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

This letter presents a wideband, low phase noise, quadrature voltage controlled oscillator (QVCO) implemented in 0.18 μm 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 dBc/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.