数字电视调谐器中压控振荡器的设计
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摘要
压控振荡器(Voltage Controlled Oscillator，简称VCO)是锁相环(PLL)频率合成器的重要组成单元，它在很大程度上决定了PLL的性能。在多种射频工艺(GaAs、SiGe、Bipolar、CMOS)中，CMOS工艺以其高的集成度，低廉的成本逐渐得到广泛的应用，因此CMOS VCO也成为当前射频研究领域的热点。
宽范围调谐VCO模块是单次变频结构的数字电视调谐器专用芯片中的一个重要模块。由于该芯片要把电视输入信号(48MHz～860MHz)下变频到中频(36MHz)，所以本课题设计的VCO模块必须具有宽带，高性能等特点。由于采用数字信号控制的自动幅值控制(AAC)环路，因而是一个典型的数模混合集成电路。
论文首先简单介绍了片上VCO设计国内外的发展状况，并提出了论文的设计目标，具体目标是实现一个输出频率范围为435．25MHz～899．25MHz，相位噪声为-85dB／Hz@10kHz的UHF频段CMOS压控振荡器。然后论文对VCO的基本理论，尤其是LC VCO的理论做了详细的总结，包括振荡器工作原理、VCO的振幅、VCO性能指标、VCO常用结构、变容管的相关理论等。着重介绍和分析了VCO的相位噪声理论，对流行的相位噪声的优化方法作了分析和总结。
论文重点阐述了本课题的宽调谐范围的VCO的数模混合电路的实现方案，在方案中，使用片外LC谐振槽路实现宽范围频率覆盖和高Q值，并对片外LC槽路做了详细的建模。利用带尾电流控制的互补交叉耦合结构设计了VCO的核心，并利用数模混合电路实现了自动幅值控制，设计了VCO buffer。在使用Eldo-RF对电路设计分析完成之后，用IC-Station软件实现了电路的版图设计，并对版图设计中的一些要点进行了说明，譬如版图的对称性，寄生效应等。仿真结果表明，VCO的幅值，调谐范围，相位噪声等性能均达到了设计要求，且具有低功耗，整个频率范围振幅稳定等特点。
VCO(Voltage Controlled Oscillator) is the core block of PLL based frequency synthesizer. Its performance determines the whole synthesizer to a large extent. Integrated voltage controlled oscillators are one of the most challenging parts of radio transceivers to integrate in standard CMOS technologies. In many RF processes (GaAs, SiGe, Bipolar, CMOS), CMOS RF process is widely applied gradually for its high integrated density, low cost. Therefore, CMOS VCOs On chip become the hotspot of many RF applications.
The CMOS wideband VCO designed in this thesis is used in an ASIC for single-conversion digital TV tuner. Because down-converter of the chip converts the wide spectrum of TV signals (48MHz～860MHz) to a fixed middle frequency (36MHz), on-chip VCO must have quite wide tuning range and high performance. This design adopts a digital signal controlled automatic amplitude control (AAC) loop, so it is a typical Mix-signal circuit.
At first, this thesis introduced the status of the design of on-chip VCO and the design request was proposed: a VCO of tuning range from 435.25 MHz-899.25MHz, phase noise is-85dBc/HZ offset 10KHz. Then, the thesis elaborated on the basic theory of the VCO (especially on LC-VCO), i.e. the oscillating theory, the amplitude calculating, the typical structure, the varactor theory, etc. This thesis highlights and analysis of the VCO phase noise theory, and make a summary analysis of the pop optimization way of phase noise.
Then the thesis focused on the scheme of the wide-tuning-range VCO, and achieved the design parameters, which is typical digital and analog mixed circuits (AMS). The scheme adopted off-chip LC oscillating tank, which provide wide tuning range and high Q value. The thesis made a precise model of the off-chip LC-tank. Using complementary cross-coupling VCO with tail-current control scheme achieve the VCO core. The automatic amplitude control loop is implemented in a mix-signal way, and then the VCO buffer is designed. EldoRF is used to simulate the performance of the circuit. Layout of the whole circuit is drawn with the help of IC-Station. The simulation results show that the amplitude of the VCO tuning range, phase noise performance met the design requirements. Besides, it has low power consumption, amplitude stability characteristics of the entire frequency range.
