CMOS 低功率電流再利用壓控震盪器之研製

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(1)國立高雄大學電機工程學系 (研究所-微電子組) 碩士論文. CMOS 低功率電流再利用壓控震盪器之研製 Design of CMOS Low Power Current Reused Voltage Controlled Oscillator. 研究生：顏玄德撰指導教授：葉文冠、王瑞祿. 中華民國九十七年六月.

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(3) CMOS 低功率電流再利用壓控震盪器之研製指導教授：葉文冠 1、王瑞祿 2 博士國立高雄大學電機工程所 1 國立高雄海洋科技大學微電子工程系 2 學生：顏玄德國立高雄大學電機工程所摘要本論文針對 L-band、WiMAX WSC、以及 WiMAX FWA 通訊系統規格設計了三顆 CMOS 低功率壓控震盪器，第一顆為應用於 1.2-1.5GHz 之低功率壓控震盪器，第二顆為應用於 WiMAX WSC 2.305-2.320GHz、2.345-2.360GHz 低功率壓控震盪器，第三顆為應用在 WiMAX FWA 3.4-3.7GHz 低功率壓控震盪器，均使用台灣積體電路製造公司 (TSMC)0.18μm CMOS 製程設計完成。以上晶片均透過國家系統晶片設計中心(Chip Implementation Center, CIC)下線製造。亦透過台南、新竹科學園區 CIC 高頻量測系統及高雄大學微電子實驗室量測並交叉驗證其資料的可信度。本論文所設計的壓控震盪器晶片，使用電流再利用的架構，以低功率為訴求在論文中的二顆電路消耗功率皆在 2mW 以下.其中訴求超低消耗功率 432 μ W 的 IC 因為製程上的與金屬連接線萃取的部份問題讓整個消耗功率變大至 3.96mW，雖有頻率飄移但有進入應用頻段。其應用頻段為 WiMAX WSC 頻段；而第其他二顆震盪器因製程變異與佈局技巧的問題使得頻率有些偏移，但是不論在操作電壓與電流都相當精準沒有第一顆的消耗功率的問題；第三顆壓控震盪器頻率飄移的非常嚴重大約有 0.5GHz 的偏移與不穩定的震盪現象，雖然可能是因受到 TSMC 製程上的變異影響.但其影響因素在佈局技巧上有更具說服力的原因.. 關鍵字：WSC, WiMAX, FWA, 控震盪器, 低功率, 射頻電路(RF), 功率, 低電壓, current reused. i.

(4) Design of CMOS Low Power Current Reused Voltage Controlled Oscillator Advisor(s): Dr.(Professor) Wen-Kuan Yeh1 and Ruey-Lue Wang2 Institute of Electrical Engineering National University of Kaohsiung1 Department of Microelectronic Engineering National Kaohsiung Marine University2 Student: Yen, Hsuan-Der Institute of Electrical Engineering National University of Kaohsiung ABSTRACT In this thesis, three CMOS low power consumption oscillators conform to L-band, WIMAX WSC and WIMAX FWA the standards of communication system has been designed. The first one is applicable on 1.2-1.5GH low power-consumed oscillator. The second is applying on WiMAX WSC 2.305-2.320GHz low power-consumed oscillator; the third is a WiMAX FWA 3.4-3.7GHz low power-consumed oscillator. These low power-consumed oscillators is implemented by TSMC 0.18μm CMOS manufacturing process applied by Chip Implementation Center (CIC) and the measurement is done by CIC RF measurement at Hsinchu Science Park and southern Taiwan Science Park as well as the microelectronic Lab. at National University of Kaohsiung The oscillator chips are designed and used current reused structure in this thesis, The first goal design is low power. Two chips are working well, power consumption below 2mW which ultra low power VCO has 432uW in WSC band but some manufacturing processing and the extraction variation do not the become to it and can not fit well and the result about 3.96mW. The other two chips no same problem as above VCO that current and operation voltage have refined results to match simulation but that have some frequency variation problem. The 3rd chip has serious frequency variation about 0.5GHz and instable oscillation which manufacturing process may influence that but layout skill should be main reason in this chip. We proved that in below section. Keywords: WSC, WiMAX, FWA, oscillator, low power, RF circuit, power, low voltage, current reused,. ii.

(5) Acknowledgement. 本論文能夠順利完成，其幕後支持的人非常多，碩士這兩年的路如果沒他們的幫忙與支持我相信就沒辦法走的那麼順利了，首先要感謝我的指導教授葉博士文冠對我這兩年來的指導與幫忙，還有環境上良好資源的提供並且給予碩士生涯的道路啟發；更要感謝王博士瑞祿，在他的教導下給予我射頻與電路設計上的觀念並給予我們其專業知識與技術，也感謝他的耐心教導才能順利的完成這三顆 VCO 的晶片，對於我射頻與半導體的學習路上他扮演了最重要啟迪角色，能不厭其煩的跟我一再討論研究內容。在此也要感謝吳博士松茂，有吳博士的專業及廣闊的人面，協助我們建構完善的量測環境，也感謝他在我碩士求學中不時的提拔與協助，並給予適時的開導，還有在日月光半導體任職的王博士陳肇在被動元件與基板觀念上給予教導與建議。也感謝安捷倫的星琿哥這兩年來在儀器上給予的協助與幫助。其次要感謝我的學長姊們，彥志、恩路、家維、韶華、振安，有你們實驗室才會有這麼好的環境與氣氛，也感謝你們在畢業的前用心的教導，還有實驗室中的同學，啟彰有你能夠一起討論學業與研究，無可厚非的是我這段日子以來最大的助力之ㄧ。還有學弟，育哲、毅覺、治忠、王昱、小白，在有你們的實驗室，感謝你們相處日子以來的協助與幫忙。讓整個實驗室運作的很好，也因為大家共同維護，讓整個實驗室氣氛和樂，做起事來非常順利，也感謝學弟們的配合與容忍，希望大家能夠朝自己既定的目標前進。最後我要感謝我的母親給予我正面的人生價值觀讓我們人生的路上，有良好的基礎面對各式各樣的挑戰，也感謝她默默對我的付出與愛的教誨。還有四哥在經濟上的支持，還有家人們在背後支持我、鼓勵我。另外要感謝最體貼我的珮如，這兩年多來我們相處的時光中不管是遇到困難、哀傷或是喜悅都有妳在我身邊跟我分享一切，並且感謝妳給予的鼓勵與支持無可厚非的這是無人能取代的。最後在這裡感謝所有在一旁支持與幫助我的長輩與夥伴。. iii.

