24 GHz phase-tunable resistively-coupled VCO

In this paper, a 24 GHz phase-tunable resistively-coupled VCO is presented. The proposed VCO consists of two identical VCOs which are coupled through resistors. By differentiating free-running frequencies of two VCOs by controlling variable capacitances of their respective resonators, continuous phase difference between the VCOs upto 90° could be established. This shows the phase noise of -95.3 dBc/Hz and tuning range of 11.8 % with 18 mW DC power consumption. This is fabricated using 0.13 um CMOS process with its chip area of 1×1 mm². The phase difference tuning capability of coupled oscillators can be used in some applications.