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Article List
2024, 22(10):1051-1055.
DOI: 10.11805/TKYDA2024102
Abstract:
As electronic technology advances towards higher integration and miniaturization, three-dimensional circuit layouts have become increasingly prevalent, making the effective transmission of millimeter-wave signals between the surface and internal circuits particularly critical. This study presents a novel design for an ultra-wideband, low-loss vertical interconnect structure transitioning from a stripline to a Grounded Coplanar Waveguide(GCPW), aimimg at addressing signal reflection and radiation issues caused by parasitic inductance and capacitance in interconnect structures. Through the analysis of an equivalent circuit model and preliminary parameter design, combined with optimization using three-dimensional field simulation, the final design parameters were determined. The interconnect structure employs a 0.2 mm diameter via for connection and features an isolation ring with a mere 0.8 mm diameter, ensuring the simplicity and ease of fabrication of the structure. Simulation results indicate that the design achieves broadband coverage from DC to 80 GHz, with S11 less than -13 dB and S21 greater than -0.4 dB, demonstrating excellent performance. To interface with the testing system, a test board was designed to convert to a coaxial connector, extending the operating frequency to 40 GHz. Actual test results show that, within the DC to 40 GHz range, return loss is less than 11 dB and insertion loss is less than 0.4 dB, further verifying the effectiveness and practicality of the design.
As electronic technology advances towards higher integration and miniaturization, three-dimensional circuit layouts have become increasingly prevalent, making the effective transmission of millimeter-wave signals between the surface and internal circuits particularly critical. This study presents a novel design for an ultra-wideband, low-loss vertical interconnect structure transitioning from a stripline to a Grounded Coplanar Waveguide(GCPW), aimimg at addressing signal reflection and radiation issues caused by parasitic inductance and capacitance in interconnect structures. Through the analysis of an equivalent circuit model and preliminary parameter design, combined with optimization using three-dimensional field simulation, the final design parameters were determined. The interconnect structure employs a 0.2 mm diameter via for connection and features an isolation ring with a mere 0.8 mm diameter, ensuring the simplicity and ease of fabrication of the structure. Simulation results indicate that the design achieves broadband coverage from DC to 80 GHz, with S11 less than -13 dB and S21 greater than -0.4 dB, demonstrating excellent performance. To interface with the testing system, a test board was designed to convert to a coaxial connector, extending the operating frequency to 40 GHz. Actual test results show that, within the DC to 40 GHz range, return loss is less than 11 dB and insertion loss is less than 0.4 dB, further verifying the effectiveness and practicality of the design.
2024, 22(10):1056-1062.
DOI: 10.11805/TKYDA2024162
Abstract:
Single-pixel imaging is a novel computational imaging technique that uses only a single-pixel detector to acquire the image of an object with the help of spatial light modulation. In the terahertz band, to overcome the problem of scarcity of array detectors and realize sub-wavelength imaging in near-field modulation, a continuous terahertz single-pixel subwavelength imaging system is presented based on an optically pumped silicon wafer all optical modulator with a spatial resolution of λ/7.62. The imaging results on the resolution test chart show that when the imaging details are not of particular interest, thick silicon wafers can be employed to obtain large modulation depths, and the compressive reconstruction algorithm can be adopted to suppress noise and smooth the output images. To pursue higher imaging spatial resolution, thin silicon wafers are needed to reduce the crosstalk between modulation units, and the correlation reconstruction algorithm is employed to retain more image details. This study provides a concise reference for terahertz subwavelength imaging.
Single-pixel imaging is a novel computational imaging technique that uses only a single-pixel detector to acquire the image of an object with the help of spatial light modulation. In the terahertz band, to overcome the problem of scarcity of array detectors and realize sub-wavelength imaging in near-field modulation, a continuous terahertz single-pixel subwavelength imaging system is presented based on an optically pumped silicon wafer all optical modulator with a spatial resolution of λ/7.62. The imaging results on the resolution test chart show that when the imaging details are not of particular interest, thick silicon wafers can be employed to obtain large modulation depths, and the compressive reconstruction algorithm can be adopted to suppress noise and smooth the output images. To pursue higher imaging spatial resolution, thin silicon wafers are needed to reduce the crosstalk between modulation units, and the correlation reconstruction algorithm is employed to retain more image details. This study provides a concise reference for terahertz subwavelength imaging.
2024, 22(10):1063-1072.
DOI: 10.11805/TKYDA2024379
Abstract:
Terahertz photothermoelectric detectors are based on the principle of thermogenerated carriers migrating under the influence of a temperature gradient to achieve terahertz wave detection. They have advantages such as fast response, ultra-wideband, self-powered, room temperature operation, and simple structure, which have attracted widespread attention. Currently, the readout of detectors mainly adopts a modulation-demodulation method, realized by cascading a current amplifier with a lock-in amplifier for measurement, which has low integration, high cost, and is difficult to achieve array readout. To meet the application requirements of spectral measurement and imaging perception, this paper studies the readout method of the photothermoelectric array detector unit. Starting from the detector mechanism, the output signal is modeled and analyzed; based on this, a board-level dedicated readout circuit is designed to achieve front-end amplification and lock-in amplification functions. Tests show that this method can achieve high-precision readout of terahertz photothermoelectric detectors in a strong noise background environment, with a gain of 140.7 dB, and the signal-to-noise ratio is improved by 38.3 dB.
