Experimental verification of the use of metal filled via holefences for crosstalk control of microstrip lines in LTCC packages

Coupling between microstrip lines in dense RF packages is a common problem that degrades circuit performance. Prior three-dimensional-finite element method (3-D-FEM) electromagnetic simulations have shown that metal filled via hole fences between two adjacent microstrip lines actually increases coupling between the lines; however, if the top of the via posts are connected by a metal strip, coupling is reduced. In this paper, experimental verification of the 3-D-FEM simulations is demonstrated for commercially fabricated low temperature cofired ceramic (LTCC) packages. In addition, measured attenuation of microstrip lines surrounded by the shielding structures is presented and shows that shielding structures do not change the attenuation characteristics of the line     

The use of laminate multichip modules for the packaging of 9-GHzdigital multichip circuits

An investigation of the high-frequency performance of laminate multichip module (MCM-L) technology was undertaken with the goal of demonstrating its appropriateness for the development of digital radar receivers operating in the X band (8 to 12 GHz). A seven-chip circuit using digital components on a Gore MCM-L was successfully tested up to 9.6 GHz. An analog-to-digital converter on an MCM-L was successfully tested up to 6 GHz. An extensive characterization of the MCM-L technology using both simulations and measurements was performed to formulate a set of design guidelines for high-frequency applications. A novel dielectric-encapsulated MCM-to-MCM interconnect scheme was proposed and tested     

Steady state thermal characterization and junction temperatureestimation of multichip module packages using the response surfacemethod

The steady state thermal performance of semiconductor packages has been traditionally reported through the utilization of a single junction-to-ambient thermal resistance constant commonly referred to as &thetas;_ja. This is particularly inadequate for multichip modules where several devices reside within the same package structure. This paper discusses how a central composite design of experiments can be applied to provide a more accurate thermal characterization of a multichip module package. The end product is a series of linear or polynomial equations which can be utilized by the customer to calculate individual device junction temperatures over a wide variation of convection cooling environments and multiple device power dissipations. A 352 plastic ball grid array package, which encompasses three individual integrated circuit devices, is used as an example. The paper steps through the sensitivity analysis and evaluates the accuracy of the resulting equations. This method of thermal characterization can be easily applied to single chip modules of varying power and cooling regimes, or multiple output devices where several power junctions reside within the same integrated circuit     

A 5-6 GHz SiGe HBT monolithic active isolator for improving reverse isolation in wireless systems

A monolithic active isolator combining common-base and common-collector configurations of SiGe heterojunction bipolar transistors (HBT) is used to improve reverse isolation in wireless system applications. This simple active isolator results in an insertion loss of 2 dB and input IP3 of +0.7 dBm over 5-6 GHz with a 1.8-mA current flow for the core circuit of a 3-V supply.     

无线数传模块的应用

文中讲解了TXD1100无线数传模块的特点,详细介绍了利用该模块设计、开发了“主—被”工作模式下的控制系统方案.该系统具有自动识别无线数传模块的工作参数和在存在同频干扰的情况下能够自动跳频等优点.     

无线数传模块的应用

文中讲解了TXD1100无线数传模块的特点,详细介绍了利用该模块设计、开发了＂主—被＂工作模式下的控制系统方案。该系统具有自动识别无线数传模块的工作参数和在存在同频干扰的情况下能够自动跳频等优点。     

一种盲孔评估的新方法

随着HDI(High Density Interconnecting)印制电路板高阶化迅速发展,现今检测盲孔的方法已暴露出很多不足。本文将提出一种盲孔评估的简单方法。通过将盲孔背面抛磨,将铜盘与盲孔分离检测两个面的匹配情况达到检测盲孔缺陷的目的。通过与现今检测方法匹配使用,该方法解决了盲孔的失效分析中众多的争议。     

