A 2.53 ~ 2.84 GHz Low-phase-noise Voltage-controlled Oscillator with Integrated Low Dropout Regulator in 0.18 μm CMOS Technology

The voltage-controlled oscillator (VCO) is one of the critical elements in many phase-locked systems, and its phase noise directly degrades the bit-error rate (BER). This paper designs and analyzes a VCO suitable for low BER phase locked systems. A low dropout regulator (LDO) with a high power supply rejection ratio (PSRR) provides low ripple and low-noise power supply to the VCO, without the need for external capacitors. Based on the architecture of the LDO, the phase noise of a LC-based VCO is further analyzed, which indicates a topology of LDO with a source follower structure. By enhancing the loop stability of the LDO, the noise spectrum density can be partially reduced, improving the overall phase noise of the VCO. The VCO with an LDO have been realized in a standard 0.18 μm CMOS technology. Simulation results show that the LDO quiescent current is 133.24 μA, and the temperature coefficient is 19.8 ppm/°C within a temperature range from −40°C to 125°C. The PSRR is −76.7 dB at 100 kHz offset frequency and the output noise is $352.8{\text{ nV}}/\sqrt {{\text{Hz}}} $. The LC-VCO can be linearly tuned from 2.53 to 2.84 GHz and its phase noise is −85.8 dBc/Hz at 1 MHz offset.