Low-phase noise variation VCO implementing resistorless digitally controlled varactor

A novel resistorless digital capacitor switching array (DCSA) has been implemented into a wideband CMOS VCO for 5-GHz WiMAX/WLAN applications. The proposed DCSA is added both in series and parallel to nMOS varactors. Based on this, a wideband VCO is achieved, which not only exhibits lower phase noise in comparison with reported state-of the-art wideband VCOs, but also has low phase noise variation of less than 5 dBc/Hz. In addition, it has demonstrated low power consumption, improved linearity of the f-V curve and extended tuning range. The proposed VCO has been designed using UMC 130 nm CMOS technology. It operates from 3.65 GHz to 6.34 GHz, with a phase noise of -132.70 dBc/Hz at 1 MHz offset, a figure of merit (FoM) of -202.9 dBc/Hz, less than -41 dBm spurious harmonics and total VCO core power consumption of 2.88 mW from a 3.2 V supply voltage.