Subwavelength elastic joints connecting torsional waveguides to maximize the power transmission coefficient

The measurement, monitoring of heartbeat and its rate are necessary to know the health of the heart of human beings. In addition, they are needed for extended applications like criminal investigation, law enforcement, defense and military usage, search, rescue operation, etc. The ultra-wideband (UWB) radars found growing interest in recent years as they are able to overcome the limitations of continuous-wave (CW) Doppler radars in detecting human heartbeat. Modeling and analysis of the UWB pulse propagation behavior through a human body is important before developing a practical UWB radar. Several researchers have estimated the reflected signals to study if their variations correlate with the heartbeat rate. However, the reflected signal strength carrying Doppler information received at the radar after a two-way propagation of the RF signal was found to be too weak for detection. This paper presents (i) a model for UWB wave propagation through a human thorax and (ii) estimation via simulation, of transmission coefficient at various frequencies in the UWB range 1–10[Formula: see text]GHz using CST Microwave Studio. The study clearly indicates that the variation of power transmission coefficient of UWB signal has a strong correlation to the instantaneous dimension of the heart in a cardiac cycle, a feature that can be exploited in detecting cardiac activity of human being using radar-based principles.

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Methods for synthesis of matching circuits for broadband radio devices with unstable load impedance

Doklady BGUIR ◽

10.35596/1729-7648-2021-19-1-61-69 ◽

2021 ◽

Vol 19 (1) ◽

pp. 61-69

Author(s):

I. A. Dubovik ◽

P. V. Boykachev ◽

V. O. Isaev ◽

A. A. Dmitrenko

Keyword(s):

Transfer Coefficient ◽

Power Transmission ◽

Synthesis Method ◽

Synthesis Methods ◽

Power Transfer ◽

Load Impedance ◽

Advantages And Disadvantages ◽

Power Transmission Coefficient ◽

Broadband Matching ◽

Comparison Of The Results

The aim of this work is to select a synthesis method for a broadband matching circuit that provides maximum power transfer from a signal source to a load in the presence of a changing load impedance of a radio engineering device. To achieve this goal, an analysis of the main directions of designing broadband matching circuits (analytical, numerical, graphic-analytical synthesis methods) was carried out. Based on the results of a comparison of synthesis methods, their features (advantages and disadvantages) were indicated. The analysis of methods of synthesis of broadband matching circuits was carried out. For the analysis, the generalized Darlington method, the method of real frequencies, the structural-parametric synthesis method based on the T-matrix apparatus, and the graphic-analytical method based on the Volpert-Smith diagram were chosen). Using these synthesis methods, broadband matching circuits were obtained for various types of loads. Comparison of the results obtained was carried out according to several indicators: the level of the power transfer coefficient in the operating frequency range, the sensitivity of the power transfer coefficient to the change in the ratings of the elements of the matching circuit and the load impedance, provided that the number of elements of the matching circuit is no more than six. Based on the comparison and analysis, it was found that the most preferable synthesis method for solving the problem posed is the method of real frequencies. Its advantage is the use of a combination approach (iterative determination of the parameters of the resistance function with an analytical representation of the transfer function). Matching circuits obtained using this synthesis method provided the highest level of power transmission coefficient, as well as the lowest sensitivity value in a given frequency band for the considered types of loads.

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Optimization of sound transmission loss of open acoustic barriers with respect to unit cell topology

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406221991579 ◽

2021 ◽

pp. 095440622199157

Author(s):

Nan Li ◽

Mabrouk Ben Tahar ◽

Fusheng Sui

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Power Transmission ◽

Transmission Loss ◽

Design Method ◽

Sound Transmission ◽

Unit Cell ◽

Sound Transmission Loss ◽

Power Transmission Coefficient ◽

Element Method

Open acoustic barriers exhibit excellent sound transmission reduction property at a certain frequency/frequencies which highly depends on the configuration of its unit cell. Design of unit cell configuration for minimum sound transmission at predefined objective frequency remains an open question. This paper aims at providing an automatic design method for open acoustic barriers with multi-material unit cell. Firstly, a wave finite element method is developed to calculate the sound transmission through an infinite array of periodic scatterers. As the unit cell contains infinite fluid domain, the application of Floquet-Bloch theorem to the boundaries of perfectly match layers (PML) is necessary and has been resolved in this paper. This wave finite element method with the implementation of PML is validated by comparing to analytical solution of sound transmission through an array of steel cylinders. Then a genetic algorithm is employed to optimize the sound transmission loss with respect to material distribution of a bi-material unit cell. Finally, the effectiveness of this inverse design is demonstrated by examples with different predefined frequencies. Corresponding unit cell typologies are obtained and the dips of sound power transmission coefficient curve are successfully tuned to objective frequencies.

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Dynamic Transmission Performances of Alumina and Mullite Refractory Ceramics in Microwave High-Temperature Heating

High Temperature Materials and Processes ◽

10.1515/htmp-2014-0167 ◽

2016 ◽

Vol 35 (1) ◽

pp. 113-119 ◽

Cited By ~ 4

Author(s):

Xiaobiao Shang ◽

Junruo Chen ◽

Jinhui Peng

Keyword(s):

Microwave Heating ◽

Power Transmission ◽

Peak Shift ◽

Transmission Peak ◽

Temperature Range ◽

Microwave Transmission ◽

Power Transmission Coefficient ◽

Mullite Refractory ◽

Refractory Ceramics ◽

Temperature Heating

AbstractThis paper proposes an analytical approach to optimize the thickness of refractories for achieving maximum microwave power transmission in microwave heating based on the analysis of power transmission coefficient (PTC). The microwave PTCs of alumina (Al2O3) ceramics over the temperature range of 22–1,379°C at 2,450 MHz, mullite ceramics in the temperature range of 27–1,027°C at 2.45 GHz and 400–1,300°C at 915 MHz are studied. The results show that there are several transmission peaks in the PTC patterns. The transmission peak amplitude depends sensitively on the thickness of the refractory and the peak shifting towards a smaller thickness as the temperature of the refractory increases. We also show that high microwave transmission can only be achieved in a refractory with a small thickness corresponding to a slight transmission peak shift in the entire microwave heating (less than one eighth wavelength in the refractory).

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