Frequency synthesizer having a speed-up circuit
AssigneeNEC Corporation
InventorsNigel Tolson, Justin Clark
Life of this patent
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Abstract
It is an object of the present invention to provide a frequency synthesiser with a lock speed-up arrangement in a simple and effective form. In accordance with the invention there is provided a frequency synthesiser including a voltage controlled oscillator, a phase detector which receives a base frequency signal and a feedback signal derived from the output of the voltage controlled oscillator and a filter circuit connecting the output of phase detector to a frequency control voltage input of the voltage controlled oscillator, the filter circuit having a reference voltage connection, and a speed-up circuit for applying a voltage signal to the reference voltage connection when a frequency change is demanded.
Claims8
A frequency synthesizer comprising:
- a voltage controlled oscillator having an oscillator output;
- a phase detector which receives a base frequency signal and a feedback signal derived from said oscillator output, and which has a phase detector output;
- a filter circuit connecting said phase detector output to a frequency control voltage input of said voltage controlled oscillator, wherein said filter circuit has a reference voltage connection;
- and
- a speed-up circuit comprising an output connection capacitively coupled to said reference voltage connection of said filter circuit, and a first resistor coupled between said reference voltage connection of said filter circuit and a reference voltage source.
Dependencies are inferred from the claim text.