| 摘要 |
PURPOSE:To obtain an AM-FM modulated wave from the output of a VCO by modulating the oscillation amplitude of a loop by a modulating signal. CONSTITUTION:At the output of a loop filter 3, a DC voltage proportional to the phase difference between an injection oscillator 1 and a VCO4 is developed, so only the DC voltage component is extracted through a filter 5 and applied as biases to diodes 91 and 92 through adders 81 and 82. Consequently, a sine wave inputted to the VCO4 is limited in such a way that upper and lower parts are symmetrical. A modulating signal 6 is supplied to said adders 81 and 82 through amplifiers 71 and 72 and added to the output of the LPF5 to obtain biases to the diodes 91 and 92. In this constitution, limit levels of the diodes 91 and 92 are controlled by the modulating signal voltage and the input to the VCO4 is processed by imposing amplitude modulation AM on the oscillation of the loop. Thus, the input to the VCO4 is AM-modulated, so an AM-FM modulated wave appears at its output 10. |
