如何减少CATV信号的传输故障

在有线电视线路中 ,许多故障是由接头松动、氧化、进水等引起的 ,如果发生在干线、支干线就会造成大片用户看不好电视 ,因此在ＣＡＴＶ线路施工中保证接头的安装质量至关重要。在施工中 ,有些施工人员认为做Ｆ接头很简单而不认真对待。有人做Ｆ头时将电缆的金属网剪掉 ,有的不加金属箍 ,这都会使接头松动 ,造成接地不良 ,在用户电视上表现为 :高频信号勉强可收看 ,低频信号电平严重降低 ,雪花大且有网纹 ,甚至收看不到信号。还有人安装分支器不加防雨盒 ,使其暴露在外 ,一旦下雨、下雪进水就造成信号短路 ,而且日久锈蚀电路板使分支器损坏。…     

A method to reduce stray signal errors in antenna patternmeasurements

The presence of stray signals in an antenna measurement range can cause errors in the measured patterns. In order to measure low sidelobe antennas in an antenna range, the stray signals in the range should be very small (at least 8-10 dB below the sidelobe level). It may not be possible to achieve such low level stray signals in a real world antenna range. Thus, alternate methods for reducing these measurement errors are needed. In this paper, such a method is presented. Using simulated examples and experimental data, it is shown that this method significantly reduces the chamber related measurement errors. The method can also be used to identify the angular regions along which the stray signal errors are most significant. Thus, the range can be qualified and, if possible, improved     

Coding to reduce both PAR and PICR of an OFDM signal

The two major drawbacks in orthogonal frequency-division multiplexing (OFDM) system are high peak-to-average power ratio (PAR) and intercarrier interference (ICI) due to frequency offset errors. Several techniques proposed in the literature treat these limitations as two separate problems. We introduce the peak interference-to-carrier ratio (PICR) to measure ICI. This paper shows the existence of codes to reduce both the PAR and PICR simultaneously. The coding scheme is based on selecting only those messages with both low PAR and PICR as valid codewords. We identify those codes by computer search. As an example of an explicit construction for such codes, we construct Golay complementary repetition codes that can reduce both PAR and PICR simultaneously.     

Methods to reduce radiation from split ground planes in RF and mixed signal packaging structures

Split ground planes are sometimes used in RF and mixed signal packages in order to isolate the RF and analog circuits from the digital circuits. Undesired radiation in a packaging environment may occur when a signal trace is routed over a slot in the ground plane. This paper examines and investigates ways to eliminate signal coupling into split ground plane structures and assesses the impact of this reduced coupling on signal integrity in a packaging environment. Suggested methods to reduce coupling of energy into the slot are to alter the shape of the slot with RF chokes or corrugations.     

降低可见光OFDM系统峰均比的新方法

可见光正交频分复用(OFDM)系统的一个主要缺点是系统的峰均比(PAPR)较高,会引起信号失真。为了降低可见光OFDM通信系统的峰均比,本文将选择性映射(SLM)方法引入可见光通信系统中,并将其进行适当的改进,使之满足可见光通信信号必须为正的实信号的要求。提出将离散傅里叶变换展开(DFTS)与SLM相结合(DFT-S-SLM)的方法来进一步降低可见光OFDM系统的峰均比。仿真结果表明,与原信号、仅采用DFT展开或者SLM方法相比,在增加一定的系统复杂度的情况下,DFT-S-SLM方法具有更好的峰均比性能。     

A novel search method to reduce PAPR of an OFDM signal using partial transmit sequences

One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak‐to‐average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. As ordinary PTS technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub‐blocks. In this paper, we propose a novel PTS technique with reduced complexity that each level inverts twice of phase factor bits from previous level. Then we also use initial random phase sequence to find the better search way of PAPR reduction. Numerical results show that the proposed method can achieve significant reduction in search complexity with little performance degradation. Copyright © 2006 John Wiley & Sons, Ltd.     

Microswitches in molecular electronics-from molecular conductors to molecular electronics

A survey is given on one of the proposed routes to molecular electronics: from conducting polymers via molecular triads to shift registered, cellular automata, and neuronal networks. Some results on photo-induced absorption, transient photoconductivity, and Langmuir-Blodgett films are presented as ‘flowers by the roadside’.     

