RADIO TRANSMISSION DEVICE

PROBLEM TO BE SOLVED: To provide a radio transmission device that is capable of stabilizing an electric field strength or reducing fluctuations of the electric field strength without stabilization of a power supply voltage.SOLUTION: A radio transmission device includes a switching circuit, a power supply voltage detection circuit, an impedance circuit, and a transmission control circuit. The switching circuit includes a first switching element and a second switching element, which are respectively provided between a first end of a transmission antenna and a power supply and between the first end and the ground, and functions as a half-bridge circuit that switches a direction of energization of the transmission antenna by the power supply between a first energization direction, in which the energization is directed from the first end to a second end of the transmission antenna, and a second energization direction opposite to the first energization direction. The power supply voltage detection circuit detects a voltage of the power supply. The impedance circuit is provided between the second end of the transmission antenna and the ground and generates a predetermined impedance value. The transmission control circuit adjusts the impedance value generated by the impedance circuit based on the detected voltage of the power supply.