Phase control for oscillator

Abstract

A phase locked loop, comprising: a controllable oscillator (50,20) requiring a control signal having a given bias voltage for generating a clock signal; an integrator (16) for developing the control signal; a source of an external synchronizing signal (HOR. SYNC.); first and second voltage sources (+15 VDC, GND) defining a voltage potential related to the given bias voltage; a first switch (A) coupled to the first and second voltage sources and responsive to the clock signal (CTRL A) for developing a regenerated clock signal having a peak to peak voltage determined by the voltage potential; and, a second switch (B) responsive to the external synchronizing signal (CTRLB) for periodically sampling portions of the regenerated clock signal and coupling the sampled portions to the to the integrator, the sampled portions charging and discharging the integrator to generate the control signal with a large enough magnitude to provide the given bias voltage, said first and second switches (A,B) forming a phase detector.

Description

technical field [0001] The present invention relates to the field of synchronous oscillators and in particular to phase locked loops with a phase detector for generating an upwardly scaled control voltage. Background technique [0002] Many voltage-controlled oscillators (VCOs), especially crystal oscillators (VCXOs), are controlled by varactor diodes. A varactor can be described as a reverse biased diode that exhibits a capacitance that depends on the magnitude of the reverse bias voltage applied across it. The resonant frequency of the oscillator can be controlled by a bias voltage. Insufficient bias voltage to achieve a given operating frequency or frequency range can cause serious problems. This situation is shown in Figure 6, which shows a phase-locked loop. A phase detector 56 has the outputs of the horizontal oscillator and the horizontal synchronizing section as respective inputs. Current flows between the output of the phase detector and an integrator 58, often ...

AI Technical Summary

Problems solved by technology

The need for a separate scaler increases the complexity and cost of the PLL, and additionally requires redesign of each PLL

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