Oscillators – With frequency adjusting means – Step-frequency change
Reexamination Certificate
2011-01-11
2011-01-11
Pascal, Robert (Department: 2817)
Oscillators
With frequency adjusting means
Step-frequency change
C331S158000, C331S17700V
Reexamination Certificate
active
07868710
ABSTRACT:
The present invention relates to a digitally-controlled crystal oscillator (DCXO) circuit having control circuitry, an active core, and a pair of thermometer-coded switched-capacitor circuits (TCSCCs), each of which is coupled to the active core and to a crystal. The active core, the crystal, and the pair of TCSCCs form a DCXO, which provides an output signal having an output frequency. Each TCSCC includes multiple capacitive elements, which are selected by a respective control signal from the control circuitry to control the output frequency. The DCXO circuit may be integrated into a digital integrated circuit (IC) without need for a digital-to-analog converter (DAC), and may be used with a wide range of crystal types. By using thermometer-coding, the pair of TCSCCs provides monotonic frequency tuning behavior. Further, by utilizing different types of tuning steps, the DCXO may have a wide tuning range with high resolution.
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Farahvash Shayan
Mak Monica
Quek Chee Kwang
Johnson Ryan
Pascal Robert
RF Micro Devices, Inc.
Withrow & Terranova, P.L.L.C.
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