High-Temperature Measurement Technology for Microwave Surface Resistance of Metal Materials

Abstract

The resonant cavity method is a commonly used method for high-temperature testing of the complex permittivity of dielectric materials. When a resonant cavity is used for high-temperature testing, the microwave surface resistance of the cavity metal material will deteriorate due to factors such as oxidation reaction and thermal fatigue, resulting in a decrease in testing accuracy and repeatability. Therefore, when designing a high-temperature resonant cavity, the temperature response characteristics of the microwave surface resistance of the cavity metal material should be obtained in advance. In this paper, a high-temperature measurement method of microwave surface resistance of metal materials based on a separate cylindrical resonator is proposed, a mathematical model of microwave surface resistance inversion based on the resonator quality factor is established, and a high-temperature measurement system of microwave surface resistance is integrated. The reliability of the proposed method and system is verified through simulation and experiment. The measurement frequency covers 7-18 GHz, and the maximum test temperature reaches 500°C. Systematic error of microwave surface resistance measurement at room temperature is less than 3%.

Radio-Frequency Conductivity Evaluation Method Based on Surface/Interface Scattering of Metallic Coatings

“…The raw data obtained from Matlab software represent the Q factor of the testing system at a specific measured frequency point. The procedure of calculating the RF conductivity from the Q factor is outlined as follows [20,[31][32][33]:…”

“…The resonant cavity testing method is non-destructive and consists of an adjustable measurement field and adjustable frequency testing for conductive coating [18][19][20]. Numerous studies have shown that, by adjusting the dimensions and coupling structures of the resonant cavity, it is possible to evaluate the conductivity of coatings with different sizes and thicknesses.…”