Forward and reverse link constraints in UHF RFID with passive tags

This paper examines the relative roles of the forward and reverse links in determining the operational range of passive UHF RFID systems. Simple free space examples in free space show when the forward or reverse link may be the main range constraint in practical systems, depending on reader and tag characteristics. Measurements of transmission and scattering off of a dipole in a real environment demonstrate showed different multipath effects; transmission power fading squared disagreed with backscattered fading in the test environment by up to 8 dB within a measurement range of 2 m.