Planar antenna for directive beam steering at end-fire using an array of surface-wave launchers

A planar surface-wave antenna (SWA) that achieves radiation at end-fire by surface-wave (SW) excitation is presented for millimetre-wave frequencies of operation. The 2D SWA is fed by a two-element array of printed SW launchers for controlled beam steering in the far-field. Measured results demonstrate a highly directive beam pattern with a 3 dB beamwidth less than 5 at 22.71 GHz. Such a planar low-cost and low-profile SWA design may be advantageous for surveillance systems and radar applications where beam steering at end-fire is of interest.     

SiO2 single layer for reduction of the standing wave effects in the interference lithography of deep photoresist structures on Si

We demonstrate that the use of a single SiO₂ film, with thickness corresponding to one standing wave (SW) period allows the recording of deep photoresist structures on silicon substrates by laser interference, without use of any additional antireflecting coating. This condition corresponds just to the opposite thickness (half SW period) previously proposed for using the SiO₂ films for phase-shifting the SW pattern. Theoretical and experimental results demonstrated that for the lithography of deep structures, the contrast of the SW pattern, the minimum light intensity of the SW pattern and the photoresist adhesion are the most important parameters of the process.     

New modified stop-and-wait ARQ protocols for mobile communications

Mobile communication channels are frequently plagued by severe noise and disturbances such as multipath fading and doppler effects that severely degrade performance. Among the automatic-repeat-request (ARQ) protocols used to improve the communication channel reliability, the stop-and-wait (SW) is positively characterized by simple implementation and negatively by low throughputs. This work describes the application of some new SW protocols that retain the simple implementation of the classical SW schemes, while reducing the transmitter's wait state time to increase throughput. The performance of the modified SW protocols, derived through computer simulations, is shown to be comparable to that of more complex ARQ protocols.     

Extended Subcarrier Weighting for Sidelobe Suppression in OFDM Based Cognitive Radio

Subcarrier weighting (SW) is a recognized technique for sidelobe suppression in OFDM systems. In this paper SW is discussed in the context of cognitive radios where some portion of the spectrum is shared with primary users so it is required to notch that portion. A major disadvantage with SW scheme is bit error rate (BER) degradation due to unequal power distribution among different subcarriers therefore the primary objective of the paper is to enhance the performance of SW without additional degradation in BER performance. To this extent we propose an Elliptical-SW scheme by expanding the locus of weights to elliptical region. Simulation results show that the proposed scheme can produce deeper notch as compared to Conventional-SW for same BER performance. In second part we present a Partial-SW scheme by applying SW to lesser number of subcarriers. It can enhance BER performance significantly with negligible loss in sidelobe suppression capacity. Another scheme namely Guarded-SW is also proposed in this paper to provide further means to obtain very deep notches without any additional degradation in BER however it has to scarify some throughput. Finally an effective way of implementing SW in MIMO systems is presented by jointly optimizing weights over selected number of antennas.     

Enhanced Wettability of Oxidized Copper with Lead-Free Solder by Ar-H<Subscript>2</Subscript> Plasmas for Flip-Chip Bumping

Enhanced solder wettability (SW) of oxidized-Cu (OC) with 96.5Sn-3Ag-0.5Cu lead-free solder (LFS) by Ar-H₂ plasmas was investigated. The SW of OC was significantly improved from 0% wetting of Cu oxidized in air at 260°C for 1 h to 100% wetting of OC modified by Ar-H₂ plasmas for 10 min. The SW of Cu was found to be highly dependent on the surface characteristics of Cu. By decreasing the total surface energy (TSE), decreasing the polar surface energy (PSE), and increasing the dispersive surface energy (DSE) on the surfaces of OC modified by Ar-H₂ plasmas, the SW with LFS improves. X-ray photoelectron spectroscopy (XPS) indicates that Ar-H₂ plasma treatment is used to remove the copper oxides CuO and Cu₂O from the OC surfaces. The ratio of the total amount of Cu₂O to CuO was found to be a good indication of how the copper oxides CuO and Cu₂O affect the PSE, DSE, and SW of Cu.     

