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This paper presents a method for the development of the impedance locus to test the dynamic characteristics of protective relays. Specifically, using the proposed method, the impedance locus can comprise three impedance points, and the speed of impedance trajectory can be adjusted by frequency deviation. This paper is divided into two main sections. The first section deals with the configuration of impedance locus with voltage magnitude, total impedance magnitude, and impedance angle. The second section discusses the control of the locus speed with the means of the deviation between two frequencies. The proposed method is applied to two machine equivalent systems with offline simulation (i.e., PSCAD) and real-time simulation (i.e., real-time simulation environment) to demonstrate its effectiveness.

Orthogonal frequency division multiple access (OFDMA) uplink in a passive optical network (PON) requires the delay alignment for OFDMA symbols from remotely distributed optical network units (ONUs). In this paper, we experimentally demonstrate and analyze the performance of a Zadoff-Chu (ZC) sequence-based upstream ranging scheme in an intensity modulation/direct detection (IM/DD)-based OFDMA-PON. The experimental results show that the proposed scheme can achieve upstream synchronization with only marginal inter-carrier interference (ICI) and requires no additional bandwidths in a typical OFDMA transmission with cyclic prefix (CP).

This paper demonstrates and characterizes a novel wavelength-tunable single-frequency erbium-doped fiber ring laser incorporating an all-fiber acoustooptic tunable bandpass filter and a self-constructed saturable absorption grating (SAG). Stable single-longitudinal-mode operation was achieved over the wavelength range of 48 nm with a sidemode suppression ratio higher than 50 dB. The wavelength tuning characteristics, and the laser dynamics in wavelength switching and sweeping are analyzed in detail. A theoretical analysis on the effect of the SAG is also described.

Directional elements are fundamental to protection scheme security and selectivity, performing such critical tasks as supervising distance elements and controlling overcurrent elements. But, conventional operating principles for directional detection, based on negative or zero sequence voltages or currents polarization in some cases do not satisfy the requirements for improved sensitivity and fast operation under vary system conditions. In this paper, new algorithm for directional elements is proposed. The proposed algorithm use the positive-sequence superimposed voltages and currents in order to be used in all fault conditions. Also, because this algorithm uses a voltage compensation method, it can be well operated under strong source conditions.

Lithographic process steps used in today's integrated circuit production require tight control of critical dimensions (CD). With new design rules dropping to 32 nm and emerging double patterning processes, parameters that were of secondary importance in previous technology generations have now become determining for the overall CD budget in the wafer fab. One of these key parameters is the intra-field mask CD uniformity (CDU) error, which is considered to consume an increasing portion of the overall CD budget for IC fabrication process. Consequently, it has become necessary to monitor and characterize CDU in both the maskshop and the wafer fab. Here, we describe the introduction of a new application for CDU monitoring into the mask making process at Samsung. The IntenCD TM application, developed by Applied Materials, is implemented on an aerial mask inspection tool. It uses transmission inspection data, which contains information about CD variation over the mask, to create a dense yet accurate CDU map of the whole mask. This CDU map is generated in parallel to the normal defect inspection run, thus adding minimal overhead to the regular inspection time. We present experimental data showing examples of mask induced CD variations from various sources such as geometry, transmission and phase variations. We show how these small variations were captured by IntenCD TM and demonstrate a high level of correlation between CD SEM analysis and IntenCD TM mapping of mask CDU. Finally, we suggest a scheme for integrating the IntenCD TM application as part of mask qualification procedure at maskshops.

As feature size continuously decreasing new techniques to improve quality of wafer are developed. Hence a lot of new problems in semiconductor industry arise. Strict control of quality of wafer during production process is very important as many factors can influence on it, but the main contribution gives scanner error and mask. Thus at least impact of mask should be reduced. In this work we apply rigorous model to predict impact of microstructures to pattern fidelity on wafer. Such microstructures are commonly generated in quartz layer to control transmittance distribution on photomask. It is shown that effect from microstructures is not only changing of mask transmittance but also distortion of the pattern fidelity on wafer. Rigorous modeling gives us possibility to calculate aerial image and CD on wafer in case of presence of microstructures in the quartz. We vary optical parameters, such as refractive indexes, number, size and location of these elements in order to reduce the distortion of pattern fidelity on wafer. Our result allows prediction of the impact of microstructures in photomask on wafer pattern fidelity instead of doing set of experiments. Moreover, the best conditions for experiment are found and discussed.

In the ArF lithography for sub-100nm, PSM (Phase Shift Mask) has been considered as one of the basic RETs (Resolution Enhancement Techniques). Nowadays, besides attenuated PSM, alternating PSM and CPL (Chromeless Phase Lithography) containing Cr patch is widely studied for targeting sub-100nm. Since 2nd process using 365nm laser tools for Cr patch has been a wide gap between the reality and the demands, various candidates using 254nm laser or e-beam exposure tool have been presented to overcome the current 2nd process limitation. And, the Cr patch operate as an assist pattern to control the transmittance of mask, therefore, the CPL mask with Cr patch have advantages of improving process margin such as dose margin and its applicable flexibility for various layers, dense or isolated pattern in the memory and logic device. In this paper, we scrutinize the feasibility of 2nd alignment using 10keV e-beam. Process issues such as the charging effects caused by 2nd e-beam exposure on the 1st Cr etched substrate were evaluated as well.

We demonstrated a novel tunable single-frequency Er/sup 3+/-doped fiber laser using all-fiber acousto-optic tunable bandpass filter. The wavelength tuning range was from 1522 to 1547 nm and side mode suppression ratio was below -55 dB.

A bidirectional wavelength-selective optical isolator that has opposite isolation directions for two interleaved sets of optical wavelengths is described. It was realised by inserting an adequate retarder in a polarisation independent optical isolator configuration. The insertion loss and extinction ratio of the demonstrated device were 1.6 and 22 dB, respectively, for a channel spacing of 0.8 nm.