Terahertz photothermoelectric detectors are based on the principle of thermogenerated carriers migrating under the influence of a temperature gradient to achieve terahertz wave detection. They have advantages such as fast response, ultra-wideband, self-powered, room temperature operation, and simple structure, which have attracted widespread attention. Currently, the readout of detectors mainly adopts a modulation-demodulation method, realized by cascading a current amplifier with a lock-in amplifier for measurement, which has low integration, high cost, and is difficult to achieve array readout. To meet the application requirements of spectral measurement and imaging perception, this paper studies the readout method of the photothermoelectric array detector unit. Starting from the detector mechanism, the output signal is modeled and analyzed; based on this, a board-level dedicated readout circuit is designed to achieve front-end amplification and lock-in amplification functions. Tests show that this method can achieve high-precision readout of terahertz photothermoelectric detectors in a strong noise background environment, with a gain of 140.7 dB, and the signal-to-noise ratio is improved by 38.3 dB.
2024, 22(10):1073-1080.
DOI: 10.11805/TKYDA2024197
Abstract:
Metasurfaces are artificial surfaces composed of sub-wavelength unit structures, demonstrating tremendous potential for manipulating electromagnetic waves. Catenary electromagnetics provides new ideas and methods for the design of metasurfaces. This paper proposes a multifunctional dichroic metasurface based on a catenary structure, capable of selectively absorbing electromagnetic waves in different directions. Simulation results show that the device can achieve 92% Linear Dichroism (LD) and 96% Circular Dichroism(CD) in the infrared region. Both functions can be realized simultaneously by merely changing the incident direction of the electromagnetic waves, and both functions have high efficiency within a certain range of incident angles. In addition, the influence of different geometric parameters on the absorption performance is analyzed, as well as the physical mechanisms for selective absorption of different electromagnetic waves. This metasurface has the advantages of simple structure, easy integration, and a wide range of applications, and has potential application prospects in the fields of imaging, sensing, and spectroscopy.
Metasurfaces are artificial surfaces composed of sub-wavelength unit structures, demonstrating tremendous potential for manipulating electromagnetic waves. Catenary electromagnetics provides new ideas and methods for the design of metasurfaces. This paper proposes a multifunctional dichroic metasurface based on a catenary structure, capable of selectively absorbing electromagnetic waves in different directions. Simulation results show that the device can achieve 92% Linear Dichroism (LD) and 96% Circular Dichroism(CD) in the infrared region. Both functions can be realized simultaneously by merely changing the incident direction of the electromagnetic waves, and both functions have high efficiency within a certain range of incident angles. In addition, the influence of different geometric parameters on the absorption performance is analyzed, as well as the physical mechanisms for selective absorption of different electromagnetic waves. This metasurface has the advantages of simple structure, easy integration, and a wide range of applications, and has potential application prospects in the fields of imaging, sensing, and spectroscopy.
2024, 22(10):1081-1087.
DOI: 10.11805/TKYDA2024256
Abstract:
Based on a flexible twisted bilayer chiral metasurface sensor, utilizing terahertz time-domain spectroscopy technology, with chiral Lactic Acid(LA) enantiomers as the research subjects, a method for sensing the concentration of chiral substances and enantiomer recognition in the terahertz band is proposed. The results show that the Transmission Circular Dichroism(TCD) of the chiral metasurface sensor shifts with the increase of concentration, and the shift amounts are different for different chiral enantiomers. The highest detection sensitivity for Levorotatory Lactic Acid(L-LA) and Dextrorotatory Lactic Acid(D-LA) are 2.6 GHz/(mg/mL) and 1.9 GHz/(mg/mL), respectively, with a detection limit as low as 0.01 mg/mL. The great potential of the chiral metasurface sensor in LA sensing and chiral recognition provides an efficient, low-cost technical method for the sensitive detection of chiral enantiomers.
Based on a flexible twisted bilayer chiral metasurface sensor, utilizing terahertz time-domain spectroscopy technology, with chiral Lactic Acid(LA) enantiomers as the research subjects, a method for sensing the concentration of chiral substances and enantiomer recognition in the terahertz band is proposed. The results show that the Transmission Circular Dichroism(TCD) of the chiral metasurface sensor shifts with the increase of concentration, and the shift amounts are different for different chiral enantiomers. The highest detection sensitivity for Levorotatory Lactic Acid(L-LA) and Dextrorotatory Lactic Acid(D-LA) are 2.6 GHz/(mg/mL) and 1.9 GHz/(mg/mL), respectively, with a detection limit as low as 0.01 mg/mL. The great potential of the chiral metasurface sensor in LA sensing and chiral recognition provides an efficient, low-cost technical method for the sensitive detection of chiral enantiomers.
