Low-power CMOS LC QVCO using zero-biased transistor coupling of MWCNT network-based VCO structure

This paper presents design, analysis and implementation of a 2.4 GHz QVCO (Quadrature Voltage Controlled Oscillator), for low-power, low-voltage applications. Cross coupled LC VCO (Inductor–Capacitor Voltage Controlled Oscillator) topology realized using integration of a micro-scaled capacitor and a MWCNT (Multi-Wall Carbon Nano-Tube) network based inductor together with the CMOS circuits is utilized together with MOS transistors as coupling elements to realize QVCO. With the passive coupling achieved from the MOS transistors, power consumption is minimized while maintaining a small chip area. The variable capacitors and the inductors are designed using ANSYS and imported through DAC components in ADS (Advanced Design software). Accurate simulation of the QVCO is performed in the software environments and the results are provided. The measurement results show that the QVCO provides quadrature signals at 2.4 GHz and achieves a phase noise of ?130 dBc/Hz 1 MHz away from the carrier frequency. The VCO produces frequency tuning from 2.1 GHz to 2.60 GHz (20.83%) with a control voltage varying from 0 to 0.3 V. It achieves a peak to peak voltage of 0.59 V with an ultra low power consumption of 3.8 mW from a 0.6 V supply voltage. The output power level of the QVCO is ?10 dBm, with an improved quality factor of 45. The phase error of the QVCO is measured as 3.1°.