TRANSMISSION CONTROL DEVICE

A transmission control device is used in an authentication system. The authentication system enables control of an authentication target based on authentication established by verification via wireless communication between the authentication target and a portable device carried by a user. The transmission control device outputs a drive current to a transmission antenna to cause the transmission antenna to transmit a signal having a predetermined frequency band. The transmission control device adjusts the output drive current. The transmission control device detects a current flowing through the transmission antenna.