanni Leone, Adriana Brancaccio, and Raffaele Solimene. "Efficient Planar Near-Field Measurements for Radiation Pattern Evaluation by a Warping Strategy." IEEE Access 9 (2021): 62255–65. http://dx.doi.org/10.1109/access.2021.3074786.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Hoque, M., M. Hamid, A. Rahman, and A. Z. Elsherbeni. "Radiation pattern of parabolic reflector antenna from near-field measurements of coupled reflector." Electronics Letters 25, no. 7 (1989): 484. http://dx.doi.org/10.1049/el:19890333.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

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

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

13

M., Suma, Goutham M.A, and Paramesha . "Moment method approach to analyze waveguide array radiator with crossed dipole as a near field sensor." International Journal of Engineering & Technology 8, no. 4 (October 19, 2019): 417. http://dx.doi.org/10.14419/ijet.v8i4.29646.

Full text

Abstract:

Moment method approach is used to estimate the error encountered by the sensor in the near field and probe measures co-pole and cross-pole voltages at the same time. Conversely, due to several reflections between the waveguide and dipole sensor, near field values are changed. Calculations are done to analyze the absolute sampled co-pole voltage pattern and relative sampled electric field (without probe) pattern in the scan plane, and inaccuracy induced by the sensor is determined. The waveguide reflection coefficient, radiation admittance and susceptance with measuring sensor are reformed with respect to the equivalent values in the absence of the sensor in the near field.

APA, Harvard, Vancouver, ISO, and other styles

14

Boopalan, Navaamsini, Agileswari K. Ramasamy, Farrukh Nagi, and Ammar Ahmed Alkahtani. "Planar Array Failed Element(s) Radiation Pattern Correction: A Comparison." Applied Sciences 11, no. 19 (October 4, 2021): 9234. http://dx.doi.org/10.3390/app11199234.

Full text

Abstract:

Phased arrays are widely used in different fields, such as broadcasting, radar, optics, and space communications. The principle of phased arrays is to generate a directed signal from a large number of antennas to be steered at any desired angle. This, however, increases the probability of defective elements in an array. Faulty elements in an array cause asymmetry and result in increased sidelobe levels which rigorously distort the radiation pattern. Increased sidelobe radiation wastes energy and can cause interference by radiating and receiving signals in unintended directions. Therefore, it is necessary to find a method that can provide accuracy in the radiation pattern transmitted or received in the presence of failed element(s) in an array. This paper compares the few available optimization methods, namely, simulated annealing (SA), Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Pattern Search (PS) methods. For each method, various types of failures were examined, and the most suitable techniques to recover the far-field radiation are recommended. The optimization is then carried out by selecting the optimal weights of the remaining working elements in the planar array. The optimized radiation pattern’s efficiency was evaluated by comparing the Signal to Noise Ratio (SNR) value of the optimized radiation with reference and failed radiation patterns. The PSO method showed a better performance compared to all the other methods in reducing the failed radiation pattern’s SNR value. In various types of failure tests, this method reduced the failed radiation pattern’s SNR from 1 to 10 dB. This method also successfully produced a radiation pattern that closely matches the reference pattern before any failed element(s) are presented in the array. The life cycle of a planar array system with faulty elements can be increased by optimizing the remaining active elements in the array with the PSO method. It also reduces the cost of restoring and replacing the failed elements in an array regularly. This approach also prevents near-field measurement that requires complicated processes using costly equipment.

APA, Harvard, Vancouver, ISO, and other styles

15

Xiao zheng, Lai, Xie Zeming, and Cen Xuanliang. "A Compact RFID Reader Antenna for UHF Near-Field and Far-Field Operations." International Journal of Antennas and Propagation 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/961042.

Full text

Abstract:

A compact loop antenna is presented for mobile ultrahigh frequency (UHF) radio frequency identification (RFID) application. This antenna, printed on a 0.8 mm thick FR4 substrate with a small size of 31 mm × 31 mm, achieves good impedance bandwidth from 897 to 928 MHz, which covers USA RFID Band (902–928 MHz). The proposed loop configuration, with a split-ring resonator (SRR) coupled inside it, demonstrates strong and uniform magnetic field distribution in the near-field antenna region. Its linearly polarized radiation pattern provides available far-field gain. Finally, the reading capabilities of antenna are up to 56 mm for near-field and 1.05 m for far-field UHF RFID operations, respectively.

APA, Harvard, Vancouver, ISO, and other styles

16

Li, Zhong Qun, Kai Xie, Ying Hao Ye, Rong Bin Guo, and Xu Fei Wang. "Reconstruct the PWM Signal of Switching Power Supplies from the Near Field Radiation." Advanced Materials Research 718-720 (July 2013): 1792–96. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.1792.

Full text

Abstract:

A non-contact testing method is proposed for encapsulation treated or insulation coated switching power supplies, which is implemented by reconstructing the pulse width modulation (PWM) signal of switching converters from the near field radiation of magnetic components. The radiation pattern of a buck converter is investigated, and the magnetic field sensing probe and PWM signal reconstruction circuit are also illustrated. The reconstruction testing is carried out on a buck converter; the duty cycle error of the reconstructed PWM signal is less than 0.2%, which validates the proposed method.

APA, Harvard, Vancouver, ISO, and other styles

17

Yinusa, K. A., C. H. Schmidt, and T. F. Eibert. "Scattering centers modeling of non-anechoic measurement environments." Advances in Radio Science 10 (September 18, 2012): 69–73. http://dx.doi.org/10.5194/ars-10-69-2012.

