In recent years, there is a case where data such as video are transmitted together with voice sounds by communication devices such as mobile phones. To handle such purpose, it is required that a single communication device supports different communication methods. In order to achieve communication devices having multiple bands, there is a case where a plurality of high frequency devices such as duplexers and amplifiers supporting a high-frequency signal are mounted to a single mobile phone terminal. Japanese Patent Application Publication No. 2010-41141 discloses a technique in which a reception filter and a transmission filter share an antenna.
In small-size communication devices having multiple bands, it becomes difficult to ensure good isolation characteristics between a plurality of circuits. When at least two transmitting/receiving circuits perform the transmission simultaneously in a state in which isolation characteristics are insufficient, there is a case where the intermodulation distortion occurs. The intermodulation distortion may cause the degradation of the receiving sensitivity and the like.