Toll collection system and its communication method

Abstract

An electronic toll collection system (ETCS) for use in a tollgate for charging a car without the need for the car to stop, in which communication failures or errors due to reflected waves from a structure or a passing car are prevented. A roadside communication antenna which communicates with a vehicle-mounted communication antenna for charging, and a car sensor which detects a car (cars) in an area wider than a designed communication area are installed at the tollgate. As an electromagnetic wave path judgment section obtains data on the profile and position of a car which has entered the tollgate, from a car data detector, it calculates electromagnetic wave paths of direct and reflected waves which connect the roadside communication antenna 21 and the vehicle-mounted antenna in each of the cars, and calculates the receiving electric field strength for each of the paths. The direction of the path which has the highest field strength among the paths to the car in the communication area is selected as radiation direction and the direction of the other paths as radiation direction; then the directional pattern which makes the radiant intensity in radiation direction the maximum and that in radiation direction null is determined to control the radiation direction of the antenna unit through a directivity controller.

Dependencies are inferred from the claim text.