A Novel Variable Inductor-Based VCO Design with 17% Frequency Tuning Range for IEEE 802.11AD Applications

Abstract

This thesis focuses on the design and analysis of a novel variable inductor (VID) based VCO solution to the frequency tuning range (TR) limitation of the IEEE 802.11ad compliant radio systems. The IEEE 802.11ad standard has drawn strong attention from the industry as the next generation affordable multi-gigabit speed wireless communication standard. Prepared for the global market, IEEE 802.11ad compliant systems are required to cover a broad 8 GHz TR centered on 60 GHz. This wide TR at V band imposes significant challenge to the VCO design in radio transceivers, and makes the TR of the integrated VCO a major bottleneck to the successful commercialization of many IEEE 802.11ad compliant radio systems today.

As an effort to solve the current TR problem for the IEEE 802.11ad compliant radio systems, 2 VCOs designs based on this novel VID-based solution and a conventional Colpitts-Clapp VCO design are presented in this thesis report. The novel VCOs integrate a VID into the differential Colpitts configuration to create a feasible solution to the aforementioned TR problem. The VID in the VCO tank eliminates the base node varactors and their fixed parasitic capacitance that degrades TR in conventional VCO designs, while the differential Colpitts configuration provides advantageous performance at mm-wave frequencies and high output power for real-world applications. Also, a fundamental 30 GHz Colpitts-Clapp VCO was developed in conjunction with the other 2 VCOs for comparison purposes.

One of the 2 VID-based VCO designs is a fundamental 30 GHz VID-based Colpitts VCO that covers 17% TR for proof of concept to the novel topology. Another is an IEEE 802.11ad compliant 60 GHz VCO chain consists of the 30 GHz VID-based Colpitts VCO and a frequency doubler covering 17% TR with 3 dBm output power and -115.7 dBc/Hz phase noise at 10 MHz offset. The conventional Colpitts-Clapp VCO is used to compare with the other 2 VID-based VCOs. As the measurement results indicate, this VID-based VCO topology provides a viable solution to overcome the TR bottleneck in the current IEEE 802.11ad compliant VCO development. All 3 VCOs are fabricated using a 130 nm SiGe BiCMOS process.