10. The Wireless Signal

Wireless signals are an integral part of many of today’s embedded system designs. Mobile computer providers talk of media convergence, where consumers will be able to browse the Internet or watch live sports on a wireless computer, mobile telephone, portable digital television, or personal digital assistant (PDA). Put simply, the media will be transparent to the wireless technology. Nevertheless, media convergence is the precursor to a myriad of complex technological issues, such as enhanced data compression, interoperability, propagation, and interference. Numerous other wireless uncertainties, such as the large number of international standards and media formats, deserve a book of their own. This chapter, in keeping with signal integrity engineering, is less concerned with media, standards, and the peculiarities of wireless propagation; it focuses on measuring and analyzing wireless signals. Wireless signals and spectrum analysis are wide-ranging subjects with several specialist areas, and it could be argued that such topics are better suited to dedicated wireless books. However, because wireless is becoming so prevalent in embedded system design and there are so many fresh wireless issues, the wireless environment deserves valuable thinking time from the signal integrity engineer. Consequently, this book would be incomplete without an explanation of modern wireless signals and their measurement. Therefore, it is the aim of this chapter to help you understand some of the new techniques in wireless signal measurement. This chapter also offers a few thought-provoking ideas about signal analysis in the modern wireless environment.

With such a rich and diverse subject as wireless signals and their measurement, it will always be debatable which wireless instruments and applications to include in a broad SI book. Nevertheless, this topic is somewhat straightforward, because it can be argued that the spectrum analyzer (SA) is the principal tool for evaluating radio frequency (RF) signal characteristics. Moreover, spectrum analysis is the dominant test setting for a wide range of wireless systems and device designs. Also, spectrum analysis currently supports research and development applications ranging from low-power radio frequency identification (RFID) systems to high-power radar and RF transmitter measurements.