Optimum near-field performance of microphone arrays subject to a far-field beampattern constraint

2000 ◽  
Vol 108 (5) ◽  
pp. 2248-2255 ◽  
Author(s):  
James G. Ryan ◽  
Rafik A. Goubran
Keyword(s):  
Near Field ◽  
Field Performance ◽  
Microphone Arrays ◽  
Far Field

Far-field performance of linear antennas determined from near-field data

2002 ◽  
Vol 50 (3) ◽  
pp. 408-410 ◽  
Author(s):  
F. Las-Heras ◽  
B. Galocha ◽  
J.L. Besada
Keyword(s):  
Field Data ◽  
Near Field ◽  
Field Performance ◽  
Far Field

Integration of non-linear, radiation, and propagation CAD techniques for MIMO link design

2011 ◽  
Vol 4 (2) ◽  
pp. 223-232 ◽  
Author(s):  
Vittorio Rizzoli ◽  
Alessandra Costanzo ◽  
Diego Masotti ◽  
Martino Aldrigo ◽  
Francesco Donzelli ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Mimo Systems ◽  
Near Field ◽  
Field Performance ◽  
Far Field ◽  
Non Linear Circuit ◽  
Non Linear ◽  
Circuit Techniques ◽  
Em Theory ◽  
Non Linear System

The paper outlines an exhaustive computer-aided design (CAD) procedure for the circuit-level simulation of entire multi-input multi-output (MIMO) links. The multiple transmitting and receiving antennas are treated as multiport radiating systems characterized by electromagnetic (EM) analysis. The effects of mutual couplings in terms of the frequency-dependent near-field and far-field performance of each element are accounted for in a straightforward and rigorous way. The set of transmitters is treated as a unique non-linear system loaded by the multiport antenna, and is analyzed by non-linear circuit techniques. The same is done for the set of receivers. In order to establish the connection between transmitters and receivers, the radiated far-field is evaluated by EM analysis, and the field incident on each receiver antenna is computed by extending to the MIMO case an available ray tracing technique. EM theory is then used to describe the receiving array as a linear active multiport network. This technique allows analysis of several MIMO systems, exploiting different array element spatial locations and frequencies of operation in a straightforward and automatic way. Bit error rate (BER) computation and minimization are demonstrated at the circuit level.

Calculating the frequency-dependent apparent source location using peak cross-correlation between near-field and far-field microphone arrays

2017 ◽  
Vol 142 (4) ◽  
pp. 2514-2514
Author(s):  
Jacob A. Ward ◽  
S. Hales Swift ◽  
Kent L. Gee ◽  
Tracianne B. Neilsen ◽  
Koji Okamoto ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Near Field ◽  
Source Location ◽  
Microphone Arrays ◽  
Far Field ◽  
Frequency Dependent ◽  
Apparent Source

scholarly journals Anapole-enabled RFID security against far-field attacks

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Anna Mikhailovskaya ◽  
Diana Shakirova ◽  
Sergey Krasikov ◽  
Ildar Yusupov ◽  
Dmitry Dobrykh ◽  
...  
Keyword(s):  
Radio Frequency Identification ◽  
Integrated Circuit ◽  
Data Exchange ◽  
Near Field ◽  
Field Performance ◽  
Sensitive Information ◽  
Far Field ◽  
Rfid Tag ◽  
Frequency Identification ◽  
Thin Metal Wire

Abstract Radio frequency identification (RFID) is a widely used wireless technology for contactless data exchange. Owing to international standardization and one-way security nature of the communication protocol, RFID tags, holding sensitive information, may be a subject to theft. One of the major security loopholes is the so-called far-field attack, where unauthorized interrogation is performed from a distance, bypassing the user’s verification. This loophole is a penalty of using a dipole-like RFID tag antenna, leaking wireless information to the far-field. Here we introduce a new concept of anapole-enabled security, prohibiting far-field attacks by utilizing fundamental laws of physics. Our design is based on radiationless electromagnetic states (anapoles), which have high near-field concentration and theoretically nulling far-field scattering. The first property enables performing data readout from several centimeters (near-field), while the second prevents attacks from a distance, regardless an eavesdropper’s radiated power and antenna gain. Our realization is based on a compact 3 cm high-index ceramic core–shell structure, functionalized with a thin metal wire and an integrated circuit to control the tag. Switching scheme was designed to provide a modulation between two radiation-less anapole states, blocking both up and down links for a far-field access. The anapole tag demonstrates more than 20 dB suppression of far-field interrogation distance in respect with a standard commercial tag, while keeping the near-field performance at the same level. The proposed concept might significantly enhance the RFID communication channel in cases, where information security prevails over cost constrains.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

2015 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
Mondher Dhaouadi ◽  
M. Mabrouk ◽  
T. Vuong ◽  
A. Ghazel
Keyword(s):  
Near Field ◽  
Far Field ◽  
Rfid Applications

Far field modeling of the Mamala Bay outfalls

1998 ◽  
Vol 38 (10) ◽  
pp. 323-330
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Field Model ◽  
Near Field ◽  
Far Field ◽  
Field Modeling ◽  
Visitation Frequency ◽  
Statistical Variation ◽  
Long Time ◽  
Harmonic Average ◽  
Ocean Outfall ◽  
Acoustic Doppler Current Profilers

The results of far field modeling of the wastefield formed by the Sand Island, Honolulu, ocean outfall are presented. A far field model, FRFIELD, was coupled to a near field model, NRFIELD. The input data for the models were long time series of oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers and density stratification measured by thermistor strings. Thousands of simulations were made to predict the statistical variation of wastefield properties around the diffuser. It was shown that the visitation frequency of the wastefield decreases rapidly with distance from the diffuser. The spatial variation of minimum and harmonic average dilutions was also predicted. Average dilution increases rapidly with distance. It is concluded that any impact of the discharge will be confined to a relatively small area around the diffuser and beach impacts are not likely to be significant.

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