TRANSMISSION SYSTEM

PURPOSE:To execute countermeasures for impedance fluctuation of a transmission antenna by inserting a phase shift circuit between a transmitter and the transmission antenna, and obtaining a phase shift required to increase the real part of a load impedance of a final stage output element based on the direction of a transmission antenna whose impedance is fluctuated so as to use the phase shift as a phase shift of a phase shift circuit. CONSTITUTION:The output of a transmitter 11 is supplied to a phase shift circuit 12, its output is fed to an antenna matching device 13, in which impedance matched and the resulting signal is sent to a transmission antenna 14 and transmitted therefrom in air. That is, when the direction of the transmission antenna 14 whose impedance is fluctuated is known, a phase shift required to increase the real part of a load impedance of a final stage output element 11 is easily obtained by calculation based on the direction. Then the phase shift circuit 12 having the said phase shift is inserted between the transmitter 11 and the transmission antenna 14. Thus, the impedance fluctuation of the transmission antenna 14 is countermeasured.