(6) Contents Abstract (Chinese) ............................................................................................................. i Abstract (English) ............................................................................................................. ii Acknowledgement ............................................................................................................ iii Contents ............................................................................................................................ iv List of Figures................................................................................................................... vi List of Tables .................................................................................................................. ix. Chapter 1. Introduction ............................................................................... 1. 1.1 Motivation ..........................................................................................................1 1.2 Thesis Organization ...........................................................................................3. Chapter 2 Basics of Voltage Controlled Oscillator...................................... 5 2.1 General Oscillators Considerations......................................................................5 2.1.1 Negative-Resistance Oscillator................................................................7 2.1.2 LC Tank and Oscillator Conditions .........................................................8 2.2 MOS Varactor....................................................................................................11 2.2.1 MOS Varactor Operation Mode ............................................................12 2.3 Phase Noise........................................................................................................15 2.3.1 A Linear and Time-Invariant Phase-Noise Theory................................16 2.3.2 A Linear and Time-Varying Phase-Noise Theory..................................18 2.4 Voltage Controlled Oscillator (VCO)................................................................23 2.4.1 Basic Properties .....................................................................................24 2.4.2 Design of LC VCO Methods .................................................................25 2.4.3 Design Follows of VCO ......................................................................28. Chapter 3 3.1 3.2 3.3. Design of Low-Power Current-Reused CMOS VCO............ 32. Induction of Low-Power Current-Reused VCO Structure..............................32 Design of Low-Power Current-Reused VCO for L-Band System..................35 VCO Simulation and Measurements For L-Band System..............................35 3.3.1 Design of structure...............................................................................35 3.3.2 L-Band VCO Simulation Characteristics.............................................36 3.3.3 L-Band VCO Measurement Characteristics ........................................47. iv.

(7) 3.4 3.5. Design of Low-Power Current-Reused VCO for WiMAX FWA System.......50 VCO Simulation and Measurements for WiMAX FWA System....................50 3.5.1 Design of Structure ..............................................................................50 3.5.2 WiMAX FWA VCO Simulation Characteristics..................................51 3.5.3 WiMAX FWA VCO Measurement Characteristics .............................61 3.6 Discussion and Summary...................................................................................65. Chapter 4. Design of Low-Power Current-Reused with Balance Resistors CMOS VCO.............................................................................. 70. 4.1 4.2. Induction Current-Reused VCO with Balance Resistors Structure ................70 Design of Current-Reused VCO with Balance Resistors for WiMAX WSC System ...........................................................................................................71 4.3 Current-Reused VCO with Balance Resistors VCO Simulation and Measurement ........................................................................................................................72 4.3.1 Design of Structure ..............................................................................72 4.3.2 WiMAX WSC System VCO Simulation Characteristics ....................74 4.3.3 WiMAX WSC System VCO Measurement Characteristics ................85 4.4 Discussion and Summary................................................................................89. Chapter 5 5.1 5.2. Conclusions and Future Work ............................................. 91. Conclusions.....................................................................................................91 Future Work ....................................................................................................91. References .................................................................................................. 93 List of Publications ...................................................................................... 95. v.

(8) List of Figures Chapter 2 Basics of Voltage Controlled Oscillators Figure 2.1 (a) Feedback oscillatory system (b) Types of Frequency Selective network.....6 Figure 2.2 One port view of oscillator .................................................................................6 Figure 2.3 LC resonator (a) series resonator (b) parallel circuit LC resonator....................6 Figure 2.4 (a) schematic of the crossed-coupled pair (b) small signal model of (a) ..........8 Figure 2.5 (a) series LC resonator (b) parallel LC resonator...............................................9 Figure 2.6 One port oscillator circuit.................................................................................10 Figure 2.7 Generally P-MOS cross section view structure................................................12 Figure 2.8 P-MOS C-V and operation mode .....................................................................12 Figure 2.9 Schematic of P-MOS Capacitor Circuits ........................................................13 Figure 2.10 Different Operation Mode of P-MOS C-V Curve..........................................13 Figure 2.11 Output power spectrum for VCO ...................................................................15 Figure 2.12 Leeson law of Phase noise..............................................................................17 Figure 2.13 Phase be changed by impulse current versus time .........................................19 Figure 2.14 The equivalent block diagram of the process .................................................19 Figure 2.15 Evolution of phase-noise ................................................................................22 Figure.2.16 Inductance and capacitance resonance circuit................................................25 Figure 2.17 VCO Circuits Design Flow ............................................................................27 Figure 2.18 Common VCO project design follows ...........................................................28 Figure 2.19 Pad & bond wire equivalent circuit ................................................................29 Figure 2.20 (a) S-parameter of substitute circuit (b) extrication of pad layout .................30 Chapter 3 Design of Low-Power Current-Reused CMOS VCO Figure 3.1 Schematic of the basic topology of current-reused Differential LC-VCO.......33 Figure 3.2 N-PMOS cross pair large-signal equivalent circuit..........................................34 Figure 3.3 Schematic of the basic topology of current-reused VCO with output-buffers .36 Figure 3.4 Transient simulation of L-band current-reused VCO .....................................38 Figure 3.5 Turning range simulation of L-band current-reused VCO ...............................38 Figure 3.6 Phase-noise simulation of L-band current-reused VCO...................................39 Figure 3.7 Interconnect lines extraction of L-band current-reused VCO ......................41 Figure 3.8 Transient post-simulation of L-band current-reused VCO ...............................43 Figure 3.9 Turning range post-simulation of L-band current-reused VCO .......................43 Figure 3.10 Phase-noise post-simulation of L-band current-reused VCO.........................44 Figure 3.11 Layout of L-band current-reused VCO .........................................................46 Figure 3.12 Microphotograph of L-band current-reused VCO ........................................46 vi.

