4GHz Broadband VCO: A Case Study

Summary

In this chapter, design and development of a 4GHz broadband VCO in 0.18μm CMOS technology as a case study for use in the RF (LO1) frequency synthesizer of WLAN radio transceiver (Chapter 9) are presented. Complementary NMOS and PMOS as well as PMOS-only active circuit topologies are evaluated. MIM capacitance and PMOS devices are investigated for band switching. Bias filtering techniques are also investigated for noise minimization.

The PMOS only VCO topology exhibits better performance parameters than the CMOS topology. The better performance of the PMOS topology is due to lower flicker noise and biasing of the varactor circuit. MIM capacitance switching which exhibits better supply sensitivity is preferred over MOS capacitance switching.