| 摘要 |
PURPOSE:To eliminate instability of a local oscillator by using the 1st local oscillator to recover a carrier from a reception signal after frequency conversion, modulating the carrier, using the 2nd local oscillator to shift the frequency and using again the 1st local oscillator to apply frequency conversion. CONSTITUTION:When a frequency fluctuation of a signal frequency (frequency FL) of a local oscillator 19 is selected as DELTAFL, a reception signal (frequency FR) is frequency-converted into FR-(FL+DELTAFL) and the result is inputted to a demodulation circuit 9. The carrier in the frequency FR-(FL+DELTAFL) recovered by the demodulation circuit 9 is outputted to a modulation circuit 7 and a shift local signal (frequency FS) shifts the frequency by the frequency difference (FS=FT-FR) between the transmission signal (frequency FT) and the reception signal. The signal is subject to frequency conversion into FR-(FL+DELTAFL)+FS +(FL+DELTAFL) by a signal of the common local oscillator 16 again. The frequency of the transmission signal is FT=FR+FS and the effect of the frequency fluctuation DELTAFL of the common local signal is lost. |
