| 摘要 |
An improved control voltage generator for use with a voltage-controlled oscillator (VCO), so as to enable VCO operation at low supply voltages of lees than three volts. The control voltage generator includes a phase comparator, a charge pump, a switched voltage multiplier, and a control voltage filter. The output voltage of the phase detector is coupled to a sampling terminal of the charge pump, a power supply terminal of the charge pump is coupled to an output terminal of the switched voltage multiplier, and a voltage input terminal of the switched voltage multiplier is coupled to a first, reference signal. The charge pump, powered from the power supply terminal, generates a waveform including a plurality of pulses. Each of the plurality of pulses has a time duration substantially proportional to the voltage present at the sampling terminal. These pulses may be used as a VCO control voltage or, alternatively, a control voltage filter, coupled to the charge pump, may be used to transform the pulses into a VCO control voltage having desired characteristics.
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