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Article List
2025, 23(6):541-568.
DOI: 10.11805/TKYDA2025015
Abstract:
Terahertz(THz) imaging technology, as an emerging imaging method, has the advantages of being non-invasive, non-destructive, and high-resolution, and has achieved significant progress in recent years. This paper reviews and analyzes terahertz imaging technology from the perspectives of technical approaches and current research status. Based on the type of signal source, the technical characteristics of pulsed terahertz imaging and continuous-wave terahertz imaging mechanisms are compared and analyzed. On this basis, the paper focuses on the technical solutions with super-resolution and high-speed imaging capabilities, analyzes their current development status, and discusses their advantages in future terahertz imaging scenarios. Finally, the challenges of application-oriented terahertz imaging technology are summarized and prospected.
Terahertz(THz) imaging technology, as an emerging imaging method, has the advantages of being non-invasive, non-destructive, and high-resolution, and has achieved significant progress in recent years. This paper reviews and analyzes terahertz imaging technology from the perspectives of technical approaches and current research status. Based on the type of signal source, the technical characteristics of pulsed terahertz imaging and continuous-wave terahertz imaging mechanisms are compared and analyzed. On this basis, the paper focuses on the technical solutions with super-resolution and high-speed imaging capabilities, analyzes their current development status, and discusses their advantages in future terahertz imaging scenarios. Finally, the challenges of application-oriented terahertz imaging technology are summarized and prospected.
2025, 23(6):569-576.
DOI: 10.11805/TKYDA2024594
Abstract:
Interferometric imaging technology can accurately measure the tiny deformations or displacements on the surface of objects in a non-contact manner, demonstrating extensive application potential. In this paper, a reflection and transmission interferometric system based on the terahertz band is designed and constructed. This system directly reconstructs images using phase information after scanning. Experiments show that at frequencies of 164 GHz, 172 GHz, 196 GHz, and 204 GHz, the imaging quality and resolution of the Michelson interferometric system are superior to those of the direct measurement method. At 150 GHz, without using any imaging algorithm, the system can achieve half-wavelength resolution, with a contrast improvement of 50% compared to direct measurement. At 180 GHz, a Mach-Zehnder interferometric system is implemented, where the dual-path difference effectively reduces phase noise, thus proving the feasibility and advantages of the system. Terahertz interferometric technology provides a noncontact, high-resolution imaging solution for the imaging field.
Interferometric imaging technology can accurately measure the tiny deformations or displacements on the surface of objects in a non-contact manner, demonstrating extensive application potential. In this paper, a reflection and transmission interferometric system based on the terahertz band is designed and constructed. This system directly reconstructs images using phase information after scanning. Experiments show that at frequencies of 164 GHz, 172 GHz, 196 GHz, and 204 GHz, the imaging quality and resolution of the Michelson interferometric system are superior to those of the direct measurement method. At 150 GHz, without using any imaging algorithm, the system can achieve half-wavelength resolution, with a contrast improvement of 50% compared to direct measurement. At 180 GHz, a Mach-Zehnder interferometric system is implemented, where the dual-path difference effectively reduces phase noise, thus proving the feasibility and advantages of the system. Terahertz interferometric technology provides a noncontact, high-resolution imaging solution for the imaging field.
2025, 23(6):577-582.
DOI: 10.11805/TKYDA2024370
Abstract:
A terahertz fourth harmonic mixer based on anti-parallel Schottky diode pair is introduced, and its Radio Frequency(RF) operating range covers 400 GHz to 600 GHz.The mixer use a multi-point ground structure at the RF ends, which effectively reduces the return loss of RF port compared to the traditional single point ground structure. By adopting an integrated RF-end design method, the number of matching branches is reduced by 30% during the design process compared to traditional methods, thereby enhancing design efficiency. The measured results show that the typical value of conversion loss is 20 dB and the optimal value is 14 dB in the whole working band when the Local Oscillator(LO) power is in the range of 7~13 dBm.
A terahertz fourth harmonic mixer based on anti-parallel Schottky diode pair is introduced, and its Radio Frequency(RF) operating range covers 400 GHz to 600 GHz.The mixer use a multi-point ground structure at the RF ends, which effectively reduces the return loss of RF port compared to the traditional single point ground structure. By adopting an integrated RF-end design method, the number of matching branches is reduced by 30% during the design process compared to traditional methods, thereby enhancing design efficiency. The measured results show that the typical value of conversion loss is 20 dB and the optimal value is 14 dB in the whole working band when the Local Oscillator(LO) power is in the range of 7~13 dBm.
2025, 23(6):583-589.
