Millimeter-wave source with quadrature CMOS VCOs

Abstract

Recently, the market of board-band mobile communication has been expanded in the world. The communication solution above 10 ~ 40 GHz is needed with low cost. This thesis proposes and implements frequency sources covering 10 ~ 40 GHz with 0.18 um analog standard CMOS process. The proposed frequency source structure is consisted of the quadrature VCO with low phase noise and the balanced frequency multiplier. Thus, two topologies of low phase noise quadrature VCOs are proposed which are suitable to the frequency multiplier. One is the balanced topology with current switching. This topology has reliable start-up, reduction of active noises and quadrature coupling, which are proved theoretically and experimentally. In addition, the coupled resonator with the transformer is used to improve the quality factor. The measured phase noise values of the single VCO and the quadrature VCO are -114.83 dBc/Hz and -116.67 dBc/Hz at the offset frequencies of 1 MHz at 10.21 GHz and 10.81 GHz, respectively. The VCO cores consume about 8.8 mA from a 1.8 V supply. The FOM’s of 183 dB and 185 dB are achieved in the single VCO and the quadrature VCO, respectively. The phase noise performance and FOM of both VCOs are comparable to ever reported VCOs. The quadrature VCO is superior to the single one in phase noise, oscillation frequency, tuning range, and FOM except start-up condition. The other topology is the differential topology. This VCO has four noise reduction mechanisms which are series connected transistors, transformer-based resonators, absent of current source and gate bias by external control. These mechanisms are related to each other complexly. The VCO has low phase noise of -117.5 dB/Hz at 1 MHz offset frequency. The VCO can operate under 1.8 V of power supply. The figure of merit (FOM) is 187.5 dB at 10.3 GHz oscillation frequency, which is the best value among X-band VCOs. Moreover, the VCO is able to connect to the frequency multiplier without a buffer and a DC lev...