宽范围调谐VCO模块是单次变频结构的数字电视调谐器专用芯片中的一个重要模块。由于该芯片要把电视输入信号(48MHz～860MHz)下变频到中频(36MHz)，所以本课题设计的VCO模块必须具有宽带，高性能等特点。由于采用数字信号控制的自动幅值控制(AAC)环路，因而是一个典型的数模混合集成电路。
论文首先简单介绍了片上VCO设计国内外的发展状况，并提出了论文的设计目标，具体目标是实现一个输出频率范围为435．25MHz～899．25MHz，相位噪声为-85dB／Hz@10kHz的UHF频段CMOS压控振荡器。然后论文对VCO的基本理论，尤其是LC VCO的理论做了详细的总结，包括振荡器工作原理、VCO的振幅、VCO性能指标、VCO常用结构、变容管的相关理论等。着重介绍和分析了VCO的相位噪声理论，对流行的相位噪声的优化方法作了分析和总结。
论文重点阐述了本课题的宽调谐范围的VCO的数模混合电路的实现方案，在方案中，使用片外LC谐振槽路实现宽范围频率覆盖和高Q值，并对片外LC槽路做了详细的建模。利用带尾电流控制的互补交叉耦合结构设计了VCO的核心，并利用数模混合电路实现了自动幅值控制，设计了VCO buffer。在使用Eldo-RF对电路设计分析完成之后，用IC-Station软件实现了电路的版图设计，并对版图设计中的一些要点进行了说明，譬如版图的对称性，寄生效应等。仿真结果表明，VCO的幅值，调谐范围，相位噪声等性能均达到了设计要求，且具有低功耗，整个频率范围振幅稳定等特点。
VCO(Voltage Controlled Oscillator) is the core block of PLL based frequency synthesizer. Its performance determines the whole synthesizer to a large extent. Integrated voltage controlled oscillators are one of the most challenging parts of radio transceivers to integrate in standard CMOS technologies. In many RF processes (GaAs, SiGe, Bipolar, CMOS), CMOS RF process is widely applied gradually for its high integrated density, low cost. Therefore, CMOS VCOs On chip become the hotspot of many RF applications.
The CMOS wideband VCO designed in this thesis is used in an ASIC for single-conversion digital TV tuner. Because down-converter of the chip converts the wide spectrum of TV signals (48MHz～860MHz) to a fixed middle frequency (36MHz), on-chip VCO must have quite wide tuning range and high performance. This design adopts a digital signal controlled automatic amplitude control (AAC) loop, so it is a typical Mix-signal circuit.
At first, this thesis introduced the status of the design of on-chip VCO and the design request was proposed: a VCO of tuning range from 435.25 MHz-899.25MHz, phase noise is-85dBc/HZ offset 10KHz. Then, the thesis elaborated on the basic theory of the VCO (especially on LC-VCO), i.e. the oscillating theory, the amplitude calculating, the typical structure, the varactor theory, etc. This thesis highlights and analysis of the VCO phase noise theory, and make a summary analysis of the pop optimization way of phase noise.
Then the thesis focused on the scheme of the wide-tuning-range VCO, and achieved the design parameters, which is typical digital and analog mixed circuits (AMS). The scheme adopted off-chip LC oscillating tank, which provide wide tuning range and high Q value. The thesis made a precise model of the off-chip LC-tank. Using complementary cross-coupling VCO with tail-current control scheme achieve the VCO core. The automatic amplitude control loop is implemented in a mix-signal way, and then the VCO buffer is designed. EldoRF is used to simulate the performance of the circuit. Layout of the whole circuit is drawn with the help of IC-Station. The simulation results show that the amplitude of the VCO tuning range, phase noise performance met the design requirements. Besides, it has low power consumption, amplitude stability characteristics of the entire frequency range.