Full text

Abstract:

Abstract. Near-field measurements are established techniques to obtain the far-field radiation pattern of an Antenna Under Test via near-field measurements and subsequent near-field far-field transformation. For measurements acquired in echoic environments, additional post-processing is required to eliminate the effects of multipath signals in the resulting far-field pattern. One of such methods models the measurement environment as a multiple source scenario whereby the collected near-field data is attributed to the AUT and some scattering centers in the vicinity of the AUT. In this way, the contributions of the AUT at the probe can be separated from those of the disturbers during the near-field far-field transformation if the disturber locations are known. In this paper, we present ways of modeling the scattering centers on equivalent surfaces such that echo suppression is possible with only partial or no information about the geometry of the scatterers.

APA, Harvard, Vancouver, ISO, and other styles

18

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

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

19

Zhao, Yang, and Weichang Li. "Model-based radiation pattern correction for interferometric redatuming in 4D seismic." GEOPHYSICS 83, no. 4 (July 1, 2018): Q25—Q35. http://dx.doi.org/10.1190/geo2017-0731.1.

Full text

Abstract:

Interferometric virtual source (VS) redatuming converts surface-triggered source records into the equivalent records as if they originated from buried receiver locations by crosscorrelating downgoing waves with the corresponding upgoing waves. The theory suggests that when the receivers are surrounded by an enclosing boundary of sources, then the VS has an isotropic radiation pattern and yields an accurate response. The resultant records should determine improvement in the seismic repeatability and image quality compared with non-VS. However, in the presence of a complex near surface, an intricate shallow structure and highly variable weathering layers can severely distort the raypath, such that it produces uneven angle coverage to the buried VS. In addition, near-surface reverberations, surface multiples, and other mode-converted waves may leak into the time-gated early arrivals and further corrupt the direct wavefields. The above-mentioned issues can result in distorted radiation patterns and contaminated responses of the VS. We address these issues explicitly by spatially filtering the potentially contaminated direct wavefields using a zero-phase matched filter, such that the filtered wavefield is consistent with a model-based ideal direct P-wavefield observed at common receiver locations. This ideal reference response is computed from a homogeneous approximation to the local near-surface overburden on top of each VS. The phases of the original direct arrivals are preserved. Components associated with the reverberations and other noises can be effectively suppressed as their spatial radiation patterns deviate from that of the ideal single P-wave mode. Toward an isotropic radiation pattern by the iterative matched filter, we reduce the unbalanced illumination arising from imperfect source coverage and near-surface complexity. Compared with previous methods, the new VS approach provides significantly improved image quality and repeatability based on a pilot field of 13 time-lapse surveys, which solved a significant repeatability problem across a 17 month survey gap.

APA, Harvard, Vancouver, ISO, and other styles

20

Wong, Kin-Lu, and Hsuan-Jui Chang. "Internal cellular handset antenna with a curved metal pattern for decreased near-field radiation." Microwave and Optical Technology Letters 54, no. 8 (May 16, 2012): 1927–32. http://dx.doi.org/10.1002/mop.26958.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Loredo, Susana, Enrique G. Plaza, and Germán León. "Fast Transmitarray Synthesis with Far-Field and Near-Field Constraints." Sensors 22, no. 12 (June 8, 2022): 4355. http://dx.doi.org/10.3390/s22124355.

Full text

Abstract:

Millimeter-wave communications can potentially provide high-data-rate transmission. In addition, in the case of indoor small cells, new needs related to the radiation pattern of the antennas are emerging. In this work, a technique for the synthesis of planar transmitarray antennas with simultaneous near-field and far-field requirements is proposed. It is based on an iterative process, going from synthesized sources to generated field and back, through three operations: near-field computation as the sum of far-field contributions from the array elements, and inverse and direct fast Fourier transforms. As a result, the technique is very efficient from the point of view of computing time. In order to demonstrate the ability of the method, two examples are studied: one of them with a null in the near-field region and the other with a focal point, both pointing simultaneously in a specific far-field direction. The results are validated by manufacturing two dielectric “quasi-planar” prototypes at 26 GHz. The measure of the prototypes is in good agreement with the results advanced by the algorithm. These preliminary results suggest that the method can be extended to more complex scenarios.

APA, Harvard, Vancouver, ISO, and other styles

22

Suslik, Lubos, Jaroslava Skriniarova, Jaroslav Kovac, Dusan Pudis, Anton Kuzma, and Jaroslav Kovac. "Complex Analysis of Emission Properties of LEDs with 1D and 2D PhC Patterned by EBL." Coatings 10, no. 8 (July 30, 2020): 748. http://dx.doi.org/10.3390/coatings10080748.

Full text

Abstract:

In this paper, we present the optical and electrical properties of surface-patterned GaAs-based Multiquantum Well (MQW) light emitting diodes (LEDs) with one- and two-dimensional photonic crystal (PhC) structures. Optical properties were analyzed in the near and far field, measured by a near-field scanning optical microscope and with a goniophotometer. We demonstrated a strong effect of patterned PhC on the radiation properties and the light extraction efficiency. Enormous surface emission enhancement reaching 110% confirmed the strong effect of the patterned structure on the coupling of the guided modes into the surface emission. Additionally, the considerable effect of the PhC structure diffraction on radiation pattern was confirmed in the near and far field and is in good agreement with the simulated shape of the optical field.

