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.