| 摘要 |
PURPOSE:To improve the reliability of communication by eliminating the effect of a surrounding person in the transmitter using a radio wave so as to send information at any time or periodically such as a sensor unit or a remote controller. CONSTITUTION:The transmitter is provided with a 1st antenna 8, a 2nd antenna 9 having a different resonance frequency characteristic from that of the 1st antenna 8, a transmission section 4 sending information through the 1st antenna 8 or the 2nd antenna 9, and an antenna changeover section 10 selecting the 1st antenna 8 or the 2nd antenna 9. The antenna changeover section 10 alternately selects the 1st antenna 8 or the 2nd antenna 9 at the transmission and even when the radiation efficiency of the 1st antenna 8 or the 2nd antenna 9 is deteriorated due to a change in the surrounding state in the operation, the other antenna is in use at the succeeding transmission and the reliability is improved without causing disable communication for a long time. |