APA, Harvard, Vancouver, ISO, and other styles

23

Dakhli, Saber, Hatem Rmili, Jean-marie Floc’h, Muntasir Sheikh, Kourosh Mahdjoubi, Fethi Choubani, and Richard W. Ziolkowski. "Capacitively Loaded Loop-Based Antennas with Reconfigurable Radiation Patterns." International Journal of Antennas and Propagation 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/523198.

Full text

Abstract:

A class of metamaterial-inspired antennas having reconfigurable radiation patterns is proposed. They consist of a driven monopole antenna with one- and two-capacitively loaded loop (CLL), near field resonant parasitic elements. Two configurations are studied by considering the state of these CLL elements as being either open or closed configurations. Simulation results explain the design features and demonstrate that the structure can change its beam direction simply by controlling the switched states. Two prototypes with one- and two-CLL elements were fabricated and tested. The measured impedance mismatch and radiation pattern results are presented and compared to the corresponding simulated values.

APA, Harvard, Vancouver, ISO, and other styles

24

Tichit, P. H., S. N. Burokur, X. Wu, D. Germain, and A. De Lustrac. "Novel antenna concepts via coordinate transformation." Advanced Electromagnetics 2, no. 1 (February 16, 2013): 25. http://dx.doi.org/10.7716/aem.v2i1.84.

Full text

Abstract:

Coordinate transformation is an emerging field which offers a powerful and unprecedented ability to manipulate and control electromagnetic waves. Using this tool, we demonstrate the design of novel antenna concepts by tailoring their radiation properties. The wave manipulation is enabled through the use of engineered dispersive composite metamaterials that realize the space coordinate transformation. Three types of antennas are considered for design: a directive, a beam steerable and a quasi-isotropic one. Numerical simulations together with experimental measurements are performed in order to validate the coordinate transformation concept. Near-field cartography and far-field pattern measurements performed on a fabricated prototype agree qualitatively with Finite Element Method (FEM) simulations. It is shown that a particular radiation pattern can be tailored at ease into a desired one by modifying the electromagnetic properties of the space around radiator. This idea opens the way to novel antenna design techniques for various application domains such as the aeronautical and transport fields.

APA, Harvard, Vancouver, ISO, and other styles

25

Payet, Nicolas, Muriel Darces, Marc Hélier, Jean-Louis Montmagnon, and Florent Jangal. "Cylindrical near-field far-field transformation in a half-space with conditions of dielectric and lossy ground." International Journal of Microwave and Wireless Technologies 4, no. 1 (September 27, 2011): 45–50. http://dx.doi.org/10.1017/s1759078711000833.

Full text

Abstract:

The direct measurement of the radiation pattern of an antenna is often unreachable. A near-field sampling followed by a near-field/far-field (NF/FF) transformation is therefore substituted. This process is, in most cases, applied to antennas placed in free-space or over a perfect electric conductor. On the contrary, few results concern real environment conditions. Nevertheless, it is well known that the nature of the soil can drastically change the radiating characteristic of an antenna. The lack of information about the behavior of the antenna in real conditions can give rise to substantial errors in the evaluation of the performances of electromagnetic devices. The aim of this paper is then to propose a new NF/FF transformation able to reliably supply the field radiated by an antenna placed over a plane, homogeneous, dielectric, and lossy interface. The method is based on the cylindrical-wave expansion of the electric field. The real soil is taken into account by means of its reflection coefficients. First results are given for simple antennas and for both transverse magnetic and transverse electric polarizations.

APA, Harvard, Vancouver, ISO, and other styles

26

Stantchev, Rayko Ivanov, Baoqing Sun, Sam M. Hornett, Peter A. Hobson, Graham M. Gibson, Miles J. Padgett, and Euan Hendry. "Noninvasive, near-field terahertz imaging of hidden objects using a single-pixel detector." Science Advances 2, no. 6 (June 2016): e1600190. http://dx.doi.org/10.1126/sciadv.1600190.

Full text

Abstract:

Terahertz (THz) imaging can see through otherwise opaque materials. However, because of the long wavelengths of THz radiation (λ = 400 μm at 0.75 THz), far-field THz imaging techniques suffer from low resolution compared to visible wavelengths. We demonstrate noninvasive, near-field THz imaging with subwavelength resolution. We project a time-varying, intense (>100 μJ/cm2) optical pattern onto a silicon wafer, which spatially modulates the transmission of synchronous pulse of THz radiation. An unknown object is placed on the hidden side of the silicon, and the far-field THz transmission corresponding to each mask is recorded by a single-element detector. Knowledge of the patterns and of the corresponding detector signal are combined to give an image of the object. Using this technique, we image a printed circuit board on the underside of a 115-μm-thick silicon wafer with ~100-μm (λ/4) resolution. With subwavelength resolution and the inherent sensitivity to local conductivity, it is possible to detect fissures in the circuitry wiring of a few micrometers in size. THz imaging systems of this type will have other uses too, where noninvasive measurement or imaging of concealed structures is necessary, such as in semiconductor manufacturing or in ex vivo bioimaging.

