Tone interference in VSAT spectrum

This paper investigates the problem of tone interference within the very small aperture terminal (VSAT) binary phase-shift keying (BPSK) signal spectrum. The degree of performance degradation of a VSAT link in the presence of a tone interference is discussed. A simple theoretical analysis is derived, and its validity is verified by experimental measurements performed using a standard commercial VSAT modem measurement setup     

Optical soliton transmission experiment in a comb-like dispersion profiled fiber loop

We discuss the properties of comb-like dispersion profiled fiber (CDPF) for an optical soliton transmission. It is found that the CDPF in which the standard single-mode fiber is placed both at the first and at the end of each section is more suitable to reduce dispersive waves if chirp-free transform limited optical pulse is used as a light source. A 10-ps optical soliton transmission experiment is performed in such a CDPF over 1000 km with the amplifier spacing of 80 km that corresponds to 3.1 times the dispersion distance.     

Linear tail-biting trellises, the square-root bound, andapplications for Reed-Muller codes

Linear tail-biting trellises for block codes are considered. By introducing the notions of subtrellis, merging interval, and sub-tail-biting trellis, some structural properties of linear tail-biting trellises are proved. It is shown that a linear tail-biting trellis always has a certain simple structure, the parallel-merged-cosets structure. A necessary condition required from a linear code in order to have a linear tail-biting trellis representation that achieves the square root bound is presented. Finally, the above condition is used to show that for r⩾2 and m⩾4r-1 or r⩾4 and r+3⩽m⩽[(4r+5)/3] the Reed-Muller code RM(r, m) under any bit order cannot be represented by a linear tail-biting trellis whose state complexity is half of that of the minimal (conventional) trellis for the code under the standard bit order     

Optimised feature map finite-state vector quantisation for imagecoding

An optimised feature map finite-state vector quantisation (referred to as optimised FMFSVQ) is presented for image coding. Based on the block-based gradient descent search algorithm used for motion estimation in video coding, the optimised FMFSVQ system finds a neighbourhood-based optimal codevector for each input vector by extending the associated state codebook stage by stage, thus rendering each state quantiser a variable rate vector quantisation. The optimised FMFSVQ system can be interpreted as a cascade of a finite-state vector quantiser and classified vector quantisers. Furthermore, an adaptive optimised FMFSVQ is obtained. Experiments demonstrate the superior rate-distortion performance of the adaptive optimised FMFSVQ compared with the original adaptive FMFSVQ and the memoryless vector quantisation     

Design criteria of 1.3-μm multiple-quantum-well lasers forhigh-temperature operation

We present design criteria for high-temperature operation in 1.3-μm multiple-quantum-well (MQW) lasers from the viewpoint of the light output power penalty, i.e., the change in the light output power at a fixed drive current with increasing temperature. It is shown that not only the characteristic temperature (T₀) but also internal loss dependence on temperature (γ) and threshold current (I_th) are significant parameters for reducing the power penalty. We compare the high-temperature performance of InGaAsP-based and AlGaInAs-based MQW lasers and demonstrate that AlGaInAs-based lasers have more potential in terms of the power penalty. Furthermore, we also demonstrate that the power penalty can be reduced by introducing a buried-heterostructure (BH) structure into AlGaInAs-based lasers. From these results, we conclude that the AlGaInAs-based BH lasers are promising for high-temperature performance     

Effects of fluorine-implanted treatment on Ba0.7Sr0.3TiO3 films

The effects of F-ion implantation on the leakage and dielectric properties of the Ba_0.7Sr_0.3TiO₃ (BST) films were investigated. The BST film implanted with 1×10¹⁵ cm^–2 shows the optimum leakage performance. The leakage current density can be decreased by one order of magnitude as compared to that of the non-implanted sample at an applied voltage of 2 V. On increasing the implanted dose from 5×10¹⁴ to 5×10¹⁵ cm^–2, the dielectric constant first increases and then decreases due to the deteriorated crystallinity. It is found that the suitable F-ion dose can reduce the –OH contaminants and improve the dielectric and leakage properties.     