Applying SMT-based verification to hardware/software partitioning in embedded systems

When performing hardware/software co-design for embedded systems, the problem of which functions of the system should be implemented in hardware (HW) or in software (SW) emerges. This problem is known as HW/SW partitioning. Over the last 10 years, a significant research effort has been carried out in this area. In this paper, we present two new approaches to solve the HW/SW partitioning problem by using verification techniques based on satisfiability modulo theories (SMT). We compare the results using the traditional technique of integer linear programming, specifically binary integer programming and a modern method of optimization by genetic algorithm. The experimental results show that SMT-based verification techniques can be effective in particular cases to solve the HW/SW partition problem optimally using a state-of-the-art model checker based on SMT solvers, when compared against traditional techniques.     

Geometrical characterizations of constant modulus receivers

Convergence properties of the constant modulus (CM) and the Shalvi-Weinstein (SW) algorithms in the presence of noise remain largely unknown. A new geometrical approach to the analysis of constant modulus and Shalvi-Weinstein receivers is proposed by considering a special constrained optimization involving norms of the combined channel-receiver response. This approach provides a unified framework within which various blind and (nonblind) Wiener receivers can all be analyzed by circumscribing an ellipsoid by norm balls of different types, A necessary and sufficient condition for the equivalence among constant modulus. Shalvi-Weinstein, zero forcing, and Wiener receivers are obtained. Answers to open questions with regard to CM and SW receivers, including their locations and their relationship with Wiener receivers, are provided for the special orthogonal channel and the general two-dimensional (2-D) channel-receiver impulse response. It is also shown that in two dimensions, each CM or SW receiver is associated with one and only one Wiener receiver     

Hierarchical rule-based and self-organizing fuzzy logic control fordepth of anaesthesia

A multi-stage hierarchical fuzzy control system with a multi-echelon structure for depth of anaesthesia (DOA) is described in this paper. There are four echelons that monitor, control, interpret and assess the whole surgical operation. Echelon 1 is a measurement and control action level that involves: instrument sensing (Dinamap); anaesthetist observations [measurement of sweating (SW), lacrimation (LA) and pupil response (PR)]; and a syringe pump (Graseby pump). Echelon 2 is an interpretation level that involves: interpreting systolic arterial pressure and heart rate to provide the primary DOA; interpreting SW, LA and PR to provide the degree of lightness; and interpreting bolus drug effects to estimate the sensitivity of patients. Echelon 3 is a regulation level that involves: controlling the drug from either a hand-crafted anaesthetists' rule-base or a self-organizing fuzzy logic controller algorithm; planning the drug profile to avoid long recovery; and managing alarm situations. Finally, echelon 4 is an assessment level that assesses the whole surgical procedure according to the patient recovery time. Testing this system in clinical trials as an intelligent adviser has provided a preliminary proof-of-concept of the applicability of this hierarchical structure for DOA management     

Memory sub-banking scheme for high throughput MAP-based SISO decoders

The sliding window (SW) approach has been proposed as an effective means of reducing the memory requirements as well as the decoding latency of the maximum a posteriori (MAP) based soft-input soft-output (SISO) decoder in a Turbo decoder. In this paper, we present sub-banked memory implementations (both single port and dual port) of the SW SISO decoder that achieves high throughput, low decoding latency, and reduced memory energy consumption. Our contributions include derivation of the optimal memory sub-banked structure for different SW configurations, study of the relationship between memory size and energy consumption for different SW configurations and study of the effect of number of sub-banks on the throughput/decoding latency for a given SW configuration.     

Diurnal Asymmetry in the GERB SW Fluxes

The launch of the Geostationary Earth Radiation Budget (GERB) instrument onboard the Meteostat 8 allows a diurnal sampling of the Earth's Radiation Budget for the first time, providing a unique and important addition to polar-orbiting measurements. However, preliminary data from the GERB instrument exhibit systematic asymmetry in the short-wave (SW) flux diurnal variation. Such asymmetries are not found in the Clouds and the Earth's Radiant Energy System angular distribution models used to convert the directional broad-band GERB SW radiances to fluxes. Comparison between angularly matched estimations of reflected SW flux at the top of the atmosphere from the Spinning Enhanced Visible and Infra Red Imager (SEVIRI) and GERB data indicates that the SEVIRI spectral modeling could be a major issue. In addition, the results indicate that other factors such as the GERB SW geolocation, the GERB detector spectral response functions, the GERB nominal footprint resolution, and cloud cover could also potentially have an influence on the diurnal evolution of the GERB SW fluxes, as they can erroneously impact on the GERB SW correction factor     

短/中波双色碲镉汞红外探测器制备研究

报道了基于分子束外延的短/中波双色碲镉汞材料及器件的最新研究进展.采用分子束外延方法制备出了高质量的短/中波双色碲镉汞材料,并通过提高材料质量将其表面缺陷密度控制在300 cm-2以内.在此基础上进一步优化了芯片制备工艺,尤其是在减小像元中心距方面作了优化.基于上述多项材料及器件工艺制备出了320×256短/中波双色碲...     