APA, Harvard, Vancouver, ISO, and other styles

27

Bogachev, Nikolay Nikolaevich, Irina L. Bogdankevich, Namik G. Gusein-Zade, and Konstantin F. Sergeychev. "OPERATION MODES AND CHARACTERISTICS OF PLASMA DIPOLE ANTENNA." Acta Polytechnica 55, no. 1 (February 28, 2015): 34–38. http://dx.doi.org/10.14311/ap.2015.55.0034.

Full text

Abstract:

<p>Existence modes of surface electromagnetic wave on a plasma cylinder, operating modes and characteristics of the plasma antenna were studied in this paper. Solutions of the dispersion equation of surface wave were obtained for a plasma cylinder with finite radius for different plasma density values. Operation modes of the plasma asymmetric dipole antenna with finite length and radius were researched by numerical simulation. The electric field distributions of the plasma antenna in near antenna field and the radiation pattern were obtained. These characteristics were compared to characteristics of the similar metal antenna. Numerical models verification was carried out by comparing of the counted and measured metal antenna radiation patterns.</p>

APA, Harvard, Vancouver, ISO, and other styles

28

Yurtsev, O. A., and R. Ch Shimanouski. "AMPLITUDE-PHASE DISTRIBUTION MEASUREMENT PLANE DIMENSIONS INFLUENCE ON THE HOLOGRAPHIC METHOD ANTENNA ARRAY RADIATION PATTERN RECONSTRUCTION ERRORS." Doklady BGUIR, no. 1 (March 6, 2020): 5–13. http://dx.doi.org/10.35596/1729-7648-2020-18-1-5-13.

Full text

Abstract:

The article explores the holographic method of measuring the antenna pattern. A flat antenna array is used as the antenna under test, and a planar rectangular surface is used as the surface on which the amplitudephase distribution in the near field is measured. Using the example of a flat antenna array, we consider the influence of the size of the measurement surface of the amplitude-phase distribution of the field in a plane orthogonal to the reconstruction plane of the radiation pattern. Antenna emitters are excited with a combined amplitude distribution and linear phase distribution. The field in the longitudinal zone of the lattice is determined using the Kirchhoff integral. The reconstructed radiation patterns are estimated using the amplitude-phase distribution over the entire measurement plane in comparison with the array radiation pattern in the far zone. A numerical analysis of the influence on the errors in determining the parameters of the lattice radiation pattern using the holographic method is also carried out: the number of columns of the amplitude-phase distribution on the measurement plane, the position of this plane in three coordinates relative to the plane of the aperture of the lattice. It is shown that if the spacing of the points of measurement of the amplitude-phase distribution and the pitch of the lattice are equal, to restore the radiation pattern using the holographic method, it is sufficient to use one column of the amplitude-phase distribution on the measurement plane. This greatly simplifies and reduces the cost of the measurement process and the necessary equipment. Examples of determining errors in measuring the parameters of the antenna array when shifting the plane of measurement of the amplitude-phase distribution in three coordinates are given.

APA, Harvard, Vancouver, ISO, and other styles

29

Šarolić, Antonio, and Borivoj Modlic. "Installation Uncertainty of Field Level Calculation around a Base Station Antenna." Journal of Communications Software and Systems 3, no. 2 (June 21, 2007): 115. http://dx.doi.org/10.24138/jcomss.v3i2.260.

Full text

Abstract:

In the near field, the antenna pattern provided by the antenna manufacturer is generally not applicable, or shouldbe considered with caution, even for the single antenna in free space. In the real life, antenna is often surrounded by other conductive objects in the immediate vicinity. These objects tend to distort the antenna radiation pattern. Since the electromagnetic field calculation for the coverage or radiation hazard analysis depends on the three-dimensional antenna gain, this effect should be taken into account. This paper suggests the use of "installation uncertainty" that should be added to the field calculation. The amount of this quantity depends on the installation geometry and can be calculated numerically for a specific situation. This paper shows the results of numerical calculations for some typical antenna installation geometries.

APA, Harvard, Vancouver, ISO, and other styles

30

Cetin, B., H. R. Benedickter, and P. Leuchtmann. "Near-field radiation pattern distortion of antenna attached to wall in through-the-wall radar imaging." Advances in Radio Science 11 (July 4, 2013): 37–45. http://dx.doi.org/10.5194/ars-11-37-2013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Cho, Jae‐Hyoung, and Se‐Yun Kim. "Wideband symmetric near‐field radiation pattern of sleeve dipole antenna by connecting additional ferrite‐loaded wire." Electronics Letters 51, no. 8 (April 2015): 610–11. http://dx.doi.org/10.1049/el.2015.0065.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Fiks, I. Sh, and G. E. Fiks. "Parametric method for retrieval of the radiation pattern of an elongated source by near-field measurements." Radiophysics and Quantum Electronics 54, no. 4 (September 2011): 284–93. http://dx.doi.org/10.1007/s11141-011-9290-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Sakonkanapong, Arnon, and Chuwong Phongcharoenpanich. "Near-Field HF-RFID and CMA-Based Circularly Polarized Far-Field UHF-RFID Integrated Tag Antenna." International Journal of Antennas and Propagation 2020 (April 24, 2020): 1–15. http://dx.doi.org/10.1155/2020/6427157.

