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六、调频—调幅变换器调频—调幅直接变换器可直接将调频信号变换为调幅信号,其变换原理如图63所示。经过限幅的调频信号(a)送到具有(b)所示的线性频率特性的电路,输出波形如(c)所示。其振幅对应于原调制信号的瞬时频率。若调频波是用电视图象信号调制,则产生既调频又调幅的信号(d)。如果把这样的信号加到二极管上,二极管的阻抗将随输入信号振幅变
Sixth, FM - AM converter FM - AM direct converter can be converted to FM signal amplitude modulation signal, the transformation principle shown in Figure 63. The amplitude modulated FM signal (a) is fed to the circuit with the linear frequency characteristic shown in (b). The output waveform is shown in (c). Its amplitude corresponds to the instantaneous frequency of the original modulated signal. If the FM wave is modulated with a television image signal, a signal that is both FM and AM is generated (d). If such a signal is applied to the diode, the impedance of the diode will vary with the amplitude of the input signal