A Fast1.9GHzFractional-N/Int eger Frequency Synthesizer with aSelf-tuning Algorithm

A self-tuning, adaptive1.9GHzfractional- N/integer frequency synthesizer isproposed inthepaper. A combined tuning technique ofdigital tuning andanalog tuning is usedtodecrease thegainofVCO. The adaptive loopis introduced forautomatic adjustment oftheloopbandwidth. Two operation modes (Fractional-N/Integer) are achieved by switching on/off theoutputsignal ofYA modulator. Justa programmable counter isneededfortheswallow pulse divider. Basedon0.18gm 1.8VCMOS technology, Simulation showsthat thefrequency synthesizer hasa 100KHz loopbandwidth, a <15gs settling time, andthephasenoise islowerthan-123dBci 600KHz. KeywordsAdaptive, Divider, Frequency synthesizer, PFD, Self-tuning

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