Low-Voltage Quadrature Voltage-Controlled-Oscillator Using Twisted Transformer

Abstract

For low supply voltage operation, the voltage-controlled oscillator (VCO) with low voltage swing is subject to the injection pulling effect. This letter presents a low-voltage CMOS four-phase VCO using two differential LC VCOs coupled by two cross-coupled transformers. The proposed oscillator mitigates the injection-pulling effect by the 8-shaped transformers with two lobes. The transformers cancel the interference noise coupling and offer a drain-to-source transformer feedback to swing the source voltage to below ground level and to increase the voltage swing. The die area of the quadrature voltage-controlled oscillator (QVCO) in the TSMC 0.18 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula> m BiCMOS process is 1.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 0.963 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}$</tex-math> </inline-formula> . At the supply of 0.49 V, the oscillation frequency of the QVCO is 4.49 GHz and the figure of merit (FOM) is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 187.032 dBc/Hz.

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