Hong Kong Applied Science and Technology Research Institute ASTRI

Hong Kong, Hong Kong

Hong Kong Applied Science and Technology Research Institute ASTRI

Hong Kong, Hong Kong

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Xie B.,Hong Kong Applied Science and Technology Research Institute ASTRI | Shi X.Q.,Hong Kong Applied Science and Technology Research Institute ASTRI | Chung C.H.,Hong Kong Applied Science and Technology Research Institute ASTRI | Lee S.W.R.,Hong Kong University of Science and Technology
Proceedings - Electronic Components and Technology Conference | Year: 2010

Through-silicon-via (TSV) becomes an emerging interconnection technology with various TSV structures, among which the annular-TSV demonstrates great application potentials because of its simple manufacturing processes and low cost. Due to the mismatch of coefficient of thermal expansion (CTE) among various materials leading to various quality and reliability issues, it is necessary to develop a novel modeling/simulation approach to help with optimizing annular-TSV structures and process parameters because the plated-Cu uniformity highly depends on Cu-plating solution, plating process and via location. Therefore, a novel sequential electro-chemical and thermo-mechanical simulation methodology was developed with simulation procedures as the electro-chemical analyses to simulate Cu-plating process, followed by the thermo-mechanical analyses (from wafer-level model, chip-level model to via-level model) to simulate key TSV insulation/plating processes using global-local and death-birth simulation methods. Based on the novel simulation methodology, this work studied the variations of plated-Cu thickness and found the stress of annular-TSVs near wafer edge was larger than that at wafer center by 16%-18% due to the Cu-plating non-uniformity. The stress of annular-TSVs would increase by 10%-31% and by 9%-27% if reducing the Cu seed thickness from 2um to 0.5um and reducing the via pitch from 300um to 150um, respectively. © 2010 IEEE.


Zhang X.,University of Sussex | Wang W.,Micro Image U.K. Ltd. | Sze G.,Hong Kong Applied Science and Technology Research Institute ASTRI | Barber D.,University of Sheffield | Chatwin C.,University of Sussex
IEEE Transactions on Medical Imaging | Year: 2014

The Sussex MK4 electrical impedance mammography system is especially designed for 3-D breast screening. It aims to diagnose breast cancer at an early stage when it is most treatable. Planar electrodes are employed in this system. The challenge with planar electrodes is the inaccuracy and poor sensitivity in the vertical direction for 3-D imaging. An enhanced image reconstruction algorithm using a duo-mesh method is proposed to improve the vertical accuracy and sensitivity. The novel part of the enhanced image reconstruction algorithm is the correction term. To evaluate the new algorithm, an image processing based error analysis method is presented, which not only can precisely assess the error of the reconstructed image but also locate the center and outline the center and outline the shape of the objects of interest. Although the enhanced image reconstruction algorithm and the image processing based error analysis method are designed for the Sussex MK4 system, they are applicable to all electrical impedance tomography systems, regardless of the hardware design. To validate the enhanced algorithm, performance results from simulations, phantoms and patients are presented. © 1982-2012 IEEE.


Ng D.C.W.,Hong Kong Applied Science and Technology Research Institute ASTRI | Kwong D.K.K.,Hong Kong Applied Science and Technology Research Institute ASTRI | Wong N.,University of Hong Kong
IEEE Transactions on Very Large Scale Integration (VLSI) Systems | Year: 2011

We present a low-power bandgap reference (BGR), functional from sub-1 V to 5 V supply voltage with either a low dropout (LDO) regulator or source follower (SF) output stage, denoted as the LDO or SF mode, in a 0.5-μm standard digital CMOS process with V tn≈ 0.6 V and |V tp| ≈ 0.7 V at 27 °C. Both modes operate at sub-1 V under zero load with a power consumption of around 26 μW. At 1 V (1.1 V) supply, the LDO (SF) mode provides an output current up to 1.1 mA (0.35 mA), a load regulation of ±8.5 mV/mA (±33 mV/mA) with approximately 10 μ s transient, a line regulation of ±4.2 mV/V (±50μV/V), and a temperature compensated reference voltage of 0.228 V (0.235 V) with a temperature coefficient around 34 ppm/° C from -20°C to 120 °C. At 1.5 V supply, the LDO (SF) mode can further drive up to 9.6 mA (3.2 mA) before the reference voltage falls to 90% of its nominal value. Such low-supply-voltage and high-current-driving BGR in standard digital CMOS processes is highly useful in portable and switching applications. © 2010 IEEE.