引文
[1]Ali Hajimiri and Thomas H. Lee, "A General Theory of Phase Noise in Electrical oscillators", IEEEJSSC VOL, 33, No, 2, Feb, 1998
[2]Troedsson, N, Sjoland. H. "High performance 1V 2.4GHz CMOS VCO" ASIC, 2002.Proceedings. 2002 IEEE Asia-Pacific Conference on, 6-8 Aug. 2002 Page(s):185-188
[3]A. Kral, F. Behbahani, and A. A. Abidi, "RF-CMOS oscillators with switched tuning," in Proc. IEEE Custom Integrated Circuits Conf., May 1998, pp. 555-558.
[4]A. Hajimid and T. H. Lee, "Design issues in CMOS differential LC oscillators,"IEEE J Solid-State Circuits, vol. 34,pp. 717-724, May. 1999.
[5]J.Bhattachaarjee, D. Mukherjee, J. Laskar, "A MONOLITHIC CMOS VCO FOR WIRELESS LAN APPLICATIONS," Georgia Institute of Technology, Atlanta,Georgia, 30332.
[6]M. Agah "1.8GHz CMOS Voltage Controlled Oscillator Designs For DCS-1800". Electrical Engineering and Computer Science Department, University of Michigan, 1301 Beal Ave., Ann Arbor, MI 48109.
[7]谢嘉奎，宜月清，《电子线路》非线性部分 高等教育出版社 1984年
[8]拉扎维，陈贵灿等译，《模拟CMOS集成电路设计》西安交通大学出版社 2003年
[9]Thomas H．Lee，余志平等译《CMOS射频集成电路设计》电子工业出版社2004年
[10]J. Craninckx and M. Steyaert, "Low-noise voltage-controlled oscillators using enhanced LC-tanks,"IEEE Trans. Circuits Syst.-Ⅱ, vol. 42, pp. 794-904, Dec. 1995.
[11]B. Razavi, "A study of phase noise in CMOS oscillators," IEEE J. Solid-State Circuits, vol. 31, pp.331-343, Mar. 1996.
[12]C. Samori, A.L. Laeaita, F.Villa, and F. Zappa, "Spectrum folding and phase noise in LC tuned oscillators," IEEE Trans. Circuits Syst.-Ⅱ, vol. 45, pp. 781-790, Jul. 1995.
[13]A. Hajimiri, and T. H. Lee, "Design issues in CMOS differential LC oscillators," IEEEJ. Solid-State Circuits, vol. 34, pp.717-724, July. 1999.
[14]J. J. Rael and A. A. Abidi, "Physcial processes of phase noise in differential LC oscillators," in Proc.IEEE Custom Integrated Circuits Conf., Oralndo, FL, 2000, pp.569-572.
[15]M. T. Dawkins, and A. P. Burdett and N. Cowley, "A Single-chip tuner for DVB-T," 1EEE J. Solid-State Circuits, vol. 38, pp. 1307-1317, Aug. 2003.
[16]E. Hegazi, H. Sjoland and A. A. Abidi, "A filtering technique to lower LC oscillator phase noise," IEEE J. Solid-State Circuits, vol. 36, pp. 1921-1930, Dec.2001.
[17]S. L. J. Gierkink, S. Levantino, R. C. Frye, C. Samori and V. Boccuzzi, "A low-phase-noise 5-GHz CMOS quadrature VCO using superharmonic coupling," IEEEJ. Solid-State Circuits, vol. 38,pp.1148-1154, July 2003.
[18]A. Kral, F. Behbahani, and A. A. Abidi, "RF-CMOS oscillators with switched tuning," in Proc. IEEE Custom Integrated Circuits Conf., May 1998, pp. 555-558.
