Crosstalk suppression in networked resistive sensor arrays using virtual ground technique

In 2D resistive sensor arrays, the interconnections are reduced considerably by sharing rows and columns among various sensor elements in such a way that one end of each sensor is connected to a row node and other end connected to a column node. This scheme results in total N?+?M interconnections for N?×?M array of sensors. Thus, it simplifies the interconnect complexity but suffers from the crosstalk problem among its elements. We experimentally demonstrate that this problem can be overcome by putting all the row nodes at virtually equal potential using virtual ground of high gain operational amplifiers in negative feedback. Although it requires large number of opamps, it solves the crosstalk problem to a large extent. Additionally, we get the response of all the sensors lying in a column simultaneously, resulting in a faster scanning capability. By performing lock-in-amplifier based measurements on a light dependent resistor at a randomly selected location in a 4?×?4 array of otherwise fixed valued resistors, we have shown that the technique can provide 86?dB crosstalk suppression even with a simple opamp. Finally, we demonstrate the circuit implementation of this technique for a 16?×?16 imaging array of light dependent resistors.     

线列探测器推扫成像中的锯齿拖影研究

在一种基于InGaAs材料的短波红外线列探测器中,光敏元呈品字形排列。在使用该探测器进行推扫成像时,图像中发现了锯齿状的拖影。这种拖影的出现降低了图像的质量。研究发现,串扰是锯齿拖影的成因,而串扰有多种来源,如探测器光敏元的光串或电串、电路的带宽不够等等。为了确定串扰的真正来源,进行了基于平行光管的单光点实验。实验观察了探测器对单光点的响应,实验结果表明这种锯齿拖影是探测器读出电路的带宽不够造成的。在改进了探测器读出电路的性能后,消除了图像中的锯齿拖影。     

Multiplexing of interferometric sensors using phase carrier techniques

This paper demonstrates the multiplexing of fiber-optic interferometric sensors using a CW phase generated carrier technique. The technique employs modulated diode laser sources at different carrier frequencies, nearly balanced interferometers (∼4-cm path difference), and phase generated carrier demultiplexing demodulation. This approach leads to a simple all-passive sensor array which has intrinsically low crosstalk. The system is analyzed in terms of shot noise performance and crosstalk. An experimental all optical implementation of a four sensor array was demonstrated; both the single sensor and multisensor arrays were limited by the laser phase noise to a sensitivity ofsim 18 murad/sqrt{Hz}. Crosstalk between individual channels was better than -60 dB and crosstalk between three sensors and the test sensor was better than -55 dB. In the absence of laser phase noise the demodulator/demultiplexer demonstratedsim 2-murad performance with both single sensor and four element array operation.     

Crosstalk Analysis of a Fiber Laser Sensor Array System Based on Digital Phase-Generated Carrier Scheme

A detailed study on analyzing the crosstalk in a wavelength division multiplexed fiber laser sensor array system based on a digital phase generated carrier interferometric interrogation scheme is reported. The crosstalk effects induced by the limited optical channel isolation of a dense wavelength division demultiplexer (DWDM) are presented, and the necessary channel isolation to keep the crosstalk negligible to the output signal was calculated via Bessel function expansion and demonstrated by a two serial fiber laser sensors system. Finally, a three-element fiber laser sensor array system with a 50-dB channel-isolation DWDM was built up. Experimental results demonstrated that there was no measurable crosstalk between the output channels.     

Characterization of crosstalk noise in submicron CMOS integratedcircuits: an experimental view

A way to characterize the crosstalk noise susceptibility for integrated circuits fabrication technologies is presented. A comparison between 0.7- and 0.35-μm technologies shows the increasing importance of crosstalk noise and, therefore, the need to consider this effect at the design level in submicron integrated circuits. An approach to measure the internal crosstalk generated by long metal interconnects based on using an RS latch sensor is proposed. An implementation and experimental measurements for 0.7-μm technology are reported, confirming the very high noise peak values     

Investigation of adjacent channel crosstalk in multichannelmonolithically integrated 1.55 μm photoreceiver arrays

We have investigated adjacent channel crosstalk in 3-, 8-, and 16-channel InP-based monolithically integrated p-i-n/HBT photoreceiver arrays, with a channel bandwidth of 11 GHz. By using a novel monolithically integrated radiation shield, we have been able to reduce the crosstalk to -35 dB at 10 GHz. These parameters represent the best performance in multichannel integrated photoreceiver arrays. The two main components of crosstalk are found to be radiation crosstalk and electrical crosstalk and these are separately dependent on interchannel spacing and single- or dual-source biasing schemes. An electromagnetic full-wave solution shows that the measured crosstalk in arrays without the radiation shield could be dominated by radiation crosstalk, which can be modeled as a capacitive coupling between adjacent channels. Similarly, electrical crosstalk can be modeled by equivalent parasitic resistive and inductive elements. Values of these circuit elements have been determined by analyzing experimental data     

