Multi-band radio terminal apparatus

A multi-band radio terminal apparatus comprising:

• transmitter/receiver for processing radio communication signals of a plurality of communication frequency bands which include a first communication frequency band and a second communication frequency band, said radio communication signals being used to communicate with a base station;
• first frequency converter for frequency-converting the frequency bands of said radio communication signals between the communication frequency bands and an intermediate frequency band;
• second frequency converter for converting said radio communication signals between base-band signals and an intermediate frequency signal;
• and
• a base-band signal processing circuit for handling a conversion between said base-band signals and audio signals,
• wherein said second frequency converter includes:
• a second transmission-sided mixer for converting a transmission signal within the base-band signal from said base-band signal processing circuit into another transmission signal within the intermediate frequency band in such a manner that the intermediate frequency signal of said first communication frequency band is different from that of said second communication frequency band, and
• a second local oscillator for supplying local oscillator signals for said first communication frequency band and said second communication frequency band to said second transmission-sided mixer,
• wherein said first frequency converter includes:
• one reception-sided mixer for converting a reception signal within the communication frequency band into another reception signal within the intermediate frequency band in such a manner that the intermediate frequency signal converted from said first communication frequency band and that converted from said second communication frequency band are the same,
• a first transmission-sided mixer for converting a transmission signal within one of said intermediate frequency bands into another transmission signal within the corresponding communication frequency band, and
• a first local oscillator for commonly supplying a local oscillator signal to both said reception-sided mixer and said first transmission-sided mixer,
• wherein said first local oscillator includes an oscillator and a switch and a frequency doubling or dividing circuit for selectively supplying a frequency of said oscillator output and a frequency obtained by doubling or frequency-dividing said oscillator output in response to the frequency band of the radio signal used in the communication between the base station and the multi-band radio terminal apparatus.