Effects of dimple and metal coating on interfacial adhesion in plastic packages

This paper reports on the effects of dimple and metallic coating of the Cu-alloy lead frame on interfacial adhesion with an epoxy-molding compound. Round dimples of varying number are introduced on one side of the lead frame by chemical etching. The plating materials studied include bare-Cu alloy and microetched Cu, Ag, Ni, Pd/Ni, and Au/Ni coatings. The surface characteristics, such as wettability, surface roughness, and element compositions, were evaluated based on several characterization tools, which, in turn, are correlated with adhesion performance. The dimples enhanced the interfacial-bond strengths through improved mechanical interlocking of the molding compound, depending on the type of coating. The improvement was much more significant for the coatings with inherently weak interfacial adhesion (e.g., microetched Cu and Ni coating) than those with inherently strong adhesion characteristics (e.g., Au and Pd coatings). The wettability of the metal surface represented by the surface energy or interfacial energy played a dominant role in the resulting interfacial adhesion. Elemental analysis of the fracture surface indicates that the silicon content had roughly a linear relationship with the interfacial-bond strengths for different coatings. The surface roughness was insensitive to the interfacial-adhesion performance. The silicon content measured from the lead-frame fracture surface was shown to directly correlate to the interfacial-bond strength. Higher silicon content was a reflection of larger surface-area coverage by the molding compound associated with cohesive failure.     

The use of multiuser detectors for multicasting in wireless ad hocCDMA networks

In this paper, we address the issue of performance of linear multiuser detectors for a multicasting application in an ad hoc wireless network. Using a code-division multiple-access (CDMA) framework, we demonstrate how capacity results for multiuser detectors can be adapted to do session admission control for the multicasting problem. We then develop a multicast routing algorithm for ad hoc wireless networks. Using the session admission control mechanism and the multicast routing algorithm, we evaluate the performance of three different linear multiuser detectors for the multicasting application     

Polling-based MAC protocols for improving real-time performance in a wireless PROFIBUS

The idea of having a wireless PROFIBUS is appealing, since this can bring benefits like reduced cabling need and mobile stations to the factory floor. However, unfortunately, wireless transmission is error prone, which affects the timeliness and reliability behavior users expect from a fieldbus system (hard real time). In this paper, we compare two different approaches for the medium access control (MAC) and link layer of a wireless PROFIBUS system with respect to their so-called real-time performance in the presence of transmission errors. Specifically, we compare the existing PROFIBUS MAC and link layer protocol with a simple round-robin protocol. It is shown that round-robin delivers significantly better real-time performance than the PROFIBUS protocol under bursty error conditions. In a second step, we propose three add-ons to round-robin and we show that they further increase the real-time performance of round-robin. The add-ons take certain characteristics of the wireless medium into account.     

高速PCB过孔设计研究进展

传输线连续性问题已成为当今高速数字电路设计的重点,尤其是多层PCB中大量使用的过孔结构。随频率的增加和上升时间的缩短,过孔阻抗不连续以及寄生电容、电感会引起信号反射和衰减,并进一步导致信号完整性（SI）问题。综述了高速电路中单端和差分过孔的孔径、孔长度等设计参数对阻抗连续性和S参数的影响,并介绍了三种提高过孔信号传输质量的方法,包括避免多余短柱、非穿导技术以及为过孔信号提供返回路径。本文能够为高速数字电路设计者进行过孔信号完整性判定提供参考。     

Considering spurious timeout in proxy for improving TCP performance in wireless networks

In this letter, we introduce a new proxy that effectively prevents unnecessary retransmissions from flowing over a wireless link on a path with sudden delay. The proposed Spurious Timeout (STD) algorithm detects spurious timeout based on the data and acknowledge sequence number. It responses to spurious timeout by filtering duplicate acknowledgements that can cause spurious fast retransmission. Simulation results show that the proposed STD algorithm performs better than, or as well as, other end-to-end mechanisms.     

