Abstract: A front-end circuit includes an antenna terminal, front-end terminals (Pfe1, Pfe2), a circulator, and frequency-variable filters. The circulator sends transmission signals of communication bands of a frequency division duplex system and a time division duplex system from the front-end terminal (Pfe1) to the antenna terminal. The circulator sends a reception signal from the antenna terminal to the front-end terminal (Pfe2). The frequency-variable filter is connected between the front-end terminal (Pfe1) and the circulator, passes transmission signals of the frequency division duplex system and the time division duplex system, and attenuates signals other than the above transmission signals. The frequency-variable filter is connected between the circulator and the front-end terminal (Pfe2), passes a reception signal of the frequency division duplex system, and attenuates signals other than the above reception signal.

Abstract: A front-end circuit includes an antenna terminal, front-end terminals (Pfe1, Pfe2), a circulator, and frequency-variable filters. The circulator sends transmission signals of communication bands of a frequency division duplex system and a time division duplex system from the front-end terminal (Pfe1) to the antenna terminal. The circulator sends a reception signal from the antenna terminal to the front-end terminal (Pfe2). The frequency-variable filter is connected between the front-end terminal (Pfe1) and the circulator, passes transmission signals of the frequency division duplex system and the time division duplex system, and attenuates signals other than the above transmission signals. The frequency-variable filter is connected between the circulator and the front-end terminal (Pfe2), passes a reception signal of the frequency division duplex system, and attenuates signals other than the above reception signal.

Abstract: In a semi-coaxial cavity resonator in which an inner conductor is fixed to an outer conductor with a screw, an inner cavity where the inner conductor does not engage with the screw is provided to extend from a bearing surface of the inner conductor to a region of an internal thread hole formed inside the inner conductor which does engage with the screw, thereby providing a region where the screw is deformable. Accordingly, deviation in perpendicularity of the screw relative to the bearing surface, deviation in perpendicularity of the internal thread hole of the inner conductor, and the like, may be accommodated by the deformation of the screw, and the bearing surface of the inner conductor is brought into contact with a bottom surface of an outer conductor evenly and reliably, thereby suppressing intermodulation distortion from occurring.

Abstract: In a semi-coaxial cavity resonator in which an inner conductor is fixed to an outer conductor with a screw, an inner cavity where the inner conductor does not engage with the screw is provided to extend from a bearing surface of the inner conductor to a region of an internal thread hole formed inside the inner conductor which does engage with the screw, thereby providing a region where the screw is deformable. Accordingly, deviation in perpendicularity of the screw relative to the bearing surface, deviation in perpendicularity of the internal thread hole of the inner conductor, and the like, may be accommodated by the deformation of the screw, and the bearing surface of the inner conductor is brought into contact with a bottom surface of an outer conductor evenly and reliably, thereby suppressing intermodulation distortion from occurring.