A dynamic impedance matching algorithm of three-stub tuners based on equivalent circuit analysis

Lai, Shimiao; Qiao, Juan; Rasool, Nouman; Li, Kang; Zhu, Huacheng; Yang, Yang

doi:10.1080/08327823.2020.1838051

Cited by 13 publications

(4 citation statements)

References 14 publications

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“…In [23], an automatic impedance matching system of a four-stub waveguide was proposed, which can make |S 11 | lower than −30 dB based on an iterative algorithm. In [24], a dynamic impedance matching algorithm of three-stub tuners based on equivalent circuit analysis was proposed. The S-parameters of the equivalent circuit were calculated using the analysis method of the stub waveguide, and the calculation formulas of the port reflection coefficient and external load were deduced to achieve real-time matching of dynamic loads.…”

Section: Introductionmentioning

confidence: 99%

A Low-Reflection Tuning Strategy for Three-Stub Waveguides

Liu,

Lai,

Hong

et al. 2024

Electronics

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In high-power microwave applications, the reflection of energy can be effectively reduced by adjusting the three-stub waveguide. However, most of the existing tuning algorithms do not make an arrangement for the adjustment sequence of stubs, and accurately calculating the depth of the stubs requires a great deal of time via electromagnetic (EM) simulations, which may cause large reflection in the matching process. To solve these problems, we first propose an improved calculation method that can accurately calculate the input impedance of a three-stub waveguide. Then, an impedance matching algorithm is designed based on the equivalent circuit model that can quickly and accurately calculate the optimal depth of the stubs. Finally, we present a low-reflection tuning strategy to suppress the large reflection during the adjustment of the stub process. An experimental system is built to verify the calculation method and the tuning strategy. The results show that the strategy can avoid large reflection in the case of load mutation and can maintain low reflection when the load changes continuously. The algorithm meets the needs of the industry and can be used for automatic and real-time adjustment of three-stub waveguides of different specifications.

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Section: Introductionmentioning

confidence: 99%

A Low-Reflection Tuning Strategy for Three-Stub Waveguides

Liu,

Lai,

Hong

et al. 2024

Electronics

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“…Lai et al designed a dynamically adjustable threestub tuner to track the impedance. 21 However, total reflection may occur during the tuning process, posing a risk of damaging the device. Chen et al established an impedance-matching structure of three dielectric plates between the heating object and the microwave generator to improve the microwave heating efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…As such, impedance-matching techniques have been suggested to enhance the heating efficiency of loads with varying dielectric constants. Lai et al designed a dynamically adjustable three-stub tuner to track the impedance . However, total reflection may occur during the tuning process, posing a risk of damaging the device.…”

Section: Introductionmentioning

confidence: 99%

Continuous-Flow Microwave Reactor for High-Performance Heating of a Dynamic Chemical Reaction System

Yang,

Xia,

Tian

et al. 2023

Ind. Eng. Chem. Res.

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Continuous-flow microwave reactors find widespread application in chemical production. However, dynamic changes in the dielectric constant of reactants result in a low microwave energy efficiency. This paper reveals a circular waveguide developed using a meta-surface unidirectional propagation of microwaves. This waveguide was integrated into a continuous-flow heating system that efficiently heats materials with varying dielectric constants. A multiphysics model incorporating electromagnetic, fluid heat transfer, and chemical engineering has been built to analyze the microwave heating performance under different loads. Based on simulation and experimental findings, the meta-surface can achieve an energy efficiency of over 90% for loads with dielectric constants from 10 to 80. Moreover, a continuous-flow heating experiment conducted for biodiesel production indicated that meta-surfaces can enhance the heating efficiency by over a quarter. This research presents a promising approach toward efficient continuous-flow microwave heating, which can potentially revolutionize large-scale chemical production in industry.

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“…A key note from this plot was the very early occurrence of t res when the system is optimised for low temperature heating (orange line, highly optimised to maximise heat transfer to the ironsand, or for temperature control within the cavity. Automatic impedance matching algorithms have been proposed [100], demonstrating the ability to automatically tune the three-stub tuner stubs to maximise power transfer to a load. This works regardless of the load's electronic properties and could find an implementation in further work.…”

Section: High Temperature Stub Optimisationmentioning

confidence: 99%

Design and optimisation of a laboratory scale microwave furnace for heating titanomagnetite ironsand

Markwitz¹

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TTM (Titanomagnetite) ironsand is an abundant source of iron oxide on the western beaches of the Waikato and Auckland regions in New Zealand, with chemical formula TixFe3-xO4 (x=0.27). This ironsand has been used for the last four decades to produce steel in New Zealand, but the reduction process releases large amounts of carbon dioxide. This is because coal is used as the primary reducing agent. Using hydrogen gas instead as a reducing agent, it is possible to reduce ironsand while avoiding the excessive production of carbon dioxide. In addition, standard electrical heating methods are generally limited by low power transfer rates to the steelmaking reactants. Microwave heating is an alternative heating method, shown to be good candidate for ironsand heating via direct power transfer to the NZ ironsand itself due to its excellent microwave absorbing features. This research focuses on modelling the dynamics of microwave power transfer in a resonant microwave cavity, and refines a computational model to improve the modelling capability of such a process. Microwave heating is known to demonstrate high direct power transfer rates to microwave absorbing materials, such as TTM ironsand. The microwave heating of ironsand as a candidate heating method is shown in this work by the optimisation of the resonant performance of a custom-built laboratory scale microwave cavity to heat ironsand to over 1000 C. The microwave furnace developed in this work was specifically designed to mimic the contemporary steelmaking standards (i.e., a continuous throughput furnace). A microwave furnace was designed with a computational model, then built and tested in a laboratory. Measurements tracking various energy fluxes throughout the furnace refined an initial transient microwave heating simulation of the computational model with a simple experimental procedure, which exploits the significant variation of the real permittivity (εr) of the ironsand at T = 430 C. From that experimental procedure, a significant variation in microwave absorption was observed as the ironsand passed through its Curie temperature. This effect was reproduced in an initial transient microwave heating simulation. Experimental results were then used to improve simulation accuracy. This encourages further refinement of the computational model as an avenue for future work in this field. In summary, this research demonstrates the feasibility of designing a microwave furnace for efficiently heating TTM ironsand. It also exhibits the feasibility of simulating microwave heating of TTM ironsand with a computational model. The results from this thesis show promise for further study on the hydrogen reduction of TTM ironsand within a microwave furnace. The findings therein present results which ‘set the scene’ for for larger-scale zero-CO2 production of techno-economically essential materials via microwave heating.

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A dynamic impedance matching algorithm of three-stub tuners based on equivalent circuit analysis

Cited by 13 publications

References 14 publications

A Low-Reflection Tuning Strategy for Three-Stub Waveguides

A Low-Reflection Tuning Strategy for Three-Stub Waveguides

Continuous-Flow Microwave Reactor for High-Performance Heating of a Dynamic Chemical Reaction System

Design and optimisation of a laboratory scale microwave furnace for heating titanomagnetite ironsand

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