FIG. 1 shows an example of a schematic configuration of a radio base station apparatus 1 for use in a mobile communication system A.
As shown in FIG. 1, the radio base station apparatus 1 includes a modulation/demodulation function section MDE-A for the mobile communication system A, an amplification function AMP (amplifier section PA), an outdoor reception amplifier OA-RA and an antenna ANT.
Note that, the modulation/demodulation function section MDE-A for the mobile communication system A and the amplification function AMP are located indoors in a station building; the antenna ANT is located outdoors in a high place; and the outdoor reception amplifier OA-RA is located in the vicinity immediately below the outdoor antenna ANT.
In recent years, it has been demanded to provide, by using a single radio base station apparatus as described above, a service not only in the mobile communication system A, but also in a mobile communication system B having a frequency band close to that of the mobile communication system A.
In order to provide a service in the mobile communication system B as well as in the mobile communication system A as described above, it is conceived, as shown in FIG. 2, that a modulation/demodulation function section MDE-B for the mobile communication system Banda shared amplification function (hereinafter, shared AMP) shared by the mobile communication systems A and B are added to the configuration of the radio base station apparatus 1 shown in FIG. 1.
Note that, the shared AMP, as well as the modulation/demodulation function section MDE-A for the mobile communication system A and the modulation/demodulation function section MDE-B for the mobile communication system B, are located indoors in the station building.    Patent Document 1: JP-A-2003-115793