Design of Wideband Low Phase Noise Class-C QVCO With Low Amplitude and Phase Errors

Abstract

This letter presents a wideband, low phase noise, quadrature voltage controlled oscillator (QVCO) implemented in 0.18 $\mu{\rm m}$ CMOS. In order to improve the phase noise while provide high efficient oscillation, the cooperation of a Class-C operation with a bulk-coupled structure are adopted into a PMOS-only VCO. With high fundamental current amplitude generated and the frequency offset of the QVCO alleviated, the phase noise is improved significantly. The measurement shows 2–8 dB phase noise improvement with a minimum value of $-124 ~{\rm dBc}/{\rm Hz}$ at 1 MHz offset. Wide tuning range of 22.6% is realized by four-bit switched-capacitor-array ranging from 5.6 to 6.9 GHz. The quadrature accuracy of the proposed QVCO is evaluated by the measured results of an image-rejection mixer (IR-mixer), which exhibits a peak image rejection ratio (IRR) of 40 dBc, indicating low amplitude and phase errors simultaneously.