| 摘要 |
PURPOSE:To easily identify a false spectrum by shifting a local oscillation frequency by a specific frequency according to the mode switching of the local oscillation frequency by harmonic mixing. CONSTITUTION:An input signal of frequency fRF is mixed by a harmonic mixer 3 with the N-th order higher harmonic of the output signal (oscillation frequency fLO1) of a local oscillator 1 and only an IF component is selected by a BPF, passed through a detector 6, and added as a deflecting signal for the longitudinal axis of a CRT 8. Further, the output of a sweep command signal generator 9 is applied as a deflecting signal for the lateral axis of the CRT 8 and the output of a generator 9 is inputted to the oscillator 1 through the sweep frequency control circuit 11 at the same time to sweep the oscillation frequency. When a mode change-over switch 10 is switched, its switching information is sent to a circuit 11 and shifted by 2fIF/N so that the basic equation fRF= NfLO1+ or -fIF holds for the frequency fLO1 while the sign is inverted. Namely, when the switch is switched to a plus or minus sign mode, only a false spectrum shifts on the screen, so the false signal is easily identified.
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