论红外焦平面器件的串音

红外探测系统通常需要将探测器密集排列以增加它们的空间分辨率。在焦平面阵列中,当投射到某一特定探测器光敏面上的红外光子在另一个探测器中产生信号时,这种现象称为串音。串音可能会影响焦平面阵列的分辨率性能。在高性能光伏阵列中,串音的主要成分是光生载流子在焦平面阵列的相邻探测器之间的横向扩散。从基本概念入手,介绍了相关串音研究的发展情况以及对串音问题的理解和体会。     

基于视觉显著性的立体显示灰阶串扰量化

为了更为合理地评价立体显示系统中的串扰现象,对传统灰阶串扰进行了加权并进一步单一数值量化。研究选取了大量涵盖各种类型和场景的立体图像,对每一灰阶转换组合出现的概率进行统计,同时提取立体图像视觉显著性,提出了平均灰阶转换显著性的概念。平均灰阶转换显著性以矩阵形式呈现,应用其对传统灰阶串扰矩阵加权后可获得更为合理的灰阶串扰。加权后的灰阶串扰矩阵求和后即可获得数值范围在0%~100%的单一数值串扰。提出的加权灰阶串扰及其数值单一化方法充分考虑了图像内容和人眼视觉关注机理的影响,得到的评价结果更加客观、合理。同时,研究结果对串扰现象的优化以及视觉舒适度的提高具有指导和推动作用。     

Multiplexing of optical fiber sensors using a frequency-modulated source and gated output

A novel method is proposed and demonstrated for multiplexing fiber-optic interferometric sensors using the FMCW technique. The method uses a gas laser whose optical frequency is modulated sinusoidally by an external modulator. The use of gating and appropriate signal processing can achieve low crosstalk between sensors. Experiments on two and three sensor systems are reported. The minimum detectable signal measured is 1 mrad/sqrt{Hz}and the crosstalk factor achieved is -35 dB. The major causes of crosstalk are also analyzed.     

用响应和串音识别焦平面探测器相连缺陷元研究

采用高倍光学显微镜和焦平面探测器测试系统对焦平面探测器相连缺陷元进行了测试分析,研究了焦平面探测器相连缺陷元的成因。研究结果表明:借助高倍光学显微镜很难识别相连缺陷元;采用焦平面探测器响应测试系统进行测试时,相连缺陷元的响应电压与正常元基本相同,相连缺陷元无法被识别;采用焦平面探测器串音测试系统进行测试时,相连缺陷元之间串音为100%,明显不同于正常元,此时两元相连缺陷元响应电压是正常元响应电压的二分之一,相连缺陷元可以被有效识别。光刻腐蚀引入的台面或电极相连,以及光刻剥离引入的铟柱相连导致了缺陷元的产生;通过光刻腐蚀、剥离工艺优化,可以有效减少焦平面探测器相连缺陷元。     

微热板阵列的热干扰

针对微热板阵列建立了热路模型,并对热干扰进行分析.结果表明,由于微热板悬窄结构的热阻比硅芯片的热阻高3个数量级.因此微热板阵列芯片的热干扰温度取决于封装对环境的热阻,而芯片上器件的间距对热干扰温度的影响可以忽略.研制了3种布局、T05和DIPl6两种封装形式的微热板阵列,并对阵列中的热干扰问题进行了实验测试.测试数据验证了热路模型的结论.因此,减小微热板阵列或集成芯片的热干扰的关键在于,尽可能增大微热板悬空结构的热阻以及选用热阻小的封装形式.     

Electrical crosstalk in p-i-n arrays - Part I: Theory

The electrical crosstalk between elements in a monolithic array of long wavelength p-i-n photodiodes is analyzed theoretically. It is shown that the parisitic capacitances in the external package are the dominant effects contributing to crosstalk, whereas resistive coupling leads to a negligible crosstalk. A general theory is derived to determine the effects of the capacitive coupling between channels on digital optical receiver sensitivity. The case of a raised cosine output waveform and an FET transimpedance amplifier is then considered to illustrate the tradeoff between crosstalk and receiver sensitivity. It is shown that the tradeoff may be optimized by varying the feedback resistance in a transimpedance amplifier.     

Statistical analysis of interferometric crosstalk: theory andoptical network examples

General, statistical properties of accumulation of interferometric crosstalk due to a number of interfering signals are analyzed. The probability density function of the total crosstalk is derived as function of the sum of the incoherent crosstalk contributions associated with the interfering signals, Because the total crosstalk level can be expected to vary only slowly as compared to the time duration of one bit, the probability p that the total crosstalk exceeds a maximum tolerable value is introduced as a parameter in the crosstalk and bit error rate analysis of optical networks. General computations show that the crosstalk requirement on optical network elements may be significantly relaxed if it can be accepted that it is possible, although most unlikely, that the total crosstalk may exceed this maximum tolerable value. The statistical crosstalk model is then illustrated by investigation of optical network examples with respect to their crosstalk and transmission properties, and, finally, compared with previous crosstalk models     

Interference filter all-fibre directional coupler for w.d.m.

Directional couplers for wavelength division multiplexing using l.e.d.s as transmitters have been realised without imaging elements. Their total insertion loss (MUX + DEMUX) is of the order of 4 dB; their crosstalk attenuation and near-end crosstalk attenuation are 30 dB and >60 dB, respectively.     