Full text

Abstract:

This research proposes an integrated high-frequency (HF) and ultrahigh-frequency (UHF) passive radio frequency identification (RFID) tag antenna for near-field (13.56 MHz) and far-field (920–925 MHz) communication. This tag antenna is advantageous for the applications with lossy material in the near-field communication and mitigates polarization loss in the far-field communications. The HF-RFID tag antenna is of square spiral structure, and the circularly polarized UHF-RFID structure consists of a square loop radiator with cascading loop feeding and shorted stub. The structure of HF-RFID tag antenna situated inside the circularly polarized UHF-RFID tag can avoid the significant effect of the near-field magnetic coupling from the square loop. The UHF-RFID tag antenna is realized by using characteristic mode analysis for wideband circular polarization. The HF-RFID structure is conjugate-matched with NXP NT3H2111 chip, and the UHF-RFID structure is conjugate-matched with NXP G2X chip. Simulations were carried out, and an antenna prototype was fabricated. The experimental results reveal that the radiation pattern of UHF-RFID tag antenna is bidirectional with a gain of 0.31 dBic. The impedance bandwidth covers the frequency range of 903–944 MHz, and the axial ratio in boresight direction at 922.5 MHz is 1.67 dB, with the axial ratio bandwidth over 863–938 MHz. The maximum near-field and far-field reading ranges are 4.9 cm and 8.7 m. The proposed integrated dual-band passive tag antenna is operationally ideal for HF-RFID and UHF-RFID applications.

APA, Harvard, Vancouver, ISO, and other styles

34

Saenz, E., K. Guven, E. Ozbay, I. Ederra, and R. Gonzalo. "Decoupling of Multifrequency Dipole Antenna Arrays for Microwave Imaging Applications." International Journal of Antennas and Propagation 2010 (2010): 1–8. http://dx.doi.org/10.1155/2010/843624.

Full text

Abstract:

The mutual coupling between elements of a multifrequency dipole antenna array is experimentally investigated byS-parameter measurements and planar near-field scanning of the radiated field. A multifrequency array with six dipoles is analyzed. In order to reduce the coupling between dipoles, a planar metasurface is placed atop the array acting as superstrate. The mutual coupling of the antenna elements in the absence and presence of the superstrate is presented comparatively. Between 3 and 20 dB mutual coupling reduction is achieved when the superstrate is used. By scanning the field radiated by the antennas and far-field measurements of the radiation pattern, it is observed that the superstrate confines the radiated power, increases the boresight radiation, and reduces the endfire radiation.

APA, Harvard, Vancouver, ISO, and other styles

35

HASHEMINEJAD, S. M., and A. H. PASDAR. "COMPUTATION OF ACOUSTIC FIELD RADIATED BY A SPHERICAL SOURCE NEAR A THERMOVISCOUS FLUID SPHERE." Journal of Computational Acoustics 15, no. 02 (June 2007): 159–80. http://dx.doi.org/10.1142/s0218396x07003342.

Full text

Abstract:

Acoustic radiation from a spherical source, vibrating with an arbitrary, axisymmetric, time-harmonic surface velocity distribution, while immersed near a thermoviscous fluid sphere suspended in an unbounded viscous thermally conducting fluid medium is computed. The formulation utilizes the appropriate wave field expansions and boundary conditions along with the translational addition theorem for spherical wave functions to develop a closed-form solution in form of infinite series. The prime objective is to investigate the thermoviscous loss effects on acoustic radiation and its associated field quantities. The analytical results are illustrated with a numerical example in which the spherical source, that may vibrate either in a monopole-like or a dipole-like mode, is suspended in a thermoviscous fluid medium near an equal-sized viscous thermally conducting fluid sphere. To avoid numerical difficulties normally arising in process of solving thermoviscous radiation/scattering problems in the frequency range of interest, a basic multiple precision FORTRAN computation package was utilized in developing specialized codes for computing special mathematical functions including spherical Bessel functions of complex argument and performing large complex matrix manipulations on floating point numbers of arbitrarily high precision. The essential acoustic field quantities such as the modal acoustic radiation impedance load on the source, the radiated far-field pressure directivity pattern and the radiated on-axis pressure are evaluated and discussed for representative values of the parameters characterizing the system. Limiting cases are examined and excellent agreements with well known solutions are attained.

APA, Harvard, Vancouver, ISO, and other styles

36

Abbasirad, Najmeh, Angela Barreda, Dennis Arslan, Michael Steinert, Stefan Fasold, Carsten Rockstuhl, Isabelle Staude, Frank Setzpfandt, and Thomas Pertsch. "Investigation of dipole emission near a dielectric metasurface using a dual-tip scanning near-field optical microscope." Nanophotonics 10, no. 18 (October 22, 2021): 4511–22. http://dx.doi.org/10.1515/nanoph-2021-0429.

Full text

Abstract:

Abstract A wide variety of near-field optical phenomena are described by the interaction of dipole radiation with a nanophotonic system. The electromagnetic field due to the dipole excitation is associated with the Green’s function. It is of great interest to investigate the dipole interaction with a photonic system and measure the near-field Green’s function and the quantities it describes, e.g., the local and cross density of optical states. However, measuring the near-field Green’s function requires a point-source excitation and simultaneous near-field detection below the diffraction limit. Conventional single-tip near-field optical microscope (SNOM) provides either a point source excitation or amplitude and phase detection with subwavelength spatial resolution. The automated dual-tip SNOM, composed of two tips, has overcome the experimental challenges for simultaneous near-field excitation and detection. Here, we investigate the dipole emission in the near-field of a dielectric metasurface using the automated dual-tip SNOM. We have analyzed the near-field pattern and directional mode propagation depending on the position of the dipole emission relative to the metasurface. This study is one further step toward measuring the dyadic Green’s function and related quantities such as cross density of optical states in complex nanophotonic systems for both visible and near-infrared spectra.

