Time-based frequency band selection method for phase-locked loops |
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Authors: | Lin T-H Lai Y-J |
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Affiliation: | Graduate Inst. of Electron. Eng., Nat. Taiwan Univ. Taipei, Taiwan; |
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Abstract: | High-performance phase-locked loops (PLLs) often require voltage-controlled oscillators (VCOs) employing both discrete and continuous tuning mechanisms to satisfy a wide frequency range and a low VCO tuning gain simultaneously. An auxiliary circuit is required to facilitate the selection among a group of discrete bands. An agile technique to search for an optimum VCO frequency band is proposed. The search is based on measuring the period difference between a reference and the VCO-divided signals. The VCO band selection circuit is implemented with a 10 GHz PLL in a 0.18 /spl mu/m CMOS process and consumes only an extra 3 mA. The band selection time is less than 4 /spl mu/s. |
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