(9) Figure 3.13 Measurement Phase Noise result of L-band current-reused VCO .................47 Figure 3.14 Measurement current result of L-band current-reused VCO..........................48 Figure 3.15 Measurement turning range result of L-band current-reused VCO ..............48 Figure 3.16 Measurement output power result of L-band current-reused VCO................49 Figure 3.17 Schematic of the WiMAX FWA current-reused VCO with source follower output-buffers.....................................................................................................................50 Figure 3.18 Transient post-simulation of WiMAX FWA current-reused VCO .................52 Figure 3.19 Turning range post-simulation of WiMAX FWA current-reused VCO..........52 Figure 3.20 Phase-noise post-simulation of WiMAX current-reused VCO ......................53 Figure 3.21 Interconnect lines extraction of WiMAX FWA current-reused VCO ............55 Figure 3.22 Interconnect lines extraction of WiMAX FWA current-reused VCO for layout ............................................................................................................................................55 Figure 3.23 Transient post-simulation of WiMAX FWA current-reused VCO .................56 Figure 3.24 Turning range post-simulation of WiMAX FWA current-reused VCO..........56 Figure 3.25 Phase-noise post-simulation of WiMAX FWA current-reused VCO .............57 Figure 3.26 Layout of WiMAX FWA current-reused VCO .............................................60 Figure 3.27 Microphotograph of WiMAX FWA current-reused VCO ..............................60 Figure 3.28 Measurement result of WiMAX FWA current-reused VCO spectrum (a) Normal state (b) frequency per 2 by divider......................................................................62 Figure 3.29 Measurement phase-noise-instable result of WiMAX FWA current-reused VCO ............................................................................................................................................63 Figure 3.30 Measurement turning range result of WiMAX FWA current-reused VCO ....63 Figure 3.31 Measurement Vtune V.S. current result of WiMAX FWA current-reused VCO ............................................................................................................................................64 Figure 3.32 Measurement output power result of WiMAX FWA current-reused VCO (dBm) ............................................................................................................................................64 Figure 3.33 Discusser layout of WiMAX FWA current-reused VCO ..............................66 Figure 3.34 Noise Current experiment for proving instable oscillation ............................67 Figure 3.35 Noise Current experiment for proving instable oscillation-normal state .......68 Figure 3.36 Noise Current experiment for proving instable oscillation-noise injected.....68 Chapter 4 Design of Low-Power Current-Reused with balance resistors CMOS VCO Figure.4.1 Schematic of the Current-Reused Configuration with balance resistors Include Output-Buffer VCO ...........................................................................................................70 Figure.4.2 Schematic of the Current-Reused Configuration with balance resistors Include Output-Buffer VCO, design by ADS ...............................................................................74 Figure.4.3 Transient simulation of WiMAX WSC current-reused VCO ...........................76 Figure.4.4 Turning range simulation of WiMAX WSC current-reused VCO ...................76 vii.

(10) Figure 4.5 Phase-noise simulation of WiMAX WSC current-reused VCO.......................77 Figure 4.6 Interconnect lines extraction of WiMAX WSC current-reused VCO ..............79 Figure 4.7 Interconnect lines extraction of WiMAX WSC current-reused VCO for layout . ............................................................................................................................................79 Figure 4.8 Transient post-simulation of WiMAX WSC current-reused VCO ...................80 Figure 4.9 Turning range post-simulation of WiMAX WSC current-reused VCO ...........80 Figure 4.10 Phase-noise post-simulation of WiMAX WSC current-reused VCO.............81 Figure 4.11 Layout of L-band current-reused VCO .........................................................84 Figure 4.12 Microphotograph of L-band current-reused VCO..........................................84 Figure 4.13 Measurement Phase-noise result of WiMAX WSC current-reused VCO ......85 Figure 4.14 Measurement current result of WiMAX WSC current-reused VCO..............86 Figure 4.15 Measurement turning range result of WiMAX WSC current-reused VCO ..86 Figure 4.16 Measurement spectrum result of WiMAX WSC current-reused VCO ........87 Figure 4.17 Microphotograph of wire bounding VCO ......................................................87 Figure 4.18 The CPW transmission line structure layout ..................................................88 Figure 4.19 Measurement result of WiMAX WSC current-reused VCO waveform.........88 Chapter 5 Conclusions and future work Figure.5.1 Inductance Q Factor of three Chip ...................................................................92. viii.

(11) List of Tables Table 1.1 2007 ITRS Power Supply and Power Dissipation—Near-term Years.................2 Table 3.1 Simulation specifications of L-band current-reused VCO.................................39 Table 3.2 Manufacture processing variation of L-band current-reused VCO....................40 Table 3.3 Temperature variation of L-band current-reused VCO......................................40 Table 3.4 L-band current-reused VCO Results of Post-simulation and pre-simulation ....44 Table 3.5 Reference of L-band current-reused VCO Results compare..............................45 Table 3.6 Results of simulation and measurement.............................................................49 Table 3.7 WiMAX FWA current-reused VCO of simulation specifications......................53 Table 3.8 Manufacture processing variation of WiMAX FWA current-reused VCO ........54 Table 3.9 Temperature variation of WiMAX FWA current-reused VCO ..........................54 Table 3.10 Results of Post-simulation of WiMAX FWA...................................................57 Table 3.11 Manufacture processing variation with interconnect effect of WiMAX FWA current-reused VCO ...........................................................................................................58 Table 3.12 Temperature variation with interconnect effect of L-band current-reused VCO. ............................................................................................................................................58 Table 3.13 Results of Post-simulation and pre-simulation ................................................58 Table 3.14 Reference of WiMAX FWA current-reused VCO Results compare ................59 Table 3.15 Simulation and measurement of WiMAX FWA Results..................................65 Table 4.1 WiMAX WSC current-reused VCO of simulation specifications .....................77 Table 4.2 Manufacture processing variation of WiMAX WSC current-reused VCO........78 Table 4.3 Temperature variation of WiMAX WSC current-reused VCO..........................78 Table 4.4 Temperature variation of WiMAX WSC current-reused VCO..........................81 Table 4.5 WiMAX WSC current-reused VCO Results of Post-simulation and pre-simulation ............................................................................................................................................82 Table 4.6 Reference of WiMAX WSC current-reused VCO Results compare..................83 Table 4.7 Simulation and measurement of WiMAX FWA Results....................................89. ix.

(12) Chapter 1 Introduction. Chapter 1. Introduction ________________________________________________________ 1.1 Motivation In order to keep longer operation time and saving energy, the development of low-power consumption IC including digital, analog or RF circuits will be very important now. But we know that is impossible to eliminated power consumption all. Recently, lots of papers were proposed on low-power operation for circuit topologies in LNA, MIXER and VOC application. In 2007 ITRS (International Technology Roadmap for Semiconductors) report indicate that device scaling is a tendency in the future, and it is necessary to reduce supply voltage for low power operating. On the other hand, it’s not only power consumption can be reduced, but also chips size can be scaled Related data for high performance and low cost application was show in Table 1 [1]:. 1.

(13) Chapter 1 Introduction. Table 1.1.2007 ITRS Power Supply and Power Dissipation—Near-term Years. The IEEE 802.16e WiMAX (mobile worldwide interoperability for microwave access) is a wireless standard that introduces orthogonal frequency division multiple access (OFDMA) and other key features to enable mobile broadband services at a vehicular speed of up to 120 km/h. WiMAX complements the and competes with wireless local area networks (WLANs) and the third generation (3G) wireless standards on coverage and data rate.. 2.

