| 摘要 |
A communication apparatus is provided which employs two oscillators to generate a transmission signal and a reception signal, and prevents harmful spurious components from being produced. As shown in FIGS. 9A and 9B, the oscillation frequency fVCO2 of a VCO 2 is given by fVCO2=Nx(2xfDD), where fDD is the difference between the transmit frequency fT and receive frequency fR. A 3/(2xN) frequency multiplier outputs a signal with a frequency 3xfDD, and a divide-by-N circuit (2/(2xN) frequency multiplier) outputs a signal with a frequency 2xfDD. Thus the transmit intermediate frequency fTIF is given by fTIF=3xfDD, and the receive intermediate frequency fRIF is given by fRIF=2xfDD. The oscillation frequency fVCO1 of a VCO 1 is fCH. The transmit frequency fT is given by fT=fCH+fTIF=fCH+3xfDD. The circuit can prevent a transmission spurious problem to its own reception band.
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