Throughput analysis of some ARQ protocols in the presence offeedback errors

Automatic-repeat-request (ARQ) protocols have been analyzed for quite some time, but the issue of errors in the feedback channel has not received much attention. In some applications, such as digital mobile communications, this issue can be important. Accordingly, this paper examines the effect of feedback errors on the throughputs of the stop-and-wait (SW), go-back-N (GBN), and selective repeat (SR) ARQ protocols for the ease of a point-to-point channel under some feedback information assumptions. It is shown that the deleterious effects of feedback errors on the throughputs of continuous (e.g., GBN and SR) ARQ protocols can be greatly reduced by a simple modification in the retransmission operation, provided that the “complete state” of the receiver is sent back with each acknowledgment     

Highly Sensitive Mechanoresponsive Smart Windows Driven by Shear Strain

Advanced optical materials with rational designs and tunable light transmission have been drawing increasing interest due to their great potential in energy-efficient buildings and on-demand optical devices. Mechanoresponsive smart windows (SWs) can modulate light transmittance by mechanical actuation, showing high energy efficiency, low cost, and chemical stability. However, current research mainly focuses on tensile strain-responsive SWs that typically require a large strain to achieve optical transparency switching-which causes great inconvenience to practical application and fatigue damage to matrix materials. Herein, a novel shear-responsive SW with high strain sensitivity is fabricated by vertically fixing a Fe₃O₄@SiO₂ nanochains (NCs) array in an elastic polyacrylamide matrix. The flexible SW exhibits optically transparent with all NCs standing vertically to the SW surface at initial relaxation state, which enables a good shielding effect, with NCs tilting along the shearing direction as the strain applied. Critically, a rather small shear displacement (1.5 mm) applied on the surface of SW gives rise to tunable optical states varying from the transparency state of 65% transmittance to the opaque state of 10%. The as-prepared SW with novel tuning modulation, high shear strain sensitivity, and optical angle-dependence holds promising potential in smart windows, optical switches, anti-voyeurism, and etc.     

Optimal mean velocity estimation for Doppler weather radars

Optimal Doppler velocity estimation is explored for a standard Gaussian signal measurement model and thematic maximum-likelihood (ML) and Bayes estimation. Because the model considered depends on a vector parameter [velocity, spectrum width (SW), and signal-to-noise ratio (SNR)], the exact formulation of an ML or Bayes solution involves a system of coupled equations that cannot be made explicit for any of the parameters. Simple computational forms are shown to exist when SW and SNR are assumed known. An information-theoretic concept is used to extend these equations to the general case of SW and SNR unknown. A Monte Carlo simulation experiment is used to verify that the method can work, with no a priori information for either SW or SNR and a very small (20 pulse) sample size. The improved performance of this new Doppler velocity estimator is documented by comparison with derived optimal bounds and with the performance of the pulse pair (PP) method. Bayes estimator results are used to provide true performance bounds for comparison. Cramer-Rao bounds are also derived and shown to be inferior to the Bayes bounds in the small sample case considered     

Diurnal bias in calibration of broad-band radiance measurementsfrom space

Examines the problem of determining the separate shortwave (SW) and longwave (LW) components of the Earth radiation budget from space. Because true broad-band longwave filters do not exist, daytime LW radiance determinations can depend entirely or in part on subtraction of the measured SW radiance from the “Total” (TW) radiance involving integration over the entire electromagnetic pectrum. Examining radiances measured in the three channels (SW, imperfectly filtered broad-band LW, TW) of the Earth Radiation Budget Experiment (ERBE) scanners on board the NOAA-9, ERBS and NOAA-10 satellites, the authors find small discrepancies in the daytime estimates of broad-band (“unfiltered”) LW radiances using the ERBE “spectral correction” procedure. The authors show that these result from errors (of order 2.5%) in the calibration of the SW channel and possibly in the spectral characterization of the SW and/or TW channel of the ERBE scanners on NOAA-9 and NOAA-10. Nighttime estimates show no such bias, and there appears to be no such error in the data from ERBS. Considering the LW radiant exitances determined from ERBE scanner data from the three satellites, the authors find systematic differences in individual satellite estimates of simultaneous instantaneous regional means and of regional monthly means, consistent with the radiance discrepancies, instantaneous daytime LW estimates can be in error by 20% in the extreme case of very bright cold cloud, and LW cloud radiative forcing may be significantly biased. They consider the implications of these small SW-dependent errors on the determination of diurnal variation and of cloud radiative forcing in the longwave domain. They show how the ERBE estimates can be corrected, and consider how procedures can be used to validate results of future experiments (ScaRaB and CERES)     