(14) Chapter 1 Introduction. The WiMAX standard supports both fixed and mobile broadband data services. That means have a much larger market in this field. Therefore, the related of product will present the Mobile WiMAX standard. In this thesis The VCO application in IEEE 802.16e WMAX Wireless Communication Services (WCS) under 2.21~2.39 GHz coverage 2.305-2.320GHz and 2.345-2.360GHz for WCS(Wireless Communication Services), 2.50-2.69GHz for MMDS （ Multi-point Microwave Distribution System or Multi-channel Multi-point Distribution System）, 3.4-3.7GHz for FWA（Fixed Wireless Access）. In addition , the business Band that also included Unlicensed Band just like 2.4-2.4835GHz for ISM Band （ Industrial Scientific and Medical Band ） and 5.15~5.35GHz, 5.470~5.725GHz, 5.725~5.825GHz for U-NII(Unlicensed National Information Infrastructure). In mobile and portable communication equipment the supply voltage should be as low as possible. To increase equipment operating time shows how importance of low-power circuits. A voltage controlled oscillator (VCO) is an important block among the blocks of any transceiver that applied in mobile and portable equipments.. 1.2 Thesis Organization In chapter 2, the basic theory for the design of VCO application was described. Related methodology including general consideration in LC tank, Phase-Noise and MOS Varactor was used to design a reasonable VCO, as shown in Chapter 3 and 4 topologies, simulation, measurement and some important skills of design. Two VCO chips which using current-reused configuration with buffer for L-band and Wimax FWA frequency applications were finished. Related characteristics were also described in this chapter.. 3.

(15) Chapter 1 Introduction. In chapter 4, the other structure for low power-consumption application with two balance resistors above N-P MOS drain node was introduced. The operating current can be reduced by half supply current and two drain resistors, which not only improve magnitude symmetry of output signals but also providing negative conductance. Related structures were compared in this chapter. In chapter 5 will summarized all of this work.. 4.

(16) Chapter 2 Basics of Voltage Controlled Oscillators. Chapter 2. Basics of Voltage Controlled Oscillators ________________________________________________________ 2.1 General Oscillators Considerations This Oscillator was viewed as feedback circuits. It has a self-sustaining mechanism which noise to grow and become periodic signal. [2] The feedback is circuits show in Figure2.1 It’s consideration of the simple linear feedback system depicted with the overall transfer function as following Y (s) H (s) = (2.1) X ( s) 1 − H ( s) A self-sustaining mechanism arises at the frequency s0 if H ( s 0) =+1, and the oscillation amplitude remains constant if s0 is purely imaginary，i.e., H ( s 0 = jw0) =+1. The above rules. are called Barkhausen’s criteria. Thus , according to the Barkhausen’s criteria，two conditions must be simultaneous met at ω0： (1) the loop gain, H ( jw0) ,must be equal to unity. (2) the total phase shift around the loop, H ( jw0) , must be equal to zero (or 180° if the dc feedback is negative).. 5.

(17) Chapter 2 Basics of Voltage Controlled Oscillators. (a). (b). Figure 2.1 (a) Feedback oscillatory system (b) Types of Frequency Selective network. The two port model in microwave theory is shown in Fig 2.1. Due to two-port network was closed feedback loop; generally we also can use one port equivalent circuit to discussion two port network oscillator illustrate in Fig 2.2:. Fig 2.2 One port view of oscillator. Generally frequency selective network had used LC tank resonator (LC tank oscillator)，the LC tank is shown in Figure 2.3 (a) and (b) with parasitic resistances.. (a). (b) parallel circuit LC resonator. series resonator. Figure 2.3 LC resonator. 6.

(18) Chapter 2 Basics of Voltage Controlled Oscillators. The LC tank does not oscillate indefinitely because the resistor was dissipation stored energy (Q). Below equation: Q=. X = Im [ Z ] X , R R = Re [ Z ]. (2.2). The Q is stored energy; X is of imaginary part, R is real part resistor. A real component sure includes some parasitic resistances. So we know the circuit hasn’t a finite Q. that will be influence Phase-Noise and Rp effect Oscillator condition.. 2.1.1 Negative-Resistance Oscillator In the idea of one-port model on feedback system, we can use negative resistance to reach oscillation. It is an active network generates an impedance equal to –Rp so that when the equivalent parallel resistance be Rp. Rp// (-Rp)= ∞ in this condition the tank oscillates indefinitely and allow steady oscillation. This active circuit is replaced by a crossed-coupled pair which supplies the negative resistance to cancel out the energy loss due to the positive resistance of the LC tank. Figure 2.4 shows the schematic of the crossed-coupled pair and its small signal model. The negative impedance is derived as Ix=gm2V2=-gm1V1 (2.3) And. Vx = V 1 − V 2= −. Ix Ix − gm1 gm2. (2.4). 7.

(19) Chapter 2 Basics of Voltage Controlled Oscillators. Thus, Vx 1 1 = Zin = −( + ) Ix gm1 gm2. (2.5). If gm1=gm2=gm then Vx 2 = Zin = − Ix gm. (2.6). (a). (b). Figure 2.4 (a) Schematic of the crossed-coupled pair (b) Small signal model of (a). 2.1.2 LC Tank and Oscillator Conditions In the LC oscillator circuits, LC tank determines main operation frequency condition. Above negative resistance exposition LC oscillator include an active part to generate the negative resistance and a resonator network. And we know the operation frequency can be expressed as f =. 1 2π LC. 8. (2.7).

(20) Chapter 2 Basics of Voltage Controlled Oscillators. L and C can be series or parallel resonator show in Fig2.5 (a) (b), Ls and Lp represent integrated circuit inductance (also be lump component), Cs and Cp represent integrated circuit capacitance (also be lump component), Rx and GX represent the negative resistance and conductance generated by active part respectively. Rs and Rp represent the loses of the resonators.. Cs. Ls. Rs Gx. Rx (a). Rp. Cp. Lp. (b). Figure 2.5 (a) Series LC resonator (b) Parallel LC resonator. In above section introduce negative resistance, who to get oscillator. One port negative resistance oscillator show in Figure2.6 Zin=Rin+jXin (active device input impendence). Usually the Zin should depend on bias voltage, current and frequency so, we can be expressed as [3] , Zin = ( I , jω ) = Rin( I , jω ) + jXin( I , jω ) and load impendence expressed as ZL=RL+jXL and (ZL+ Zin)I=0 When oscillator should be RL+ Rin=0, XL+Xin=0 (RL>0, Rin<0), in the stable. 9.

