CMOS balanced regenerative frequency dividers for wide-band quadrature LO generation

CMOS regenerative frequency dividers, based on a fully balanced Gilbert cell, are analyzed in this paper for quadrature local oscillator (LO) signal generation. Driven in opposite phase by double frequency signals, they provide quadrature waveforms while simultaneously driving large mixers LO input capacitances, thereby avoiding power hungry buffers typically required. Experimental results, carried out on 0.18 μm CMOS prototypes, show 68% bandwidth around 2 GHz center frequency, with a quadrature accuracy better than 1°, making them suitable for multi-standard wireless receivers. To keep the output amplitude constant while simultaneously minimizing the average power consumption, a digital calibration loop regulates each divider biasing current.