自由空间单站反射系数测量中校准方法的比较

杨若楠; 梁伟军; 徐浩

doi:10.12338/j.issn.2096-9015.2024.0080

自由空间单站反射系数测量中校准方法的比较

doi: 10.12338/j.issn.2096-9015.2024.0080

中国计量科学研究院，北京 100029

基金项目: 国家重点研发计划（2022YFF0605901）。

详细信息

作者简介:
杨若楠（2001-），中国计量科学研究院在读研究生，研究方向：微波测量技术与计量，邮箱：yangrn@nim.ac.cn

通讯作者:
梁伟军（1978-），中国计量科学研究院副研究员，研究方向：无线电导波基本参数计量与测试技术，邮箱：liangwj@nim.ac.cn

中图分类号: TB973
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出版历程
- 收稿日期: 2024-03-13
- 录用日期: 2024-03-13
- 修回日期: 2024-03-18
- 网络出版日期: 2024-05-30

Comparison of Calibration Methods in Free-Space Monostatic Reflection Coefficient Measurement

National Institute of Metrology, Beijing 100029, China

摘要

摘要: 微波黑体为微波辐射计提供高精度的亮温信号以精确标定观测目标的辐射信号。微波黑体的发射率是影响其辐射特性的重要参数，因此准确测量黑体发射率对于提高辐射计的定标精度和保证量值的溯源性和有效传递具有重要意义，目前黑体发射率主要通过测量反射率来间接计算得到。实现了自由空间单站反射系数测量中的两种校准方法：偏移短路校准法和滑动负载校准法，采用时域门技术解决了小反射测量过程中多径反射信号的影响。搭建了反射率测量系统，在75～110 GHz频段内测量了同一黑体目标的反射率，并对测量结果进行了分析和比较。两种校准方法解算的误差项具有高度一致性，测量发射率均能到达0.999～0.9999量级。当测量目标满足近似条件时，使用滑动负载校准法具有更高的效率。最后，以偏移短路法为例，采用蒙特卡洛方法对求解的黑体目标反射系数进行了不确定度评定。
- 计量学 /
- 微波黑体 /
- 发射率 /
- 反射率测量 /
- 单端口校准 /
- 偏移短路法 /
- 滑动负载法
Abstract: Abstract:Microwave blackbodies provide high-precision brightness temperature signals for microwave radiometers to accurately calibrate observed target radiation signals. The emissivity of a microwave blackbody is a crucial parameter affecting its radiative characteristics. Therefore, accurately measuring blackbody emissivity is significant for enhancing radiometer calibration precision and ensuring measurement value traceability and effective transfer. Currently, blackbody emissivity is mainly obtained indirectly by measuring reflectivity. This study implements two calibration methods in free-space monostatic reflection coefficient measurement: the offset-short calibration method and the sliding-load calibration method. Time-domain gating techniques are utilized to address multipath reflection signals during small reflection measurements. A reflectivity measurement system was established, and the reflectivity of the same blackbody target was measured within the 75-110 GHz frequency band, with results analyzed and compared. The error terms solved by the two calibration methods exhibit high consistency, with measured emissivity reaching levels of 0.999-0.9999. When the measurement target satisfies approximation conditions, the sliding-load calibration method proves more efficient. Finally, using the offset-short method as an example, the Monte Carlo method was employed to evaluate the uncertainty of the solved blackbody target reflection coefficient.
- metrology /
- microwave blackbody /
- emissivity /
- reflectivity measurement /
- one-port calibration /
- offset-short method /
- sliding-load method

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图 1 辐射计两点定标原理

Figure 1. Two-point calibration principle of radiometers

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图 2 反射率测量系统示意图

Figure 2. Schematic diagram of reflectivity measurement system

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图 3 自由空间单端口反射系数测量信号流图

Figure 3. Signal-flow graph for free-space monostatic reflection coefficient measurement

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图 4 半参数圆拟合法拟合$ {\mathit{\varGamma }}_{\mathbf{m}\mathbf{e}\mathbf{a}\mathbf{s}} $

Figure 4. Semi-parametric circular fitting method for $ {\mathit{\varGamma }}_{\mathbf{m}\mathbf{e}\mathbf{a}\mathbf{s}} $

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图 5 自由空间单站反射系数测量系统示意图

Figure 5. Schematic diagram of free-space monostatic reflection coefficient measurement system

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图 6 滑动负载校准法中任意两个频点半参数圆拟合示例

Figure 6. Example of semi-parametric circular fitting for any two frequency points in sliding-load calibration method

