A low noise, wide variable range and high linearity VCXO-IC using linearity designable on-chip varactor arrays for fundamental AT-cut crystal resonators

This paper describes a circuit architecture of integrated circuits (ICs) applied to the development of a high performance voltage controlled crystal oscillator (VCXO). By using multi-stage MOS varactor arrays and a differential PIERCE circuit, a VCXO-IC was developed which simultaneously realize low noise, wide variable range and high linearity. The designed IC has achieved +/- 115 ppm output frequency variation range with 4% linearity and -148 dBc/Hz phase noise at 10 kHz offset frequency by using 122.88 MHz fundamental AT-cut crystal resonator. The developed IC based on a 0.35 μm SiGe BiCMOS covers 60 MHz to 200 MHz and integrates all circuits except a resonator.