Propagation of Electromagnetic Waves Excited by Half-Wave Dipole Antenna in Time-Varying Media

Рассматривается полуволновый диполь с установленным рефлектором, который позволяет производить сканирование пространства с использованием вращения рефлектора вокруг диполя. Для полученной конструкции производилось моделирование основных параметров, которые показали высокую стабильность при различных положениях рефлектора, постоянное значение коэффициента направленного действия, ширины главного лепестка. Изменение направления излучения совпадает с текущим положением рефлектора. По сравнению с ситуацией, когда у антенны отсутствовал рефлектор, КНД антенны увеличился, так как произошла фокусировка электромагнитных волн. Коэффициент полезного действия и передне-заднее отношение сохраняют высокие значения во всем диапазоне рабочих частот. Применение предложенной конструкции позволяет упростить конструкцию сканирующих антенн, так как для ее реализации требуются лишь полуволновой диполь и плоский рефлектор, установленный на малом расстоянии от источника излучения. В процессе управления характеристиками требуется вращать рефлектор вокруг диполя, при этом диполь остается неподвижным, что позволяет повысить эффективность предложенной конструкции, так как не требуется формировать сложных антенных систем или устанавливать комбинацию из нескольких антенн для фокусировки излучения в одном направлении от источника The article discusses a half-wave dipole with an installed reflector, which allows scanning space using the rotation of the reflector around the dipole. For the resulting structure, we simulated the main parameters, which showed high stability at various positions of the reflector, a constant value of the directivity factor, and the width of the main lobe. The change in the direction of radiation coincides with the current position of the reflector. Compared to the situation when the antenna did not have a reflector, the directivity of the antenna increased since the focusing of electromagnetic waves took place. The efficiency and the front-to-back ratio remain high throughout the entire operating frequency range. The use of the proposed design makes it possible to simplify the design of scanning antennas since the implementation of the proposed design requires only a half-wave dipole and a flat reflector installed at a short distance from the radiation source. In the process of controlling the characteristics, it is required to rotate the reflector around the dipole, while the dipole remains stationary, which makes it possible to increase the efficiency of the proposed design, since it is not required to form complex antenna systems or install a combination of several antennas to focus radiation in one direction from the source

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Coding of time-varying signals in spike trains of linear and half-wave rectifying neurons

Network Computation in Neural Systems ◽

10.1080/0954898x.1996.11978655 ◽

1996 ◽

Vol 7 (1) ◽

pp. 61-85 ◽

Cited By ~ 7

Author(s):

Fabrizio Gabbiani

Keyword(s):

Spike Trains ◽

Time Varying ◽

Half Wave

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Design of Broadband Compact Canonical Triple-Sleeve Antenna Operating in UHF Band

Journal of Electromagnetic Engineering and Science ◽

10.26866/jees.2021.4.r.36 ◽

2021 ◽

Vol 21 (4) ◽

pp. 291-298

Author(s):

Chandana SaiRam ◽

Damera Vakula ◽

Mada Chakravarthy

Keyword(s):

Wireless Communication ◽

Instantaneous Frequency ◽

Dipole Antenna ◽

Frequency Range ◽

Broadband Antenna ◽

Operating Frequency Range ◽

Half Wave ◽

Measurement Results ◽

Antenna Configuration ◽

Good Agreement

In this paper, a novel compact broadband antenna at UHF frequencies is presented with canonical shapes. Hemispherical, conical and cylindrical shapes have all been considered for antenna configuration. The designed antenna provides an instantaneous frequency range from 370 to 5,000 MHz with omnidirectional characteristics. The antenna was simulated in CST Microwave Studio, fabricated and evaluated; the results are presented. The simulated and measurement results are in good agreement. The antenna has voltage standing wave ratio (VSWR) ≤ 1.9:1 in 400–570 MHz, 2,530–3,740 MHz and 4,180–4,620 MHz; it has VSWR ≤ 3:1 over the operating frequency range 370–5,000 MHz and the measured gain varies from -0.6 to 4.5 dBi over the frequency band. The concept of canonical-shaped antenna elements and the incorporation of triple sleeves resulted in a reduction of the length of the antenna by 62% compared to the length of a half-wave dipole antenna designed at the lowest frequency. The antenna can be used for trans-receiving applications in wireless communication.

