Research And Implementation Of Novel RFID Tag Antenna For Applications Near Metallic Objects

Radio Frequency Identification (RFID) is an automatic data exchange technology for identification by using electromagnetic field contactless communication. RFID is developed quite fast in recent years, however, it is challenging by metallic objects in wide fields. RFID of UHF and microwave band are more sensitive to conductive material than low frequency, resulting in the passive tag out of work when attached on metallic objects such as container and steel goods shelf .etc.In order to meet the urgent need for metal products identification, work has been done by researching on the performance of tag antenna in metal environment. A novel folded quasi-Yagi tag antenna has been proposed for applications near metallic objects.When a tag antenna attached on the metal, the radiation efficiency diminishes for the reduction of radiation resistance and other antenna parameters will also be seriously changed due to the effects of conductive material. The folded dipole structure has high radiation resistance in free space, it can keep a suitable value when getting close to metal with other antenna parameters less changed. This character of folded dipole combines with staggered array and the material with high permittivity can be used to fit the low profile requirement of tag.A novel 2.4GHz metal-mount tag Antenna has been designed and tested successfully. Low profile of 3mm is achieved. The antenna has lower profile with high Gain of 5dBi comparing to normal Yagi antenna. It can work reliably when mounting on different metallic surfaces with impedance stability ( VSWR <2) within the bandwidth required and the Gain is higher than 5dBi.The novel tag antenna with passive IC chip inside meets the specification of the metallic objects identification by using the SLS-61100 RFID system which is produced by Hitachi. It has a reading range of 10.4cm larger than 5.5cm of the passive tags provided by Hitachi. The reading range can be larger due to higher Gain when the antenna attached on the metallic objects. Practice shows that the novel tag antenna is an effective way for RFID applications near metallic objects.