一种CCD相机的视频处理电路设计与噪声分析

为使CCD相机系统能够捕获到高信噪比的图像,介绍了一种视频处理器TDA9965的应用电路设计,简述了其内部组成框图及工作原理。利用某型号TDI CCD作为系统传感器,成功实现了对CCD输出模拟视频信号的量化处理,能够使相机系统完成实时采集图像等任务。同时分析了视频处理器电路设计对相机系统图像信噪比的影响,以电源噪声为干扰源,具体计算了在电路设计不合理和改进设计后两种情况下,CCD相机图像信噪比的变化,并通过试验测试验证,合理的电路设计可以使图像的信噪比提高20 dB以上,从而说明了视频处理电路合理设计的重要性,为高速高信噪比CCD相机的研制提供了技术基础。     

Convection heat transfer from a hybrid circuit

Accurate values of heat transfer coefficient are needed for simulation of the thermal characteristics of a thick film resistor. In this paper, the results of an investigation are presented where an optical technique is used to study the convection plumes from a horizontally positioned hybrid resistor package. The observations have shown that simplifying approximations to the convection coefficients may be made in thermal analysis of such devices. Using these approximations and an optimization technique, values have been estimated for the coefficients.     

科学级CCD三维噪声模型及其评估

为了评估科学CCD噪声带给激光近场分布测量的影响,采用三维噪声模型,分析了科学级CCD的噪声,并将CCD的噪声分解为空间噪声和时间噪声。空间噪声用来评估CCD像元之间响应不一致性对测量的影响,时间噪声用来评估多次测量不一致性对测量的影响。通过设计测量系统对CCD三维噪声进行测量,并分析时空噪声的统计分布规律,发现两者均是依赖于信号、近似服从正态分布,建立了依赖于信号的时空噪声的数学模型,并实验验证了该模型是有效的。     

A physics-based MOSFET noise model for circuit simulators

Discussed is a physics-based MOSFET noise model that can accurately predict the noise characteristics over the linear, saturation, and subthreshold operating regions but which is simple enough to be implemented in any general-purpose circuit simulator. Expressions for the flicker noise power are derived on the basis of a theory that incorporates both the oxide-trap-induced carrier number and correlated surface mobility fluctuation mechanisms. The model is applicable to long-channel, as well as submicron n- and p-channel MOSFETs fabricated by different technologies, and all the model parameters can be easily extracted from routine I-V and noise measurements     

大幅度CCD输出信号降噪的相关双取样电路

电荷耦合器件(CCD)的输出信号构成复杂,包含有典型的KTC、1/f等类型的噪声,需要进行专门处理后才能获得与入射光信号相对应的高信噪比信号。文章针对具有较大幅度的CCD输出信号,采用宽电压工作的独立运放满足幅度较大的信号处理要求;通过在同一个运算放大器上实现噪声保持及信号采样的形式,消除了不同通道增益差异对信号的影响,获得了较高线性度的信号处理效果;同时结合CCD驱动器的设计,获取相关双取样技术所需的采样及保持脉冲信号,增强了采样与CCD输出信号间的关联程度,从而进一步提高了相关双取样技术消除CCD噪声的效果。采用这种信号处理电路后,将原来噪声处理的水平从约22 mV提高到了约1 mV,并且在一种精密的位移测量系统中得到应用,最后就具体电路设计的难点及注意事项进行了阐述。     

传感器电路中乘法器噪声模型分析

本文对两输入端都带噪声情况下乘法器的响应进行了理论推导,得到其噪声模型:乘法器输出噪声包括载波携带信号噪声项、信号携带载波噪声项以及噪声相乘项.设计传感器电路时,通过提高载波纯度及其幅度、在信号输入端加性能优良的带通滤波器,可以得到优异的噪声性能.本文用实验验证了该模型的正确性.     

Correlation between most 1/f noise and CCD transfer inefficiency

The 1/f noise in MOS transistors has been investigated and is shown to correlate with charge transfer inefficiency experiments on surface-channel CCDs. Both independent phenomena can be quantitatively explained by the same interface state model. The oxide trap density turns out to vary by more than a factor 10. The 1/f noise is compared with McWhorter's number fluctuation model and with the mobility fluctuation model. The oxide trap density is calculated from the charge transfer inefficiency in surface CCDs. Both the quantitative agreement between oxide trap density and 1/f noise and the observed dependence of 1/f noise on gate voltage here give strong arguments in favour of the McWhorter model. The investigated MOS transistors fall into a category that cannot be explained by the present mobility fluctuation model.     

