阿尔卡特朗讯

AbstractThe Yagi–Uda antenna is one of the most practical and commonly used antennas. It features high gain, low weight and profile, and is inexpensive to manufacture. In this article, the fundamental operation of the Yagi–Uda, as well as a classic graphical technique for obtaining a fixed gain design, is discussed. Several modern versions of the Yagi–Uda antenna are also described, which permit the antenna to be operated at microwave frequencies and allow for simple integration into planar arrays in various applications including modern wireless communications.

Cyber attacks are on the increase, in terms of both the number of attacks and the damage they cause. Encouraging organisations to improve their cyber security has had only a limited effect. Now it’s the turn of legislation and regulation, with the Cyber Resilience Act (CRA) and Network and Information Security Directive (NIS2) coming into force in the EU. But what kind of impact are they likely to have?

Thermal fatigue is a major source of failure of solder joints in surface mount electronic components and it is critically important in high reliability applications such as telecommunication, military, and aeronautics. The electronic packaging industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu alloys first established as replacements for eutectic SnPb. This paper discusses the results from Pb-free solder joint reliability programs sponsored by two industry consortia. The characteristic life in accelerated thermal cycling is reported for 12 different Pb-free solder alloys and a SnPb control in 9 different accelerated thermal cycling test profiles in terms of the effects of component type, accelerated thermal cycling profile and dwell time. Microstructural analysis on assembled and failed samples was performed to investigate the effect of initial microstructure and its evolution during accelerated thermal cycling test. A significant finding from the study is that the beneficial effect of Ag on accelerated thermal cycling reliability (measured by characteristic lifetime) diminishes as the severity of the accelerated thermal cycling, defined by greater ΔT, higher peak temperature, and longer dwell time increases. The results also indicate that all the Pb-free solders are more reliable in accelerated thermal cycling than the SnPb alloy they have replaced. Suggestions are made for future work, particularly with respect to the continued evolution of alloy development for emerging application requirements and the value of using advanced analytical methods to provide a better understanding of the effect of microstructure and its evolution on accelerated thermal cycling performance.