| 摘要 |
PURPOSE:To obtain a signal from the output of a band pass filter (BPF) with inversion given to the FM signal with no distortion of polarity, by setting the frequency of the carrier wave signal delivered from an oscillation circuit at a level double as high as the center frequency of an input signal. CONSTITUTION:The oscillation circuit 2 produces the signal of a frequency double as high as the center frequency of the FM signal 20. This signal is used as the carrier wave signal of a balanced modulation circuit 1. In such a case, the output signals of the circuit 1 include a carrier wave signal 22, a lower side wave signal 21 obtained by modulating the input signal 20 by the signal 22 and an upper side wave signal 23. The arrow heads showing the polarities of these signals are set in the opposite directions. Thus the center frequency of the signal 21 is exactly equal to that of the signal 20 since the frequency of the signal 22 is set double as high as that of the signal 20. The signal 21 is selected by a BPF 3 to obtain the signal 21 having the center frequency equal to that of the signal 20 and the inverted modulation polarity. |
