| 摘要 |
PURPOSE:To prevent a signal before conversion from affecting a converted signal as an unnecessary wave by connecting two stages of frequency converter elements each composed of a frequency converter, a band-pass filter, and an oscillator in series and making their shift frequency different from each other. CONSTITUTION:A signal of transmission frequency fTX is converted to fSH1(=fTX- fLO1) by a frequency conversion circuit 1a with a signal of shift frequency fLO1. Then, the signal is passed through a band-pass filter 1b to remove unnecessary signals of frequencies fTX and fLO1. Then, a signal of frequency fSHT is converted to fRX(=fSHT-fLO2) by a frequency conversion circuit 1d with a signal of shift frequency fLO2 and then passed through a band-pass filter 1e to remove unnecessary signals of frequencies fSHT and fLO2 Consequently, the transmission frequency fTX is converted to a reception frequency fLO2. Therefore, even when the transmission frequency fTx and reception frequency fRX are extremely close to each other and a signal with a band is frequency-converted, the conversion is performed so that the transmitted signal affects the reception signal as an unnecessary wave.
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