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图 7 两种校准方法解算的误差项对比

注：蓝色曲线为测量结果，橘色曲线为差值。

Figure 7. Comparison of error terms calculated using two calibration methods

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图 8 黑体目标两种自由空间单端口反射系数测量结果对比

注：蓝色曲线为测量结果，橘色曲线为差值。

Figure 8. Comparison of free-space one-port reflection coefficient measurement results for the blackbody target

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图 9 偏移短路校准法75.656 GHz反射系数实部单批次MCM概率分布

Figure 9. Single-batch MCM probability distribution of the reflection coefficient real part at 75.656 GHz using the offset-short calibration method

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表 1 两种校准方法在不同测量设置下所需时间对比

Table 1. Comparison of time required for the two calibration methods under different measurement settings

校准方法	频点数	校准件移动次数（负载/金属板）	程序解算时间（秒）
滑动负载校准法	701	4	0.011754
	1601	4	0.036484
		5	0.036092
		8	0.030351
	2500	4	0.059153
偏移短路校准法	701	4	93.747827
	1601	4	319.017061
		5	334.650704
		8	355.390375
	2500	4	447.168423

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表 2 反射系数输入量

Table 2. Reflection coefficient input quantities

输入量	测量值
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{m}\mathrm{a}\mathrm{t}\mathrm{c}\mathrm{h}} $	−0.0012 − 0.0060i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{s}\mathrm{h}\mathrm{o}\mathrm{r}\mathrm{t}} $	−0.0470 − 0.0773i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(1\right)} $	−0.0802 − 0.0350i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(2\right)} $	−0.0830 + 0.0164i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(3\right)} $	−0.0536 + 0.0605i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(5\right)} $	−0.0045 + 0.0780i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(6\right)} $	0.04580 + 0.0641i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(7\right)} $	0.0778 + 0.0210i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(8\right)} $	0.0781 − 0.0318i
$ {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}} $	−0.0019 − 0.0055i

下载: 导出CSV

表 3 反射系数幅值测量误差正态分布参数

Table 3. Normal distribution parameters for reflection coefficient amplitude measurement error

输入量	均值（$ \times {10}^{-4} $）	方差（$ \times {10}^{-4} $）
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{m}\mathrm{a}\mathrm{t}\mathrm{c}\mathrm{h}}\right\| $	9.1762	1.1900
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{s}\mathrm{h}\mathrm{o}\mathrm{r}\mathrm{t}}\right\| $	9.0422	5.3508
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(1\right)}\right\| $	9.0462	5.9843
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(2\right)}\right\| $	9.0429	5.5828
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(3\right)}\right\| $	9.0433	5.3509
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(4\right)}\right\| $	9.0438	5.1816
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(5\right)}\right\| $	9.0468	5.3670
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(6\right)}\right\| $	9.0472	5.3670
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(7\right)}\right\| $	9.0491	5.5869
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}^{\mathrm{o}\mathrm{f}\mathrm{f}\left(8\right)}\right\| $	9.0515	6.1805
$ \left\|\delta {\varGamma }_{\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{s}}\right\| $	9.7156	1.1962

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参考文献(30)