2024, 22(10):1088-1093.
DOI: 10.11805/TKYDA2024314
Abstract:
A pixel-level digital focal plane readout circuit was designed to overcome the charge capacity limitations of traditional analog readout circuit technology, enabling a larger dynamic range and lower noise digital image readout. Additionally, digital image processing is performed internally at the pixel level, enabling functions such as Non-Uniformity Correction(NUC), dead pixel compensation, digital Time-Delay Integration(TDI), and spatial filtering for image preprocessing. The circuit was fabricated using a 40 nm CMOS process with an array specification of 640×512, a pixel pitch of 30 μm, and the overall chip size is approximately 22 mm×19 mm. Test results indicate that the circuit can significantly reduce(by approximately 90% and 63%, respectively) the spatial noise in the output image through TDI and spatial filtering functions, thereby enhancing the image quality.
A pixel-level digital focal plane readout circuit was designed to overcome the charge capacity limitations of traditional analog readout circuit technology, enabling a larger dynamic range and lower noise digital image readout. Additionally, digital image processing is performed internally at the pixel level, enabling functions such as Non-Uniformity Correction(NUC), dead pixel compensation, digital Time-Delay Integration(TDI), and spatial filtering for image preprocessing. The circuit was fabricated using a 40 nm CMOS process with an array specification of 640×512, a pixel pitch of 30 μm, and the overall chip size is approximately 22 mm×19 mm. Test results indicate that the circuit can significantly reduce(by approximately 90% and 63%, respectively) the spatial noise in the output image through TDI and spatial filtering functions, thereby enhancing the image quality.
2024, 22(10):1094-1103.
DOI: 10.11805/TKYDA2024359
Abstract:
High-performance wide-spectrum upconversion imaging devices play an important role in fields such as medical care, food safety, non-destructive testing, and national security. However, existing semiconductor upconversion devices are limited by their narrow detection range and low upconversion efficiency. In order to achieve a wider spectrum and efficient upconversion, this study significantly improves the performance of the ratchet upconversion device by optimizing the LED structure. The improved LED's electroluminescence efficiency has been increased by two orders of magnitude. It can turn on light at a driving current of μA level, and its electroluminescence spectrum is closer to the theoretical regular Lorentz line. The overall surface luminescence uniformity of the device is also significantly improved. The research clarifies the performance optimization principles and provides a reference for future improvements in upconversion devices.
High-performance wide-spectrum upconversion imaging devices play an important role in fields such as medical care, food safety, non-destructive testing, and national security. However, existing semiconductor upconversion devices are limited by their narrow detection range and low upconversion efficiency. In order to achieve a wider spectrum and efficient upconversion, this study significantly improves the performance of the ratchet upconversion device by optimizing the LED structure. The improved LED's electroluminescence efficiency has been increased by two orders of magnitude. It can turn on light at a driving current of μA level, and its electroluminescence spectrum is closer to the theoretical regular Lorentz line. The overall surface luminescence uniformity of the device is also significantly improved. The research clarifies the performance optimization principles and provides a reference for future improvements in upconversion devices.
2024, 22(10):1104-1110.
DOI: 10.11805/TKYDA2024371
Abstract:
Based on the fundamental principles of quasi-optical and Gaussian beams, research has been conducted on quasi-optical reflectors and lenses, leading to the design of a quasi-optical feed system for millimeter-wave and submillimeter-wave antennas. This system is capable of simultaneously receiving electromagnetic radiation signals in the 89~115 GHz and 176~183 GHz frequency bands through two optical paths. Elliptical reflectors and lenses are utilized to focus the beams and control the system's structural envelope. Polarization grid networks are employed to separate channels, and calculations and preliminary analysis of dual-channel performance are conducted. The system operates in a low-temperature environment, and in response to practical requirements and cold optical analysis, constraints are proposed and optimized for the spatial position and beam radius of quasi-optical components. Theoretical calculations and simulation results indicate that the system meets the design requirements for cold optics and quasi-optics.
Based on the fundamental principles of quasi-optical and Gaussian beams, research has been conducted on quasi-optical reflectors and lenses, leading to the design of a quasi-optical feed system for millimeter-wave and submillimeter-wave antennas. This system is capable of simultaneously receiving electromagnetic radiation signals in the 89~115 GHz and 176~183 GHz frequency bands through two optical paths. Elliptical reflectors and lenses are utilized to focus the beams and control the system's structural envelope. Polarization grid networks are employed to separate channels, and calculations and preliminary analysis of dual-channel performance are conducted. The system operates in a low-temperature environment, and in response to practical requirements and cold optical analysis, constraints are proposed and optimized for the spatial position and beam radius of quasi-optical components. Theoretical calculations and simulation results indicate that the system meets the design requirements for cold optics and quasi-optics.
