Importance

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Abstract

A hybrid frequency synthesizer includes an analog phase lock loop (PLL), a PLL, and a control circuit to control an output oscillator. The control circuit combines a control signal from the analog PLL with a control signal from the digital PLL to form a composite control signal. The composite control signal is conditioned depending on a state of lock of the analog PLL and/or the digital PLL. The composite signal controls the phase and frequency of the output oscillator. The analog control signal and the digital PLL control signal may be given a percentage of over the hybrid frequency synthesizer depending on the state of lock of the PLL and/or the digital PLL. The composite control signal provides both rapid, accurate, and robust acquisition by the digital PLL, and a smooth transition thereafter to low noise phase lock by the analog PLL.

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First Claim