A signal transmission system including an antenna that is used for transmitting and receiving and that is connected, via a transmission cable, to a radio base station of a radio communication system operating under a TDD scheme is disclosed. The signal transmission system includes: a detection part for detecting a synchronization pattern that is included in a DOWN LINK signal received from the radio base station via the transmission cable; and a part for determining timing for switching between transmitting and receiving for the antenna on the bases of the detection result.