Non-blocking four-port optical router based on thermo- optic silicon microrings

By using silicon-on-insulator(SOI) platform, 12 channel waveguides, and four parallel-coupling one-microring resonator routing elements, a non-blocking four-port optical router is proposed. Structure design and optimization are performed on the routing elements at 1 550 nm. At drop state with a power consumption of 0 m W, the insertion loss of the drop port is less than 1.12 d B, and the crosstalk between the two output ports is less than-28 d B; at through state with a power consumption of 22 m W, the insertion loss of the through port is less than 0.45 d B, and the crosstalk between the two output ports is below-21 d B. Routing topology and function are demonstrated for the four-port optical router. The router can work at nine non-blocking routing states using the thermo-optic(TO) effect of silicon for tuning the resonance of each switching element. Detailed characterizations are presented, including output spectrum, insertion loss, and crosstalk. According to the analysis on all the data links of the router, the insertion loss is within the range of 0.13—3.36 d B, and the crosstalk is less than-19.46 d B. The router can meet the need of large-scale optical network-on-chip(ONo C).     

Evaluation of Thermal Crosstalk in Quantum Cascade Laser Arrays

The continuous-wave operation, thermal crosstalk measurements, and thermal modeling of a quantum cascade (QC) laser array are presented. Measurements and thermal modeling predict that the thermal crosstalk between array elements can be minimized by improving the heat management when the spacing of neighboring laser elements is greater than 500 mum. The output power of the demonstrated QC laser array significantly exceeds the output power of the individual lasers in the array. This shows the potential of the QC arrays as a candidate for the realization of high-power optical sources in mid-infrared (3-20 mum) spectral range     

Frequency multiplexing of remote all-fiber Michelsoninterferometers with lead insensitivity

A scheme to frequency multiplex a group of sensors based on all-fiber Michelson interferometers is presented. Lead insensibility is obtained by using the two fiber leads of the configuration as an extra Michelson interferometer whose differential phase is kept constant by active compensation. Topics concerning the system design, sensor sensitivity, and crosstalk between sensors are investigated. Experimental and numerical computational results are presented     

T型微带线间串扰问题的FDTD分析与抑制

T型微带线的串扰是高速电路信号完整性问题中的重要组成部分。采用PML(Perfectly Matched Layer)-FDTD方法首次对T型微带线间的串扰问题进行全波分析,并给出抑制串扰的具体措施。PML-FDTD仿真结果表明,不同的改进结构参数对串扰的影响不同:(1)开口距离S越大线间串扰越小,最多减小10dB;(2)开口角度 越小线间串扰越小,减小幅度最多达14dB。由此得出,在T型微带线上开三角形口,通过改变开口距离S和开口角度 可实现对邻近微带线串扰的有效抑制。     

Time-domain addressing of remote fiber-optic interferometric sensor arrays

This paper describes and analyzes a particular application of high duty-cycle time-division multiplexing to the separation and identification of signals from an interferometric sensor array. Using the method discussed here, the coherence length of the laser is no longer a severe design constraint. Also, the source phase-induced intensity noise which limits some other multiplexing methods may be overcome, leading to a higher sensitivity. The arrays of all-passive remote sensors exhibit minimal crosstalk between sensors, and have downlead insensitivity. A synthetic heterodyne demodulation technique prevents environmentally induced signal fading. Analysis includes coupling ratios for all directional couplers in the system, signal and noise spectra, minimum detectable phase shift, and the effect of ac coupling on noise and crosstalk. An experimental all-fiber implementation of a two sensor array has yielded a measured sensitivity of approximately 10 μrad/sqrt{Hz}over a range of signal frequencies, and a crosstalk level of better than 55 dB.     

A monolithic image sensor for a reading aid for the blind

A compact optical-tactile reading aid that allows a blind person immediate access to virtually all printed reading material used by sighted people has been developed. A singular feature of this instrument is a silicon monolithic image-sensing array that serves as the "retina" of the reading aid: signals from the retina are used to control an array of piezoelectric stimulators that form tactile images of printed characters. The image sensor consists of a 24×6 matrix of bipolar phototransistors integrated on a chip approximately 3×5 mm in size, and is designed on the basis of electrical, optical, psychological, and psychophysical considerations. The column-isolated structure incorporates a 2 to 1 aspect ratio to provide sufficient resolution and field of view for unambiguous letter-by-letter detection using a minimum number of sensor elements. A one-dimensional scanning technique minimizes fixed pattern noise and reduces the complexity of the total system. The individual 150×300 µm photosensing elements are optimized for maximum responsivity, uniformity, and dynamic range. The doping profile, featuring a 2 µm base depth and 12 µm epitaxial thickness, is based on spectral response and on a detailed electrical analysis of array operation. Output nonuniformity is minimized, and electrical crosstalk is virtually eliminated by designing for hFE≥ 200 and CTC/CTE≥ 5. Array performance correlates well with the predicted characteristics and has led to improved reading speeds greater than 50 words per minute.