[19]A. Bonfanti, S. Levantino, C. Samori, et al. A Vamctor Configuration Minimizing the Amplitude-to-Phase Noise Conversion in VCOs. IEEE Transactions on Circuitsand Systems Ⅰ, 2005
[20]赵凯华 陈熙谋《电磁学》下册 高等教育出版社 1985年
[21]J. Bhattachaarjee, D. Mukherjee, J. Laskar, "AMONOLITHIC CMOS VCO FOR WIRELESS LAN APPLICATIONS," Georgia Institute of Technology, Atlanta,Georgia, 30332.
[22]Ham D, Hajimid A. Concepts and methods in optimization of integrated LC VCOs[J]. IEEE JSSC, 2001, 36(6): 896-909.
[23]Zachi A, Samori C. A 22V 2.5GHz 2104dBc/Hz at 100 kHz fully integrated VCO with wide-band low-noise automatic amplitude control loop[J]. IEEE JSSC, 2001, 36(4):611-619.
[24]孙文，罗岚，”一种新型的压控振荡器用自动幅度控制电路”应用科学学报 第 24卷 第3期
[25]T. H. Lee, A. Hajimiri, "Oscillator Phase Noise: A Tutorial," IEEE J Solid-State Circuits, vol. 35, no. 3.March. 2000.
[26]D.B. Leeson, "A simple model of feedback oscillator noises spectrum," Proc.IEEE, Vol. 54, pp.329-330, Feb. 1966.
[27]Zanchi A, Samori C. Impact of AAC design on phase noise performance of VCOs[J]. IEEE Trans Circuits Syst Ⅱ, 2001,48(6):537-547.
[28]李天望，“1V 2．5GHZ压控振荡器的设计”，半导体学报，2003年01期
[29]Tommy K. K. Tsang, Mourad. N. E1-Gamal. Microelectronics, etc. A high figure of merit and area-efficient low-voltage 12 GHz CMOS VCO[C]Radio Frequency Integrated Circuits(RFIC) SymposiumlPhiladelphia, PA, USA, 2003.
[30]唐长文，何捷，闵吴．“一种采用开关阶跃电容的压控振荡器”半导体学报，2005，26(10)：2010
[2]Troedsson, N, Sjoland. H. "High performance 1V 2.4GHz CMOS VCO" ASIC, 2002.Proceedings. 2002 IEEE Asia-Pacific Conference on, 6-8 Aug. 2002 Page(s):185-188
[3]A. Kral, F. Behbahani, and A. A. Abidi, "RF-CMOS oscillators with switched tuning," in Proc. IEEE Custom Integrated Circuits Conf., May 1998, pp. 555-558.
[4]A. Hajimid and T. H. Lee, "Design issues in CMOS differential LC oscillators,"IEEE J Solid-State Circuits, vol. 34,pp. 717-724, May. 1999.
[5]J.Bhattachaarjee, D. Mukherjee, J. Laskar, "A MONOLITHIC CMOS VCO FOR WIRELESS LAN APPLICATIONS," Georgia Institute of Technology, Atlanta,Georgia, 30332.
[6]M. Agah "1.8GHz CMOS Voltage Controlled Oscillator Designs For DCS-1800". Electrical Engineering and Computer Science Department, University of Michigan, 1301 Beal Ave., Ann Arbor, MI 48109.
[7]谢嘉奎，宜月清，《电子线路》非线性部分 高等教育出版社 1984年
[8]拉扎维，陈贵灿等译，《模拟CMOS集成电路设计》西安交通大学出版社 2003年
[9]Thomas H．Lee，余志平等译《CMOS射频集成电路设计》电子工业出版社2004年
[10]J. Craninckx and M. Steyaert, "Low-noise voltage-controlled oscillators using enhanced LC-tanks,"IEEE Trans. Circuits Syst.-Ⅱ, vol. 42, pp. 794-904, Dec. 1995.