APA, Harvard, Vancouver, ISO, and other styles

37

Kai Loon, Goh, and Mohd Hafiz Baharuddin. "Development of a Magnetic Field Probe for Near-Field Measurement." Jurnal Kejuruteraan 33, no. 4 (November 30, 2021): 853–61. http://dx.doi.org/10.17576/jkukm-2021-33(4)-08.

Full text

Abstract:

Current electronic circuits are characterised by their compact design of miniaturisation; however, such a feature has also contributed to the rise of electromagnetic compatibility issues. This study introduces a technique to develop a magnetic field probe for near-field measurement. The probe aims at performing the debugging of electromagnetic interference on an integrated circuit. Certain processes, such as designing a microstrip line in simulation and a prototype for the validation as well as developing a functional magnetic field probe for near-field scanning and calibration measurement to determine the probe factor, have been performed under a frequency domain. The microstrip line model is built both as a simulation and a real prototype, and the handcrafted loop probe is developed with the same diameter as a commercial probe. Calibration measurement is set-up with a vector network analyser (VNA) to capture the magnetic field on radiated plane. The performance of the handcrafted probe in terms of measuring the configuration of the H-field source on the scattering region is conducted. Two types of measurements which are S11 and S21 will be conducted using a VNA. The comparison of the S11 and S21 results against simulation results are plotted using MATLAB. S11 represents the return loss of the microstrip line while S21 represents the power received by the magnetic field probe relative to power input to the microstrip line. The results of the S11 parameter indicate that the customised microstrip line board has a similar waveform pattern that matches the one on the simulation model. The S21 results for the handcrafted probe revealed that it can only function well up to the frequency of 2.644 GHz, the abnormal result obtained after the frequency mentioned. Some factors may have affected the results, such as material loss, fabrication tolerance and interferences from other devices. Therefore, calibration measurement is conducted under a less reflected radiation environment, and the designated substrate should be a perfect material correlated with the measurement.

APA, Harvard, Vancouver, ISO, and other styles

38

Cao, L. H., Wei Yu, M. Y. Yu, and C. Y. Yu. "Terahertz Radiation from a Plasma Cylinder with External Radial Electric and Axial Magnetic Fields." Laser and Particle Beams 2021 (January 29, 2021): 1–6. http://dx.doi.org/10.1155/2021/6666760.

Full text

Abstract:

Terahertz (THz) radiation from a plasma cylinder with embedded radial electric and axial magnetic fields is investigated. The plasma density and the electric and magnetic fields are such that the electron plasma frequency is near the electron cyclotron frequency and in the THz regime. Two-dimensional particle-in-cell simulations show that the plasma electrons oscillate not only in the azimuthal direction but also in the radial direction. Spectral analysis shows that the resulting oscillating current pattern has a clearly defined characteristic frequency near the electron cyclotron frequency, suggesting resonance between the cyclotron and plasma oscillations. The resulting far-field THz radiation in the axial direction is also discussed.

APA, Harvard, Vancouver, ISO, and other styles

39

Gaborit, Gwenael, Philippe Artillan, Cedric Bermond, Guillaume Revillod, Guillaume Chevrier-Gros, and Lionel Duvillaret. "20 GHz Antenna Radiation Pattern Obtained From Near-Field Mapping With Electrooptic Probe on a Single Plane." IEEE Antennas and Wireless Propagation Letters 19, no. 7 (July 2020): 1177–81. http://dx.doi.org/10.1109/lawp.2020.2994263.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Hwang, Chulsoon, Hark-Byeong Park, and Hyun Ho Park. "A simple estimation of TRP and radiation pattern for mobile antennas using planar near-field scanning method." Microwave and Optical Technology Letters 58, no. 6 (March 28, 2016): 1437–43. http://dx.doi.org/10.1002/mop.29834.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Zhou, Chaobiao, Tianyao Pu, Jing Huang, Menghui Fan, and Lujun Huang. "Manipulating Optical Scattering of Quasi-BIC in Dielectric Metasurface with Off-Center Hole." Nanomaterials 12, no. 1 (December 25, 2021): 54. http://dx.doi.org/10.3390/nano12010054.

Full text

Abstract:

Bound states in the continuum (BICs) correspond to a particular leaky mode with an infinitely large quality-factor (Q-factor) located within the continuum spectrum. To date, most of the research work reported focuses on the BIC-enhanced light matter interaction due to its extreme near-field confinement. Little attention has been paid to the scattering properties of the BIC mode. In this work, we numerically study the far-field radiation manipulation of BICs by exploring multipole interference. By simply breaking the symmetry of the silicon metasurface, an ideal BIC is converted to a quasi-BIC with a finite Q-factor, which is manifested by the Fano resonance in the transmission spectrum. We found that both the intensity and directionality of the far-field radiation pattern can not only be tuned by the asymmetric parameters but can also experience huge changes around the resonance. Even for the same structure, two quasi-BICs show a different radiation pattern evolution when the asymmetric structure parameter d increases. It can be found that far-field radiation from one BIC evolves from electric-quadrupole-dominant radiation to toroidal-dipole-dominant radiation, whereas the other one shows electric-dipole-like radiation due to the interference of the magnetic dipole and electric quadrupole with the increasing asymmetric parameters. The result may find applications in high-directionality nonlinear optical devices and semiconductor lasers by using a quasi-BIC-based metasurface.

