A fully integrated CMOS VCXO-IC with low phase noise, wide tuning range and high tuning linearity

This paper describes a low phase noise, wide tuning range and high tuning linearity CMOS voltage controlled crystal oscillator IC (VCXO-IC) with LVCMOS and LVPECL output. A differential coupled frequency doubling Colpitts oscillator is adopted to obtain low noise 2x frequency output. Wide tuning range and high linearity are simultaneously achieved by using MOS varactor arrays. The measurement results show that the designed VCXO- IC achieves 134 dBc/Hz phase noise at 1 kHz offset frequency and +/- 135 ppm output frequency tuning range within 3% linearity by using 40 MHz fundamental AT- ut crystal. The VCXO-IC is fabricated in the chartered 0.35 mu m standard CMOS process and occupies a total silicon area of 2.4 mm(2).