scholarly journals Specific Resonant Properties of Non-Symmetrical Microwave Antennas

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 939
Author(s):  
Ján Labun ◽  
Pavol Kurdel ◽  
Alexey Nekrasov ◽  
Mária Gamcová ◽  
Marek Češkovič ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Measurement Process ◽  
Microwave Antenna ◽  
Experimental Measurements ◽  
Constant Parameter ◽  
Microwave Antennas ◽  
Resonance Parameters ◽  
Series Resonant ◽  
Scale Models ◽  
Modernization Process

The aircraft avionics modernization process often requires optimization of the aircraft itself. Scale models of aircraft and their antennas are frequently used to solve this problem. Here we present interesting properties of the resonant antennas, which were discovered serendipitously during the measurement process of some microwave antennas’ models as part of an aircraft modernization project. Aircraft microwave antennas are often designed as non-symmetric flat microwave antennas. Due to their thin, low and longitudinally elongated outer profile, they are also called tail antennas. An analysis of the resonant properties of non-symmetric antennas was performed in the band from 1 GHz to 4 GHz. The length of the antenna models ranged from 2 cm to 7 cm. The width of the antennas, together with the thickness of the strip, was always a constant parameter for one measured set of six antennas. In the measurement and subsequent analysis, attention was focused on the first-series resonant frequency (λ/4) of each antenna. During the evaluation of the resonance parameters, the flat microwave antenna models showed specific resonant properties different from those of conventional cylindrical microwave antennas. This article aims to inform professionals about these unknown specific properties of non-symmetrical antennas. The results of experimental measurements are analyzed theoretically and then visually compared using graphs so that the reader can more easily understand the properties observed. These surprising observations open up some new possibilities for the design, implementation, and use of flat microwave antennas, as found in modern aircraft, automobiles, etc.

scholarly journals A MEMS Fabrication Process with Thermal-Oxide Releasing Barriers and Polysilicon Sacrificial Layers for AlN Lamb-Wave Resonators to Achieve fs·Qm > 3.42 × 1012

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 892
Author(s):  
Jicong Zhao ◽  
Zheng Zhu ◽  
Haiyan Sun ◽  
Shitao Lv ◽  
Xingyu Wang ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Lamb Wave ◽  
Piezoelectric Layer ◽  
Sacrificial Layer ◽  
High Quality ◽  
Micro Electro Mechanical Systems ◽  
Mems Fabrication ◽  
Thermal Oxide ◽  
Series Resonant ◽  
Releasing Process

This paper presents a micro-electro-mechanical systems (MEMS) processing technology for Aluminum Nitride (AlN) Lamb-wave resonators (LWRs). Two LWRs with different frequencies of 402.1 MHz and 2.097 GHz by varying the top interdigitated (IDT) periods were designed and fabricated. To avoid the shortcomings of the uncontrollable etching of inactive areas during the releasing process and to improve the fabrication yield, a thermal oxide layer was employed below the platted polysilicon sacrificial layer, which could define the miniaturized release cavities well. In addition, the bottom Mo electrode that was manufactured had a gentle inclination angle, which could contribute to the growth of the high-quality AlN piezoelectric layer above the Mo layer and effectively prevent the device from breaking. The measured results show that the IDT-floating resonators with 12 μm and 2 μm electrode periods exhibit a motional quality factor (Qm) as high as 4382 and 1633. The series resonant frequency (fs)·Qm values can reach as high as 1.76 × 1012 and 3.42 × 1012, respectively. Furthermore, Al is more suitable as the top IDT material of the AlN LWRs than Au, and can contribute to achieving an excellent electrical performances due to the smaller density, smaller thermo-elastic damping (TED), and larger acoustic impedance difference between Al and AlN.

scholarly journals On the Practical Evaluation of the Switching Loss in the Secondary Side Rectifiers of LLC Converters

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5915
Author(s):  
Manuel Escudero ◽  
Matteo-Alessandro Kutschak ◽  
Francesco Pulsinelli ◽  
Noel Rodriguez ◽  
Diego Pedro Morales
Keyword(s):  
Resonant Frequency ◽  
High Voltage ◽  
Low Voltage ◽  
Hysteresis Loss ◽  
Resonant Converters ◽  
Switching Loss ◽  
Operating Modes ◽  
Switching Losses ◽  
Series Resonant ◽  
Secondary Side

The switching loss of the secondary side rectifiers in LLC resonant converters can have a noticeable impact on the overall efficiency of the complete power supply and constrain the upper limit of the optimum switching frequencies of the converter. Two are the main contributions to the switching loss in the secondary side rectifiers: on the one hand, the reverse recovery loss (Qrr), most noticeably while operating above the series resonant frequency; and on the other hand, the output capacitance (Coss) hysteresis loss, not previously reported elsewhere, but present in all the operating modes of the converter (under and above the series resonant frequency). In this paper, a new technique is proposed for the measurement of the switching losses in the rectifiers of the LLC and other isolated converters. Moreover, two new circuits are introduced for the isolation and measurement of the Coss hysteresis loss, which can be applied to both high-voltage and low-voltage semiconductor devices. Finally, the analysis is experimentally demonstrated, characterizing the switching loss of the rectifiers in a 3 kW LLC converter (410 V input to 50 V output). Furthermore, the Coss hysteresis loss of several high-voltage and low-voltage devices is experimentally verified in the newly proposed measurement circuits.