APA, Harvard, Vancouver, ISO, and other styles

42

Choudhary, Abhishek, Krishan Gopal, Deepak Sood, and Chandra Charu Tripathi. "Development of compact inductive coupled meander line RFID tag for near-field applications." International Journal of Microwave and Wireless Technologies 9, no. 4 (July 15, 2016): 757–64. http://dx.doi.org/10.1017/s1759078716000751.

Full text

Abstract:

The development of compact radio frequency identification (RFID) tag is the key requirement for wireless tracking of precious small size goods/packages in transport. A design of compact meander line tag antenna having inductive coupling feed is presented for RFID system operating at ultra high frequency band of865–867 MHz. The size of the proposed tag antenna is43 mm × 10 mm, and is designed using Higgs 4 IC chip (made Alien Technology, USA) having impedance of20.55− j191.45 Ωat centre frequency866 MHz.The antenna characteristics such as impedance, radiation pattern, bandwidth, and effect of ground on gain and tag size are analyzed and found to closely match with the simulated values. The observed value of reading range varies from87.5 to 35 cmsdepending on mounting on non-metal and metal packages, respectively.

APA, Harvard, Vancouver, ISO, and other styles

43

Li, Xin, and Henk F. Arnoldus. "Propagation of Electric Dipole Radiation through a Medium." ISRN Optics 2012 (November 14, 2012): 1–7. http://dx.doi.org/10.5402/2012/856748.

Full text

Abstract:

When electromagnetic energy propagates through a material medium, the paths of energy flow may be altered, as compared to propagation in free space. We consider radiation emitted by an electric dipole, embedded in a medium with permittivity and permeability . For a linear dipole in free space, the field lines of energy flow are straight, but when the imaginary part of is finite, the field lines in the material become curves in the near field of the dipole. Therefore, the energy flow is redistributed due to the damping in the material. For a circular dipole in free space, the field lines of energy flow wind around the axis perpendicular to the plane of rotation of the dipole moment. When has an imaginary part, this flow pattern is altered drastically. Furthermore, when the real part of is negative, the direction of rotation of the flow lines reverses. In that case, the energy in the field rotates opposite to the direction of rotation of the dipole moment. It is indicated that in metamaterials with a negative index of refraction this may lead to an observable effect in the far field.

APA, Harvard, Vancouver, ISO, and other styles

44

LE DIZÈS, STÉPHANE, and CHRISTOPHE MILLET. "Acoustic near field of a transonic instability wave packet." Journal of Fluid Mechanics 577 (April 19, 2007): 1–23. http://dx.doi.org/10.1017/s0022112006004472.

Full text

Abstract:

We consider the problem of acoustic radiation generated by a spatial instability wave on a weakly developing shear flow. Assuming a local WKBJ approximation for the instability wave near its maximum, we compute the acoustic pressure field by using a Fourier transform along the streamwise direction. When the instability wave is close to transonic near its maximum amplitude, approximations for this pressure field are obtained by a steepest descent method. A branch cut and several saddle points are shown possibly to contribute to the approximation. A detailed analysis of these contributions is provided. The modifications of the acoustic field when we pass from subsonic to supersonic are examined. In particular, the superdirective character of the acoustic field of subsonic instability waves and the directivity pattern of supersonic waves are shown to be both compatible with our mathematical description and associated with a single saddle-point contribution.The acoustic near field is also shown to possess a caustic around which a specific approximation is derived. In a large region of the physical space, the near field is composed of two saddle-point contributions. Close to the shear flow, one of these contributions degenerates into a branch-point contribution which always becomes dominant over the instability wave downstream of a location that is computed. An interesting phenomenon is observed in certain regions downstream of the maximum: the transverse behaviour of the instability wave has to be exponentially growing far from the shear layer to match the acoustic field. We demonstrate that this phenomenon neither requires a branch-point contribution nor a supersonic instability wave.

APA, Harvard, Vancouver, ISO, and other styles

45

Appleby, J. C., and D. G. Crighton. "Internal gravity waves generated by oscillations of a sphere." Journal of Fluid Mechanics 183 (October 1987): 439–50. http://dx.doi.org/10.1017/s0022112087002714.

Full text

Abstract:

We consider the radiation of internal gravity waves from a spherical body oscillating vertically in a stratified incompressible fluid. A near-field solution (under the Boussinesq approximation) is obtained by separation of variables in an elliptic problem, followed by analytic continuation to the frequencies ω < N of internal wave radiation. Matched expansions are used to relate this solution to a far-field solution in which non-Boussinesq terms are retained. In the outer near field there are parallel conical wavefronts between characteristic cones tangent to the body, but with a wavelength found to be shorter than that for oscillations of a circular cylinder. It is also found that there are caustic pressure singularities above and below the body where the characteristics intersect. Far from the source, non-Boussinesq effects cause a diffraction of energy out of the cones. The far-field wave-fronts are hyperboloidal, with horizontal axes. The case of horizontal oscillations of the sphere is also examined and is shown to give rise to the same basic wave structure.The related problem of a pulsating sphere is then considered, and it is concluded that certain features of the wave pattern, including the caustic singularities near the source, are common to a more general class of oscillating sources.