(21) Chapter 2 Basics of Voltage Controlled Oscillators. Figure2.6 One port oscillator circuit. ZL= -Zin and two Γ relationships must be below relation:. ΓL =. Z L − Z 0 − Z in − Z 0 Z in + Z 0 1 = = = (2.8) Z L + Z 0 − Z in + Z 0 Z in − Z 0 Γin. The Equation Explain the circuit instable when ( Rin ( I , jω ) + RL < 0 ),in any time any noise or signal can driver circuit in the LC oscillator operation frequency ω . When I increase some value makes Rin( I , jω 0) + RL = 0 and Xin ( I , jω 0) + XL = 0 , that oscillator continuing stable. However, it isn’t promises stable oscillator at all time, so we must be quantification Z become to ZT ( I , s ) = Zin( I , s ) + ZL ( s) using Taylor series: ZT ( I , s ) = ZT ( I 0 , s0 ) +. ∂ZT ∂s. S0 , I 0. δS +. ∂ZT ∂I. S0 , I 0. δ I (2.9). (2.9) equal zero, at oscillator ZT ( I , s ) must be zero. At (2.9) S 0 = jω 0 original oscillator frequency. define ZT ( I 0 , s0 ) =0 and. ∂ZT ∂Z = − j T , ∂s = ∂α + j∂ω can get (2.10) ∂s ∂ω. 10.

(22) Chapter 2 Basics of Voltage Controlled Oscillators. δ S = δα + jδW =. −∂ZT ∂ZT. ∂I S0 , I 0. δI =. ∂s. − j(. ∂ZT. ∂I. )(. ∂ZT ∗. ∂ZT ∗ 2. ) ∂ω δ I (2.10). ∂ω. When δ I >0 then δα <0 so we can get (2.11). ⎧ ∂Z ∂ZT ∗ ⎫ Im ⎨ T ⎬<0 ⎩ ∂I ∂ω ⎭ ∂RT ∂X T ∂X T ∂RT − > 0 (2.11) ∂I ∂ω ∂I ∂ω Due to passive load, ∂RL / ∂I = ∂XL / ∂I = ∂RL / ∂ω = 0 follow (2.11) to (2.12) ∂Rin ∂ ∂X ∂R ( X L + X in ) − in in > 0 (2.12) ∂I ∂ω ∂I ∂ω Usually, ∂Rin / ∂I > 0 , if ∂ ( X L + X in ) / ∂ω 0 can make steady oscillate, so we can use high Q circuits to get high steady. Designing a good Oscillator not only considers steady oscillate that has other consider just like voltage bias (operation point), but also maximum output power and noise.. 2.2 MOS Varactor In this thesis, we design VCO used MOS varactor that has much advantage that just like high turning rang and low phase-noise for VCO circuits than common PN junction varactor. Generally VCO was used the p-n junction varactor or MOS varactor in LC tank. In this section we will study the MOS varactors operation mode in CMOS process [4].. 11.

(23) Chapter 2 Basics of Voltage Controlled Oscillators. 2.2.1 MOS Varactors Operation Mode. Fig 2.7 Generally P-MOS cross section view structure. Fig 2.8 P-MOS C-V and operation mode. Figure 2.7 is shown the cross section view and capacitance V.S. voltage (C-V) of general P-MOS. Figure 2.8 is shown we connect D,S,B together and bias a variation voltage to get the result. Generally accumulation and inversion often used operation mode for vractor in VCO. We use three cases explanation which the operation mode, capacitor with bias voltage and C-V curve each other relationship.. 12.

(24) Chapter 2 Basics of Voltage Controlled Oscillators. Case 2: DS=Vtune B=VDD. Case 1:DS=Vtune B=GND Term Term7 Num=7 Z=50 Ohm. Term Term3 Num=3 Z=50 Ohm. TSMC_CM018RF_PMOS_RF M10 Type=1.8V twin-well lr=0.18 um wr=8 um vtune nr=64. vdd. TSMC_CM018RF_PMOS_RF M2 Type=1.8V twin-well lr=0.18 um wr=8 um vtune nr=64. Case 3:DS=Vtune B=VDD Bias=0.8 DC_Feed DC_Feed1. Term Term2 Num=2 Z=50 Ohm. DC_Block DC_Block1 vdd. V_DC SRC3 Vdc=vddp. TSMC_CM018RF_PMOS_RF M7 Type=1.8V twin-well lr=0.18 um vtune wr=8 um nr=64. Figure 2.9 Schematic of P-MOS Capacitor Circuits. Figure 2.10 Different Operation Mode of P-MOS C-V Curve. 13.

(25) Chapter 2 Basics of Voltage Controlled Oscillators. In those cases, we had been used different bias voltage explanation that: Case 1: Using VD and VS to connect to Vturn, MOS and Body connect to ground which shown Figure 2.9 and the C-V curve is shown Figure 2.10, the case 1 is a normal operation mode that show capacitance increase form -5V to 5V,In the circuits application the Vturn was defined by maximum operation voltage . In here, we discuss 0-1.8V Voltage variation in all case. The MOS capacitance value had been increased by Vtrun sweep when Voltage been increased which MOS’s depletion region also became to narrow at the same time. Following the depletion region narrow, the capacitance value will increase. In case 2, we connected Vbody to VDD =1.8V as shown in Figure 2.9 and Figure 2.10. The capacitance values were 5.5E-13 F and 4E-13 F reference at 0V in case 1 and 2 results respectively which enhance capacitance turning range that meaning can increase frequency turning range because the narrow speed of MOS depletion region is cause by the Vbody potential. Last case, case 3: The case of fundamental purpose in simulation real VCO consideration at VG voltage. It has been reduced enhance capacitance of case 2 by VG potential influence.. 14.

(26) Chapter 2 Basics of Voltage Controlled Oscillators. 2.3 Phase Noise The Phase-Noise is a very important parameter for VCO that is influencing down-converter or up-converter signal noise rate (SNR) in mixer. It will make signal interference RF transceivers normally working. General the noise generated main by the active devices but passive also make it that will include some active/passive noise to output signal. Due to CMOS devices are a nonlinear component, which uses CMOS device to design circuits that will have nonlinear phenomenon. It makes noise voltage, AM/PM modulation current-noise and all nonlinear problems to include carrier signal. The phase-noise was defined show in fig 2.11 and uses equation (2.13) to explain the conception of phase-noise formation. From (2.13) sample defends for phase-noise L(Δf ) ,. fig 2.11 Output power spectrum for VCO. 15.

(27) Chapter 2 Basics of Voltage Controlled Oscillators. that domain parameter Pout and N (1Hz − BW ) mean given some offset frequency fixed noise power. The ideal Oscillator that phase-noise should be - ∞ . we can refer above Fig 2.11 and define basic phase-noise equation below Equation2.13. L(Δf ) =. N (1Hz − BW ) Pout. (2.13). L(Δf ). ：Reference at Δf Hz phase-noise. N (1Hz − BW ). ：1Hz bandwidth fixed noise-power at Δf Hz. Pout. ：Carrier output-power (dBm). 2.3.1 A Linear and Time-Invariant Phase-Noise Theory But phase-noise should be more complex, We can follow phase-noise theory paper [5]. Get Equation 2.14. From Equation (2.14), The units is thus proportional to the log of a density. That are commonly expressed as “decibels below the dBc/Hz, specified at a particular offset frequency from the carrier frequency . For example, one oscillator center frequency at 1.5Ghz. we went to get phase noise at 100Khz or 1MHz as “-107 dBc/Hz at a 100kHz offset” and “-123 dBc/Hz at a 1MHz offset” respectively. We can know Q factor one of do mainly effect phase-noise, the other Psig .If we hope get. 16.

