A wide tuning range CMOS differential ring VCO using an active inductor for wireless applications

A differential ring voltage-controlled oscillator (DRVCO) is proposed in this paper as one of the critical blocks in communication systems. It consists of four stages of delay cells connected in a chain, creating a ring structure with auxiliary path interconnections. The oscillation frequency of the DRVCO can be controlled by adjusting the tuning voltage that controls the charging current. To achieve the desired performance for wireless applications, the Wu active inductor, which is a low-noise and high-quality factor active inductor, is employed in each delay cell for the first time. Using an active inductor provides a wide tuning range and also allows for proper phase noise and low power consumption. The proposed circuit is designed and simulated using standard 180-nm CMOS technology with a 1.8-V voltage source (VDD). The circuit is designed to achieve a tuning range of 2.15 GHz with a center frequency oscillation of 2.745 GHz, over the control voltage variation of 1.4 V (0 to 1.4 V). To achieve the desired performance, the circuit consumes an average power of 1.99 mW. It achieves a phase noise of - 91.2 dBc/Hz at 1 MHz offset frequency, indicating effective noise suppression. The figure of merit (FoM) for the circuit is - 156.9 dBc/Hz, representing its overall performance. The final layout of the circuit estimates an area of 0.00072 mm2. Various analyses, including Monte-Carlo simulations, PVT (process, voltage, temperature) variation analysis, and other relevant analyses, have been performed to ensure the reliable performance of the proposed circuit. A differential ring voltage-controlled oscillator (DRVCO) is proposed as a critical block in communication systems, employing Wu active inductors for the first time to achieve low noise, wide tuning range, and low power consumption. Designed in 180 nm CMOS technology, it operates at 2.745 GHz with a tuning range of 2.15 GHz, consuming 1.99 mW. The phase noise is -91.2 dBc/Hz at 1 MHz offset, with a FoM of -156.9 dBc/Hz, covering 0.00072 mm2. image