Theory of spontaneous mode locking in lasers using a circuit model

A theory is presented of mode locking in lasers with dispersion in the resonator and a saturable absorber, using as a starting point a circuit representation of the physical processes in the system. A set of equations for mode amplitudes and phases is obtained that entails no significant approximations and is suitable in form for an iterative method of solution. The specific advantages of the method include 1) treating the problem without limiting the order of interaction in the absorber, and 2) introducing a circuit model that allows some intuitive approximations. A general expression for mode phases in a certain situation is developed as an example and the results are compared with published material.     

An integrated equivalent circuit model for relative intensity noise and frequency noise spectrum of a multimode semiconductor laser

Relative intensity noise (RIN) and the frequency/phase noise spectrum (FNS) equivalent circuit of a multimode semiconductor laser diode are derived from multimode rate equations with the inclusion of noise Langevin sources. FNS is an important parameter in optical communication systems, and its circuit model is presented, for the first time, in this paper. Both circuit models for RIN and FNS are integrated in one circuit. RIN and FNS are calculated as functions of frequency, output power, and mode number. It is shown that the RIN of the main mode is increased in the multimode lasers with higher mode numbers. Furthermore, we show that RIN and FNS are enhanced for higher output power. The dependency of a multimode laser diode linewidth on output power is also analyzed using the model.     

CCD低噪声读出电路设计

以红外增强型图像传感器TH7888A所得的微弱电压信号为输入,对图像传感器的模拟前端处理电路进行设计。采用巴特沃斯低通滤波器和全差分双相关采样的方法,提高整体电路的信噪比为67 dB,从而减少了后续电路的输入噪声。使用Proteus对所设计的低噪声、高增益放大电路的功能和噪声分析等特性进行全面的实验。实验结果表明,该设计能有效放大微弱电压信号,并可以对放大的电压信号进行准确的相关双采样去除KTC噪声、复位噪声。最后,在实际应用中,使用FPGA为硬件设计载体,以vivado作为软件开发环境,使用Verilog语言对时序发生器进行了硬件描述。FPGA生成的模拟信号分别作为读出电路的输入和采样的触发信号,并验证了其正确性和可行性。     

CCD噪声分析及处理技术

为了提高CCD的工作性能,根据CCD器件的工作原理,对CCD图像的噪声组成进行了较完整的分析,给出了其噪声的详细分类。根据各噪声的特点,提出了相应的噪声处理技术,并针对输出噪声,给出了双相关采样法、双斜积分法、钳住采样法三种相关双采样电路处理方式,使器件的信噪比得以提高。     

Dynamic noise model and its application to high speed circuit design

A dynamic noise model is developed and applied to analyze the noise immunities of precharge-evaluate circuits. With cross-talk being the main source of noise injection in the circuit, a simple metric represented as voltage-time product can be used to quantify the dynamic noise-margin. This is verified through HSPICE simulation on DOMINO gates. Based on this dynamic noise model, a tool is developed and applied to find the static and dynamic noise-margins at various points in the circuit with the effects of charge share and power/ground bounce taken into account. Obtained noise-margins are translated into maximum allowable coupling capacitances between the nodes for different types of precharge-evaluate logic circuits. The results show the difference in dynamic noise immunities in different logic families. Accurate estimates of dynamic noise-margins and coupling capacitance bounds will help design robust CMOS circuits.     

1/f noise synthesis model in discrete-time for circuit simulation

Flicker noise, popularly known as 1/f noise is a commonly observed phenomenon in semiconductor devices. To incorporate 1/f noise in circuit simulations, models are required to synthesize such noise in discrete time. This paper proposes a model based on the fact that 1/f processes belong to the class of statistically self-similar random processes. The model generates 1/f noise in the time domain (TD) with a simple white noise input and is parameterized by a quantity whose value can be adjusted to reflect the desired 1/f parameter, that is, the slope of the 1/f spectrum. It thus differs from most of the earlier modeling approaches, which were confined to the spectral domain. To verify fit between the model and actual 1/f noise measurements, experiments were conducted using discrete devices such as a PIN photodiode at various bias conditions and sampling frequencies. The noise synthesized by the model was found to provide a good match to the measurements. Furthermore, it is demonstrated that the proposed 1/f noise model can also be incorporated in circuit simulations as a noise current or noise voltage source, which was not feasible earlier with the conventional spectral domain representation. To validate the inclusion of 1/f noise in circuits as TD current or voltage, simulations were carried out on a CMOS ring oscillator and the clock jitter due to 1/f noise was investigated.     

