Near-Field-Focused Microwave Antennas: Near-field shaping and implementation

Nepa, Paolo; Buffi, Alice

doi:10.1109/map.2017.2686118

Cited by 175 publications

(101 citation statements)

References 62 publications

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“…Once the inverse model of the antenna array is obtained, it is used to calculate the weights that must be applied to the array in order to obtain a simultaneous focus on three focal points at {x, y, z} = {2λ, 0, 7λ}, {−λ, 0, 4λ} and {−3λ, 0, 4λ}, to reproduce the experiment presented in [14]. A target field distribution is built using Equation 14, using C m = 1 for the assigned focal points and 0 for any other position, and the resulting vector e is applied to Equation (10). The resulting weights have been used in the MoM model of the antenna to evaluate the resulting radiated field.…”

Section: Resultsmentioning

confidence: 99%

“…NFF allows antenna arrays to concentrate the energy on an assigned position or spot in the near-field (NF) region of the antenna, reducing the waste of energy directed to positions of space where it is not necessary. The conjugate-phase (CP) method proposed in [2,10,11] is an excellent technique for calculating the phase-shift that must be applied to each array element so that all the signal contributions from the individual elements arrive in-phase to the position of interest, creating a constructive interference that increases the field level at such position. This is a robust and simple approach whose performance has been undoubtedly proven.…”

Section: Introductionmentioning

confidence: 99%

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Support Vector Regression for the Modeling and Synthesis of Near-Field Focused Antenna Arrays

Ayestaran

2019

Electronics

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The powerful support vector regression framework is proposed in a novel method for near-field focusing using antenna arrays. By using this machine-learning method, the set of weights required in the elements of an array can be calculated to achieve an assigned near-field distribution focused on one or more positions. The computational cost is concentrated in an initial training process so that the trained system is fast enough for applications where moving devices are involved. The increased learning capabilities of support vector machines allow using a reduced number of training samples. Thus, these training samples may be generated with a prototype or a convenient electromagnetic analysis tool, and hence realistic effects, such as coupling or the individual radiation patterns of the elements of the arrays, are accounted for. Illustrative examples are presented.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Support Vector Regression for the Modeling and Synthesis of Near-Field Focused Antenna Arrays

Ayestaran

2019

Electronics

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“…When compared with the conventional focused antennas where a lens is adopted in front of the antenna aperture, the near‐field‐focused (NFF) arrays can realize the similar performance by an appropriate feeding network in such a way that the electromagnetic power density is enhanced in a specific region close to the array. Some figure of merits are adopted to characterize NFF antennas such as the sidelobe level (SLL), the −3‐dB focal spot, the focal shift, and the depth of focus . Particularly, the −3‐dB focal spot characterized by its area represents the region where the electromagnetic energy is congregated at the focal plane parallel to the array and passing through the focal point.…”

Section: Introductionmentioning

confidence: 99%

“…Some figure of merits are adopted to characterize NFF antennas such as the sidelobe level (SLL), the 23-dB focal spot, the focal shift, and the depth of focus. 18,19 Particularly, the 23-dB focal spot characterized by its area represents the region where the electromagnetic energy is congregated at the focal plane parallel to the array and passing through the focal point. The focused power at the focal plane can be basically reflected by the SLL and 23-dB focal spot.…”

Section: Introductionmentioning

confidence: 99%

Impact of amplitude weights on power focusing for near-field-focused planar arrays

Wang

Gao

et al. 2018

Int J RF Microw Comput Aided Eng

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Near‐field‐focused (NFF) arrays have gained great interest owing to its ability to focus the electromagnetic power at a point near to the antenna. The power focusing can basically be reflected by the sidelobe level and the area of the −3‐dB focal spot at the focal plane. For an ordinary NFF array with the given phase tapering, it would be an effective way to realize the changing of focused power by controlling the feeding‐current amplitude of the array element. In this article, the effects of the amplitude weights of array element rings on the power focusing with reference to an original NFF array are investigated to address this issue. The focus is on the power focusing changing introduced by amplitude weights changing of element rings, in which different cases of amplitude weights changing are considered. The results from amplitude weights changing are compared with that from an original amplitude weights combination, and compared among those from different cases of amplitude weights changing.

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“…In addition, compared with the NFF antennas with tapered phase distributions of the radiation sources, far‐field‐focused antennas are with uniform phase distributions of the radiation sources. There are some focal figures of merit adopted to characterize NFF antennas such as the half power beam width (BW), the −3‐dB spot diameter (∆ s ), the sidelobe level (SLL), the focal shift, the depth of focus, and the focusing gain . In particular, the focal shift (FS) is the location deviation between the focal point and the field amplitude peak.…”

Section: Introductionmentioning

confidence: 99%

Impact on focal parameters for near‐field‐focused aperture antennas

Wang

Gao

et al. 2018

Int J Numerical Modelling

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Near‐field‐focused (NFF) antennas have been studied to focus the electromagnetic power in the near‐field (NF) region of the antenna aperture over a long time. Some focal parameters have been adopted to evaluate the focused performance of NFF antennas. Research work on smaller NFF aperture antennas with electrically large size is limited for the similarities between array antennas and aperture ones increasing with their size increasing. It is meaningful to study smaller aperture (several wavelengths) antennas because the physical size of antennas is limited for low‐frequency applications. This paper investigates the impacts of four factors on six focal parameters for NFF aperture antennas when the electrical size is not large enough. The results of six focal parameters are given as functions of the focal distance for different aperture shapes, aperture sizes, and aperture amplitude distributions, respectively. Finally, the differences of two focal parameters between the focal plane and the focal sphere are discussed as well. Unlike the previous work on the scalar diffraction field of NFF aperture antennas using the Fresnel region field approximation, the integral expression of scalar diffraction field is calculated directly and exactly in this paper to produce the focused field at an arbitrarily selected point.

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Near-Field-Focused Microwave Antennas: Near-field shaping and implementation

Cited by 175 publications

References 62 publications

Support Vector Regression for the Modeling and Synthesis of Near-Field Focused Antenna Arrays

Support Vector Regression for the Modeling and Synthesis of Near-Field Focused Antenna Arrays

Impact of amplitude weights on power focusing for near-field-focused planar arrays

Impact on focal parameters for near‐field‐focused aperture antennas

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