Comparative study of micro-BGA reliability under bending stress

The micro-ball grid array (/spl mu/BGA), a form of chip scale package (CSP), was developed as one of the most advanced surface mount devices, which may be assembled by ordinary surface mount technology. In the latest /spl mu/BGA type, eutectic tin-lead solder ball bumps are used instead of plated nickel and gold (Ni/Au) bumps. Assembly and reliability of the /spl mu/BGA's PCB, which is soldered by conventional surface mount technology, has been studied in this paper. The bending cycle test (1000 /spl mu//spl epsi/ to -1000 /spl mu//spl epsi/), is used to investigate the fatigue failure of solder joints of /spl mu/BGA, PBGA, and CBGA packages reflowed with different heating factors (Q/sub /spl eta//), defined as the integral of the measured temperature over the dwell time above liquidus (183/spl deg/C). The fatigue lifetime of the /spl mu/BGA assemblies firstly increases and then decreases with increasing heating factor. The greatest lifetime happens while Q/sub /spl eta// is near 500 second-degree. The optimal Q/sub n/ range is between 300 and 750 s/spl deg/C. In this range, the lifetime of the /spl mu/BGA assembly is greater than 4500 cycles if the assemblies are reflowed in nitrogen ambient. SEM micrographs reveal that both /spl mu/ & P-BGA assemblies fail in the solder joint at all heating factors. All fractures are near and parallel to the PCB pad. In the /spl mu/BGA assemblies cracks always initiate at the point of the acute angle where the solder joint joins the PCB pad, and then propagate in the section between the Ni/sub 3/Sn/sub 4/ intermetallic compound (IMC) layer and the bulk solder. In the CBGA assembly reliability test, the failures are in the form of delamination, at the interface between the ceramic base and metallization pad.     

The weighted diagnostic distortion (WDD) measure for ECG signal compression

In this paper, a new distortion measure for electrocardiogram (ECG) signal compression, called weighted diagnostic distortion (WDD) is introduced. The WDD measure is designed for comparing the distortion between original ECG signal and reconstructed ECG signal (after compression). The WDD is based on PQRST complex diagnostic features (such as P wave duration, QT interval, T shape, ST elevation) of the original ECG signal and the reconstructed one. Unlike other conventional distortion measures [e.g. percentage root mean square (rms) difference, or PRD], the WDD contains direct diagnostic information and thus is more meaningful and useful. Four compression algorithms were implemented (AZTEC, SAPA2, LTP, ASEC) in order to evaluate the WDD. A mean opinion score (MOS) test was applied to test the quality of the reconstructed signals and to compare the quality measure (MOSerror) with the proposed WDD measure and the popular PRD measure. The evaluators in the MOS test were three independent expert cardiologists, who studied the reconstructed ECG signals in a blind and a semiblind tests. The correlation between the proposed WDD measure and the MOS test measure (MOSerror) was found superior to the correlation between the popular PRD measure and the MOSerror.     

Data hiding approach for efficient image indexing

A data hiding approach to embed the indexing keys inside the JPEG compressed images for their retrieval, inspired from the spirit of digital watermarking, is proposed. At the stage of database population, the existing approach is to compress all images by standard JPEG in order to save their storage space, but this ignores the compression of their indexing keys under the notion that the size of each indexing key is negligible. When a large image database is established, however, this part of storage space becomes non-trivial. By hiding the indexing keys inside the JPEG compressed codes, significant advantages are gained in that the indexing keys can be compressed naturally by JPEG without any additional cost. Experiments on hiding an indexing key of 256 bytes illustrate that: no noticeable distortion is introduced in comparison with non-watermarked images; and their storage space is reduced into the region of 7-27% of their original size.     

Arsenic/phosphorus LDD optimization by taking advantage ofphosphorus transient enhanced diffusion for high voltage input/outputCMOS devices

Optimization of a LDD doping profile to enhance hot carrier resistance in 3.3 V input/output CMOS devices has been performed by utilizing phosphorus transient enhanced diffusion (TED). Hot carrier effects in hybrid arsenic/phosphorus LDD nMOSFET's with and without TED are characterized comprehensively. Our result shows that the substrate current in a nMOSFET with phosphorus TED can be substantially reduced, as compared to the one without TED. The reason is that the TED effect can yield a more graded n^- LDD doping profile and thus a smaller lateral electric field. Further improvement of hot carrier reliability can be achieved by optimizing arsenic implant energy. Secondary ion mass spectrometry analysis for TED effect and two-dimensional (2-D) device simulation for electric field and current flow distributions have been conducted. The phosphorus TED effects on transistor driving current and off-state leakage current are also investigated