Loop filter for a frequency synthesizer
AssigneeNokia Mobile Phones Ltd.
InventorEsko Satomaki
Life of this patent
Estimating the term…
Abstract
A loop filter for the feedback branch of a frequency synthesizer includes a low pass filter and an integrator having a first zero point in the frequency response, in order to achieve stability. The frequency response curve of the loop filter contains a second zero point above the characteristic frequency of the loop to increase the phase margin. The loop filter also has a pole at a frequency higher than the first zero point, whereby the influence of the second zero point on the amplitude response is essentially eliminated.
Claims5
Loop filter situated in the feedback branch of the frequency synthesizer, said loop filter comprising an integrator with a zero point int eh frequency response in order to achieve stability, and a low pass filter, characterized in that to the frequency response curve of the loop filter there has been added
- a second zero point above the characteristic frequency of the loop, thus increasing the phase margin, and
- a pole at a frequency higher than the first-mentioned zero point, whereby the influence of the added second zero point on the amplitude response is essentially eliminated.
Dependencies are inferred from the claim text.