| 摘要 |
PURPOSE:To obtain a modulating circuit where the carrier signal and the input signal are not leaked to the input side and the output side respectively, by connecting four varactor diodes into a ring and energizing the output signal by a differential amplifier. CONSTITUTION:Input resistances 22 and 22' are equal to each other, and diodes D1-D4 are equal to one another, and carrier signals at both ends of a secondary winding of an energizing transformer have the same magnitude and polarities opposite to each other for the earth point. When a signal to be modulated of a positive polarity is inputted to a terminal 20, the impedance of diodes D2 and D3 and the impedance of diodes D1 and D4 are changed to a low value and a high value respectively, and potentials at apexes 25 and 25' are changed from the balanced state to directions opposite to each other by the same quantity, but the potential of the terminal 20 is not changed. Consequently, the carrier signal is not leaked to the input side. Further since potentials due to the input signal of apexes 25 and 25' are equal to each other, no output is generated at output terminals 28 and 29 of a differential amplifier 27, and the input signal is not leaked to the output side. By this constitution, an effective wide-band modulator is obtained. |
