In the field of CMOS image sensors research, the design and application of Low-Voltage Differential Signaling (LVDS) drivers are key to achieving efficient video signal transmission. As the frequency of LVDS signals continues to increase, issues of signal loss and attenuation during long-distance cable transmission have become more prominent, posing greater challenges to the performance stability of LVDS drivers. This paper establishes a model for CMOS image sensor LVDS drivers and transmission lines, detailing the attenuation mechanisms of LVDS transmission lines and their impact on differential signal transmission. The study focuses on methods for matching the design of LVDS drivers with transmission line characteristics, while also analyzing the interaction mechanisms between the operating states of MOS transistors in the circuit and key variables of the RLGC transmission line model. Using 1Gbps LVDS data and a 20cm flexible transmission ribbon cable as an example, the effectiveness of the matching method was validated through simulation experiments. This method provides technical support for the reliable design of high-speed LVDS drivers in image sensors or other chips, and offers useful references for the engineering selection of LVDS high-frequency transmission lines.
The interfacial asymmetry and compositional disorder caused by atomic segregation and exchange significantly affect the electrical properties of the InAs/InAsSb superlattice, leading to deviations from original designs. The study presents a quantitative analysis of the compositional asymmetry of the superlattice and its effects using a segregation model and 8-band k.p model. The composition disorder at each interface, primarily induced by Sb segregation, is examined through the reconstruction of the actual atomic sequence structure based on scanning tunneling microscopy results. Three different atomistic structures of the superlattice are modeled using the k.p method, including the ideal MBE-growth structure, a rebuilt structure with Sb segregation only at the InAs-on-InAsSb interface, and a rebuilt structure with Sb segregation at both interfaces. The results of the modeling highlight the significant influence of Sb segregation on the electronic properties of InAs/InAsSb superlattices.
The band structures of the InAs/GaSb type-Ⅱ superlattice are investigated using the 8-band k.p method. The finite difference method (FDE) is used for solving the Schrödinger equation. It is found that a small variation in the valence band offset (VBO, one of the input parameters) could cause a great change in cut-off wavelength, especially at the long-wavelength range. We also developed a GUI application based on this method. Users could quickly get band structure details, such as bandgap energy, miniband energy, and wavefunctions with this GUI. The program and its code are available at https://github.com/STONEDIY/K.p-Mehtod-for-InAs-GaSb-Superlattice-Band-Structure-Calculation.
Infrared detectors for astronomy application are supposed to work under cryogenic temperature due to lower dark current and readout noise. A prototype for infrared detector front electronics which can operate under cryogenic temperature is presented on this paper. Several commercial off-the-shelf (COTS) devices from different technologies were extensively characterized at as low as 4K including voltage reference, operational amplifier, ADC, MCU and etc.. The results demonstrate that AD8616 could perfectly work under 4K, Cortex-M4 ARM MCU operates well above roughly around 35K, AD7983 start to loss code at 180K and XFET reference ADR433 begin to show a significant voltage drop at 120K. The failure mechanism of COTS devices is also analyzed based on the cryogenic test results.
KEYWORDS: Signal to noise ratio, Short wave infrared radiation, Infrared detectors, Analytical research, Sensors, Amplifiers, Analog electronics, Interference (communication), Signal detection, Resistance
SWIR (Short Wave Infrared) imaging is an important imaging technology in space remote sensing. According to the characteristics of SWIR detector, the whole scheme of low noise imaging circuit is presented in this paper. For certain key circuit which noise is sensitive in the design, such as bias generation circuit, analysis of noise sources and calculation of theoretical noise value of actual circuit which is usually ignored in previous researches are proposed in order to estimate the level of circuit noise and optimize the circuit to reduce noise. The structure of analog filter amplifier circuit is also analyzed by introducing noise-factor analytic approach, based on the analysis result some design principles of the circuit are proposed. The noise suppression methods in the design are separately analyzed in both time suppression and space suppression; some specific methods for these two kinds of measures are listed in this paper. The final experiment results indicate that the low noise imaging circuit design based on above methods is reasonable and effective, the circuit has a higher SNR and can work normally at room temperature, and the whole design meets the original requirement of low noise. This low noise circuit for SWIR detector and its methods to analyze and calculate noise value are valuable examples for future similar designs.
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