2.45GHz low phase noise LC VCO design using Flip Chip on low cost CMOS technology

Phase Noise performance of LC VCOs is strongly dependent on the Quality Factor of the Inductors. As known, low cost CMOS technologies, the on-chip inductors have low quality factors compared to external inductors. But, using external inductors connected by traditional bonding technologies limits the integration capacity. To implement high performance RF circuits, the use of the Flip Chip technology is growing in ICs packaging. This work presents a comparison between two LC VCOs operating at 2.4GHz ISM band, using a standard 0.35μm CMOS process. One using internal inductor (OC-VCO), and a second using a high-Q external inductor connected by Flip Chip Technology (FC-VCO). The results for the designed FC-VCO are a low phase noise of -121dBc/Hz@1MHz and -132dBc/Hz@3MHz, tuning range of 203MHz and power consumption of 10.8mW at 3V. FC-VCO improves -9.7dBc/Hz@1MHz if compared with the OC-VCO using the same power consumption and inductance value. Additionally, FC-VCO presents a better figure of merit (FOM) than other published works, even for more advanced technologies.