Behaviour of the series resonant frequency in electrolyte solutions

2006 ◽  
Vol 115 (2) ◽  
pp. 567-574 ◽  
Author(s):  
Pedro J. Lamas-Ardisana ◽  
A. Costa-García
Keyword(s):  
Resonant Frequency ◽  
Electrolyte Solutions ◽  
Series Resonant

scholarly journals Peter John Bell Clarricoats. 6 April 1932—17 January 2020

2021 ◽  
Author(s):  
Christopher Snowden ◽  
Yang Hao
Keyword(s):  
Optical Waveguides ◽  
Academic Career ◽  
Vice President ◽  
Gold Medal ◽  
Advisory Council ◽  
Microwave Antenna ◽  
Electromagnetic Propagation ◽  
Microwave Antennas ◽  
Radio Science ◽  
Applied Electromagnetics

Peter Clarricoats made fundamental contributions as a microwave engineer in the fields of applied electromagnetics for microwave and optical waveguides, and microwave antenna feeds. Peter was also a pioneer of optical fibres, and established the theory of electromagnetic propagation on dielectric and ferrite structures. In the course of this, he discovered that such structures can, under some conditions, support ‘backward waves’ and that guides can propagate complex modes. Over 40 years of his academic career, Peter Clarricoats had numerous notable achievements, including pioneering designs for shaped reflectors, reconfigurable reflectors and especially corrugated horns for microwave antennas. The latter are now universally used in satellite ground stations and in spacecraft. He published what became standard reference texts on corrugated horns for microwave antennas, microwave horns and feeds. He served as vice-president of both the Institution of Engineering and Technology and the International Union of Radio Science, and from 1998 to 2000 was chairman of the Defence Scientific Advisory Council. He was appointed a CBE in 1996. He is the recipient of the 2001 Distinguished Achievement Award of the Institute of Electrical and Electronics Engineers Antennas and Propagation Society, and in 2015 he received the Sir Frank Whittle Gold Medal from the Royal Academy of Engineering.

BISMUTH NIOBATE-BASED GLASS-CERAMICS FOR DIELECTRICALLY LOADED MICROWAVE ANTENNAS

2008 ◽  
Vol 01 (01) ◽  
pp. 25-30 ◽  
Author(s):  
MEHDI MIRSANEH ◽  
BEATA ZALINSKA ◽  
OLIVER P. LEISTEN ◽  
IAN M. REANEY
Keyword(s):  
Heat Treatment ◽  
Resonant Frequency ◽  
Glass Ceramic ◽  
Heat Treatment Temperature ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
Ceramic Processing ◽  
Ceramic System ◽  
Microwave Antennas ◽  
Microwave Applications

A castable, low melting temperature glass-ceramic system (30% Bi 2 O 3, 30% Nb 2 O 5, 30% B 2 O 3 and 10% SiO 2, in mol%) suitable for microwave applications is fabricated and characterized. Depending on heat treatment temperature, the glass ceramic exhibits permittivity, 15 ≤ ε r ≤ 41, temperature coefficient of resonant frequency of -160 ≤ τ f ≤ +100 MK -1 and microwave quality factor of 300 GHz ≤ Qf ≤ 15000 GHz . The highest Qf occurs at 960°C heat treatment with ε r = 15, τ f = -80 MK -1 and Qf = 15000 GHz . Applications are envisaged such as castable dielectrically-loaded antenna pucks, removing the need for complex ceramic processing.

scholarly journals Application of metamaterials for the microwave antenna realizations

2012 ◽  
Vol 9 (1) ◽  
pp. 1-7
Author(s):  
Tatjana Asenov ◽  
Nebojsa Doncov ◽  
Bratislav Milovanovic
Keyword(s):  
Microwave Antenna ◽  
Gradient Index ◽  
Microwave Antennas ◽  
Lens Antennas ◽  
Left Handed

In this paper, the application of left-handed metamaterials for the realization of microwave antennas has been considered. Special emphasis is placed on lens antennas based on gradient-index metamaterials, and their advantages and enhanced features in comparison with conventional microwave antennas are highlighted.

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