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Low-power static frequency divider using an InP-based monolithic RTD/HBT technology
Kim, T.,Jeong, Y.,Yang, K. Inst. of Eng. and Technol 2006 Electronics letters Vol.42 No.1
A low-power static frequency divider using an RTD/HBT MOnostable-BIstable transition Logic Element (MOBILE) scheme is proposed for the first time and operation of the circuit is demonstrated up to 20 GHz. The divided-by-two static frequency divider has been successfully implemented in an InP-based monolithic RTD/HBT IC technology. The number of devices used in the static frequency divider has been significantly reduced by using the proposed MOBILE scheme. The fabricated frequency divider operates at a clock frequency up to 20 GHz and dissipates d.c. power of 51 mW at a power supply of 3.3 V
Inertia identification algorithm for high-performance speed control of electric motors
Choi, J.-W.,Lee, S.-C.,Kim, H.-G. Inst. of Eng. and Technol 2006 IEE proceedings, Electric power applications Vol.153 No.3
An estimation algorithm for identifying the moment of inertia, which is essential for the design of a high performance controller for a motor drive system, is presented. The proposed algorithm finds the moment of inertia by observing the position error signal generated by the speed observer, which contains error information on the moment of inertia. The proposed algorithm is easy to realise in an observer-based speed detection method. Simulation and experimental results are presented to confirm the performance of the moment of inertia estimation method, and show that the moment of inertia converges to an actual value within several speed changes. As a result, the speed control responses and designed speed controller performance match well.
Ultra-wideband uniplanar MMIC balun using field transformations
Kim, H.-T.,Lee, S.,Park, J.-H.,Kim, Y.-K.,Kwon, Y. Inst. of Eng. and Technol 2006 Electronics letters Vol.42 No.6
A new wideband three-port balun is developed using a standard uniplanar monolithic microwave integrated circuit (MMIC) process. This structure does not rely on bulky resonant circuits, and thus can be realised in a small size and show ultra-wideband characteristics. Out of phase characteristic between two output ports is inherently achieved by field transformations through physical transitions of uniplanar transmission lines. A fabricated back-to-back balun pair showed insertion loss less than 1.85 dB and return loss more than 10 dB over an ultra-wideband frequency range from 1 to 92.5 GHz.
Lee, U.,Lee, H.-J.,Kim, S.,Shin, H.-C. Inst. of Eng. and Technol 2006 Electronics letters Vol.42 No.4
An intracranial brain-computer interface (BCI) system using the neuronal activity of a non-motor brain area to fulfil a series of motor functions has been developed. The presented BCI system encodes a series of motor functions into a small number of neuronal units of the primary somatosensory cortex of a rat and generates real-time command signals to control a machine according to the animal's motor intentions. The results of this study demonstrate the practical usability of the BCI system using a non-motor brain area in the field of rehabilitation.
Robust Kalman filtering with perturbation estimation process for uncertain systems
Inst. of Eng. and Technol 2006 IEE proceedings. Control theory and applications Vol.153 No.5
A robust Kalman filtering method is suggested by adopting a perturbation estimation process which is to reconstruct total uncertainty with respect to the nominal state equation of a physical system. The predictor and corrector of the discrete Kalman filter are reformulated with the perturbation estimator. In succession, the state and perturbation estimation error dynamics and the covariance propagation equations are derived. In the sequel, the recursive algorithm of combined discrete Kalman filter and perturbation estimator is obtained. The proposed robust Kalman filter has the property of integrating innovations and the adaptation capability to the time-varying uncertainties. An example of application to a mobile robot is shown to validate the performance of the proposed scheme.
Hybrid error concealments based on block content
Jo, M.-H.,Kim, H.-N.,Song, W.-J. Inst. of Eng. and Technol. 2007 IET image processing Vol.1 No.2
<P>We present a novel error-concealment method for MPEG-2 video decoders. Imperfect transmission of block-based compressed images may result in the loss of blocks, degrading the quality of the received video signal. Since an I-picture is used as a reference picture for forward and backward predictions of neighbouring pictures, transmission errors in an I-picture are propagated both spatially in the I-picture and temporally to P-/B-pictures, and thus may severely degrade the video signal, compared with the errors in P-/B-pictures. To minimise the quality degradation of the video signal, error concealment has been performed in I-pictures through adaptive spatial and temporal interpolations in the respective domains. Using edge information extracted from the neighbourhoods of the erroneous macroblocks, we categorise each erroneous macroblock (MB) based on the characteristics of neighbouring MBs. The categorised MB is reconstructed by the spatial or temporal error concealment methods selected by the category-dependent criteria reflecting the properties of the block content. The proposed technique solves blocky artefacts and blurring problems of existing error concealment methods and thus effectively conceals the lost blocks in an error video signal. Through computer simulations on damaged images, we show that the proposed method is robust to image characteristics and obtains better subjective quality than other error concealment methods.</P>
Kim, N.,Yun, H.,Kang, M. Inst. of Eng. and Technol 2007 IET COMMUNICATIONS Vol.1 No.3
<P>Performances of differentiated services in the upstream transmission of Ethernet passive optical network (E-PON) are affected by bandwidth reservation algorithm of an optical network unit, since data packets can be transmitted to an optical line termination only during the reserved transmission window. The effects of time-slot reservation on differentiated services are analysed and an adaptive class-based excess bandwidth reservation algorithm, called service quality pre-engagement (SQP), which reserves a time-slot based on the backlog queue and traffic arrival pattern of class is proposed. SQP applies the prediction-based bandwidth reservation to selected forward reservation classes (FRCs) which are determined by the introduced dynamic FRC selection. The proposed short-term service work-based time-slot reservation and long-term adaptive FRC selection optimise time-slot reservation according to traffic load of class. Analytic and simulation results show that this approach improves the performance of differentiated services, especially in terms of system buffer size, light-load penalty and service fairness, while guaranteeing high link utilisation and throughput</P>
Lee, J.H.,Chang, Y.M.,Han, Y.-G.,Chung, H.,Lee, S.B. Inst. of Eng. and Technol 2006 Electronics letters Vol.42 No.14
A novel tunable microwave photonic FIR filter incorporating a wavelength spacing tunable multiwavelength filter based on a programmable arrayed micro-mirror device (AMMD) is demonstrated. Owing to the unique characteristic of the AMMD, that an arbitrary optical filter shape can be produced by defining a desired spatial pattern on an array of ∼800 000 micro-mirrors, a wavelength spacing tunable multiwavelength optical filtering pattern is readily obtainable. By controlling the optical filter wavelength spacing, flexible resonance RF frequency tuning is achieved over a range of 2.3 GHz.
Lee, J.H.,Kim, H.D.,Song, J.-W. Inst. of Eng. and Technol 2006 Electronics letters Vol.42 No.13
A micro-optic Mach-Zehnder interferometric filter composed of two fibre-pigtailed collimators and an optical plate with a periodic refractive index modulation is presented. The measured extinction ratio of the filter is greater than 28 dB and the polarisation-dependent loss in the passband is less than 0.15 dB.
Continuously tunable photonic microwave true-time delay based on tunable chirped fibre Bragg grating
Han, Y.-G.,Lee, J.H.,Lee, S.B. Inst. of Eng. and Technol 2006 Electronics letters Vol.42 No.14
A simple scheme for the photonic microwave true-time delay with high tunability based on a tunable chirped fibre Bragg grating without centre wavelength shift is experimentally demonstrated. A large dynamic range of true-time delay from 20 to 200 ps was achieved for a microwave signal carried over an optical signal.