Patent ID: 7342500

Claim:
A transponder for use in an electronic toll collection (ETC) system, the transponder operating using radio frequency (RF) signals, the transponder comprising: a circuit substrate having a longitudinal axis and having a transverse axis perpendicular to the longitudinal axis; a ground plane formed on the circuit substrate; a planar antenna formed on the circuit substrate; an RF transceiver connected to the antenna for receiving RF signals from the ETC system and for sending RF signals to the ETC system; a controller for controlling the RF transceiver in accordance with an ETC communication protocol; and a battery for supplying DC power to the controller and the RF transceiver, wherein the antenna is disposed on one side of the transverse axis and the controller, the battery, and the RF transceiver are disposed on the other side of the transverse axis, wherein the antenna is arranged in an antenna pattern, and wherein the ground plane includes at least three connected segments and is disposed on at least three sides of the antenna pattern.