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Abstract

An adaptive frequency calibration unit employing an N-target algorithm for a high speed automatic frequency calibration for CDMA application is provided. The adaptive frequency calibration device calibrating a frequency of a voltage controlled oscillator (VCO) bank of a phase-locked loop (PLL), the adaptive frequency calibration device includes: a reference frequency divider dividing an output frequency of a temperature compensated crystal oscillator (TCXO); a feedback frequency divider dividing an output frequency of a prescaler; a frequency comparator comparing a frequency with the reference frequency divider output and the feedback frequency divider output; and a state machine providing a predetermined bit with a predetermined frequency resolution for the VCO to calibrate the frequency of the VCO bank using the frequency comparison result. Accordingly, it is possible to reduce power consumption and have a small silicon region by designing the adaptive frequency calibration device using the TCXO input and the prescaler output. In addition, a short switching time, phase noise reduction, and low power consumption can be achieved.

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First Claim