A Low Phase Noise, High Phase Accuracy Quadrature LC-VCO With Dual-Tail Current Biasing to Insert Reconfigurable Phase Delay

This brief presents a novel low phase noise and low phase error quadrature LC-tank voltage controlled oscillator (LC-VCO), which utilizes the dual-tail current biasing technique to insert a phase shift in the coupling path. The dual-tail current bias each oscillation branch, and are gated by quadrature signals. One tail current, named coupling-tail current, is gated by the quadrature phase signal to force the voltage controlled oscillator to keep quadrature state. The other tail current, named self-tail current, is gated by the anti-phase signal to introduce a phase shift in total bias current. The phase shift is reconfigurable by adjusting the DC biasing voltage of tail current transistors to resist the performance deterioration caused by process variations. Compared with the conventional quadrature LC-VCO, the proposed quadrature LC-VCO enhances the phase accuracy and optimize the phase noise simultaneously. Additionally, it has the distinct advantage of reconfigurability. The core was fabricated in 180 nm 1P6M CMOS process, and occupied a die area of 0.96 mm² totally. The measurement results show it achieves a phase noise of −129.3 dBc/Hz @1 MHz offset and a phase error of 0.09° while <inline-formula> <tex-math notation="LaTeX">$k=0.4$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$V_{\mathrm {b0}}= 0.8$ </tex-math></inline-formula> V, and <inline-formula> <tex-math notation="LaTeX">$V_{\mathrm {b1}}= 0.6$ </tex-math></inline-formula> V @2.5 GHz. The total power consumption is 20.6 mW with a supply voltage of 1.8 V.