A Wide Locking Range Differential Colpitts Injection

Locked Frequency Divider

Chien-Feng Lee, Sheng-Lyang Jang, Senior Member, IEEE, and M.-H. Juang, Senior Member, IEEE

Presenter: 楊 楊 楊

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Abstract• A new wideband Colpitts injection locked frequency divider (ILFD)

• Divide-by-two ILFD can provide wide locking range, supply voltage of 2.4 V, the tuning range of the free running ILFD is from 4.46 to 5.6 GHz,about 1.14 GHz, and the locking range of the ILFD is from 8.03 to 11.63 GHz, about 3.6 GHz

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Outline• Introduction• Single-ended Colpttis oscillator topology

• Differential Colpttis ILFD topology

• Measurement and discussion• Conclusion

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Introduction• For high speed operation, the FD utilizing an LC resonator is the most suitable one among various types of FDs , because the operating frequency is determined by the resonant frequency

• Tuning varactors and degrading the resonator Q-factor are often used to extend the locking range.

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Single-ended Colpttis oscillator topology

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•Schematic of a pMOS core Colpitts oscillator & Small-signal equivalent circuit with parasitic.

Differential Colpttis ILFD topology

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•Proposed differential Colpitts ILFD topology

Differential Colpttis ILFD topology

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•Relationship between ac input voltage and ac output voltages of the differential ILFD

Measurement and discussion

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•Chip photograph of the proposed differential Colpitts ILFD

Measurement and discussion

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•Measured frequency tuning characteristics of the free running oscillator,Vinj = 1.2, 1.4, 1.6 V

Vinj =1.4 V, as the tuningvoltage sweeps from 0 to 2.4 V, the oscillation frequency variesfrom 4.46 to 5.6 GHz, indicating a tuning range of 1.14 GHz

Measurement and discussion

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•Measured relationship between input sensitivity and operating frequency•supply voltage = 2.4 V. •Vtune = 0, 1.2,1.5,2.4 V •Vinj = 1.4 V

Measurement and discussion

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•Measured phase noises of the free-running, injection-reference and injection-locked of the ILFD at low band Vdd = 2.4v,Vtune = 1.2v,fo = 4.93GHz,Injection power = -4dBm

The phase noise of thefree-running ILFD at 1-MHz offset is about -110.8 dBc/Hz at the output frequency of 4.93 GHz

After the injection signalis applied to the ILFD, the phase noise of the ILFD becomes-135.4 dBc/Hz

Conclusion

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