Zhu L.,Chinese University of Hong Kong | Yum T.-S.P.,Hong Kong Applied Science and Technology Research Institute ASTRI
IEEE Transactions on Communications | Year: 2010

The anti-collision algorithm is an important part of the Radio-Frequency Identification (RFID) system. Of the various possible algorithms, the Framed Aloha based (FA) algorithms have been most widely used due to their simplicity and robustness. Previous studies have focused mainly on the tag population estimation, choosing the frame size based on the classical results of Random Access (RA) systems. We show that a new theory is needed for algorithm design for RFID systems, because RFID and RA systems are fundamentally different. The Philips RFID system is studied in this paper. We model the reading process as a Markov Chain and derive the optimal reading strategy by first-passage-time analysis. The optimal frame sizes are derived analytically and numerically. © 2010 IEEE.


Chao S.-C.,Hong Kong Applied Science and Technology Research Institute ASTRI
IEEE Technology Time Machine Symposium on Technologies Beyond 2020, TTM 2011 | Year: 2011

In Hong Kong, an aging population and rising healthcare cost have put a lot of stress on the healthcare infrastructure. By 2033, almost one in four in the population will be 65 or older, while the healthcare expenditure will take up 9.2% of the GDP. It becomes an increasingly challenging problem to provide sustainable, accessible and good quality of health care to the elderly citizens. © 2011 IEEE.


Sun P.,Hong Kong Applied Science and Technology Research Institute ASTRI | Leung V.,Hong Kong Applied Science and Technology Research Institute ASTRI | Yang D.,Hong Kong Applied Science and Technology Research Institute ASTRI | Lou R.,Hong Kong Applied Science and Technology Research Institute ASTRI | And 2 more authors.
Proceedings - Electronic Components and Technology Conference | Year: 2010

Package-on-Package (PoP) is one of the major 3D packaging approaches. It vertically combines discrete memory and logic Ball Grid Array (BGA) packages, where one package rests on the top of the other. Recently, PoP technologies have attracted more interests, especially for portable electronics related products and applications. ASTRI has developed a new PoP structure, which employs a new bottom package which is over molded Finepitch Ball Gird Array (FBGA) format with mechanically balanced package structure. For the top package, it is a commercial FBGA format with two die stacked inside. Since the new bottom package structure is based on an existing FBGA format, the mold chase is independent of the mold cap and size of the bottom PoP package. The final mold layer for bottom package has a thickness of 0.50mm. The top interface of the bottom PoP package has 136 pads with 0.65mm pitch and a two-row peripheral format, while the bottom interface has 272 pads with 0.65mm pitch and a four-row peripheral format. The size of both top and bottom packages is 14 × 14mm2. The 3D finite element (FE) simulator Ansoft HFSS was used to evaluate the high-frequency performance of the new PoP structure. The low-loss and low cross-coupling results indicate that the above PoP offers a promising solution for communication-related products. Physical configuration of the package was evaluated by cross section & scanning electron microscopy (SEM) examination, which showed a favorable interconnection structure. The warpage of the bottom PoP package after assembly process was characterized by a shadow moiré system. The warpage was well controlled by adopting a fully molded structure. The average package warpage value was around 30μm that was well below the warpage target of 80μm widely used in the industry. In this work, the moisture sensitivity level-3 (MSL-3) test was applied to evaluate the reliability of the above package. Board-level reliability including temperature cycling (TC) & drop tests were also evaluated. The results of the reliability tests showed good performance and demonstrated that the above PoP is a viable design. In summary, the above PoP design exhibited promising RF performance, excellent warpage performance, qualified package-level and boardlevel reliability. It offers an effective solution for high-density packages used in the portable consumer electronics. © 2010 IEEE.


