Appendix G

Near Fields from Radiated Radio-Frequency Identification (RFID) Power Data

We assume the radiation is from a printed circuit antenna on an RFID-like transponder that has the shape of a planar coil, and represent this source as a magnetic dipole M oscillating at an angular frequency ω = 2π 109/s. (Note: we do not take into account any differences in the magnitude of the current at different portions of the antenna.)

The magnetic and electric fields from this dipole are given by the following expressions. Note that the bolded letters are vectors, a bolded x represents the vector (i.e., cross) product of two vectors, and a bolded dot represents the scalar (i.e., dot) product of two vectors:

  [1]

  [2]

In these expressions:

μo = 4π10− 7 H/m ...

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