Copyright (c) 2009 All rights reserved. http://works.bepress.com/jan_vanderspiegel Recent documents in Jan Van der Spiegel en-us Sun, 31 May 2009 06:58:21 PDT 3600 http://works.bepress.com/jan_vanderspiegel/40 http://works.bepress.com/jan_vanderspiegel/40 Wed, 16 Jan 2008 17:24:44 PST A silicon retina chip with a central foveal region for smooth-pursuit tracking and a peripheral region for saccadic target acquisition is presented. The foveal region contains a 9 x 9 dense array of large dynamic range photoreceptors and edge detectors. Two-dimensional direction of foveal motion is computed outside the imaging array. The peripheral region contains a sparse array of 19 x 17 similar, but larger, photoreceptors with in-pixel edge and temporal ON-set detection. The coordinates of moving or flashing targets are computed with two one-dimensional centroid localization circuits located on the outskirts of the peripheral region. The chip is operational for ambient intensities ranging over six orders of magnitude, targets contrast as low as 10%, foveal speed ranging from 1.5 to 10K pixels/s, and peripheral ON-set frequencies from <0.1 to 800 kHz. The chip is implemented in 2-μm N well CMOS process and consumes 15 mW (V dd = 4 V) in normal indoor light (25 μW/cm2). It has been used as a person tracker in a smart surveillance system and a road follower in an autonomous navigation system. Ralph Etienne-Cummings http://works.bepress.com/jan_vanderspiegel/39 http://works.bepress.com/jan_vanderspiegel/39 Wed, 16 Jan 2008 17:24:41 PST We present a CMOS image sensor capable of both voltage- and current-mode operations. Each pixel on the image has a single transistor acting as either source follower for voltage readout, or transconductor for current readout. The two modes share the same readout lines, but have their own correlated double sampling (CDS) units for noise suppression. We also propose a novel current-mode readout technique using a velocity saturated short-channel transistor, which achieves high linearity. The 300x200 image array is a mixture of 3 types of pixels with identical photodiodes and access switches; while the readout transistors are sized for their designated mode of operation. This ensures a fair comparison on the performance of the different modes. Zheng Yang http://works.bepress.com/jan_vanderspiegel/38 http://works.bepress.com/jan_vanderspiegel/38 Wed, 16 Jan 2008 17:24:39 PST In this paper, a novel method for single-channel speech enhancement is proposed, which is based on a spectral conversion feature denoising approach. Spectral conversion has been applied previously in the context of voice conversion, and has been shown to successfully transform spectral features with particular statistical properties into spectral features that best fit (with the constraint of a piecewise linear transformation) different target statistics. This spectral transformation is applied as an initialization step to two well-known single channel enhancement methods, namely the iterativeWiener filter (IWF) and a particular iterative implementation of the Kalman filter. In both cases, spectral conversion is shown here to provide a significant improvement as opposed to initializations using the spectral features directly from the noisy speech. In essence, the proposed approach allows for applying these two algorithms in a user-centric manner, when "clean" speech training data are available from a particular speaker. The extra step of spectral conversion is shown to offer significant advantages regarding output signal-to-noise ratio (SNR) improvement over the conventional initializations, which can reach 2 dB for the IWF and 6 dB for the Kalman filtering algorithm, for low input SNRs and for white and colored noise, respectively. Athanasios Mouchtaris http://works.bepress.com/jan_vanderspiegel/37 http://works.bepress.com/jan_vanderspiegel/37 Wed, 16 Jan 2008 17:24:36 PST This paper presents a phase noise model for clock buffers. The model can be used to predict the phase noise introduced by clock buffers and to gain insight into phase noise transfer mechanisms in clock buffers. Based on the models, techniques for low phase noise clock buffer design are derived. The analytical results presented here have good agreement with simulation and measurement results. Chao Xu http://works.bepress.com/jan_vanderspiegel/36 http://works.bepress.com/jan_vanderspiegel/36 Wed, 16 Jan 2008 17:24:34 PST A motion detection algorithm, based on biological and computational models, for focal plane implementation has been developed. This Temporal Domain Optical Flow Measurement (TDOFM) algorithm uses computational components which have direct and compact electronic counterparts. It uses a binary image of zero-crossings, 2 level analog signals, the signs of spatiotemporal derivatives, 1-b multiplication and pulse widths to measure image velocity. Compared to other IC visual motion detectors, this sensor represents the first instance of a robust, wideband and general purpose 2-D motion sensor which reports speed and direction explicitly, has a wide dynamic range and has a compact IC implementation. The front-end of the motion cells is an edge detection circuit which responds to 5-6 orders of magnitude of light intensity and produces near maximum outputs for contrasts as low as 40% in bright and dim ambient conditions. The theoretical velocity measurement dynamic range of the sensor is 4-5 orders of magnitude, and motion ranging over three orders of magnitude has been measured. The variation in the measured speed is less than 15% across 1- and 2-D implementations, multiple chips, cells and directions. The complete system, including the photoreceptors and edge detection circuits, consumes less than 0.4 mW per cell at ± 3.5 V. Ralph Etienne-Cummings http://works.bepress.com/jan_vanderspiegel/35 http://works.bepress.com/jan_vanderspiegel/35 Wed, 16 Jan 2008 17:24:30 PST The Iterative Wiener Filter (IWF) for speech enhancement in additive noise is an effective and simple algorithm to implement. One of its main disadvantages is the lack of proper criteria for convergence, which has been shown to introduce severe degradation to the estimated clean signal. Here, an improvement of the IWF algorithm is proposed, when additional information is available for the signal to be enhanced. If a small amount of clean speech data is available, spectral conversion techniques can be applied for esimating the clean short-term spectral envelope of the speech signal from the noisy signal, with significant noise reduction. Our results show an average improvement compared to the original IWF that can reach 2 dB in the segmental output Signal-to-Noise Ratio (SNR), in low input SNR's, which is perceptually significant. Athanasios Mouchtaris http://works.bepress.com/jan_vanderspiegel/34 http://works.bepress.com/jan_vanderspiegel/34 Wed, 16 Jan 2008 17:24:28 PST An architectural overview of an image sensor with general spatial processing capabilities on the focal plane is presented. The system has been fabricated on two separate tiers, implemented on silicon-on-insulator technology with vertical interconnect capabilities. One tier is dedicated to imaging, where photosensitivity and pixel fill have been optimized. The subsequent layers contain noise suppression and digitally controlled analog processing elements, where general spatial filtering is computed. The digitally controlled aspect of the processing unit allows generic receptive fields to be computed on read out. The image is convolved with four receptive fields in parallel. The chip provides parallel readout of the filtered results and the intensity image. Viktor Gruev http://works.bepress.com/jan_vanderspiegel/33 http://works.bepress.com/jan_vanderspiegel/33 Wed, 16 Jan 2008 17:24:25 PST This paper described a novel current-mode active pixel sensor (APS) imager. Conversion of photodiode voltage to output current is done using transistors operating in velocity saturation region. The high output impedance of this region makes it more suitable for current-sourcing operation than the linear region. The transistors also exhibit high linearity, allowing us to suppress fixed pattern noise (FPN) by correcting for both offset and gain variations among pixels. Experimental results on the fabricated 110×200 pixel array are presented. With conventional correlated double sampling (CDS), FPN is reduced from 3.8% to 0.85%. Further reduction requires compensation of gain variations, and results in a final FPN of 0.19%. A triple sampling approach is introduced to implement the described correction in hardware. Zheng Yang http://works.bepress.com/jan_vanderspiegel/32 http://works.bepress.com/jan_vanderspiegel/32 Wed, 16 Jan 2008 17:24:22 PST This paper presents an extended frequency range CMOS monolithic voltage-controlled oscillator (VCO) design. A negative feedback control algorithm is used to automatically adjust the VCO range according to the control voltage. Based on this analog feedback control algorithm, the VCO achieves a wide range without any pre-register settings. Low phase noise is achieved by using both coarse control and fine control in VCO. A 600 MHz to 3.3 GHz monolithic CMOS PLL based on this wide range and low phase noise VCO has been fabricated in TSMC 0.18 μm, 1.8V CMOS technology and is used in many different applications such as FC, GE, and SONET etc. Chao Xu http://works.bepress.com/jan_vanderspiegel/31 http://works.bepress.com/jan_vanderspiegel/31 Wed, 16 Jan 2008 17:24:19 PST The authors report the results of a project to reemphasize high quality, hands-on laboratory courses in the engineering curriculum while reducing their costs through the application of web-based teaching tools. The project resulted in substantial gains in productivity of faculty and staff, increased utilization of laboratory space, cost reductions in equipment, and improved quality of learning for our students. Rita M. Powell