APA, Harvard, Vancouver, ISO, and other styles

46

de Souza, Janilson L., Karlo Q. da Costa, Victor Dmitriev, and Felipe Bamberg. "Broadband Dipole-Loop Combined Nanoantenna Fed by Two-Wire Optical Transmission Line." International Journal of Antennas and Propagation 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/4903747.

Full text

Abstract:

This paper presents a broadband nanoantenna fed by a two-wire optical transmission line (OTL). The antenna is defined by a combination of a dipole and a loop, where only the dipole element is connected to the OTL. The analysis is fulfilled by the linear method of moments with equivalent surface impedance to model the conductors. Firstly, the nanoantenna alone is investigated, where the input impedance, current distribution, reflection coefficient, fractional bandwidth, radiation efficiency, and radiation pattern are analyzed. Then, the input impedance matching of this antenna with the OTL is considered. In this case the current, near field distribution, radiation pattern, and reflection coefficient are calculated for different geometrical parameters. The results show that the loop inserted in the circuit can increase the bandwidth up to 42% and decreases the reflection coefficient in the OTL to −25 dB.

APA, Harvard, Vancouver, ISO, and other styles

47

Abujetas, Diego R., and José A. Sánchez-Gil. "Near-Field Excitation of Bound States in the Continuum in All-Dielectric Metasurfaces through a Coupled Electric/Magnetic Dipole Model." Nanomaterials 11, no. 4 (April 13, 2021): 998. http://dx.doi.org/10.3390/nano11040998.

Full text

Abstract:

Resonant optical modes arising in all-dielectric metasurfaces have attracted much attention in recent years, especially when so-called bound states in the continuum (BICs) with diverging lifetimes are supported. With the aim of studying theoretically the emergence of BICs, we extend a coupled electric and magnetic dipole analytical formulation to deal with the proper metasurface Green function for the infinite lattice. Thereby, we show how to excite metasurface BICs, being able to address their near-field pattern through point-source excitation and their local density of states. We apply this formulation to fully characterize symmetry-protected BICs arising in all-dielectric metasurfaces made of Si nanospheres, revealing their near-field pattern and local density of states, and, thus, the mechanisms precluding their radiation into the continuum. This formulation provides, in turn, an insightful and fast tool to characterize BICs (and any other leaky/guided mode) near fields in all-dielectric (and also plasmonic) metasurfaces, which might be especially useful for the design of planar nanophotonic devices based on such resonant modes.

APA, Harvard, Vancouver, ISO, and other styles

48

Vendhan, C. P., and C. Prabavathi. "Determination of Far-Field Pattern of Rigid Scatterers Using Independent Finite Element Method and Eigenfunction Expansion, Part 1: Axisymmetric Scattering." Journal of Vibration and Acoustics 118, no. 4 (October 1, 1996): 575–82. http://dx.doi.org/10.1115/1.2888337.

Full text

Abstract:

The near-field steady state scattered potential around a rigid scatterer subjected to plane incident wave is computed using the finite element method with radiation boundary dampers on a finite truncation boundary. Then the solution in the outer domain is sought in the form of an eigenfunction expansion and the expansion coefficients are obtained using the finite element solution on the truncation boundary as Dirichlet boundary condition. The scattered far-field pattern is derived from this solution for prolate spheroid and hemispherically capped cylinder problems.

APA, Harvard, Vancouver, ISO, and other styles

49

Tseng, Vincent, and Cheng-Yuan Chang. "Linear Tapered Slot Antenna for Ultra-Wideband Radar Sensor: Design Consideration and Recommendation." Sensors 19, no. 5 (March 9, 2019): 1212. http://dx.doi.org/10.3390/s19051212.

Full text

Abstract:

Radar is a type of wireless, noncontact sensor that does not need to be placed on or near a test object for detection. A key component of any radar sensor is the antenna. Among different types of antennas, the linear tapered slot antenna (LTSA) is a wideband antenna that has the advantages of small size, design simplicity, and easy adaptation to an array. This study examined and analyzed the 10 primary parameters that define the LTSA design when operated in the ultra-wideband (UWB) frequency range. The study method involved varying each of the 10 parameters to discern how the variations impact the three critical characteristics of an antenna, namely, (1) return loss, (2) the far field radiation pattern on the E-plane, and (3) the far field radiation pattern on the H-plane. By analyzing the changes in these critical characteristics, a set of design recommendations for the 10 parameters was developed for the LTSA.

APA, Harvard, Vancouver, ISO, and other styles

50

Carro, Pedro Luis, Jesús de Mingo, Paloma García-Dúcar, and Antonio Valdovinos. "Statistical Antenna Proximity Effect Modeling with Uncertainty Impedance Ellipses." International Journal of Antennas and Propagation 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/7192491.

Full text

Abstract:

User effects on portable antennas can decrease the global terminal performance, such as reducing the battery life or the wireless coverage. People presence will modify the input impedance, the far field radiation pattern, the radiation efficiency, and the near field. In this paper, we investigate the influence of the user on the input impedance by means of a new statistical approach which relies on uncertainty, where a handheld antenna works in two modes (data and talk) while people couple to the antenna. Studying some reflection coefficient measurements performed with a vector network analyzer (VNA), a standard framework based on uncertainty ellipses is developed. Finally, the method is applied to some antenna prototypes, showing its advantages and reliability to quantify and compare proximity effects.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Near-Field Radiation Pattern'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles