Here is Part III of Chapter 3--Radio Basics For UHF RFID--from The RF in RFID: Passive UHF RFID in Practice. Written for the electrical engineer but not the RFID expert, Dr. Dobkin explains what to expect, develop, and use while implementing an RFID system.
A periodic signal that persists indefinitely, without changing its amplitude, frequency, or Phase--a continuous wave (CW) signal--carries no information other than the fact that it is present. In order to convey data, a signal needs to change. We normally think of this change as
a relatively slowly changing variation--modulation--imposed on the periodic signal.