(28) Chapter 2 Basics of Voltage Controlled Oscillators. good phase-noise performance, that can use High Q factor inductance (resonator) or increase output power. ⎡ 2kT L{Δω} = 10 log ⎢ ⎢⎣ Psig. ⎛ ω0 ⎞ ⎜ ⎟ ⎝ 2QΔω ⎠. 2. ⎤ ⎥ (2.14) ⎥⎦. fig 2.12 Leeson law of Phase noise But Equation (2.14) can’t perfect expect phase-noise that show in figure 2.12 oblique line that don’t has consider Δω 1 / f 3 corner. So we can use Leeson’s model. Equation (2.15) that included Δω 1 / f 3 corner and it uses measurement results to fit and got this Leeson’s curve fit model. Although Δω 1 / f 3 generates from 1/ f noise or is call as flicker noise by active devices (MOS…ect.) but how to transform and up-convert become Δω 1 / f 3 region. Leeson law doesn’t have sensible exposition. The Linear time-invariant and phase-noise theory has been presented in 1966 by Leeson.. 17.

(29) Chapter 2 Basics of Voltage Controlled Oscillators. Equations (2.15) F is device excess noise number experience parameter, Q factor tell us Improve phase-noise the same above considers. ⎡ 2 FkT L{Δω} = 10 log ⎢ Psig ⎣⎢ Q=. ⎡ ⎛ ω 0 ⎞ 2 ⎤ ⎛ Δω 1 / f 3 ⎞ ⎤ ⎢1 + ⎜ ⎟⎥ ⎟ ⎥ ⎜1 + Δω ⎠⎟ ⎥ ⎢⎣ ⎝ 2QΔω ⎠ ⎥⎦ ⎝⎜ ⎦. (2.15). R 1 = ω 0 L ω 0GL. 2.3.2 A Linear and Time-Varying Phase-Noise Theory. A Linear and Time-Varying Phase-Noise Theory considered impulse current inject to LC resonator that made phase and amplitude influence although influence reduce by time but phase change doesn’t restore by that. Show in fig 2.12 upper Fig inject a noise at π time, that waveform only changed amplitude no phase change, if inject noise at zero crossing point just like fig 2.12 lower Fig that no amplitude changed but waveform move front mean phase will be changed. Follow the increase time above change phenomenon, amplitude and phase both be changed. Therefore analyze oscillators’ noise injection used two theory to improve phase-noise phenomenon.. 18.

(30) Chapter 2 Basics of Voltage Controlled Oscillators. fig 2.13 phase be changed by impulse current versus time Show fig 2.13 The signal transport phase and amplitude be influenced. Following. fig 2.14 The equivalent block diagram of the process time we integration all signal and signal be modulated (PM) finally signal output. Among the signal transport follow. i (t ) form thermal noise and active device (MOSFET) such as 1/ f qmax. 19.

(31) Chapter 2 Basics of Voltage Controlled Oscillators. noise and Γ(ω0t ) (ISF(Impulse Sensitivity Function)) generated by LC oscillator such as. figure 2.14 theory that will changed LC oscillator output signal phase-noise and amplitude by injection noise. and all signal be integrated to φ (t ). φ (t ) =. 1 ⎡ c0 qmax ⎢⎣ 2. ∞ t ⎤ + ( ) τ τ i d c ∑ n ∫−∞ i (τ ) cos( nω0τ ) dτ ⎥ ∫−∞ n =1 ⎦ t. (2.16). Current noise source Equation (2.17) and ω0 >> Δω (2.17) to (2.16) i (t ) = I m ⋅ cos ⎡⎣( mω0 + Δω ) t ⎤⎦. (2.17). Get Equation (2.18). φ (t ) ≈. I m cm sin(Δωt ) 2qmax Δω. (2.18). Assume Equation (2.18) small amplitude disturbance get results in two equal-power sidebands symmetrically disposed about the carrier ⎛ Im Cm ⎞ PSBC ( Δω ) ≈ 10 log ⎜ ⎟ ⎝ 4q max Δω ⎠. (2.19). And using above result can derive the white noise source. The current of white noise source can be expressed as. in 2 Im = +f. ⎛ i 2n ∞ 2 ⎞ ⎜ Δf ∑ cm ⎟ PSBC ( Δω ) ≈ 10 log ⎜ 2 m =0 2 ⎟ ⎜ 4q max Δω ⎟ ⎜ ⎟ ⎝ ⎠. (2.20). 20.

(32) Chapter 2 Basics of Voltage Controlled Oscillators. From Parseval’s theorem ∞. ∑c. m=0. 2 m. =. 1. π∫. 2π. 0. Γ ( x ) dx = 2Γ 2rms 2. (2.21). And sinusoid voltage (2.20) can get phase noise by white noise ⎛ i 2n 2 ⎞ ⎜ Δf Γ rms ⎟ ⎟ L ( Δω ) ≈ 10 log ⎜ 2 2 ⎜ 2q max Δω ⎟ ⎜ ⎟ ⎝ ⎠. And I m =. (2.22). in 2 4 KT = +f R. 2 2 ⎡ 4 KT ⎤ 2 ⎛ ω0 ⎞ Γ rms ⎜ L ( Δω ) ≈ 10 log ⎢ ⎟ ⎥ ⎢⎣ Ps ⎝ QΔω ⎠ ⎥⎦. (2.23). (2.21) tell us, that can enhance Q values and fit waveform (reduce Γ 2rms (ISF) value) to improve phase-noise interference from white noise source. And VCO inside 1/ f spectrum noise power density I n2,1/ f = in 2. ω1/ f +ω. (2.24). (2.24) is 1/ f corner frequency into (2.22) we can get 1/ (+ω )3 region phase-noise (2.25) ⎛ i 2n 2 ⎞ ⎜ Δf C0 ω 1 / f ⎟ ⎟ (2.25) ⋅ L{Δω} = 10 log ⎜ 2 ⎜ 8qmax Δω 2 Δω ⎟ ⎜ ⎟ ⎝ ⎠. 21.

