LDPC码的多路并行编码器实现

针对空间数据系统咨询委员会(CCSDS)标准下低密度奇偶校验(LDPC)码编码器低硬件实现复杂度的应用需求,提出一种适用于不同码长、码率LDPC码的多路并行编码器实现架构。该架构通过重复利用编码器中的存储单元,将矩阵信息共享到所有并行的运算单元中从而提高资源利用率。进一步,在现场可编程门阵列(FPGA)平台上验证并测试码率分别为1/2、2/3及4/5的单路和多路编码器,测试结果表明采用多路并行架构的编码器吞吐量比单路编码器有明显的提高且均达到1 Gbps以上;与达到基本相同吞吐量的单路多组编码器相比,其查找表资源分别减少40%、44%和46%。该架构充分利用FPGA的存储资源进而有效降低硬件实现复杂度。     

面向 PDR 定位系统的多层感知机 IMU 阵列数据融合方法

为提高低成本惯性测量单元(intertial measurement unit,IMU)阵列的行人航位推算(pedestrian dead reckoning,PDR)定位 精度,首次提出了采用多层感知机(multi-layer perceptron,MLP)实现低成本 IMU 阵列数据融合的算法,通过将自主设计的 IMU 阵列和高精度 IMU 同步运动来获得 IMU 阵列的测量数据(包括三轴加速度和三轴角速度)和高精度 IMU 的测量数据,以高精 度 IMU 的测量数据作为标签,利用 MLP 将 IMU 阵列的测量数据融合,预测出物体的实际加速度和角速度,并用定位算法进行 验证。 在定位实验中,使用 MLP 融合后的预测数据的 PDR 定位精度比使用单个 IMU 测量数据的 PDR 定位精度提高了 33. 9%;比使用简单平均处理的 IMU 阵列测量数据的 PDR 定位精度提高了 20. 8%;比使用最小二乘法融合的 IMU 阵列测量数 据的 PDR 定位精度提高了 11. 6%,证明了本文所提出方法的可行性和有效性。     

基于SISL的介质填充双通带滤波器设计

为实现滤波器的小型化,基于介质集成悬置线(substrate integrated suspended line, SISL)结构提出了一种介质填充双通带滤波器的设计方案. 首先将高介电常数的介质块填充入SISL的空气腔中,提升SISL的等效介电常数,实现电路的小型化,高介电常数介质块可以直接被SISL固定;然后利用T型结连接两组工作在不同频段的滤波器从而使得两个通带相对独立;最后利用仿真软件进行优化,确定介质填充双通带滤波器的尺寸,并进行加工与测试. 仿真与测试结果表明,二者具有较好的一致性,两个通带频率内的回波损耗均优于15 dB,电路的核心尺寸为0.058λ_g×0.139λ_g(λ_g为SISL在第一通带中心频率处的导波波长). 此双通带滤波器具有小尺寸、自封装等优势,且所有层介质基板均采用低成本的FR4板材,降低了制造成本.     

Eliminating bandwidth estimation from adaptive video streaming in wireless networks

Dynamic Adaptive Streaming over HTTP (DASH) is the state-of-the-art technology for video streaming and has been widely deployed in both wired and wireless environments. However, mobile DASH users often suffer from video quality oscillation and even video freeze in wireless environments, which results in poor user experience. This is mainly because most quality adaptation algorithms in DASH rely highly on bandwidth estimation to adjust the video quality while wireless network bandwidth is unstable in nature and changes frequently according to wireless channel contention and condition. To provide stable performance, even during severe bandwidth fluctuation, this paper proposes the Wireless Quality Adaptation (WQUAD) algorithm, which eliminates bandwidth estimation from quality adaptation. Thanks to the Scalable Video Codec (SVC), the proposed scheme always prioritizes to lower layers over higher ones as long as the play-out buffer is not completely filled by the lower layers. As a result, the client always fills the buffer with the base layers first and then the upper enhancement layers sequentially. This horizontal adaptation is straightforward and does not require any bandwidth estimation. Through NS-2 simulations, we show that WQUAD achieves (i) stable performance, keeping the video quality level with respect to the long-term network bandwidth, (ii) effective video freeze prevention, and (iii) high video quality on average.     

Core-shell structure of polypyrrole grown on W18O49 nanorods for high performance gas sensor operating at room temperature

In this work, uniform core-shell structure of polypyrrole wrapped on tungsten oxide nanorods (PPy@W₁₈O₄₉ core-shell nanorods) were synthesized via a two-step process for gas-sensing applications. The core-nanorods of W₁₈O₄₉ were first grown by solvothermal method with tungsten hexachloride (WCl₆) as precursor. The PPy-shell layer was then formed uniformly on the solvothermally synthesized W₁₈O₄₉ nanorods by in-situ chemical polymerization of pyrrole monomer (Py), with sodium dodecyl benzene sulfonic acid (DBSA) as dopant and ammonium persulfate (APS) as oxidant. High dispersion of Py achieving in ethanol is proved to be crucial to form the uniform PPy-shell layer, and the layer thickness of PPy-shell is highly controlled by adjusting the Py concentration in polymeric solution. The morphology and structure of the nanocomposite were characterized systematically; it shows that the composite exhibits perfect core-shell structure of one-dimensional (1D) nanorods with average diameter of around 70–90 nm. The NH₃-sensing properties of the sensors based on the PPy@W₁₈O₄₉ core-shell nanorods were investigated at operating temperature of 15–130 °C over NH₃ concentration ranging from 1 to 200 ppm. The response magnitude of the PPy@W₁₈O₄₉ sensor can be affected seriously by temperature fluctuation, even in room temperature range (15–30 °C), and meanwhile, a temperature-dependent p-n response characteristic reversal is observed for the heteronanorods sensor. At much low room temperature of 15 °C, the present PPy@W₁₈O₄₉ nanorods show quick and sensitive response to NH₃ gas mainly due to the ultrathin, uniform PPy shell and the special heterojunction effect between p-type PPy and n-type W₁₈O₄₉. The underlying gas-sensing mechanism is analyzed.     

