Loop filter with gear shift for improved fractional-N PLL...

Details Loop filter with gear shift for improved fractional-N PLL... Loop filter with gear shift for improved fractional-N PLL...

2004-12-17

2008-07-08

Phu, Sanh D. (Department: 2618)

Telecommunications

Receiver or analog modulated signal frequency converter

Local control of receiver operation

C455S161200, C455S165100, C455S139000, C455S180300, C331S015000, C331S017000

Reexamination Certificate

active

07398071

ABSTRACT:
An integrated circuit radio frequency (RF) transmitter includes a phase locked loop having a multi-mode loop filter that is operable to provide wide band response with a fast settle time in a startup mode of operation and a relatively more narrow response with a longer settle time but with improved filtering in a steady state mode of operation according to one embodiment of the invention. The multi-mode loop filter includes, in one embodiment, selectable resistance circuitry for selecting between a plurality of resistance values based upon a two-state multi-mode control signal to provide the selected resistance values and selectable capacitance circuitry for selecting between a plurality of capacitance values based upon the two-state multi-mode control signal and for operatively coupling selected capacitors to selected resistors to provide the selected capacitance values. As a further aspect of the embodiment of the present invention, the multi-mode loop filter includes buffers for charging non-selected capacitors while not operationally coupled to the multi-mode loop filter to avoid additional settle time for the circuitry.

REFERENCES:
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patent: 6546044 (2003-04-01), Dent
patent: 6831523 (2004-12-01), Pastorello et al.

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