CMOS 1.98-5.58 GHz transformer-based VCO with current-reused topology

A fully integrated ultra-wideband voltage-controlled-oscillator (VCO) constructed in a current-reused configuration is proposed. An ultra-wide tuning range is achieved thanks to the adopted transformer-based resonator, which makes use of the transformer and the proper arrangement of capacitors, while the current-reused topology can dramatically save DC power consumption. The transformer layout has been properly designed to attain a die area comparable to a single inductor VCO. Fabricated in a 0.18 μm CMOS technology, the VCO provides a frequency tuning range as high as 95% from 1.98 to 5.58 GHz and exhibits a phase noise of -122.8 to -108.6 dBc/Hz at 1 MHz offset from the carrier across the entire frequency range. The VCO core consumes 5.6-7.2 mA of current from a 1.8 V supply and occupies approximately an area of 0.8 mm². Despite the ultra-wide tuning range, the proposed VCO has the outstanding figure-of-merit (FOM_T) of -192 to -199 dBc/Hz.