| 摘要 |
PROBLEM TO BE SOLVED: To suppress a harmful effect to a use frequency band of a second communication system when transmission power is large and to improve power efficiency by reducing passing loss in a bandlimiting filter when the transmission power is small. SOLUTION: An output side of a transmitting part 33 for a first communication system is provided with a cutoff frequency variable filter 34. When the transmission power in the first radio communication system is large, by making a cutoff frequency of the cutoff frequency variable filter 34 close to a transmission frequency, the level of a transmission signal that interferes with the use frequency band of the second radio communication system to be a noise component is suppressed to the extent of not having an influence on receiving performance of a receiving part 42 for the second communication system. This secures a receiving function of the other communication system even during transmission. When the transmission power is small, by separating the cutoff frequency of the cutoff frequency variable filter 34 from the transmission frequency, the passing loss in the cutoff frequency variable filter 34 is reduced and useless power consumption is reduced. COPYRIGHT: (C)2004,JPO&NCIPI
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