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Efficient and Compact Near-Field Coupled Hybrid Antenna Using a Single Radiating Subwavelength Split-Ring Resonator

Electronics ◽

10.3390/electronics8050527 ◽

2019 ◽

Vol 8 (5) ◽

pp. 527

Author(s):

Zinching Dang ◽

Marco Rahm

Keyword(s):

Resonance Frequency ◽

Electromagnetic Waves ◽

Ring Resonator ◽

Near Field ◽

Low Frequency ◽

Split Ring Resonator ◽

Dipole Antenna ◽

Angular Width ◽

Split Ring ◽

Broadband Internet

Modern applications in the realms of wireless communication and mobile broadband Internet increase the demand for compact antennas with well defined directivity. Here, we present an approach for the design and implementation of hybrid antennas consisting of a classic feeding antenna that is near-field-coupled to a subwavelength resonator. In such a combined structure, the composite antenna always radiates at the resonance frequency of the subwavelength oscillator as well as at the resonance frequency of the feeding antenna. While the classic antenna serves as impedance-matched feeding element, the subwavelength resonator induces an additional resonance to the composite antenna. In general, these near-field coupled structures are known for decades and are lately published as near-field resonant parasitic antennas. We describe an antenna design consisting of a high-frequency electric dipole antenna at f d = 25 GHz that couples to a low-frequency subwavelength split-ring resonator, which emits electromagnetic waves at f SRR = 10.41 GHz. The radiating part of the antenna has a size of approximately 3.2 mm × 8 mm × 1 mm and thus is electrically small at this frequency with a product k · a = 0.5 . The input return loss of the antenna was moderate at − 18 dB and it radiated at a spectral bandwidth of 120 MHz. The measured main lobe of the antenna was observed at 60 ∘ with a − 3 dB angular width of 65 ∘ in the E-plane and at 130 ∘ with a − 3 dB angular width of 145 ∘ in the H-plane.

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The velocity of propagation of electromagnetic waves derived from the resonant frequencies of a cylindrical cavity resonator

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1950.0172 ◽

1950 ◽

Vol 204 (1077) ◽

pp. 260-277 ◽

Cited By ~ 27

Keyword(s):

Electromagnetic Waves ◽

Correction Term ◽

Wave Length ◽

Cavity Resonator ◽

End Effects ◽

Steel Cylinder ◽

A Value ◽

Half Wave ◽

Velocity Of Propagation ◽

Cylindrical Cavity Resonator

The cavity resonator used in this investigation is a silver-plated steel cylinder 6.5 cm. in diameter and of adjustable length. Resonance in the H 011 mode is established at a frequency in the region of 9000 Mc./sec., and the length is then varied to give successive resonances at half wave-length intervals. The wave-length is thus determined and this, together with the frequency, the diameter and a correction term involving the sharpness of resonance, enables the velocity to be calculated. This procedure has some advantage over that used previously by Essen & Gordon-Smith in which the measurements were made with a resonator of fixed dimensions. The wave-length is determined only from differences in length, the first resonant length not being used, and in this way certain end-effects, such as those due to the coupling loops and to surface imperfections, are eliminated or greatly reduced. Moreover, by using different frequencies, or different modes at the same frequency, the diameter can be eliminated from the calculations and a value of c thus obtained in terms of frequency and length both of which can be measured with high precision. The result obtained is 299,792.5 ± 3 km./sec., and is thus in close agreement with that obtained by Essen & Gordon-Smith with a fixed cavity and also with the value of c determined recently by Bergstrand with an optical method.

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Transmission Control of Electromagnetic Waves by Using Quarter-Wave Plate and Half-Wave Plate All-Dielectric Metasurfaces Based on Elliptic Dielectric Resonators

International Journal of Antennas and Propagation ◽

10.1155/2017/8215291 ◽

2017 ◽

Vol 2017 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Ali Yahyaoui ◽

Hatem Rmili ◽

Karim Achouri ◽

Muntasir Sheikh ◽

Abdullah Dobaie ◽

...

Keyword(s):

Numerical Analysis ◽

Electromagnetic Waves ◽

Quarter Wave Plate ◽

Dielectric Resonators ◽

Transmission Control ◽

Half Wave Plate ◽

Wave Plate ◽

Polarized Waves ◽

Half Wave ◽

Quarter Wave

We present the design of all-dielectric Quarter-Wave Plate (QWP) and Half-Wave Plate (HWP) metasurfaces based on elliptic dielectric resonators (EDRs) for the transmission control of electromagnetic waves over the frequency band 20–30 GHz. First, an extensive numerical analysis was realized by studying the effect of the resonators geometry (thickness and ellipticity) on the transmission of both x- and y-polarized waves. Then, based on the numerical analysis, we have realized and characterized experimentally both QWP and HWP all-dielectric metasurfaces.

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