Design of Microwave and Millimeter-wave CMOS VCOs

• Main Authors: Yi-Hsien Cho, 卓宜賢
• Other Authors: 王暉
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/54061091113754167310

碩士 === 國立臺灣大學 === 電信工程學研究所 === 93 === A low phase noise VCO is indispensable in modern communication systems. The demand for high data transmission drives us to investigate high frequency systems. Therefore, to design a high frequency oscillator with low phase noise is important. The goal of the thesis is to design and implement VCOs in microwave and millimeter-wave region using CMOS technology. This research focuses on millimeter-wave oscillators and quadrature VCO (QVCO) in the 5-GHz band. The thesis can be divided into three parts. The first part introduces the application of oscillators and discusses the theory of LC-VCO. A complementary LC-tank VCO is designed and implemented in this part. The theory and advantages of push-push VCO are introduced, next, and a new low phase noise push-push VCO is implemented. The last part of this thesis discusses the basics and application of QVCO. Three new QVCOs are proposed and implemented. The design concepts together with their advantages are also discussed. In the thesis, a VCO combining complementary cross-coupled and push-push topology is proposed. The circuit is fabricated by TSMC 0.18-μm CMOS process and it achieved a phase noise of -97 dBc/Hz at 1-MHz offset at 52 GHz with a miniature chip size of 0.2-mm2 area. Besides high frequency oscillators, QVCOs applied to the 5-GHz band is also covered. Firstly, a switchable QVCO with wide tuning range is designed and fabricated by TSMC 0.18-μm CMOS process. The circuit is realized by using serial coupled techniques to combine two complementary cross-coupled VCOs. From the measurement results, the circuit achieves a phase noise of -120 dBc/Hz at 1-MHz offset at 5.5 GHz with 20% tuning range. Next, a QVCO is implemented by Colpitts oscillator because Colpitts oscillator shows better phase noise than cross-coupled topology. The quadrature phase is realized by using parallel coupling techniques. However, the parallel coupling methods degrade the phase noise performance and increase power consumption. Therefore, the parallel coupled Colpitts QVCO does not show lower phase noise than serial coupled complementary QVCO. Finally, a Colpitts QVCO with a new coupling approach is presented. The circuit has the advantages of low power consumption and low phase noise. From simulations, the QVCO achieves a phase noise of -123 dBc/Hz at 1-MHz offset at 5 GHz with 6-mW dc power consumption.