SIW-based portable liquid dielectric constant measurement system

Abstract

The present invention discloses a SIW-based portable liquid dielectric constant measurement system. The system uses a traditional resonant cavity perturbation method as a measurement method and extracts the dielectric constant information of the liquid through a phase-locked loop circuit in connection with a feedback voltage-controlled oscillator based on a substrate integrated waveguide SIW resonator, wherein the SIW resonator places the to-be-measured liquid by inserting a quartz transistor in the middle; the relationship between the oscillation frequency deviation and the dielectric constant is extracted based on the feedback voltage-controlled oscillator in connection with the SIW; finally, the deviation of the oscillation frequency is converted into the voltage deviation through the phase-locked loop circuit, thereby measuring the information of the dielectric constant by simply measuring the voltage signal. Compared with the existing resonant cavity measurement technology that the dielectric constant can be only measured by depending on a vector network analyzer, the SIW-based portable liquid dielectric constant measurement system in the invention eliminates the dependence onlarge experimental equipment under the premise of ensuring accuracy and greatly reduces the cost of measurement.

Description

technical field [0001] The invention belongs to the technical field of microwave and millimeter wave circuits and intelligent sensing, and proposes a portable liquid dielectric constant measurement system that is independent of vector network analyzers. Background technique [0002] The measurement of material permittivity has attracted more and more attention due to its potential application value in aerospace, new material development, gas-liquid monitoring, and biomedicine. Among them, the medium detection method based on microwave technology has become more and more popular in recent years due to its unique non-contact and non-destructive characteristics. At present, the microwave dielectric constant measurement methods mainly include lumped circuit method, transmission line method, resonant cavity perturbation method, free space method and so on. Among them, the resonant cavity perturbation method is the most commonly used and accurate method. It usually puts dielectri...

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Problems solved by technology

[0003] In addition, the resonant cavity perturbation method needs to measure the dielectric constant by measuring the magnitude of the resonant frequency shift before and after the medium is placed, and the measurement of the resonant frequency requires a bulky and expensive vector network analyzer to complete

However, the vector network analyzer is inconvenient to use and the cost is too high, so it is urgent to get rid of its use

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