Wide-band CMOS VCO and frequency divider design for quadrature signal generation

We present the design, implementation, and measurement of a fully integrated wide-band (3.3GHz-4GHz) CMOS VCOs and frequency divider, as well as the analysis and comparison of VCO topologies for their uniform phase noise performance in the wide tuning range. In addition, the dynamic range of the frequency divider is analyzed based on experimental results for the first time. The different VCO topologies have been investigated by using the measured results. It is demonstrated that the NMOS-PMOS VCO (NP-core VCO) without a current source has as low as 2dB of phase noise variation in the entire tuning range of 650MHz as well as achieving superior phase noise performance of -118.5 dBc/Hz at 1MHz offset compared to the NMOS VCO (N-core VCO) which shows severe phase noise degradation of 17dB due to AM-FM conversion in the high varactor gain region. A frequency divider is designed to generate the quadrature signal for direct conversion. The measured results exhibit the dynamic range limit of the frequency divider along with sensitivity curve of the divider. To the best of our knowledge, this is the first report analyzing the dynamic range of the frequency divider based on the experimental results.