Growth of Epitaxial (110) 0.7Pb(Mg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>-0.3PbTiO<Subscript>3</Subscript> Thin Films on r-Plane Sapphire Substrates by RF Magnetron Sputtering

The role of substrate temperature and substrate surface geometry in determining the crystal structure and crystallinity of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) thin films grown on r-plane sapphire substrates is examined. A 30-nm-thick amorphous PMN-PT seed layer deposited at 250°C and subjected to rapid thermal annealing at 850°C results in the formation of an epitaxial (110) perovskite PMN-PT growth template that can be used for subsequent growth of single-crystal (110) perovskite PMN-PT films at elevated temperature. The data show that single-crystal perovskite is promoted when the films nucleate with the \( \langle \overline{1} 11 \rangle \) PMN-PT direction parallel to the \( \langle 0\bar{2}21 \rangle \) Al₂O₃ direction.     

Supervised learning and frequency domain averaging-based adaptive channel estimation scheme for filterbank multicarrier with offset quadrature amplitude modulation

Filterbank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is an attractive alternative to the orthogonal frequency division multiplexing (OFDM) modulation technique. In comparison with OFDM, the FBMC-OQAM signal has better spectral confinement and higher spectral efficiency and tolerance to synchronization errors, primarily due to per-subcarrier filtering using a frequency-time localized prototype filter. However, the filtering process introduces intrinsic interference among the symbols and complicates channel estimation (CE). An efficient way to improve the CE in FBMC-OQAM is using a technique known as windowed frequency domain averaging (FDA); however, it requires a priori knowledge of the window length parameter which is set based on the channel's frequency selectivity (FS). As the channel's FS is not fixed and not a priori known, we propose a k-nearest neighbor-based machine learning algorithm to classify the FS and decide on the FDA's window length. A comparative theoretical analysis of the mean-squared error (MSE) is performed to prove the proposed CE scheme's effectiveness, validated through extensive simulations. The adaptive CE scheme is shown to yield a reduction in CE-MSE and improved bit error rates compared with the popular preamble-based CE schemes for FBMC-OQAM, without a priori knowledge of channel's frequency selectivity.     

Passive coupling of InGaAsP/InP laser array and singlemode fibres using silicon waferboard

Passive alignment of semiconductor lasers and singlemode fibres has been achieved for the first time using a micro-machined silicon substrate. Mechanical alignment features fabricated on the substrate surface were used to align the active regions of an InGaAsP/InP laser array to four singlemode fibres held in V grooves. Optical coupling efficiencies have been achieved that are comparable to values obtained using the conventional technique of active fibre manipulation. The approach, called silicon waferboard, offers the potential for low-cost optoelectronic device packaging as well as a means for dense hybrid integration of optoelectronic, electronic and optical components required for multifibre, multichip systems.<>     

VIP10高速运算放大器的PSPICE数据库

从零开始创建运算放大器的SPICE电路仿真模型不仅困难而且很费时间。美国国家半导体公司建立了OrCAD Capture数据库(nationalhighspeed.olb)以及PSPICE电路模型数据库(nationalhighspeed.lib),用以存储业内领先的 VIP10工艺的高速运算放大器资料,其中包括 LMH 系列高速运算放大器的性能模型及运算放大器的电路原理图符号。登录amplifiers.national.com网页便可下载这两个数据库的资料。VIP10 工艺技术是一种高速的电介质绝缘的互补双极集成电路技术,可以将深沟技术应用到压焊晶片上实现完全的电介质绝缘,以及最佳的高速放大器性能…     

Iterative timing recovery

The last decade has seen the development of iteratively decodable error-control codes of unprecedented power, whose large coding gains enable reliable communication at very low signal-to-noise ratio (SNR). A by-product of this trend is that timing recovery must be performed at an SNR lower than ever before. Conventional timing recovery ignores the presence or error-control coding and thus doomed to fail when the SNR is low enough. This article describes the iterative timing recovery, a method for implementing timing recovery in cooperation with iterative error-control decoding so as to approximate a more complicated receiver that jointly solves the timing recovery and decoding problems.     

用于电源、继电器和螺线管的协同式线路保护

在各种新型先进设备上实施协同式电路保护可有助于提高设备可靠性、减少元器件数量,并使其符合严格的安规要求。协同式方法能够帮助保护电源、继电器和螺线管,避免因线路故障或过载造成电流增大以及尖峰电压或暴露在稳态过压状态带来的危害。     

Effects of Ar and O2 additives on photopatternable sol-gel etching in an SF6-based plasma for planar lightwave circuit fabrication

We present a novel study of the interaction of SF₆-based plasmas with sol-gel materials in a parallel plate reactive ion etching (RIE) system. The purpose of these experiments was to obtain quantitative measures and optimisation of the RIE parameters, which can be used in the microfabrication of planar lightwave circuit (PLC) devices. The sulfur hexafluoride chemistry is chosen due to its excellent etching properties of SiO₂, which is one of the components of the photopatternable sol-gel materials and is not present in typical photoresist materials. Fast process etching rate and good selectivity is achieved by varying SF₆ flow and power delivered to the electrodes. The study also reveals a marginal influence of oxygen and argon flow on the character of the sol-gel etching. The experimental data obtained can be used as a reference for any sol-gel devices fabricated using widely available RIE reactors.     

A novel medium access control protocol for WDM-based LAN's andaccess networks using a master/slave scheduler

We describe an architecture and medium access control (MAC) protocol for wavelength-division multiplexing (WDM) networks. Our system is based on a broadcast star architecture and uses an unslotted access protocol and a centralized scheduler to efficiently provide bandwidth-on-demand in WDM networks. To overcome the effects of propagation delays the scheduler measures the delays between the terminals and the hub and takes that delay into account when scheduling transmissions. Simple scheduling algorithms, based on a look-ahead capability, are used to overcome the effects of head-of-line blocking. An important application area for this system is in optical access networks, where this novel MAC protocol can be used to access wavelengths in a WDM passive optical network (PON)     

Minimalist counting in sensor networks (Noise helps)

We propose a novel algorithm for counting N indistinguishable objects, called targets, by a collection of sensors. We adopt a minimalist scenario where sensors are unaware of the (non-empty) intersections of sensing regions, and so simple addition of all sensor counts inflates estimates of the total number of targets. The multiple counting in intersections must be accounted for, but with nothing more than the sensor counts, this is clearly impossible. However, noise is typically present in the target counting of many, if not most, applications. We make the key observation that if there is a (target-dependent) noise source affecting all sensors simultaneously, then it couples those with non-empty intersections. Exploitation of this coupling allows us to extract multiple-counting statistics from stochastic correlation patterns, and hence to compute accurate estimates of N via the classical inclusion–exclusion formula. Cumulants are the correlation measures of choice. Our analysis brings out and resolves certain technicalities that arise in our statistical counting algorithm. Examples are worked out to show the potential of the new algorithm. The paper concludes with a discussion of alternative models and open problems.