A 0.9-V Double-Balanced Quadrature-Input Quadrature-Output Frequency Divider

A double-balanced quadrature-input quadrature-output (QIQO) divider is proposed. By making use of the quadrature phase outputs from a quadrature VCO (QVCO) or the other quadrature signal generator, the proposed QIQO divider provides a mechanism to achieve an output IQ phase sequence that is inherently tracked with the input IQ phase sequence. Moreover, compared with conventional dividers, the QIQO divider not only provides smaller and better-matched input loading to the QVCO but also improved quadrature phase accuracy for both QVCO and the divider itself. Fabricated in a 0.18-mum CMOS process and operated at 0.9 V, the QIQO divider measures an image rejection of -62 dBc while consuming 7.2 mW