Chan C.-F.,City University of Hong Kong | Yu E.W.M.,Hong Kong Applied Science and Technology Research Institute ASTRI
European Signal Processing Conference | Year: 2010

A detection and classification system for sound surveillance is presented. A human/non-human voice classifier is firstly applied to separate the input sound into human voice sound or non-human emergency sound. It utilizes a sliding window Hidden Markov Model (HMM) with trained background, human voice and non-human sound templates. In case of human voice, a scream/non-scream classification is performed to detect screaming in an abnormal situation such as screaming for help during bank robbery. In case of nonhuman sound, an emergency sound classifier capable of identifying abnormal sounds such as gun shot, glass breaking, and explosion, is employed. HMM is used in both scream/non-scream classification and emergency sound classification but with different sound feature sets. In this research, a number of useful sound features are developed for various classification tasks. The system is evaluated under various SNR conditions and low error rates are reported. © EURASIP, 2010.


Liu Y.,Hong Kong Applied Science and Technology Research Institute ASTRI
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2010

This letter proposes a unified loop filter for video coding, which suppresses the quantization noise optimally and improves the objective and subjective qualities of the reconstructed picture simultaneously. The proposed filter unifies nonlinear enhancement filter and linear restoration filter within the classical optimization framework of least mean square error. To adapt to locally diverse quantization error characteristics, classification-based strategy is employed to design unified loop filters with different characteristics, which further improves the capability of picture restoration. Experimental results show that the proposed filter achieves superior objective coding gain and better visual quality improvement around edges and textures, compared with H.264/AVC high profile. © 2010 IEEE.


Liu Y.,Hong Kong Applied Science and Technology Research Institute ASTRI | Huo Y.,Hong Kong Applied Science and Technology Research Institute ASTRI
2010 IEEE International Conference on Multimedia and Expo, ICME 2010 | Year: 2010

In this paper, we propose a unified loop filter for high-performance video coding, which suppresses the quantization noise optimally and improves the objective and subjective quality of the reconstructed picture simultaneously. The proposed filter unifies nonlinear enhancement filter (for removing blocking and ringing artifacts) and linear restoration filter (for improving coding efficiency) within the classical optimization framework of least mean square error (LMSE). Experimental results show that the proposed unified loop filter achieves on average 11.53% objective coding gain in combination with better visual quality improvement around edges and textures, compared with H.264/AVC High Profile. © 2010 IEEE.


Jiao Y.,Hong Kong Applied Science and Technology Research Institute ASTRI | Cheung R.Y.P.,Hong Kong Applied Science and Technology Research Institute ASTRI | Chow W.W.Y.,Hong Kong Applied Science and Technology Research Institute ASTRI | Mok M.P.C.,Hong Kong Applied Science and Technology Research Institute ASTRI
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2013

Least mean square (LMS) adaptive filter has been used to extract life signals from serious ambient noises and interferences in biomedical applications. However, a LMS adaptive filter with a fixed step size always suffers from slow convergence rate or large signal distortion due to the diversity of the application environments. An ideal adaptive filtering system should be able to adapt different environments and obtain the useful signals with low distortion. Adaptive filter with gradient adaptive step size is therefore more desirable in order to meet the demands of adaptation and convergence rate, which adjusts the step-size parameter automatically by using gradient descent technique. In this paper, a novel gradient adaptive step size LMS adaptive filter is presented. The proposed algorithm utilizes two adaptive filters to estimate gradients accurately, thus achieves good adaptation and performance. Though it uses two LMS adaptive filters, it has a low computational complexity. An active noise cancellation (ANC) system with two applications for extracting heartbeat and lung sound signals from noises is used to simulate the performance of the proposed algorithm. © 2013 IEEE.

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