Multi-band radio terminal apparatus

Abstract

In a multi-band radio terminal apparatus, when communication frequency bands are switched, a reception intermediate frequency is selected to be equal to each other in respective communication frequency bands. As a result, the circuit arrangements of this multi-band radio terminal apparatus succeeding to the intermediate frequency signal circuit stage are commonly used in the respective communication frequency bands. While a local oscillator signal is produced by a voltage-controlled oscillator, a phase-locked loop, and a doubler, in a case where communication is established within a plurality of communication frequency bands, the transmission/reception frequency intervals are different from each other. A mixer for a reception system and a mixer for a transmission system are commonly used so as to convert the frequency of the local oscillator signal into a frequency existing between the communication frequency and the intermediate frequency.

1 . 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 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 same,    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,    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,    a first local oscillator for commonly supplying a local oscillator signal to both said reception-sided mixer and said second transmission-sided mixer, 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 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.