一种32 Bit SoC软硬件协同验证环境的实现

软硬件协同验证是系统芯片设计的重要组成部分。针对基于32 Bit CPU核的某控制系统芯片的具体要求,提出了一种系统芯片软硬件协同验证策略,构建了一个软硬件协同验证环境。该环境利用处理器内核模型支持内核指令集的特性运行功能测试程序,实现SoC软硬件的同步调试,并能够快速定位软硬件的仿真错误点,有效提高了仿真效率。该SoC软硬件协同验证环境完成了设计目的,并对其他系统芯片设计具有一定的参考价值。     

Existence and performance of Shalvi-Weinstein estimators

The Shalvi-Weinstein (1990) criterion has become popular in the design of blind linear estimators of i.i.d. processes transmitted through unknown linear channels in the presence of unknown additive interference. Here, we analyze SW estimators in a general multiple-input multiple-output (MIMO) setting that allows near-arbitrary source/interference distributions and noisy noninvertible channels. The main contributions of this paper are (i) simple tests for the existence of SW estimators for the desired source and (ii) bounding expressions for the MSE of SW estimators that are a function of the minimum attainable MSE and the kurtoses of the source and interferers     

The sliding-window packet switch: a new class of packet switch architecture with plural memory modules and decentralized control

Shared-memory based packet switches are known to provide the best possible throughput performance for bursty data traffic in high-speed packet networks and internets compared with other buffering strategies under conditions of identical memory resources deployed in the switch. However, scaling of shared-memory packet switches to a larger size has been restricted mainly due to the physical limitations imposed by the memory-access speed and the centralized control for switching functions in shared-memory switches. A new scalable architecture for a shared-memory packet switch, called the sliding-window (SW) switch, is proposed to overcome these limitations. The SW switch introduces a new class of switching architecture, where physically separate multiple memory modules are logically shared among all the ports of the switch, and the control is decentralized. The SW switch alleviates the bottleneck caused by the centralized control of switching functions in large shared-memory switches. Decentralized switching functions enable the SW switch to operate in a pipeline fashion to enhance scalability and switching capacity compared with that of previously known classes of shared-memory switch architecture.     

基于OFDM的数字广播系统模型研究及子载波数目确定

作为时变的多径信道,中短波信道的时变性导致基于OFDM数字调幅广播系统各个子信道间产生干扰,简称ICI。该文首先分析OFDM系统在一般时变多径信道的模型,在此基础上推导了中短波信道时变特性在OFDM系统中所产生的ICI公式,最后利用该公式通过计算机数值计算确定在ICI可忽略不计的情况下,OFDM系统的总的子载波数目N的最大值,而该值的确定对于基于OFDM的数字调幅广播系统是非常重要的。     

An FPGA implementation of HW/SW codesign architecture for H.263 video coding

In this paper, we present an efficient HW/SW codesign architecture for H.263 video encoder and its FPGA implementation. Each module of the encoder is investigated to find which approach between HW and SW is better to achieve real-time processing speed as well as flexibility. The hardware portions include the Discrete Cosine Transform (DCT), inverse DCT (IDCT), quantization (Q) and inverse quantization (IQ). Remaining parts were realized in software executed by the NIOS II softcore processor. This paper also introduces efficient design methods for HW and SW modules. In hardware, an efficient architecture for the 2-D DCT/IDCT is suggested to reduce the chip size. A NIOS II Custom instruction logic is used to implement Q/IQ. Software optimization technique is also explored by using the fast block-matching algorithm for motion estimation (ME). The whole design is described in VHDL language, verified in simulations and implemented in Stratix II EP2S60 FPGA. Finally, the encoder has been tested on the Altera NIOS II development board and can work up to 120 MHz. Implementation results show that when HW/SW codesign is used, a 15.8-16.5 times improvement in coding speed is obtained compared to the software based solution.