VOLTAGE CONTROLLED OSCILLATOR WITH INPUT SWITCH

摘要

PURPOSE:To attain circuit integration by switching an input signal of a voltage controlled oscillator VCO as a current signal and constituting an FM modulator- demodulator with one VCO without using a high performance switch. CONSTITUTION:A modulation signal inputted to an input terminal 1 is converted into a current signal at a voltage-current converter 28 and an error voltage signal outputted from a phase comparator 9 outputted from a phase comparator 9 constituting a PLL system is converted into the current signal at a voltage-current converter 29. On the other hand, the modulation signal converted into the curent signal and an error voltage signal are added and the result is inputted to a current control type oscillator 31. When the modulator-demodulator acts like an FM modulator, a switch 30 is thrown to the position M, a power input at a power terminal 32 is fed to the converter 28 so as to activate only the modulator 28 at the modulation signal side and when the modulator-demodulator acts like an FM demodulator, the switch 30 is thrown to the position D and the power input is fed to the converter 29 so as to activate the converter 29 only at the error voltage.