2007电感市场回望

电感器具有滤波、抑制瞬间电流、降低EMI噪声及功率转换等功能特性，长久以来广泛地应用于各种电子产品，是电子产品中不可或缺的零组件。     

Electromigration mechanism in aluminium conductors

The mechanism of electromigration in the aluminium conductors of Integrated Circuits has been studied with radioactive tracers (Al²⁶ and Ni⁶³) employing high resolution autoradiographic techniques. It has been proved that the mass transport from the negative to the positive pole takes place predominantly by migration through the aluminium film grain boundaries. The surface diffusion mechanism was discarded as an important contribution to the process. Measurements of MTF (mean time to failure) in pure aluminium and in nickel-doped aluminium (200–700 ppm of nickel) showed a ten-fold advantage for the doped conductor. The electromigration activation energy of doped specimens was determined from the MTF variation with temperature. This result, 23.9 kcal mol^?1, is in agreement with the activation energy for grain boundary diffusion of nickel in aluminium taken from the literature [1].     

Recessed gate-data line-crossover structures employing an air-gapto reduce signal delay for TFT-LCD panel

Two new line-crossover structures entitled "recessed air-bridge structure" and "recessed gate-line structure," which have improved mechanical durability and reduced data-tine signal delay in active matrix liquid crystal display (AMLCD) panel, have been proposed and fabricated. In the recessed air-bridge structure, the air-gap line-crossover is located at the bottom of the oxide trench so that the floated upper lines lie flush with the panel's surface. The recessed gate-line structure was fabricated by recessing the whole gate-line into the bottom of an oxide trench. Both of the fabricated structures, without any passivation layer, were proved sufficiently robust to withstand a rubbing process, which applied realistic mechanical stresses to the AMLCD panel. Experimental results show that the signal delays of the proposed structure are less than about 20% of the conventional structure     

Electromigration-induced failures in thin-film Al-Cu conductors

The effect of CuAl₂ precipitates on the electromigration lifetime of thin film Al-Cu conductors was studied by varying the Cu concentration in the 0–12 wt per cent range. Experiments show that the conductor lifetime does not increase monotonically with an increase in precipitate content. It is shown that the precipitates, when present in sufficient quantity, can greatly modify the grain size distribution and hence can affect the electromigration lifetime. These results are interpreted in terms of a model relating the vacancy and the copper atom flux along the grain boundaries. The roles of annealing treatments, copper concentration, structural non-homogeneities and test temperatures are explained by the present model.     

On charge relaxation in good conductors

The charge relaxation in a good conductor is reexamined. It is shown that the fallacy in the prediction of the very rapid decay of free charge implanted in a metal lies in the use of the dc conductivity. The corrected decay time is some six orders of magnitude greater than that predicted on a dc theory.     

减小CMOS逻辑器件的ΔI噪声的方法

通过确定 CMOS逻辑器件的各种参数与馈通电流和容性负载充放电电流的定量关系 ,得出设计 CMOS逻辑器件的各种参数以减小ΔI噪声 ,从电磁兼容的角度提出了设计 CMOS器件的方法。     

Scale model experiments to study low-frequency electromagneticresolution of multiple conductors

Low-frequency analog modeling experiments were conducted to investigate the response of two vertical half-planes to the horizontal loop electromagnetic method. Both insulating and conducting environments are considered. Several characteristic profiles of in-phase and quadrature components caused by diffracting objects were obtained. The results include the following: (1) the response of closely spaced conducting scatterers can be discriminated only if their separation S⩾ the transmitter-receiver separation L; (2) the distance W between the two extreme zero crossovers of in-phase and quadrature components; (3) the quadrature profiles are more sensitive than in-phase curves in resolving the target conductors; (4) for S<0.5 L, much higher estimates of conductance and lower estimates of the depth than actual situations will be obtained if the data is interpreted with the conventional half-space phasor diagrams     

Failure of small thin-film conductors due to high current-density pulses

Current pulses at high repetition rates and extremely high current density (> 10⁷A/cm²) were applied to small geometry, thin-film aluminum-copper alloy conductors. The conductor lifetimes were measured as a function of current density and duty cycle. While the observed open-circuit failures are evidently related in some way to the temperature excursions produced by Joule heating, the exact mechanism(s) causing failure is not so clear, and probably varies depending on test conditions. A previously described [8] ohmic nonlinearity measurement was used to characterize the conductor's ability to dissipate heat. A strong inverse correlation was found between the ohmic nonlinearity and time to failure.     

