Patent ID: 7715802

Claim:
A multi-band radio apparatus comprising: a frequency synthesizer including: a first synthesizer which outputs signal of which frequency is within one of a plurality of frequency bands; a second synthesizer which outputs a fixed frequency signal; a first mixer which mixes the signal output from the first synthesizer with the fixed frequency signal output from the second synthesizer; a first divider which divides a signal output from the first mixer by a first division ratio; a second divider which divides the fixed frequency signal output from the second synthesizer by a second division ratio; a second mixer which mixes the signal output from the first synthesizer with a signal output from the second divider; a third divider which divides a signal output from the second mixer by a third division ratio to output a signal to be used as a first local signal; a switch which outputs either a signal output from the first divider or a signal output from the third divider as a second local signal; a quadrature demodulator connected to the frequency synthesizer, which demodulates a received signal by use of said second local signal; and a quadrature modulator connected to the frequency synthesizer, which modulates a signal to be transmitted by use of said first local signal; wherein said first divider includes a first π/2 phase shifter and said third divider includes a second π/2 phase shifter, and wherein said switch outputs first and second phase signals having phases different from each other by π/2.