[11]B. Razavi, "A study of phase noise in CMOS oscillators," IEEE J. Solid-State Circuits, vol. 31, pp.331-343, Mar. 1996.
[12]C. Samori, A.L. Laeaita, F.Villa, and F. Zappa, "Spectrum folding and phase noise in LC tuned oscillators," IEEE Trans. Circuits Syst.-Ⅱ, vol. 45, pp. 781-790, Jul. 1995.
[13]A. Hajimiri, and T. H. Lee, "Design issues in CMOS differential LC oscillators," IEEEJ. Solid-State Circuits, vol. 34, pp.717-724, July. 1999.
[14]J. J. Rael and A. A. Abidi, "Physcial processes of phase noise in differential LC oscillators," in Proc.IEEE Custom Integrated Circuits Conf., Oralndo, FL, 2000, pp.569-572.
[15]M. T. Dawkins, and A. P. Burdett and N. Cowley, "A Single-chip tuner for DVB-T," 1EEE J. Solid-State Circuits, vol. 38, pp. 1307-1317, Aug. 2003.
[16]E. Hegazi, H. Sjoland and A. A. Abidi, "A filtering technique to lower LC oscillator phase noise," IEEE J. Solid-State Circuits, vol. 36, pp. 1921-1930, Dec.2001.
[17]S. L. J. Gierkink, S. Levantino, R. C. Frye, C. Samori and V. Boccuzzi, "A low-phase-noise 5-GHz CMOS quadrature VCO using superharmonic coupling," IEEEJ. Solid-State Circuits, vol. 38,pp.1148-1154, July 2003.
[18]A. Kral, F. Behbahani, and A. A. Abidi, "RF-CMOS oscillators with switched tuning," in Proc. IEEE Custom Integrated Circuits Conf., May 1998, pp. 555-558.
[19]A. Bonfanti, S. Levantino, C. Samori, et al. A Vamctor Configuration Minimizing the Amplitude-to-Phase Noise Conversion in VCOs. IEEE Transactions on Circuitsand Systems Ⅰ, 2005
[20]赵凯华 陈熙谋《电磁学》下册 高等教育出版社 1985年
[21]J. Bhattachaarjee, D. Mukherjee, J. Laskar, "AMONOLITHIC CMOS VCO FOR WIRELESS LAN APPLICATIONS," Georgia Institute of Technology, Atlanta,Georgia, 30332.
[22]Ham D, Hajimid A. Concepts and methods in optimization of integrated LC VCOs[J]. IEEE JSSC, 2001, 36(6): 896-909.
[23]Zachi A, Samori C. A 22V 2.5GHz 2104dBc/Hz at 100 kHz fully integrated VCO with wide-band low-noise automatic amplitude control loop[J]. IEEE JSSC, 2001, 36(4):611-619.
[24]孙文，罗岚，”一种新型的压控振荡器用自动幅度控制电路”应用科学学报 第 24卷 第3期
[25]T. H. Lee, A. Hajimiri, "Oscillator Phase Noise: A Tutorial," IEEE J Solid-State Circuits, vol. 35, no. 3.March. 2000.
[26]D.B. Leeson, "A simple model of feedback oscillator noises spectrum," Proc.IEEE, Vol. 54, pp.329-330, Feb. 1966.
[27]Zanchi A, Samori C. Impact of AAC design on phase noise performance of VCOs[J]. IEEE Trans Circuits Syst Ⅱ, 2001,48(6):537-547.
[28]李天望，“1V 2．5GHZ压控振荡器的设计”，半导体学报，2003年01期
[29]Tommy K. K. Tsang, Mourad. N. E1-Gamal. Microelectronics, etc. A high figure of merit and area-efficient low-voltage 12 GHz CMOS VCO[C]Radio Frequency Integrated Circuits(RFIC) SymposiumlPhiladelphia, PA, USA, 2003.
[30]唐长文，何捷，闵吴．“一种采用开关阶跃电容的压控振荡器”半导体学报，2005，26(10)：2010