Patent ID: 8274371

Claim:
A method for measuring a vehicle speed by using an RFID reader installed on a road or on a roadside, the method comprising: transmitting a continuous wave; receiving a reflected wave with respect to the continuous wave from an RFID tag attached to a vehicle which has received the continuous wave; extracting a Doppler shift value from the continuous wave and the reflected wave; and calculating the speed of the vehicle by using the Doppler shift value, wherein, in calculating the vehicle speed, the vehicle speed is calculated by the equation shown below: v 0 = c 2 ⁢ ⁢ f 0 · r r 2 - h 2 · Δ ⁢ ⁢ f wherein v 0 is a vehicle speed, ‘c’ is a signal propagation speed, f 0 is the transmission frequency of the RFID reader, ‘r’ is the distance in straight line between the RFID reader and the RFID tag, ‘h’ is the height of the RFID reader, and Δf is the Doppler shift value.