Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression
Reexamination Certificate
2005-08-30
2005-08-30
Le, Dinh T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Unwanted signal suppression
C327S552000
Reexamination Certificate
active
06937089
ABSTRACT:
A resistor capacitor (RC) tracking loop includes a parasitic insensitive integrator (211) charged by a buffer (207) with offset compensation. The integrator (211) operates to provide an accurate ramped voltage proportional to a measured RC time constant. A single comparator (213) is used for sensing the voltage ramp rate by detecting two multiplexed reference voltages (VREFLOVREFHI). A timer within controller (201) is triggered by the VREFLOcrossing at comparator (213). The timer counts the number of precision reference clock periods (FREF) that occur between the VREFLOand VREFHIcrossings and adjusts an accumulator within controller (201) to a value (M). This value (M) is directly used to adjust a resistor and/or capacitor array used in a continuous time filter whose bandwidth and corner frequency can be precisely tuned.
REFERENCES:
patent: 4137504 (1979-01-01), Simmons
patent: 5245646 (1993-09-01), Jackson et al.
patent: 5914633 (1999-06-01), Comino et al.
Lindros, Saska et al., A 3-V Continuous-Time Filter with On-Chip Tuning for IS-95, IEEE Journal of Solid-State Circuits, vol. 34, No. 8, Aug. 1999, pp. 1150-1154.
Halonen, Kari et al., A 3V gm C-Filter with On-Chip Tuning for CDMA, IEEE 1997 Custom Integrated Circuits Conference, 1997, pp. 5.6.1-5.6.4.
Simon, M. K., The True Performance of the Simplified Data-Transition Tracking Loop, TDA Progress Report 42-31, Nov. 15, 1997, pp. 1-9.
Freescale Semiconductor Inc.
Miller Johnson
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