Design and Implementation of 24-GHz and 48-GHz VCOs Using Noise Filtering Technique in 90-nm CMOS

This work proposes two voltage-controlled oscillators using noise-filtering technique. The first one is a 24-GHz voltage-controlled oscillator, and the second one is based on a push-push architecture with a λ/4 transmission line to further increase the frequency up to 48 GHz. The designs are implemented and verified in a standard 90-nm CMOS process. Typically, the current mirror transistor in the tail current has a nonlinear effect. When the transistor operates in the nonlinear region, noise will be introduced. Therefore, a set of LC filters with a resonant frequency at 2f0 are added to the design of this section to filter the noise at 2f0 through the capacitor to the ground. The measurement results show that the design of a single oscillator has an oscillation frequency of 24.37 GHz, a tuning range of 6.5%, and a phase noise of -97.19 dBc/Hz @1MHz. The measurement results of the push-push architecture show that the double oscillation frequency is 49.8 GHz, the tuning range is 7.2%, and the phase noise is -80.52 dBc/Hz @1MHz. The chip areas of 24-GHz LC VCO and 48-GHz push-push LC VCO are 0.68 mm × 0.69 mm and 0.7 mm × 0.7 mm, respectively.