A 2.45 GHz RFID System for Electronic Toll Collection
B. Tech. Project
Praneeth Tammiraju 04007032
1. Introduction 2. RFID in ETC a. RFID – a review b. The actual role c. Technicalities in brief 3. The Reader Design a. The transceiver design b. Circuit description c. The PCB of the reader d. Programmability of the reader 4. The Transponder Design a. Broad Overview b. Redesigning rectifier 5. Communication Protocol 6. Conclusion 7. References 2 3 3 3 4 6 6 7 9 9 11 11 11 13 14 15
Tolling on roads and highways today is done mostly on a manual basis i.e. vehicles stop at a check gate and the toll is collected manually by authorized personnel. This poses a lot of problems such as traffic congestion, inefficient use of human resources, vast amount fuel and time wastage apart from, of course seeming very primitive in today’s world of automation. There are already methods in practice that attempt to automate the whole process. Systems that use installed video cameras that scan the license plates of the vehicles to identify the vehicles and initiate the tolling process are a viable solution but with their own problems in execution – the most important being the logistical diversity in the nature of vehicles which makes a universal protocol impossible. In this context, RFID puts forward a very efficient solution to the automation problem in the case of electronic toll collection. This document discusses the use of RFID in Electronic Toll Collection. It discusses the requirements of such an application and how RFID systems should be customized to meet these needs. It describes a circuit for the transceiver at frequency 2.45 GHz and its interfacing with a computer. A brief note about the specifications of the antenna used and an introduction to the transponder design are made.
RFID in ETC
RFID – a review
The basic working of an RFID is well described in Fig. 1 below.
Fig. 1: Schematic of an RFID system 
The actual role
Given this background of RFID and its working, its application in toll collection becomes obvious. The use of RFID in tolling can be explained simply with the analogy of pre-paid mobile phone users. Every mobile phone user pays a certain amount of credit amount and gets a calling card. Now, whenever he makes a call, the stipulated amount of call charges is deducted from his credit amount. This is the basic idea of electronic toll collection. Vehicle owners pay some credit amount and get an RFID transponder or tag on which information as to the vehicle identity and credit amount is coded. This tag is stuck on the vehicle itself. Whenever the vehicle crosses a highway toll gate where RFID transceivers or readers are installed, the vehicle is identified with the help of communication between the readers and the tag and the information is passed onto the centralized network and database from where the toll amount is deducted. Ideally, this is a perfect remedy for manual toll collection where complete automation is possible. Still for purpose of policing and legal issues, video cameras can be installed for video confirmation of the vehicle and some personnel can be appointed to supervise the processes. 3
Fig. 2: Electronic Toll Collection  An improvement in this system could be if this installation is made in two stages i.e. if two gateways are installed some distance apart so that when a vehicle passes through the first gateway the tolling process is initiated and the toll deduction is confirmed at the second gateway whereby a check gate can be opened thereby enabling law enforcement and automation.
Technicalities in brief
The technical issues involved in building the above described system are : The RFID reader at the gateway The RFID tag on the vehicle Proper communication between the above The network connectivity
The RFID reader The RFID reader must be equipped enough to perform functions such as initiating...
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