Reflection loss field visualization of curved RAS based on scanning free-space measurement and curvature compensation using perfect electric conductor

Son, Dae-Sung; Hyun, Jong-Min; Lee, Jung-Ryul

doi:10.1016/j.measurement.2019.107408

Cited by 4 publications

(7 citation statements)

References 14 publications

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“…Therefore, overall, a positive curvature increases the return loss value of the resonant frequency. A similar result was obtained by Son et al 24 for S-shaped specimens using two-axis SFM. To conclude, the negative curvature reduces the resonant frequency return loss due to the compression of the outer surface of the specimen, as shown by region A, and the positive curvature increases the resonant frequency return loss due to the expansion of the specimen, as shown by region C. These results show that six-axis RSFM has been applied to EM evaluation as well as non-destructive testing by Lee et al 25 of curvature specimens.…”

Section: Resultssupporting

confidence: 89%

Section: Curvature Effect On the Resonant Frequencysupporting

confidence: 89%

“…Therefore, the results are only affected by curvature, as shown in Table 3. The curvature effect was removed from the results using the curvature compensation method developed by Son et al 24 From Figure 16, we can see that the results revert to their original return loss values obtained for the flat specimen above. However, the resonant frequency return loss values show some difference from the flat specimen resonant frequency values.…”

Section: Resultsmentioning

confidence: 86%

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Robotic scanning free-space measurement system for electromagnetic performance evaluation of curved radar absorbing structures

Din

Hyun

Son

et al. 2022

International Journal of Advanced Robotic Systems

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Radar absorbing structures are manufactured for stealth missions and total quality inspection applies to evaluate their performances before assembly to stealth weapon systems. This study adopted a six-axis robot arm to move a target specimen in a scanning free-space measurement system for electromagnetic performance evaluation. The six-axis robot arm completely enables the system to maintain the specimen at the focal point of the antenna and solves the issue of curvature effect on the return loss results of the curved specimens, faced in the two- and three-axis scanning free-space measurement systems. The six-axis robotic scanning free-space measurement system uses a RobotStudio to extract the position and orientation of each target point on the specimen to be evaluated and uses a robotic scanning algorithm to transform all the points into a scan path. The system was verified by variable and constant curvature radar absorbing structure specimens with frequency selective surfaces. Return losses ( S 11s) of the nonsymmetrical cambered airfoil specimen and S-shaped double curvature specimen that could not be accurately evaluated with a three-axis stage-based scanning free-space measurement system were measured by the six-axis robotic scanning free-space measurement system. All the specimen results adhere to the theoretical parameters of the specimen. The transition region results of the S-shaped specimen were studied using effective radius of curvature. Finally, the inspected results of the S-shaped specimen were curvature compensated to check the effect of negative and positive curvature on the specimen resonance frequency performance.

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Section: Resultssupporting

confidence: 89%

Section: Curvature Effect On the Resonant Frequencysupporting

confidence: 89%

Section: Resultsmentioning

confidence: 86%

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Robotic scanning free-space measurement system for electromagnetic performance evaluation of curved radar absorbing structures

Din

Hyun

Son

et al. 2022

International Journal of Advanced Robotic Systems

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“…A curvature compensation method based on a perfect electric conductor (PEC) was proposed to improve the result through postprocessing [15]. Three of the major geometrical parameters that affect the scan result (θ, ρ, D) are compensated based on the same shape PEC results, where θ is the incident angle (the angle at which the EM waves hit a particular portion of the target, which depends upon the shape of the specimen and its orientation to the antenna), ρ = 1/R is the curvature of the specimen, and D is the distance of any target point from the specimen edge.…”

Section: Introductionmentioning

confidence: 99%

“…In this new system, a coordinate-based scanning algorithm is implemented to scan variable curvature specimens such as wing leading edges at lower incident angles to obtain desirable SNRs for curvature compensation of the results. The accuracy of the geometry-based PEC reflection loss prediction algorithm developed by [15] is improved by adding the effect of specimen stand-off distance (SOD) from the antenna to the algorithm, which is also a part of this paper.…”

Section: Introductionmentioning

confidence: 99%

Rotation included 3-axis scanning free-space measurement and curvature compensation for electromagnetic evaluation of leading-edge and curved stealth structures

Din¹,

Hyun²,

Son³

et al. 2022

Meas. Sci. Technol.

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Since the last decade, stealth technology has been developing at a much higher speed with much research going on to evaluate the properties of radar absorbing structures (RASs) and scattering parameters of the developed stealth structures at different phases of practical use. Conventional evaluation systems can scan a single point at a time. A scanning free-space measurement (SFM) system was an initial step toward automated scanning of large stealth structures. However, the two-dimensional SFM is no applicable to leading-edge and cylindrical structures, and the signal-to-noise ratio is highly affected by the specimen curvature. In this paper, a 3-axis scanning free-space measurement (3-axis SFM) system was developed. The system has two linear stages and a rotational stage for raster scanning of the specimen. The system performance was checked by scanning cylindrical RAS specimens with a radius of 100 mm. The results were then compared to the SFM system, which showed that the SNR of the 3-axis SFM is quite high compared to the SFM system. A coordinate-based scanning algorithm was also developed for 3-axis SFM to ensure a fixed interval scan of complex geometrically shaped specimens, such as wing leading edges, at lower incident angles. The algorithm achieved a zero-degree incident angle scan with ±1 degree of accuracy for the NACA-M3 symmetrical leading-edge specimen. Different scan parameters and results are visualized in the developed GUI software. Finally, the inspected results were curvature-compensated to obtain the actual RAS performance of the specimen. The accuracy of the geometry-based PEC reflection-loss prediction algorithm was further improved by adding a stand-off distance effect and more specimen curvature data to the algorithm. The accuracy of the algorithm was verified by comparing the predicted PEC results to the measured PEC results of the corresponding specimen.

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Evaluation of electromagnetic characteristics of 3D-printed radar absorbing structures based on three-dimensional period pattern surface

Hyun,

Lee

2024

Measurement

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Reflection loss field visualization of curved RAS based on scanning free-space measurement and curvature compensation using perfect electric conductor

Cited by 4 publications

References 14 publications

Robotic scanning free-space measurement system for electromagnetic performance evaluation of curved radar absorbing structures

Robotic scanning free-space measurement system for electromagnetic performance evaluation of curved radar absorbing structures

Rotation included 3-axis scanning free-space measurement and curvature compensation for electromagnetic evaluation of leading-edge and curved stealth structures

Evaluation of electromagnetic characteristics of 3D-printed radar absorbing structures based on three-dimensional period pattern surface

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