(33) Chapter 2 Basics of Voltage Controlled Oscillators. So white noise injection by current 1/ f noise into VCO that make VCO output signal phase be changed and changed phase quantity by noise or waveform. Above section we know phase-noise formation that from noise injection and device inside 1/ f noise. We discuss figure 2.15 final step “phase-modulation”, the 1/ ( +ω ) and 3. 1/ ( +ω ) corner frequency +ω1/ f 3 can get equation by compare (2.22) and (2.25) that below 2. equation. Δω 1 / f. 3. ⎛Γ ⎞ C2 = ω 1 / f ⋅ 02 = ω 1 / f ⋅ ⎜ dc ⎟ 4Γ rms ⎝ Γ rms ⎠. 2. (2.26). fig 2.15 Evolution of phase-noise. 22.

(34) Chapter 2 Basics of Voltage Controlled Oscillators. The noise signal into circuit become phase-noise that from c0 , c1 , c2 , c3 by ω0 , 2ω0 , 3ω0 integrate total signal and become phase-noise (middle Figure).and phase-modulation will signal up convert to ω0 . Finally, In this theory gets good phase-noise performance that must reduce 1/ ( +ω ). 3. phase-noise and Δω 1 / f 3 but it relate to c0 (ISF DC).so we need have odd-symmetry (output waveform) to improve .the other way, active component noise (1/ f noise) we can use increase gm to reduce phase-noise but that will consume more power and increase voltage swing also need more current. So power- consumption trade-off between Q-factor, voltage swing and odd-symmetry waveform.. 2.4 Voltage Controlled Oscillator (VCO) The Voltage-Controlled-Oscillator (VCO) is provided signal to mixer up/down convert frequency supply Analog-digital convert (ADC or DAC) or antenna to transport relate signals and that also can be used on frequency divider, phase-locked loops, clock recovery circuits and frequency synthesizers. In the VCO that have some important specification, like output power/power flat in turning voltages, turning range (different voltages different output frequency), Phase-noise (it’s very important spec. for VCO) and power-consumed. In different standards may need narrow channel spacing, low-Phase-noise and some designates request.. 23.

(35) Chapter 2 Basics of Voltage Controlled Oscillators. 2.4.1 Basic Properties Above section, we knew oscillator condition and how to oscillator. In this section we will introduction VCO spec. detail following below : 1.. Pulling effect: In different (non-ideal load) of output impedance may made oscillator. frequency variation. Usually uses VSWR (Voltage Standing Wave Ratio, equation (2.27)) by 1.5 to determine signal variation. In the real communication system, device operation may be on/off in any time and some operation mode, like saving mod that will made some on/off and changes output impedance that may have some frequency variation. +ω ≅. 2.. ω0. 1+ Γ VSWR − VSWR ) ,VSWR = ( 2Q 1− Γ −1. (2.27). Pushing effect: The result of variation by power supply change that will change output. frequency. The power supply be changed, the reason often come form share power source In the circuits. So we need a stable circuit make sure voltage change situation to be minimums. 3.. Phase noise: An active device operation mode(gm), inductance Q-factor, output power. amplitude, above parameter will effect phase-noise. A bad phase-noise would corrupt wanted signal in the receiver. we called reciprocal mixing. 4.. Output power and harmonic rejection: we need to follow and consider. communication system specification to determine how much output power we need to drive the next stage, that harmonic rejection means it is closed to a sinusoidal waveform and often need under -20dbm difference main frequency output power.. 24.

(36) Chapter 2 Basics of Voltage Controlled Oscillators. 5. Turning range: the same of all parameter for communication request specification. Every communication standards has immobile frequency just like WiMAX WSC (Wireless Communication Services) that has two band 2.305~2.320GHz and 2.345~2.360GHz.Reference relate standards to design be requests. Generally VCO uses capacitance and bias voltage to change frequency to request frequency band. In next section, we will use sample methods and follow to introduce design of VCO.. 2.4.2 Design of LC VCO Methods Recently differential VCO topology be used in many paper that had two output signal phase difference 180 degree feature. In fig.2.16 inductance and capacitance can generate resonance frequency by equation (2.28). L C Figure 2.16 Inductance and capacitance of resonance circuit. f resonance =. 1 2π LC. (2.28). We can follow (2.28) to get to want oscillator frequency. Usually we use the equation to determine our oscillator. But actuality VCO oscillator should be fixed to become equation (2.29). Due to MOS also like a capacitance structure that has some parasitic Capacitor and that will effect on resonance frequency. So we must consider MOS parasitic Capacitor to make sure get reasonable frequency. 25.

(37) Chapter 2 Basics of Voltage Controlled Oscillators. f resonance =. 1 2π L(C + Cmos ). (2.29). But, real oscillation frequency we have defined to (2.30), that not only consideration. Cmos but also CV var which real operation mode of VCO circuits. The CV var is MOS gate depletion capacitance by voltage VG potential.. f real _ MOS =. 1 2π L(C + Cmos + CV var). (2.30). 26.

(38) Chapter 2 Basics of Voltage Controlled Oscillators. Circuits Design Flow is shown in Figure 2.17 :. Active circuit structure. L-Q optimization LC TANK. C- turning range. Buffer Figure 2.17 VCO Circuits Design Flow First step, we must know what kind of characteristics are we need it, just like High output power, low phase-noise , high turning range and power consumption…etc. If we were determined structure, next step. Selecting right LC Tank that cause characteristics of VCO, generally inductance Q factor determine to the Phase-noise good or bad which selecting a High Q factor is important for low phase-noise and use LC component to select oscillation frequency. Usually inductance already be defined then determined capacitance and frequency turning range at operation frequency. Finally Buffer is using to DC-block and 50Ω matching for measurement instrument.. 27.

(39) Chapter 2 Basics of Voltage Controlled Oscillators. 2.4.3 Design Follows of VCO Figure 2.18 common design follows for RFIC. Generally we must know what kind of topology that will be used to designs VCO. Example: high output power, low phase-noise. Consideration of VCO topology. Get design spec. and circuit goal. Use CAD software simulations (goal spec.). Consideration of Circuits of PAD parasitic effect (circuit level). Use Cadence Virtuoso layout and check DRC and LVS. Correct layout-rule. extract all parasitic of layout connect line and uses ADS computing that effect for circuits.(PEX) NO. Check Post- Simulation result data cover spec.? YES. Fabricate. Figure 2.18 Common VCO project design follows. 28. (Goal spec.).

(40) Chapter 2 Basics of Voltage Controlled Oscillators. , wide turning range ...ect. Moreover circuits must be goal spec. and we design and simulate circuits uses by simulation software ADS. This is important for RFIC. The Pad and layout lines parasitic effect often direct influence circuit performance. So about parasitic extract detail must be careful that has two methods to equivalent pad parasitical quantities: 1.uses equivalent circuit illustration Figure 2.19:. Bond wire. Pad. Fig 2.19 pad & bonding wire equivalent circuit The values are appraised. Pad C ≅ 60fF, R ≅ 250Ohm, L ≅ 2nH and parasitical-resistor about 10Ohm. 2: uses EM software (ADS Momentum, HFSS and IE3D) to extract pad layout 2-port S-parameter substitute circuit illustration Fig 2.20:. 29.