Partition noise in CCD signal detection

Reset noise in CCD signal charge detection is analyzed experimentally and theoretically. From a reset noise measurement experiment, it has been inferred that reset noise consists of two parts: the sensing capacitance (Cs) dependent part and the effective reset channel length (L) dependent part. Conventional reset noise theory, where the Johnson noise in the reset MOS channel was regarded as the only noise source, agrees with the Csdependent part of measured reset noise. However, it cannot explain the L dependent part. To explain theLdependence, the authors propose "partition noise" caused by carrier partition in the reset MOS channel. Partition noise is analyzed by the unique technique of solving the one-dimensional diffusion equation. As a result, a reset channel capacitance dependent characteristic for partition noise has been derived, which agrees with theLdependent part for measured reset noise. Consequently, in addition to Johnson noise, partition noise is found to be a noise source in CCD signal detection.     

CCD noise removal in digital images.

In this work, we propose a denoising scheme to restore images degraded by CCD noise. The CCD noise model, measured in the space of incident light values (light space), is a combination of signal-independent and signal-dependent noise terms. This model becomes more complex in image brightness space (normal camera output) due to the nonlinearity of the camera response function that transforms incoming data from light space to image space. We develop two adaptive restoration techniques, both accounting for this nonlinearity. One operates in light space, where the relationship between the incident light and light space values is linear, while the second method uses the transformed noise model to operate in image space. Both techniques apply multiple adaptive filters and merge their outputs to give the final restored image. Experimental results suggest that light space denoising is more efficient, since it enables the design of a simpler filter implementation. Results are given for real images with synthetic noise added, and for images with real noise.     

Theory of emission noise from silicon field emitters

A calculation is made of the spectral density of emission fluctuations for silicon emitter tips for two emission mechanisms: emission mainly from surface states, and emission mainly from the conduction band edge. In both cases surface-state occupancy fluctuations, calculated from the generalized Nyquist formula, modulate the field emission current. The basic idea is that emission is likely to come from either surface states or from carriers in the conduction band, or both. If there are generation-recombination (G-R) fluctuations in the surface states at the emission surface, then there will be corresponding fluctuations from surface states. This G-R noise will also cause fluctuation in carrier concentrations in the emission area, and hence noise in emission from the conduction band. A discussion is given of whether the differing spectral densities for these two mechanisms may be compared with measurements to clarify which mechanism is dominant     

Determination of transfer noise from transfer-loss measurements in SCCD's

A simple technique is described that allows the determination of surface-state-induced transfer noise from transfer-loss measurements in surface-channel charge-coupled devices (SCCD's). Transfer noise has been measured on two-phase overlapping polysilicon electrode long-channel SCCD's at temperatures between 77 and 325 K in a frequency range of 1 KHz to 1 MHz. The validity of the technique is supported by the close agreement of the experimentally obtained data and the theoretically calculated values based upon independent measurements of the surface-state density and capture cross section in SCCD's.     

A compact model for flicker noise in MOS transistors for analog circuit design

Designers need accurate models to estimate 1/f noise in MOS transistors as a function of their size, bias point, and technology. Conventional models present limitations; they usually do not consistently represent the series-parallel associations of transistors and may not provide adequate results for all the operating regions, particularly moderate inversion. In this brief, we present a consistent, physics-based, one-equation-all-regions model for flicker noise developed with the aid of a one-equation-all-regions dc model of the MOS transistor.     

基于CPLD的面阵CCD驱动电路设计

在透射电子显微镜相机的研制中,针对SONY行间转移面阵CCD ICX285AL图像传感器,设计了一款基于CPLD的面阵CCD驱动电路。以Altera公司的CPLD芯片EPM570T100作为时序发生器产生CCD驱动信号和相关双采样控制信号,并搭建了驱动器电路和直流偏压电路。在QuartusⅡ13.1开发环境下利用Verilog HDL语言编程,并利用Model Sim SE 10.1进行仿真测试。实验结果表明,以CPLD为核心的驱动电路能够产生符合CCD要求的驱动脉冲和偏置电压,可稳定地输出CCD视频信号。     

溅射法制备硫化锌薄膜的XPS剖析

用Ｘ射线光电子能谱（ＸＰＳ）技术，测量了射频磁控溅射法（ＲＦＭＳ）制备的硫化锌薄膜（ＺｎＳ：Ｅｒ＾３＋）的表面及内部构态，认为氧吸附形成的表面构态是产生薄膜界面态和界面陷阱能级的主要原因，对研究器件的激发过程有参考意义