A differential coupled frequency doubling voltage-controlled crystal oscillator in a 0.35 μm CMOS process

This paper presents a high-performance differential coupled frequency doubling voltage-controlled crystal oscillator (VCXO). Frequency doubling and low phase noise are realized through a novel gm-boosted differential Colpitts oscillator. Distributed varactor arrays are used to obtain wide frequency tuning range and high tuning linearity simultaneously. The proposed VCXO is fabricated in a 0.35 μm 2P3M standard complementary metal-oxide semiconductor process at a supply voltage of 3.3 V, and the power dissipation is 7 mW. Measurement results show that the designed VCXO achieves ±135 ppm output frequency variation range with 5 % linearity and −133 dBc/Hz phase noise at 1 kHz frequency offset by using a 40 MHz fundamental AT-cut crystal resonator.