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

1948 ◽  
Vol 194 (1038) ◽  
pp. 348-361 ◽  
Keyword(s):  
Electromagnetic Waves ◽  
Cavity Resonator ◽  
Space Velocity ◽  
Maximum Error ◽  
Internal Diameter ◽  
Experimental Conditions ◽  
Resonant Frequencies ◽  
Half Wave ◽  
Velocity Of Propagation ◽  
Cylindrical Cavity Resonator

The frequency of resonance of an evacuated cavity resonator in the form of a right circular cylinder is given by the formula f = v 0 √[( r/πD ) 2 + ( n /2 L ) 2 ][1-1/2 Q ], in which v 0 is the free-space velocity of electromagnetic waves, D and L are the internal diameter and length respectively of the cylinder, r is a constant for a particular mode of resonance, n is the number of half-wave-lengths in the resonator and Q is the quality factor. Assuming the validity of this equation the value of v 0 can be obtained from measured values of f , D , L and Q . A copper cylinder of diameter approximately 7.4 cm. and length 8.5 cm. was constructed with the greatest uniformity of diameter and squareness of end-faces and its dimensions were measured. The resonant frequencies for a number of different modes were measured and experiments were made to show that the effects on frequency of the coupling probes to the oscillator and detector were negligibly small. It was concluded from these measurements that the most favourable experimental conditions can be obtained for the E 010 and E 011 modes. Final measurements on these gave v 0 = 299,792 km. /sec. The estimated maximum error of the result is 9 km. /sec. (3 parts in 10 5 ). This is the error of a single measurement and, since most of the errors are not necessarily random, little is gained by making a large number of measurements. The value is 16 km. /sec. greater than the recently determined values of the velocity of light, although the results are not in disagreement when the combined limits of accuracy are taken into account.

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

1950 ◽  
Vol 204 (1077) ◽  
pp. 260-277 ◽  
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.

Microwave resonance method for measuring microliter volumes of free moisture in aviation fuels

2020 ◽  
pp. 49-56
Author(s):  
Vitaly V. Volkov ◽  
Michael A. Suslin ◽  
Jamil U. Dumbolov
Keyword(s):  
Solid Surface ◽  
Free Water ◽  
Resonance Method ◽  
Cavity Resonator ◽  
Maximum Error ◽  
Aviation Fuel ◽  
Fuel Quality ◽  
Microwave Resonance ◽  
Free Moisture ◽  
Microwave Losses

One of the conditions for ensuring the safety of air transport operation is the quality of aviation fuel refueled in aircraft. Fuel quality control is a multi-parameter task that includes monitoring the free moisture content. Regulatory documents establish the content of free water no more than 0.0015% by weight. It is developed a direct electrometric microwave resonance method for controlling free moisture in aviation fuels, which consists in changing the shape of the water drops by pressing them on a solid surface inside a cylindrical cavity resonator. This can dramatically increase dielectric losses. Analytical and experimental analysis of the proposed method is carried out. The control range from 0,5 to 30 μl of absolute volume of moisture in aviation fuels with a maximum error of not morethan 25 % is justified. The sensitivity of the proposed method for monitoring microwave losses in free moisture drops transformed into a thin layer by pressing is an order of magnitude greater than the sensitivity of the method for monitoring microwave losses in moisture drops on a solid surface in a resonator. The proposed method can be used as a basis for the development of devices for monitoring the free moisture of aviation fuels in the conditions of the airfield and laboratory. The direction of development of the method is shown.

FORMATION OF A SCANNING ANTENNA BASED ON A HALF-WAVE DIPOLE

2021 ◽  
pp. 20-24
Author(s):  
С.М. Фёдоров ◽  
Е.А. Ищенко ◽  
И.А. Баранников ◽  
К.А. Бердников ◽  
В.В. Кузнецова
Keyword(s):  
Short Distance ◽  
Electromagnetic Waves ◽  
High Stability ◽  
Frequency Range ◽  
Current Position ◽  
Form Complex ◽  
Operating Frequency Range ◽  
Half Wave ◽  
Focus Radiation ◽  
Antenna Systems

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

Modeling and Experimental Validation of a Reed Check Valve for Hydraulic Applications

2016 ◽  
Author(s):  
Anthony L. Knutson ◽  
James D. Van de Ven
Keyword(s):  
Internal Combustion Engines ◽  
Check Valve ◽  
Maximum Error ◽  
Fast Response ◽  
Single Element ◽  
Hydraulic Systems ◽  
Test Bed ◽  
Experimental Conditions ◽  
Wide Range ◽  
Reed Valve

Reed valves are a type of check valve commonly found in a wide range of applications including air compressors, internal combustion engines, and even the human heart. While reed valves have been studied extensively in these applications, published research on the modeling and application of reed valves in hydraulic systems is severely lacking. Because the spring and mass components of a reed valve are contained in a single element, it is light and compact compared to traditional disc, poppet, or ball style check valves. These advantages make reed valves promising for use in high frequency applications such as piston pumps, switch-mode hydraulics, and digital hydraulics. Furthermore, the small size and fast response of reed valves provide an opportunity to design pumps capable of operating at higher speeds and with lower dead volumes, thus increasing efficiency and power density. In this paper, a modeling technique for reed valves is presented and validated in a hydraulic piston pump test bed. Excellent agreement between modeled and experimentally measured reed valve opening is demonstrated. Across the range of experimental conditions, the model predicts the pump delivery with an error typically less than 1% with a maximum error of 2.2%.

