Chapter 1: The Physics of RFID

RFID+ Exam Objectives Covered in this Chapter:

ü	8.1 Identify RF propagation/communication techniques
ü	8.2 Describe antenna field performance/characteristics as they relate to reflective and absorptive materials (may use scenarios)
ü	8.3 Given a scenario, calculate radiated power output from an antenna based on antenna gains, cable type, cable length, interrogator transmit power (include formulas in scenario)

If your only memory of high-school physics is of your wrapping some copper wire around a hunk of metal and seeing if you could make it stick to your friend's braces, you might have missed the lovely nuances of the science while simultaneously ensuring continued income for the local orthodontist. Physics is the foundation and basis for everything that happens in radio frequency identification (RFID). All too often people (usually in marketing) try to blame physics for the failures of RFID systems, when in actuality knowledge of physics can be the biggest asset in deploying RFID.

This chapter may make you feel like you are going back to high-school or college physics, but I assure you there will be no goofy experiments, only sage advice that will help you to deploy faster and more-accurate RFID systems and to troubleshoot the real sticklers you might one day encounter.

The physics of RFID revolve mostly around the behavior of the magnetic fields and electromagnetic waves generated by an RFID system. Because physics dictates how these fields and waves are generated, behave, and react, the RFID+ exam has a significant number of questions that will test your base knowledge of the physics of RFID. To get you ready for that part of the exam and to help you begin deploying real-world systems, this chapter will cover the following:

• The types of waveforms surrounding radio frequency (RF)

• The characteristics of those waves

• How to measure things that can't be seen

• The basics regarding some of the equations of RF