Phase locked loop arrangement in which VCO frequency is a fraction of reference frequency
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorRobert Eriksson
Life of this patent
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Abstract
In a phase locked loop arrangement of a frequency synthesiser, a signal outputted from a voltage controlled oscillator is locked to a reference oscillator. A phase detector is arranged so that the frequency of the reference oscillator is a multiple of the frequency of the voltage controlled oscillator, which significantly reduces the phase noise emitted by the voltage controlled oscillator.
Claims9
A phase locked loop arrangement comprising a voltage controlled oscillator (201), delivering an output signal with a frequency having a predetermined relationship to the frequency of a signal delivered by a reference oscillator (204);
- and a phase detecting means (202) receiving an output signal from said voltage controlled oscillator (201) at a first input (a) and the output signal from the reference oscillator (204) at a second input (b) and outputting an error signal at an output (c) depending on the phase difference between said inputted signals for regulating said voltage controlled oscillator (201) characterised in that the frequency of the signal outputted from the voltage controlled oscillator (201) is a fraction 1/N of the frequency of the signal outputted from the reference oscillator (204), where N is an integer that is greater than 1.
An arrangement for regulating a voltage controlled oscillator (201) in a phase locked loop (200) in a frequency synthesiser, said arrangement comprising a phase detecting means (202) delivering an output signal having a magnitude depending on the phase relationship between the signal outputted from said voltage controlled oscillator (201), inputted at a first input (a) and a signal outputted from a reference oscillator (204), inputted at a second input (b), filter means (205) for filtering the output signal from said phase detecting means (202), an amplifier (206) for amplifying the filtered output signal, a summer unit emitting to said voltage controlled oscillator a sum of the output from said amplifier (206) and a coarse tune voltage characterised in that said phase detecting means (202) is devised so that the frequency of the signal outputted from said voltage controlled oscillator (202) is a fraction of the frequency of the signal outputted from said reference oscillator (204).
Dependencies are inferred from the claim text.