Low power considerations and design for CMOS VCOs applied for direct conversion receivers at 5GHz

Low power design often requires direct conversion architectures, such as low-IF or zero-IF. Any of these two possibilities needs a low power, low phase noise voltage control oscillator (VCO) in the frequency synthesizer. This work is focused on low power considerations applied to the practical modem conception of this device. Fulfilling the standard specifications (output power, phase noise, frequency range) should be completed with this deeper step. A conscious design leads moreover to an improvement in the results obtained by the classical considerations. The increase of the quality factor of the passive elements is one of the key points, followed by an accurate design of the architecture scheme. Furthermore, lower current consumption provides higher oscillation frequencies and facilitates higher frequency ranges, which follow the trends of modem wireless and wideband communication standards. In order to validate the aforementioned assumptions, a CMOS VCO has been implemented in UMC 0.18 mu m 1P6M technology, with power consumption down to 3.4mW.