An Inhomogeneously Filled Rectangular Waveguide Capable of Supporting TEM Propagation (Correspondence)

Heeren, R.G.; Baird, J.R.

doi:10.1109/tmtt.1971.1127660

Cited by 15 publications

(3 citation statements)

References 4 publications

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“…One well-known solution to this problem is the dielectric slab loaded rectangular waveguide (TEM waveguide). A number of researchers have analyzed, designed and used this waveguide structure for various applications [3,4,5,6,7]. Such a TEM waveguide could guarantee the product to be exposed uniformly but the high-permittivity dielectric slabs add extra weight and may be quite expensive.…”

Section: Toward a Uniform E-field Waveguidementioning

confidence: 99%

Metal waveguides with uniform electric field distributions

Zhou

Joines

2008

2008 IEEE Antennas and Propagation Society International Symposium

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Section: Toward a Uniform E-field Waveguidementioning

confidence: 99%

Metal waveguides with uniform electric field distributions

Zhou

Joines

2008

2008 IEEE Antennas and Propagation Society International Symposium

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“…In a previous study [18], the position of the standing wave was changed by moving the short-circuit plate attached to a waveguide in the range of 𝜆 g /4 to make the time-averaged irradiation energy uniform. In another study [19], a square waveguide was partially filled with a dielectric to create a uniform electric field distribution by generating transverse electromagnetic (TEM) modes [20], and the resulting apparatus was applied to microwave heating. The challenges this approach poses, however, are the need for an object with an optimal dielectric constant and the large losses in the dielectric.…”

Section: Introductionmentioning

confidence: 99%

Uniform Microwave Heating via Electromagnetic Coupling Using Zeroth-Order Resonators

TAKAHARA,

MITANI,

SHINOHARA

2024

IEICE Trans. Electron.

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We propose microwave heating via electromagnetic coupling using zeroth-order resonators (ZORs) to extend the uniform heating area. ZORs can generate resonant modes with a wavenumber of 0, which corresponds to an infinite guide wavelength. Under this condition, uniform heating is expected because the resulting standing waves would not have nodes or antinodes. In the design proposed in this paper, two ZORs fabricated on dielectric substrates are arranged to face each other for electromagnetic coupling, and a sample placed between the resonators is heated. A single ZOR was investigated using a 3D electromagnetic simulator, and the resonant frequency and electric field distribution of the simulated ZOR were confirmed to be in good agreement with those of the fabricated ZOR. Simulations of two ZORs facing each other were then conducted to evaluate the performance of the proposed system as a heating apparatus. It was found that a resonator spacing of 25 mm is suitable for uniform heating. Heating simulations of SiC and Al 2 O 3 sheets were performed with the obtained structure. The heating uniformity was evaluated by the width 𝐿 50% over which the power loss distribution exceeds half the maximum value. This evaluation index was equal to 0.397𝜆 0 for SiC and 0.409𝜆 0 for Al 2 O 3 , both of which exceed 𝜆 0 /4, the distance between a neighboring node and antinode of a standing wave, where 𝜆 0 is the free-space wavelength. Therefore, the proposed heating apparatus is effective for uniform microwave heating. Because of the different electrical parameters of the heated materials, SiC can be easily heated, whereas Al 2 O 3 heats little. Finally, heating experiments were performed on each of these materials. Good uniformity in temperature was obtained for both SiC and Al 2 O 3 sheets.

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“…While microwave heating is known for its ability to improve the efficiency and quality of a variety of applied thermal processes, the intrinsic non-uniformity of microwave-induced temperature fields remains a central challenge in designing many practical applicators. Numerous techniques aiming to homogenize temperature distribution have been reported, (Heeren and Baird, 1971; Kashyap and Wyslouzil, 1977; Bernhard and Joines, 1996; Chan and Reader, 1996; Bradshaw et al , 1997; Wäppling-Raaholt and Ohlsson, 2000; Dincov et al , 2004; Domínguez-Tortajada et al , 2005; Wäppling-Raaholt and Ohlsson, 2005; Wäppling-Raaholt et al , 2006; Cordes and Yakovlev, 2007; Domínguez-Tortajada et al , 2007; Geedipalli et al , 2007; Pedreño-Molina et al , 2007; Basak and Badri, 2011; Koskiniemi et al , 2011; Liao et al , 2016; Wäppling-Raaholt et al , 2016). It has also been shown (Lurie and Yakovlev, 2002) that the method of optimal material design can be used to determine the position and micro-geometry of composite dielectric layers that bring the electric field of the dominant mode within a rectangular dielectric prizm closest to uniformity.…”

Section: Introductionmentioning

confidence: 99%

Computer-aided design of a dielectric insert supporting uniformity of fast microwave heating

Moon¹,

Yakovlev

2018

COMPEL

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Purpose This paper aims to introduce and illustrate a computational technique capable of determining the geometry and complex permittivity of a supplementary dielectric insert making distributions of microwave-induced dissipated power within the processed material as uniform as possible. Design/methodology/approach The proposed technique is based on a 3D electromagnetic model of the cavity containing both the processed material and the insert. Optimization problem is formulated for design variables (geometrical and material parameters of the insert) identified from computational tests and an objective function (the relative standard deviation [RSD]) introduced as a metric of the field uniformity. Numerical inversion is performed with the method of sequential quadratic programming. Findings Functionality of the procedure is illustrated by synthesis of a dielectric insert in an applicator for microwave fixation. Optimization is completed for four design variables (two geometrical parameters, dielectric constant and the loss factor of the insert) with 1,000 points in the database. The best three optimal solutions provide RSD approximately 20 per cent, whereas for the patterns corresponding to all 1,000 non-optimized (randomly chosen) sets of design variables this metric is in the interval from 27 to 136 per cent with the average of 78 per cent. Research limitations/implications As microwave thermal processing is intrinsically inhomogeneous and the heating time is not a part of the underlying model, the procedure is able to lead only to a certain degree of closeness to uniformity and is intended for applications with high heating rates. The initial phase of computational identification of design variables and their bounds is therefore very important and may pre-condition the “quality” of the optimal solution. The technique may work more efficiently in combination with advanced optimization techniques dealing with “smart” (rather than random) generation of the data; for the use with more general microwave heating processes characterized by lower heating rates, the technique has to use the metric of non-uniformity involving temperature and heating time. Practical implications While the procedure can be used for computer-aided design (CAD) of microwave applicators, a related practical limitation may emerge from the fact that the material with particular complex permittivity (determined in the course of optimization) may not exist. In such cases, the procedure can be rerun for the constant values of material parameters of the available medium mostly close to the optimal ones to tune geometrical parameters of the insert. Special manufacturing techniques capable of producing a material with required complex permittivity also may be a practical option here. Originality/value Non-uniformity of microwave heating remains a key challenge in the design of many practical applicators. This paper suggests a concept of a practical CAD and outlines corresponding computational procedure that could be used for designing a range of applied systems with high heating rates.

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An Inhomogeneously Filled Rectangular Waveguide Capable of Supporting TEM Propagation (Correspondence)

Cited by 15 publications

References 4 publications

Metal waveguides with uniform electric field distributions

Metal waveguides with uniform electric field distributions

Uniform Microwave Heating via Electromagnetic Coupling Using Zeroth-Order Resonators

Computer-aided design of a dielectric insert supporting uniformity of fast microwave heating

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