HDI板通盲孔同时开窗电镀的制作方法

现阶段通盲孔位于同一层的HDI板,生产流程较长,制作成本较高,文章通过从优化生产流程,缩短生产周期,降低制作难度角度出发,设计出一种通盲孔同时开窗电镀的工艺技术,对通盲孔同时开窗电镀的工艺技术提出一些见解。     

Low-latency algorithm for improving data persistence in mobile low-duty-cycle wireless sensor network

Mobile low-duty-cycle wireless sensor network (MLDC-WSN) are a kind of new ad hoc networks that are appeared in recent years.In MLDC-WSN,the nodes only have limited storage spaces.Moreover,the nodes would move or sleep from time to time.Therefore,these networks have some problems such as connectivity is hard to be maintained and data are hard to be transmitted to their destinations for storage in time.As a result,data persistence (i.e.,the probability that all data can be recovered after some nodes die in the networks) is low.A distributed algorithm named LT-MDS for improving data persistence in MLDC-WSN was proposed.The algorithm used a new infectious data dissemination method to transmit the data,which enabled the data to be received by almost all the mobile nodes in a network with low latency and improved the reliability of the network.When a node receives the data,it would use LT (Luby transform) codes to encode and save them.By this way,the nodes with limited storage spaces can save more data information.Theoretical analyses and simulations show that LT-MDS can complete the process of data dissemination and preservation with low latency,and it can achieve high data persistence.     

HDI板通盲不匹配产生的原因与改善方法

HDI板通盲孔不匹配会导致PCB产品的开路、短路以及图形偏位,本文通过改进定位方式,提高对位精度,探索出一种改善通盲不匹配问题的方法,就对位、定位系统及板材涨缩几个方面对HDI板通盲不匹配产生的原因及改善方法提出看法。     

The effect of edge metal profiles on the accuracy of electrical modeling of advanced packages

Electronic package edge metal profiles have an effect on package characteristics on an order increasingly close to the tolerances expected for the package electrical performance. Several two-dimensional (2-D) tools are available that can be used to evaluate predesign and layout issues with nonrectangular edge profiles. However, tools that extract models from actual designs using the most up-to-date computer-aided design/computer-aided engineering (CAD/CAE) design and modeling flows do not yet take into account these real-world metal geometries. Variations in impedance and crosstalk associated with real profiles versus rectangular idealizations are identified for some typical cases and a computational procedure is discussed which may efficiently address this problem.     

Way-Point Multicast Routing Framework for improving QoS in hybrid wireless mesh networks

Since internet access is used by billions of people worldwide and the number of internet user is also increasing every day, a new technology called as wireless mesh network (WMN) is becoming popular. This is because it has some desirable characteristic, but it has some limitation for multi-hop routing, bandwidth, and many more. In order to overcome these issues, we proposed Way-Point Multicast Routing Framework (WPMRF) for improving the quality of service (QoS) in Hybrid WMN. Initially, the multicast framework is established based on the minimum load factor. The route established with least load factor is considered, as it avoids any kind of congestion in the network. After that, segmentation of route is done, and the way-point nodes are selected to join the multicast session. After that, the transmission is performed using MAODV and ODMRP protocol. In addition, an estimated route disconnection parameter is used for fast route recovery process and helps to select more reliable route path. The advantage of the proposed work is that it provides more reliable routing path to increase the quality of service (QoS) with fast route recovery process.     

The use of titanium metal in vacuum devices

The excellent gettering and gas retention properties of titanium metal make it highly suitable for use in vacuum devices. Tiny receiving tubes made with titanium parts are described which are capable of operating at high cathode emission densities. These high densities reduce the electron transit times and give better high-frequency performance. They permit the use of small electrodes and reduced heater and plate input powers. Vacuum devices made with titanium and ceramic parts can be operated for long periods of time at temperatures up to 700°C.     

一种串联RFMEMS开关的隔离度补偿措施

提出了采用陷波电路结构来补偿串联RFMEMS开关断开时的耦合电容,提高其隔离度的一种方法。理论分析显示,采用这种方法,在2～5GHz的频率范围内,可以使开关的隔离度最多提高15郾6dB,而插入损耗只受到0郾07dB的影响。