Responses of maize ecosystem to warming based on WATDPED experiment under near-field condition

Beam pattern measurement is essential to verifying the performance of an array sonar. However, common problems in beam pattern measurement of arrays include constraints on achieving the far-field condition and reaching plane waves mainly due to limited measurement space as in acoustic water tank. For this purpose, the conventional method of measuring beam patterns in limited spaces, which transform near-field measurement data into far-field results, is used. However, the conventional method is time-consuming because of the dense spatial sampling. Hence, we devised a method to measure the beam pattern of a discrete line array in limited space based on the subarray method. In this method, a discrete line array with a measurement space that does not satisfy the far-field condition is divided into several subarrays, and the beam pattern of the line array can then be determined from the subarray measurements by the spatial convolution that is equivalent to the multiplication of beam pattern. The proposed method was verified through simulation and experimental measurement on a line array with 256 elements of 16 subarrays.

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Empirical Doppler Characterization of Signals Scattered by Wind Turbines in the UHF Band under Near Field Condition

International Journal of Antennas and Propagation ◽

10.1155/2013/804690 ◽

2013 ◽

Vol 2013 ◽

pp. 1-11 ◽

Cited By ~ 2

Author(s):

Itziar Angulo ◽

Jon Montalbán ◽

Josune Cañizo ◽

Yiyan Wu ◽

David de la Vega ◽

...

Keyword(s):

Wind Turbines ◽

Field Condition ◽

Communication Systems ◽

Goodness Of Fit ◽

Near Field ◽

Spectral Characteristics ◽

Doppler Spectrum ◽

Time Variability ◽

Uhf Band

Time variability of the scattering signals from wind turbines may lead to degradation problems on the communication systems provided in the UHF band, especially under near field condition. In order to analyze the variability due to the rotation of the blades, this paper characterizes empirical Doppler spectra obtained from real samples of signals scattered by wind turbines with rotating blades under near field condition. A new Doppler spectrum model is proposed to fit the spectral characteristics of these signals, providing notable goodness of fit. Finally, the effect of this kind of time variability on the degradation of OFDM signals is studied.

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Ray tracing with multi-radiation transmitters

Advances in Radio Science ◽

10.5194/ars-10-75-2012 ◽

2012 ◽

Vol 10 ◽

pp. 75-78

Author(s):

R. Brem ◽

T. F. Eibert

Keyword(s):

Integral Equation ◽

Ray Tracing ◽

Field Condition ◽

Fast Multipole Method ◽

Near Field ◽

Far Field ◽

Field Region ◽

Equation Solving ◽

Close Proximity ◽

Modeling Accuracy

Abstract. A restriction in using electromagnetic ray tracing for field prediction is given by the far-field condition: the results are only valid in the far-field region of the radiator. In this paper, it will be shown how ray tracing for accurate field computation can also be applied in the near-field regions of transmitters. The reduction of required large distances between transmitter and receiver is achieved by subdividing the transmitter in smaller subtransmitters. Even for complex transmitters, e.g. antennas with objects in close proximity such as metallic carrier platforms, subtransmitter models can be very efficiently generated by using the Multilevel Fast Multipole Method (MLFMM). This well-known integral equation solving technique makes very large problems in computational electromagnetics manageable. The subtransmitters can be directly generated based on this algorithm. A simulation example will show the improved modeling accuracy and options for simplification and refinement will also be discussed.

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Multiport Analysis of Massive MIMO System under Near-Field Condition

2019 8th Asia-Pacific Conference on Antennas and Propagation (APCAP) ◽

10.1109/apcap47827.2019.9471935 ◽

2019 ◽

Author(s):

Wen Qiu ◽

Jianing Zhao ◽

Guangming Deng

Keyword(s):

Field Condition ◽

Massive Mimo ◽

Mimo System ◽

Near Field

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Near-field scanning optical microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144644 ◽

1986 ◽

Vol 44 ◽

pp. 642-643

Author(s):

E. Betzig ◽

A. Harootunian ◽

M. Isaacson ◽

A. Lewis

Keyword(s):

Near Field ◽

Optical Microscope ◽

Visible Radiation ◽

Field Methods ◽

Optical Elements ◽

Optical Region ◽

Order Of Magnitude ◽

Nondestructive Imaging ◽

Scanning Optical Microscopy ◽

Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

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