DOI: 10.11805/TKYDA2024558
Abstract:
The quality of the insulation layer of high-voltage cables is crucial for the long-term reliability of power transmission and transformation systems. Non-uniformity in the thickness of the insulation layer can lead to localized tangential electric fields, which are prone to creating safety hazards. A reflective terahertz detection system, combined with a cylindrical coordinate scanning device, is employed to achieve full-angle scanning measurements of the insulation layer thickness of cross-linked polyethylene high-voltage cables. The non-roundness of the insulation layer thickness is quantified, and its distribution uniformity is assessed. The terahertz images intuitively display the interface wrinkle texture features of the insulation layer, which are highly consistent with the actual specimen morphology. This validates the effectiveness of terahertz imaging technology in the quality inspection of high-voltage cables, providing a new detection method and evaluation approach for the quality assessment of high-voltage cables.
The quality of the insulation layer of high-voltage cables is crucial for the long-term reliability of power transmission and transformation systems. Non-uniformity in the thickness of the insulation layer can lead to localized tangential electric fields, which are prone to creating safety hazards. A reflective terahertz detection system, combined with a cylindrical coordinate scanning device, is employed to achieve full-angle scanning measurements of the insulation layer thickness of cross-linked polyethylene high-voltage cables. The non-roundness of the insulation layer thickness is quantified, and its distribution uniformity is assessed. The terahertz images intuitively display the interface wrinkle texture features of the insulation layer, which are highly consistent with the actual specimen morphology. This validates the effectiveness of terahertz imaging technology in the quality inspection of high-voltage cables, providing a new detection method and evaluation approach for the quality assessment of high-voltage cables.
2025, 23(6):590-596.
DOI: 10.11805/TKYDA2025079
Abstract:
Millimeter-wave holographic imaging systems based on phase imaging have been extensively applied in fields such as security screening and non-destructive testing, due to their special penetration capabilities and high-resolution advantages. While extending operational frequencies to higher bands for achieving better resolution, the problems of dense transceiver arrangements and high system complexity need to be considered. This study presents a W-band short-range high-resolution millimeter-wave holographic imaging system utilizing linear array scanning. By implementing a 25-transmitter and 100-receiver array configuration with integrated electronic circuitry design, the system achieves high-quality short-range imaging across the 85~105 GHz operational band. Experimental results demonstrate the system can obtain spatial resolutions superior to 2 mm in the horizontal direction and 2.5 mm in the vertical direction at an imaging distance of 0.5 m, confirming its enhanced performance in practical applications.
Millimeter-wave holographic imaging systems based on phase imaging have been extensively applied in fields such as security screening and non-destructive testing, due to their special penetration capabilities and high-resolution advantages. While extending operational frequencies to higher bands for achieving better resolution, the problems of dense transceiver arrangements and high system complexity need to be considered. This study presents a W-band short-range high-resolution millimeter-wave holographic imaging system utilizing linear array scanning. By implementing a 25-transmitter and 100-receiver array configuration with integrated electronic circuitry design, the system achieves high-quality short-range imaging across the 85~105 GHz operational band. Experimental results demonstrate the system can obtain spatial resolutions superior to 2 mm in the horizontal direction and 2.5 mm in the vertical direction at an imaging distance of 0.5 m, confirming its enhanced performance in practical applications.
2025, 23(6):597-603.
DOI: 10.11805/TKYDA2023324
Abstract:
To meet the low electromagnetic scattering requirements of optical instrument windows, a metal microstructure model based on Voronoi diagrams is employed, arranging the metasurface structures in a checkerboard array. This design achieves effective reduction of Radar Cross-Section(RCS) while satisfying the transparency and imaging quality requirements of the instrument windows. Experiments shows that the checkerboard metasurface without transparentizing could achieve more than 10 dB RCS reduction in the frequency band of 11.6~17.9 GHz, and the phase response of the metasurface unit remains consistent before and after transparentizing. The designed transparent RCS-reducing metasurface has high light transmittance, can uniformly diffract stray light distribution, and possesses the characteristic of wideband RCS reduction. The research results provide a new idea for the design of low-RCS transparent windows.
To meet the low electromagnetic scattering requirements of optical instrument windows, a metal microstructure model based on Voronoi diagrams is employed, arranging the metasurface structures in a checkerboard array. This design achieves effective reduction of Radar Cross-Section(RCS) while satisfying the transparency and imaging quality requirements of the instrument windows. Experiments shows that the checkerboard metasurface without transparentizing could achieve more than 10 dB RCS reduction in the frequency band of 11.6~17.9 GHz, and the phase response of the metasurface unit remains consistent before and after transparentizing. The designed transparent RCS-reducing metasurface has high light transmittance, can uniformly diffract stray light distribution, and possesses the characteristic of wideband RCS reduction. The research results provide a new idea for the design of low-RCS transparent windows.
