| 摘要 |
The invention relates to a frequency-modulating device operating as astable circuit. A current source 1 controlled by the output signal G from a comparator 2 and modulated by a modulating signal Vm, delivers a current I0 + Vm/R (I0: direct current, R: constant) whose direction varies, under the control of the comparator, so as to charge or discharge a capacitor C. The comparator has a reference voltage provided by a circuit 3 under the control of its output signal G, which takes two different values: V1 and V2-K.Vm. By choosing the modulation coefficient K equal to 2 pi /RC ( pi : total delay time of the comparator and of the current source), the "output frequency/input amplitude" characteristic of the device is linearised. Application to frequency-modulated transmitters. <IMAGE>
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