Design Of The Wireless Signal Module In ETC System

ETC(Electronic Tolling Collection) is an intelligent charging system, it has been used in the highways> bridges and tunnels in our country. It helps the car which has been installed the OBU can pass the toll station automatically, and the transaction time is less than2s. The drivers neither stop the car nor pay the fees in the entire process.The part of RF consists of two parts, radio signal module and microstrip antenna. The BK5822is selected as the chip of RF module, it can complete the job of exchange information between the RSU and OBU. It can be waken up and repones to the RSU action in the two BST intervals. The microstrip antenna is the bridge of the OBU and RSU when they exchange information. This microstrip antenna’s structure is simply and operation band is in the5.8GHz, it’s VSWR is less than1.5and the gain can reach3.4dB. All the electrical characters are tested in this paper and conform to Kuaitong’s request.The information safety part is a important composed of the OBU, it includes two parts, they are ESAM and IC card. The ESAM and IC card’s information can be previewed in the two instructions interval and in order to reduce the transaction time. The IC card’s information can be read quickly through improve the speed of reading card. At the same time, the IC card information can be read through two methods, the are contact reading mode and non-contact reading mode. The customer do not consider if he is right when they insert the card. When the contact reading mode goes wrong, the OBU can change to non-contact reading mode automatically.Finally, the OBU can exchange the information with all the RSU that has been used in the highway toll station. The transaction time is less than270ms, it meets the Beijing’s standard requirement.