On the design considerations and limitations of passive RFID tag antennas

Passive radio frequency identification (RFID) system is an emerging solution to identify and track various objects now-a-days [1]. A basic RFID system consists of a reader, tag and a host computer. And the tag comprises of an antenna and a microchip called application specific integrated circuit (ASIC), both with complex impedances. The basic communication of passive RFID is based on backscattering. In this method, reader antenna sends a radio signal into the air to activate the tag and commands data from tag which then responds by backscattering its identification data back to the reader. As there is no internal source of energy in the tag’s microchip in passive RFID tags, they will get all the energy for functioning from the electromagnetic radiation emitted by the reader as shown in Figure 1. Proper tag antenna design comes of a paramount importance depending on the several significant parameters such as impedance matching between the antenna and tag chip, materials and locations of objects, cost, radiation pattern, antenna polarization etc. Several papers have dealt with the performance criteria in passive RFID tags as impedance matching concepts in [2], a practical antenna design considerations have been reviewed in [3], design of RFID tag antenna for metallic surfaces is discussed in [4] and performance of quasi-isotropic radiation pattern for broadband RFID tag antenna is also narrated in [5]. Since, most of the papers are concentrating on separate design issues for passive RFID tag antenna at different frequencies, there is a significant need to review the design considerations of passive tag antenna as a whole to provide a detailed insight to the design perspectives. And hence, this paper deals with the design considerations for the passive RFID tag antenna with a view to pin-pointing some limitations of the same to establish a bridge between the considerations and limitations in RFID research.