A Simple Permittivity Calibration Method for GPR-Based Road Pavement Measurements

Frequenz ◽  
2016 ◽  
Vol 70 (9-10) ◽  
Author(s):  
Pekka Eskelinen
Keyword(s):  
Dielectric Material ◽  
Quality Measurement ◽  
Cavity Resonator ◽  
Calibration Method ◽  
Frequency Range ◽  
Cylindrical Resonator ◽  
Road Pavement ◽  
Asphalt Quality ◽  
Cylindrical Cavity Resonator

AbstractCylindrical resonator principle can be used in GPR asphalt quality measurement calibration. This method relies on ordinary drill core samples that are regularly taken from measured road sections, but now only analyzed for dimensions, density and sometimes chemically. If such a drill sample is covered with proper conductive surfaces, a cylindrical cavity resonator is formed. The baseline of the GPR permittivity recordings can so be found by measuring the resonance behaviour of this covered sample, which can later still be used for those traditional analyses. A clear benefit is the resonator’s 1–2 GHz frequency range which equals that of common commercial GPR systems. Example results and reference readings from known dielectric material are shown. The obtained uncertainty in this case study is 0.02 units of permittivity, when measuring the same sample repeatedly.

Design and Development of Low-Profile Multi-Band Antenna Fed by SIW Cavity Resonator Using Twin Apertures

Frequenz ◽  
2019 ◽  
Vol 73 (7-8) ◽  
pp. 235-243
Author(s):  
Meenakshi Sharma ◽  
Manish Zadoo ◽  
Ashwani Kumar ◽  
Pramod Kumar ◽  
Shailendra Singh
Keyword(s):  
Secure Communication ◽  
Cavity Resonator ◽  
Band Spectrum ◽  
Resonant Frequencies ◽  
Low Profile ◽  
Data Rates ◽  
X Band ◽  
Linearly Polarized ◽  
Novel Design ◽  
Multi Band

Abstract A novel design of compact, linearly polarized and low-profile planar antenna which is electrified by Substrate Integrated Waveguide (SIW) resonator has been developed for multi-band applications of X-band spectrum. Radiating patch has been excited through two closely spaced longitudinal apertures of identical length but non-identical width, incorporated in SIW resonator. These apertures are responsible for multiple operating bands. The achieved fractional bandwidths are 1.29 %, 0.49 % and 1.60 % having resonant frequencies at 10.07 GHz, 10.85 GHz and 11.82 GHz respectively for |S11| ≤ -10 dB. The measured peak gain for first, second and third operating band is 6.54 dB, 6.86 dB and 7.68 dB respectively. The proposed antenna is a highly selective antenna for various applications of X-band microwave spectrum. This band has been particularly selected for military communication because it provides a trade-off between the characteristics (i. e. interference and rain resilience, data rates and remote coverage) of different frequency bands which are particularly suited to the needs of military users. It is very much suitable for secure communication i. e. to deny unauthorized access to sensitive unclassified information and prevent disruption of telecommunication. A comparative analysis of antenna’s parameters has been examined by Ansys HFSS and results are verified through experimental outcomes.

scholarly journals Differential Pulse Polarographic Determination of Procymidone in Formulations and Wine

2002 ◽  
Vol 85 (3) ◽  
pp. 731-735 ◽  
Author(s):  
Neelam Y Sreedhar ◽  
Thommandru R Babu ◽  
Kethamreddy Samatha ◽  
Devarapalli Sujatha ◽  
Thenepalli Thriveni
Keyword(s):  
Reduction Process ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Experimental Conditions ◽  
Controlled Potential Electrolysis ◽  
Pulse Polarography ◽  
Half Wave ◽  
Single Well ◽  
Controlled Potential ◽  
Ph Range

Abstract The dicarboximide fungicide procymidone was studied systematically by using direct current polarography, cyclic voltammetry, differential pulse polarography (DPP), controlled potential electrolysis, and millicoulometry in the universal buffer medium with dimethylformamide as the solvent. Procymidone exhibited a single well-defined polarographic wave in the pH range 2.0–6.0, leading to the formation of the hydroxy compound. The overall reduction process was diffusion-controlled and adsorption-free. The variation of half-wave potential with pH, the concentration of the analyte, and other experimental conditions are described. The reduction mechanism proposed is an overall 4-electron process, in which the dicarboximide group is reduced. DPP was used to determine procymidone in agricultural formulations and wine at the optimum conditions found; a detection limit of 2.4 × 10−9M was estimated. The results obtained by the proposed method were also compared with those obtained by other methods.

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

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
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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