Propagation characteristics of a 2.45 GHz microwave radio frequency identification system

The propagation characterisation of a 2.45 GHz microwave semi-passive radio frequency identification system in real indoor environment is presented and the effects of three system parameters: the reader orientation, tag antenna designs and propagation environment are evaluated. The unmodulated forward propagation is evaluated by reader signal strength measurements at different tag positions while the modulated backscattered propagation evaluation employs tag read rate as a function of range under horizontal or vertical reader polarisation in an uncluttered or cluttered indoor environment for different tag antenna types. Measured results are used to quantify the variations introduced by the reader polarisation, indoor propagation environment relative to free-space and tag antenna design on the tag response.