Phase locked loop control via inner and outer feedback control circuits
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorsMats Wilhelmsson, Rolf Mårtensson
Life of this patent
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Abstract
A phase locked loop includes at least one control circuit, where a voltage-controlled oscillator provides an output frequency which is arranged to strive to follow an input frequency. The phase locked loop also includes an outer, slow, negative feedback control circuit, having the input frequency as a setpoint, the output frequency as a process value and an outer output signal. The phase locked loop also includes an inner, fast, negative feedback control circuit, having the sum of a reference frequency from a stable oscillator and the outer output signal as a setpoint, the output frequency as the process value and an inner output signal for controlling the voltage controlled oscillator.
Claims11
A phase locked loop comprising:
- at least one control circuit, in which a voltage controlled oscillator generates an output frequency, arranged to follow an input frequency;
- an outer, slow, negative feedback control circuit, having the input frequency as setpoint, the output frequency as process value, and an outer output signal;
- and
- an inner, fast, negative feedback control circuit having the sum of a reference frequency from a stable oscillator and the outer output signal as setpoint, the output frequency as process value and an inner output signal connected to control the voltage controlled oscillator.
A method of controlling a voltage controlled oscillator which provides an output frequency striving to follow an input frequency, wherein jitter in the input frequency signal is eliminated in an outer, slow, negative feedback control circuit and wherein interferences in the voltage controlled oscillator is eliminated in an inner, fast, negative feedback control circuit.
Dependencies are inferred from the claim text.