**1. Introduction**

176 Wireless Communications and Networks – Recent Advances

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Cloud computation and always-connected Internet attracts the most industrial attention for the past few years. Meanwhile, with the development of IC technologies advancing toward higher operating frequencies and the trend of miniaturization on wireless communication products, the circuits and components are placed much closer inside the wireless communications devices than ever before. The system with highly integrated high-speed digital circuits and multi-radio modules are now facing the challenge from performance degradation by even more complicated platform EMI noisy environment. The EMI noises emitted by unintentionally radiated interference sources may severely impact the receiving performance of antenna, and thus result in the severe performance degradation of wireless communications. Due to the miniaturization of a variety of wireless communications products, the layout and trace routing of circuits and components become much denser than ever before. Therefore, we have investigated and analyzed the EMI noise characteristics of commonly embedded digital devices for further high performance wireless communications design. Since the camera and display module is most adopted to the popular mobile devices like cellular phone or Netbook, we hence focus on EMI analysis of the built-in modules by application of IEC 61967[1][2] series measurement method.

Since the causes of reduction of throughput or coverage due to receiving sensitivity degradation of wireless system could result from decreased S/N via conducted or radiated EMI noises from nearby digital components shown in Figure 1. This chapter discusses RF de-sensitivity analysis for components and devices on mobile products. To improve the TIS performance of wireless communication on notebook computer, we investigated the EMI noise from the built-in camera and display modules as examples and analysed the impact of various operation modes on performance with throughput measurement. We also utilized the near-field EM surface scanner to detect the EMI sources on notebook and locate the major noisy sources around antenna area. From the emission levels and locations of the noisy components, we can then figure out their impact on throughput and receiving sensitivity of wireless communications and develop the solutions to improve system performance. Finally, we designed and implemented periodic structures for isolation on the notebook computer to effectively suppress noise source-antenna coupling and improve the receiving sensitivity of wireless communication system.

Fig. 1. S/N ratio decreases due to digital components for multi-functions.
