Practical Evaluation and Analysis Of Passive UHF RFID Tags

Abstract

In this thesis, we have identified the important parameters that impact the performance of passive UHF RFID tags and developed a testing methodology to evaluate and characterize tags. We have also developed the theory to validate the empirical data and analysis. The high performance, low cost and increased storage capacity of the RFID tags has led to the economic adoption of this technology by many industries. Choosing the right tag for the right application might be quite a task with the number of commercially available tags today. It is very important to test the tags and analyze the results to gain an insight into the impact of the products being tagged and the environment, on the tags themselves. Hence, there is a potential need to understand the impact of some of the factors such as tag sensitivity, backscatter signal strength and tag communication range on the performance of tags. A systematic testing methodology to test and analyze passive UHF RFID tags are also provided. A general theory is developed to enumerate the factors affecting tag performance. Analytical evaluations are provided to validate the theory with practical results. It is shown that the sensitivity of the tag, backscatter signal strength, electric field strength at the tag, communication range, reflection efficiency of the tag, reader sensitivity and tag antenna design are all inter-related and specific relationship between them is described and analyzed in detail. Testing is also performed in an anechoic chamber to validate the test results under lab conditions. Performance of tags on water and detergent are also analyzed and validated with the test results in an anechoic chamber.