Use of data permutation to reduce the peak‐to‐average power ratio of an OFDM signal

A set of fixed permutations is used in this paper to reduce the peak‐to‐average power ratio (PAR) of an orthogonal frequency division multiplexing (OFDM) signal. For this technique, K − 1 interleavers are used to produce K − 1 permuted sequences from the same information sequence. The peak powers of the permuted sequences and the original information sequence are computed using K inverse discrete Fourier transforms; the sequence with the lowest PAR is chosen for transmission. Before the optimization process begins the identity of each interleaver is embedded into the data frame as side information (SI). SI which is critical to the receiver operation, is coded using a simple forward error correction code in order to increase its reliability. An adaptive approach is proposed for the reduction of this technique's complexity. Furthermore, theoretical expressions are derived for the complementary cumulative distribution function of the PAR and for the average number of permutations required by the adaptive approach. Computer simulations are performed for finding the PAR reduction capability of several types of interleavers. It is subsequently found that random interleavers and odd–even symmetric interleavers are performing equally well in reducing the PAR. Results are also presented for the out of band radiation and the bit error rate performance of interleaved OFDM (IOFDM) and conventional OFDM in an additive white Gaussian noise channel. IOFDM also has less adjacent channel interference than that of conventional OFDM. Copyright © 2002 John Wiley & Sons, Ltd.     

Working-zone encoding for reducing the energy in microprocessoraddress buses

The energy consumption due to input-output pins is a substantial part of the overall chip consumption. To reduce this energy, this work presents the working-zone encoding (WZE) method for encoding an external address bus, based on the conjecture that programs favor a few working zones of their address space at each instant. In such cases, the method identifies these zones and sends through the bus only the offset of this reference with respect to the previous reference to that zone, along with an identifier of the current working zone. This is combined with a one-hot encoding for the offset. Several improvements to this basic strategy are also described. The approach has been applied to several address streams, broken down into instruction-only, data-only, and instruction-data traces, to evaluate the effect on separate and shared address buses. Moreover, the effect of instruction and data caches is evaluated. For the case without caches, the proposed scheme is specially beneficial for data address and shared buses, which are the cases where other codings are less effective. On the other hand, for the case with caches the best scheme for the instruction-only and data-only traces is the WZE, whereas for the instruction-data traces it is either the WZE or the bus-invert with four groups (depending on the energy overhead of these techniques)     

Recursive partitioning to reduce distortion

Adaptive partitioning of a multidimensional feature space plays a fundamental role in the design of data-compression schemes. Most partition-based design methods operate in an iterative fashion, seeking to reduce distortion at each stage of their operation by implementing a linear split of a selected cell. The operation and eventual outcome of such methods is easily described in terms of binary tree-structured vector quantizers. This paper considers a class of simple growing procedures for tree-structured vector quantizers. Of primary interest is the asymptotic distortion of quantizers produced by the unsupervised implementation of the procedures. It is shown that application of the procedures to a convergent sequence of distributions with a suitable limit yields quantizers whose distortion tends to zero. Analogous results are established for tree-structured vector quantizers produced from stationary ergodic training data. The analysis is applicable to procedures employing both axis-parallel and oblique splitting, and a variety of distortion measures. The results of the paper apply directly to unsupervised procedures that may be efficiently implemented on a digital computer     

Conductance fluctuations in mesoscopic conductors at lowtemperatures

This paper is a tutorial introduction to the subject of conductance fluctuations observed in mesoscopic conductors at low temperatures, and the universal conductance fluctuation (UCF) theory proposed to explain them. The discovery of the fluctuations less than a decade ago has been followed by an intensive flurry of research activity, published almost entirely in the journals of solid-state physics. This paper surveys the subject from the viewpoint of a practising electron device engineer, with bias in favor of intuitive appeal rather than rigor, and should be helpful in understanding the primary literature on the subject. The nature of fluctuations and mesoscopic conduction are briefly introduced. Both theoretical and experimental results from the sizable literature on the subject are summarized here, emphasizing the characteristics of the fluctuations, the conditions under which they are observed, the mechanism of fluctuations, and the range of applicability of the UCF theory     

碳纳米管在集成电路中代替金属导线

德国Infineon技术公司的集成电路研究人员取得了一项碳纳米管技术突破，他们在6英寸圆片的预先指定的地方生长出了碳纳米管（carbonnanotubes, CNT）。Infineon希望利用这个发现用CNT取代芯片中的所有金属导线。CNT的众多特色（包括更高的可靠性和更高的片上时钟频率）使它成为未来半导体技术的最佳材料选择。不过，到目前为止，制作CNT的方法，如激光烧蚀和弧光放电，难以同半导体技术相结合。CNT的最重要性质之一是高电导率，允许通过大电流密度——高达1010A/cm2（铜在107A/cm2就开始熔化）。研究人员预计10年内芯片接线必须能承…