Solution processable PEDOT:PSS based hybrid electrodes for organic field effect transistors

We report high performance solution processed conductive inks used as contact electrodes for printed organic field effect transistors (OFETs). Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) electrodes show highly improved very low sheet resistance of 65.8 ± 6.5 Ω/square (Ω/□) by addition of dimethyl sulfoxide (DMSO) and post treatment with methanol (MeOH) solvent. Sheet resistance was further improved to 33.8 ± 8.6 Ω/□ by blending silver nanowire (AgNW) with DMSO doped PEDOT:PSS. Printed OFETs with state of the art diketopyrrolopyrrole-thieno[3,2-b]thiophene (DPPT-TT) semiconducting polymer were demonstrated with various solution processable conductive inks, including bare, MeOH treated PEDOT:PSS, single wall carbon nanotubes, and hybrid PEDOT:PSS-AgNW, as the source and drain (S/D) electrode by spray printing using a metal shadow mask. The highest field effect mobility, 0.49 ± 0.03 cm² V⁻¹ s⁻¹ for DPPT-TT OFETs, was obtained using blended AgNW with DMSO doped PEDOT:PSS S/D electrode.     

Stereoscopic view synthesis based on region-wise rendering and sparse representation

Depth image-based rendering (DIBR), which is used to render virtual views with a color image and the corresponding depth map, is one of the key techniques in the 2D to 3D conversion process. One of the main problems in DIBR is how to reduce holes that occur on the generated virtual view images. In this paper, we make two main contributions to deal with the problem. Firstly, a region-wise rendering framework, which divides the original image regions into three special classes and renders each with optimal adaptive process respectively, is introduced. Then, a novel sparse representation-based inpainting method, which can yield visually satisfactory results with less computational complexity for high quality 2D to 3D conversion, is proposed. Numerical experimental results demonstrate the good performance of the proposed methods.     

A portable high-density absolute-measure NIRS imager for detecting prefrontal lobe activity under fatigue driving

Driving fatigue is one of the primary causes of traffic accidents nowadays. It is thus imperative to develop a technique to monitor levels of driving fatigue. The emergent near-infrared spectroscopy (NIRS) is now capable of measuring functional cerebral activities noninvasively and sensitively in terms of hemodynamic responses, shedding light on the possibility to detect signals regarding fatigue-specified cerebral activities. This work innovatively developed a NIRS device aimed at fatigue detection of drivers, and the device was designed to be portable so that it can be easily operated during driving. Moreover, the device is absolute-measure so that the data can be compared among drivers. The probe is high-density and we can visualize brain functional responses after imaging. The high sensitivity, stability, and reliabilities of our device were fully tested in the order of ink experiment, cuff experiment, and on-human test. For the in-situation on-human test, we recruited 3 taxi drivers and collected data by our device during 8 h' driving. It's found that the hemodynamics-represented cerebral activation decreased with driving duration, which indicated our device's strong potential in monitoring fatigue.     

Nanoseed-assisted rapid formation of ultrathin ZnO nanorods for efficient room temperature NO2 detection

The influence of ZnO nanoseeds on the formation of ZnO nanorods from ε-Zn(OH)₂ in NaOH solution at 80 °C was investigated, using ZnO nanoparticles with a diameter of 4–10 nm as the seeds. The experimental results indicated that the presence of ZnO nanoseeds promoted the rapid heterogeneous formation of ultrathin ZnO nanorods. Compared with the ZnO submicron rods with a diameter of 0.5–1.0 µm, the ultrathin ZnO nanorods with a diameter of 10–15 nm were found to be more sensitive for detecting NO₂ at room temperature owing to their higher variation of channel conduction to the diameter.     

Investigations on immunity of interfaces between intelligent media processor and DDR3 SDRAM memory

Due to the complexity of IC, electromagnetic immunity plays a critical role towards evaluating the EMC performance to avoid the high cost of redesign. This paper focuses on the Direct Power Injection (DPI) immunity of processor chips with different external double data rate3 (DDR3) synchronous dynamic random access memory (SDRAM) in consumer electronics. To complete the DPI test, a test board complying with the standard IEC62132-4 and a dedicated test code have been designed. The effect of DC power injection interference on same DDR model but different DDR pins and the same DDR pin but different DDR models were analysed, the results can be used to locate the system-level EMC issues and optimize the design.