Here is Part VI 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.
We have been able to conclude that using an isotropic antenna, an RFID reader might achieve a read range of a few meters with 1 watt of output power. This configuration might be fine if RFID tags of interest are equally likely to be located in any direction with respect to the reader. However, such a circumstance is itself rather improbable.
