GB/T 35680-2017 in English
VALIDMeasuring method for electromagnetic parameters of liquid materials at microwave frequencies using an open-ended coaxial probe
- Issued on:2017-12-29
- Implemented on:2018-07-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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《GB/T 35680-2017液体材料微波频段使用开口同轴探头的电磁参数测量方法》由TC323（全国电磁屏蔽材料标准化技术委员会）归口，主管部门为中国电器工业协会。
Introduction
1. Standard Overview
GB/T 35680—2017 specifies the method of measuring the electromagnetic parameters of liquid materials using an open coaxial probe in the microwave frequency band, which is applicable to the detection of the relative dielectric constant and loss tangent of uniform and isotropic liquid materials in the frequency band of $100~\mathrm{MHz}{\sim}50~\mathrm{GHz}$.
2. Background of Standard Formulation
With the widespread application of microwave technology in the field of materials science, it is particularly important to accurately measure the electromagnetic parameters of liquid materials. This standard was proposed by the China Electrical Equipment Industry Association and is under the jurisdiction of the National Technical Committee for Standardization of Electromagnetic Shielding Materials. It aims to provide unified technical specifications for the microwave frequency band electromagnetic parameter testing of liquid materials.
3. Comparison of standard frameworks
| Standard dimensions | GB/T 35680—2017 | References |
|---|---|---|
| Scope of application | Liquid materials, microwave frequency band ($100~\mathrm{MHz}{\sim}50~\mathrm{GHz}$) | Solid dielectric test method |
| Measurement parameters | Relative permittivity, loss tangent | Complex permittivity |
| Test equipment | Vector network analyzer, open coaxial probe | Perturbation method, open cavity method |
4. Analysis of core technologies
Complex relative permittivity is the core concept of this standard and is defined as:
$$ \varepsilon = \varepsilon_{0} \cdot \varepsilon_{r} = \varepsilon_{0}(\varepsilon' - j\varepsilon'') $$Wherein, $\varepsilon'$ is the real part of the relative permittivity, $\varepsilon''$ is the imaginary part, and $\tan\delta_{\varepsilon} = \varepsilon''/\varepsilon'$ represents the dielectric loss tangent.
Application case: Electromagnetic parameter test of deionized water
The relative dielectric constant of deionized water at different temperatures is calculated by Cole-Cole relationship, and the comparison between theoretical value and measured value is shown in Table D.1. The results show that this standard method has high accuracy and reliability.
5. Implementation suggestions
- Equipment selection:It is recommended to use a vector network analyzer with a frequency range covering the microwave band, and ensure that its noise level is ≤-110dBm.
- Probe calibration:The single-port probe terminal is calibrated regularly, and air, deionized water and short circuit are used as standard parts.
- Sample preparation:Ensure that the liquid is uniform and free of bubbles, and the test depth meets the requirements of formula (2).
- Data processing: Combined with the inversion method in Appendix C, the Bessel function is used for iterative solution to obtain the accurate relative dielectric constant.
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