Low-Phase-Noise Wide-Frequency-Range Differential Ring-VCO with Non-Integral Subharmonic Locking in 0.18 μm CMOS

A low-phase-noise ring voltage-controlled oscillator (VCO) with subharmonic injection locking is presented. The ring VCO topology is designed to obtain not only an acceptable spurious level but also satisfactory phase-noise characteristics by enabling the use of short-pulse-width injection signals (83.3 ps). We also present the measurement results in the case of nonintegral subharmonic locking such as quarter-integral subharmonic locking and half-integral subharmonic locking. The proposed VCO has a wide frequency tuning range, namely, 0.62-1.5 GHz. This range is realized by combining pMOS resistive loads and a circuit for shifting the bias level. Thus, rail-to-rail voltages can be used for control. The 1-MHz-offset phase noise of the VCO is -1 2 6 dBc/ Hz at an output frequency of 1.35GHz (= 1 3. 5 x 1 0 0 MHz) and a spurious level of -4 8 dBc. At a spurious level of -40 dBc, the phase noise of the VCO at the same frequency (= 6. 7 5 x 2 0 0 MHz) is -126 dBc/ Hz. At a VCO output frequency of 1.35 GHz, the power consumption from a 1.8V power supply is 41mW. The VCO was fabricated by 0.18 mu m CMOS technology and occupies an area of .