hi this is vebi , i want to design rfid tag antenna with moisture sensor can any body suggest me how to design
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This wiki link is packed full of good information. From it, I checked one of their references on the subject for humidity and did a "Google Scholar" search, and found this paper if you have access to IEEE material.Welcome to the PF.
Have a read through this introductory article, and let us know if you have specific questions in the article.
The paper presents a concept where pairs of ordinary RFID tags are exploited for use as remotely read moisture sensors. The pair of tags is incorporated into one label where one of the tags is embedded in a moisture absorbent material and the other is left open. In a humid environment the moisture concentration is higher in the absorbent material than the surrounding environment which causes degradation to the embedded tag's antenna in terms of dielectric losses and change of input impedance. The level of relative humidity or the amount of water in the absorbent material is determined for a passive RFID system by comparing the difference in RFID reader output power required to power up respectively the open and embedded tag. It is similarly shown how the backscattered signal strength of a semi-active RFID system is proportional to the relative humidity and amount of water in the absorbent material. Typical applications include moisture detection in buildings, especially from leaking water pipe connections hidden beyond walls. Presented solution has a cost comparable to ordinary RFID tags, and the passive system also has infinite life time since no internal power supply is needed. The concept is characterized for two commercial RFID systems, one passive operating at 868 MHz and one semi-active operating at 2.45 GHz.
thank you for replying, but i read that ieee paper already but i am searching for design specifications of tag antenna i mean the length should be like this or imepedence should be like this my chip impedence is 25-110j i have to design my tag antenna must be 25+110j to transfer total power but i need at what specification can i match chip impedence and for designing antenna with aluminum wire how much length i need or antenna shape either diople or somthing like that........
i am doing masters,i studied this book rf in uhf rfid book by denial.dobkin but i am doing project on differential rfid sensor design and characteristics but this is my starting of project still my supervisor dint provide any software for simulation may be i will get this week. then i will post all things still now he said that design two antennas one with senor and another without sensor on same tag so i cheked the impedence of given chip by using smith chart analysis then i posted any suggestions on design of antenna.
Both temperature and moisture sensors in diffrent tags not in the same tag. for temperature i have to design one rfid tag antenna and moisture measurement i have to design another rfid tag antenna.