[1]	Cho K, Naoki K, Nakayama M, et al. The Relationship Between Microwave Brightness Temperature, Salinity, and Thickness of Sea Ice Acquired With a Tank Experiment[J]. ITGRS, 2024, 62: 1-9.
[2]	Ulaby FT, Long DG. Microwave Radar and Radiometric Remote Sensing[M]. Michigan: The University of Michigan Press, 2014.
[3]	关越, 高福生. 黑体辐射源发射率对测量误差的影响[J]. 轻工标准与质量, 2018(1): 82-83,7.
[4]	年丰, 于杰, 陈云梅, 等. 中国星载微波辐射计地面定标技术的研究进展[J]. 宇航计测技术, 2007(S1): 27-33.
[5]	李彬. 一种新型全极化微波辐射计定标源研制及定标方法研究[D]. 北京: 中国科学院大学(中国科学院国家空间科学中心), 2017.
[6]	Khatib O, Gu D, Smith J, et al. Planar Metamaterial Absorbers for Calibration of Microwave Radiometers for Atmospheric Remote Sensing[C]. IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium, 2022.
[7]	ISO. Space systems-- Calibration requirements for satellite-based passive microwave sensors: ISO 20930: 2018[S]. Geneva: ISO, 2018.
[8]	A. Murk AD. ALMA Calibration Device Prototype Calibration Load Test Report. [R]. Institute of Applied Physics, University of Bern, 2007.
[9]	A. Murk, A. Duric, Patt F. Characterization of ALMA Calibration Targets[C]. 19th International Symposium on Space Terahertz Technology.
[10]	Hein WHCBASM. Challenges of RF Absorber Characterization: Comparison Between RCS- and NRL-Arch-Methods[C]. 2019 International Symposium on Electromagnetic Compatibility (EMC Europe ), 2019.
[11]	Hofmann W, Schwind A, Bornkessel C, et al. Bi-static reflectivity measurements of microwave absorbers between 2 and 18 GHz[C]. 2021 Antenna Measurement Techniques Association Symposium (AMTA), 2021.
[12]	李彬, 金铭, 白明, 等. 微波黑体发射率计量标准装置的准光照射天线设计[J]. 宇航计测技术, 2018, 38(6): 7. doi: 10.12060/j.issn.1000-7202.2018.06.02
[13]	Jin M, Li B, Bai M. On the Reflectivity Measurements of Microwave Blackbody in Bistatic Near-Field Configuration[J]. IEEE Transactions on Antennas and Propagation, 2021, 69(11): 8027-8032. doi: 10.1109/TAP.2021.3083762
[14]	Jin M, Li B, Bai M. Development of the Standard Facility for the Microwave Blackbody Emissivity Determination in China[C]. 2021 International Conference on Microwave and Millimeter Wave Technology (ICMMT), 2021.
[15]	Dazhen G, Houtz D, Randa J, et al. Reflectivity Study of Microwave Blackbody Target[J]. ITGRS, 2011, 49(9): 3443-3451.
[16]	Houtz DA, Gu D. A Measurement Technique for Infrared Emissivity of Epoxy-Based Microwave Absorbing Materials[J]. IEEE Geoscience and Remote Sensing Letters, 2018, 15(1): 48-52. doi: 10.1109/LGRS.2017.2772783
[17]	Cheng CY, Li F, Yang YJ, et al. Emissivity measurement study on wide aperture microwave radiator[C]. 2008 International Conference on Microwave and Millimeter Wave Technology, 2008.
[18]	Cheng J, Cao Y, Zhai H, et al. Development of New Calibration Targets for FY-3 Satellites Microwave Radiometer[C]. 2021 International Conference on Microwave and Millimeter Wave Technology (ICMMT), 2021.
[19]	Wang T, Zeng J, Chen K-S, et al. Comparison of Different Intercalibration Methods of Brightness Temperatures From FY-3D and AMSR2[J]. ITGRS, 2022, 60: 12-17.
[20]	程春悦, 何巍. 140GHz~220GHz微波黑体发射率测量研究[C]. 2011年全国微波毫米波会议, 2011.
[21]	Wang J, Miao J, Yang Y, et al. Scattering Property and Emissivity of a Periodic Pyramid Array Covered With Absorbing Material[J]. IEEE Transactions on Antennas and Propagation, 2008, 56(8): 2656-2663. doi: 10.1109/TAP.2008.927570
[22]	金铭. 锥形阵列微波辐射计定标源的电磁波散射和发射率研究 [D]. 北京: 北京航空航天大学, 2012.
[23]	Junhong W, Yujie Y, Jungang M, et al. Emissivity Calculation for a Finite Circular Array of Pyramidal Absorbers Based on Kirchhoff's Law of Thermal Radiation[J]. IEEE Transactions on Antennas and Propagation, 2010, 58(4): 1173-1180. doi: 10.1109/TAP.2010.2041148
[24]	Jin M, Fan B, Li X, et al. On the Total Reflectivity Estimation of Microwave Calibration Targets by Backscattering Measurements[J]. ITGRS, 2022, 60: 1-11.
[25]	Houtz DA. NIST MICROWAVE BLACKBODY: The design, testing, and verification of a conical brightness temperature source [D]. Boulder : University of Colorado Boulder, 2017.
[26]	andersteen GV. It is possible to improve the Sliding Load Calibration Procedure using a Semi-Parametric Circle Fitting Algorithm [D]. Brussel : Vrije Universiteit Brussel, 1997.
[27]	Yang R, Liang W, Xu H. Design and Fabrication of WR-28 Blackbody Target[C]. 2023 16th UK-Europe-China Workshop on Millimetre Waves and Terahertz Technologies (UCMMT), 2023.
[28]	倪育才. 实用测量不确定度评定[M]. 北京: 中国质量标准出版传媒有限公司, 2020.
[29]	Dirix M, Enayati A. On the Uncertainty Evaluation of Absorber Reflectivity Measurements[C]. 2023 Antenna Measurement Techniques Association Symposium (AMTA), 2023.
[30]	Doug Rytting. Network analyzer error models and calibration methods [R]. 1998.