A mobile communication system has a multi-band antenna capable of receiving and processing signals of GPS, CDMA, and PCS bands. In the system, a GPS processing section receives a signal of a first frequency band, so as to generate global positioning information. A communication signal processing section receives signals of a second frequency band lower than the first frequency band and a third frequency band higher than the first frequency band, demodulates the received signals , while modulating signals to be transmitted of the second frequency band and the third frequency band and outputting the modulated signals. The multi-band antenna has a dual-pitch helical antenna which includes first and second helical coil portions having different pitches, so that the first and second helical coil portions have different impedances for the signals of the first to third frequency bands. A frequency band separator section connected between the multi-band antenna and the GPS processing section and communication processing section supplies the signal of the first frequency band to the GPS processing section while supplying the signals of the second and third frequency bands to the communication processing section.