A Divide-by-Four Transformer-Coupled Regenerative Frequency Divider With Quadrature Outputs

A divide-by-four transformer-coupled regenerative frequency divider implemented by a TSMC 90 nm CMOS process is presented. A transformer-coupling technique and a source-injected current-mode-logic divider were proposed to increase the injection signal level and widen the operation range of the loop divider. A subharmonic mixer with bottom-switching pairs was used to reduce dc power consumption and optimize the conversion gain. The divider core consumes 6.8 mW at 1.2 V supply voltage. Without using the tuning techniques, the measured locking range is 4.7 GHz (20.9%) from 20.1 to 24.8 GHz. The phase deviation of the quadrature output is less than 0.72 ^°.