Title :
AM-FM conversion by the active devices in MOS LC-VCOs and its effect on the optimal amplitude
Author :
Soltanian, Babak ; Kinget, Peter
Author_Institution :
Dept. of Electr. Eng., Columbia Univ., New York, NY
Abstract :
Large oscillation amplitudes in differential MOS LC-VCOs change the operation region of the MOS negative-resistance devices and thus modulate their parasitic capacitances. As a result, the effective tank capacitance and the oscillation frequency change with respect to the oscillation amplitude for a fixed tuning voltage. The resulting frequency-versus-amplitude curve has a maximum for differential amplitude approximately equal to the threshold voltage of the MOS devices which corresponds to the optimum amplitude that minimizes AM-to-FM conversion. The presented analysis is confirmed with simulation and measurement results for a 2 GHz differential NMOS VCO fabricated in a 0.25 mum BiCMOS process. The optimum amplitude for lowest AM-to-FM conversion also yields the lowest phase noise for this oscillator
Keywords :
BiCMOS integrated circuits; UHF oscillators; amplitude modulation; frequency convertors; frequency modulation; integrated circuit noise; phase noise; voltage-controlled oscillators; 0.25 micron; 2 GHz; AM-FM conversion; BiCMOS process; MOS negative-resistance devices; active devices; differential MOS LC-VCO; effective tank capacitance; fixed tuning voltage; oscillation amplitudes; oscillation frequency; parasitic capacitances; phase noise; voltage controlled oscillator; Amplitude modulation; Analytical models; BiCMOS integrated circuits; Frequency conversion; MOS devices; Parasitic capacitance; Phase noise; Threshold voltage; Tuning; Voltage-controlled oscillators;
Conference_Titel :
Radio Frequency Integrated Circuits (RFIC) Symposium, 2006 IEEE
Conference_Location :
San Francisco, CA
Print_ISBN :
0-7803-9572-7
DOI :
10.1109/RFIC.2006.1651102
