Abstract
This paper aims to propose an online relative complex permittivity measurement system at high temperature based on microwave interferometer. A ridge waveguide with a TE10 mode was used in which the sample was heated and measured simultaneously at a frequency of 2450 MHz, and the microwave interferometer is used to collect the amplitude and phase difference of the incident signal. The Extreme Gradient Boosting (XGBoost) algorithm trained by the corresponding simulation data is used to construct the inversion model to calculate the complex dielectric coefficient of the tested material. Besides, this paper uses linear regression algorithm (LR) to calibrate the measurement system in order to improve the measurement accuracy. The entire system was tested using different materials at room temperature, and the maximum error of the measurement accuracy is less than 8% compared to the theoretical data. The robustness of the entire system was also tested by measuring Macor materials up to 800 °C. This proposed method provides an effective way to understand the mechanism between microwaves and matter at high temperatures.
Highlights
The dielectric property of material mainly relies on the frequency and temperature
This paper proposes an on-line temperature relative complex permittivity measurement system at the frequency of 2450 MHz based on microwave interferometer
When XGBoost algorithm is used to inverse the dielectric properties, it often encounters multi-value problems, which means that different relative complex it often encounters multi-value problems, which means that different relative complex dielectric dielectric coefficients correspond to the same S parameters
Summary
The dielectric property of material mainly relies on the frequency and temperature. In the high power application of microwaves, the microwave frequency is usually fixed, and the interaction between microwaves and matter at different temperature, especially high temperature, should be investigated [1,2,3,4,5]. In the microwave heating process, thermal runaway always happens. It is essential to study the complex permittivity of matter at high temperature in order to avoid the issue of thermal runaway and guide the design of the microwave equipment [6]. The measurement of relative permittivity of materials in high temperature environment has very important requirements in the fields of aerospace, metallurgy, and chemical industry [7,8,9,10,11,12]. When designing the radome, it is necessary to measure the relative complex permittivity of the material of the radome in the high temperature range to ensure that the temperature does not affect the transmission of electromagnetic waves when the temperature rises.
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