(41) Chapter 2 Basics of Voltage Controlled Oscillators. (a). (b). Figure 2.20 (a) S-parameter of substitute circuit (b) extrication of pad layout. We substitute the circuits by employ EM software extract data s-parameter file SXP(X=1,23…) and run simulation again that has almost get real characteristic before fabrication.(because maybe have some manufacturing process inaccuracy),we say parasitical-. 30.

(42) Chapter 2 Basics of Voltage Controlled Oscillators. quantity maybe make circuit fail , so we usually incessant check S-parameters of layout lines whether it influence the origin (goal) circuit characteristic or not and do some fixes on circuits to keep circuit characteristic.. 31.

(43) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Chapter 3 Design of Low-Power Current-Reused CMOS VCO. In this chapter, we will introduce to design of low power VCO. Low phase-noise is very important for any wireless communication systems that want to get low phase-noise and low power. We need some circuits techniques reach it. In below section, we will introduce low power structure circuit and explain it what different to convention.. 3.1 Induction of Low-Power Current-Reused VCO Structure In mobile and portable communication equipment the supply voltage should be as low as possible. To increase equipment operating time, this shows how importance of low-power circuits. A voltage controlled oscillator (VCO) is an important block and among the blocks of any transceiver that applied in mobile and portable equipments. Show Figure3.1,It is low-power VCO structure[6] that uses one current path improve on conventional VCO circuits and the two currents path by this way in generally can reduce half current costs in the circuits.. 32.

(44) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Figure 3.1 Schematic of the basic topology of current-reused Differential LC-VCO [6] The VCO be used P-MOS and N-MOS transistors in the cross-connected pair. The P&N-MOS can be reduced by half supply current and the degeneration source resistors can reduce body effect and improve magnitude symmetry of output signals. Also it is only one current the core power-consumed will be controlled. Figure 3.2 Shows N-PMOS cross pair large-signal equivalent circuits, left circuit is no resistance original circuit that will discuss this form here, middle circuit is first-half period equivalent circuit (when the voltage at node X is high and low) and two parasitic capacitances Cx=C/2+Cpx and Cy=C/2+Cpy respectively from P-NMOS. The first-half period. 33.

(45) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. During the first half-period as shown in the Figure 3.2, the M1 and M2 are ON and the current flows from VDD through the turning inductor L to ground. During the second half-period, the M1 and M2 are off and the current flows in the opposite direction through the capacitors Cx and Cy. (Note that in the conventional differential VCO, the cross-connected transistors switch alternately, the P-N MOSFETs switch at the same time. During the first half-period of oscillation, the P-N MOSFETs operate in triode mode near the peak of the voltage swing.. . Figure 3.2 N-PMOS cross pair large-signal equivalent circuit [6]. 34.

(46) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Gn = −. gmp ⋅ gmn gmp + gmn + Rs ⋅ gmp ⋅ gmn. (3.1). From Equation (3.1), Gn (negative conductance) of Figure 3.1 gmp(transconductance of PMOS) , gmn (transconductance of NMOS) and source resistor Rs.. 3.2 Design of Low-Power Current-Reused VCO for L-Band System The L-band application uses frequencies from 1GHz to 2GHz that covered some mobile broadcast band like T-DMB, DVB-H, GPS, Galileo and some cell-phone band likes WCDMA, so lower power-consumed device development is requested. In next section, we will show my circuits that not only use in L-band and the other circuit uses on new wireless application WiMAX.. 3.3 VCO Simulation and Measurements for L-Band System. 3.3.1 Design of Structure In this chapter, all circuit uses current-reused topology that has low-current and saves Power, because the N-P MOS pair operates in triode region near the peak of the voltage swing, the voltage swing is only limited by the power supply and can use source Rs to control the DC as current well as the peak dynamic current. Show in Figure 3.2, this circuit used in L-Band application and the fabricated by TSMC 0.18μm mixed signal/RF CMOS 1P6M process technology. It is a 1.8V and current 1mA. 35.

(47) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. low-power CMOS voltage-controlled oscillator with the output buffer is matched to 50 ohm for standard. The output buffer used 1V voltage supplyand current 3.77mA (Left) and 3.74mA (Right) two sides respectively.. Figure 3.3 Schematic of the basic topology of current-reused VCO with output-buffers. 3.3.2 L-Band VCO Simulation Characteristics The study of circuit simulated, analyzed and extracted layout parasitic by Agilent-ADS software. The VCO core operates voltage, current, power-consumed, 1.8V and 1mA, 1.854mW respectively and output power is -4.375dBm.. 36.

(48) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Shown in Figure 3.4 oscillation frequency at 1.61 Ghz and has -15dbm 2nd harmonic error value. Figure 3.5 turning range is from 1.367 GHz to 1.639 Ghz. The phase noise 100 KHz and 1MHz offset are -107 dBc/hz and -128.388 dBc/hz respectively. The total specifications are shown in Table 3.1. In Table 3.2 and 3.3 are manufacture process and temperature variation respectively. The simulation are little variation results that can be accepted.. 37.

(49) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. ( No manufacture processing variation and interconnect effect ) Transient Characteristics. Figure 3.4 Transient simulation of L-band current-reused VCO. Harmonic Characteristics Turning Range. Figure 3.5 Turning range simulation of L-band current-reused VCO. 38.

(50) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Phase-noise：. Figure 3.6 Phase-noise simulation of L-band current-reused VCO. Table 3.1 Simulation specifications of L-band current-reused VCO. #. Operation Voltage. 1.8 V. Operating Frequency. 1.367GHz ~1.639GHz. Turning Range. 19.21%. Power consumption. (core). 1.854mW. Power consumption. (Buffer). 7.51mW. Pout.(dBm). -4.375. Phase-Noise@100KHz (dBc/Hz). -107. Phase-Noise@1MHz(dBc/Hz). -128. (#) Power consumption(Buffer) Total of two side buffer power-consumed. 39.

(51) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. (Manufacture processing variation) Table 3.2 Manufacture processing variation of L-band current-reused VCO Manufacture processing variation results TT FF Turning Range Pout (dBm). 18.10 -4.3. Phase-Noise@100KHz (dBc/Hz) Phase-Noise@1MHz (dBc/Hz) Power consumption(core) Power consumption(Buffer). 19.12 -5.1. SS 17.18 -5.3. -103.219. -105.250. -101.195. -128.157. -128.704. -127.043. 1.8mW. 2.5mW. 1.3mW. 7.5mW. 10.7mW. 5.05mW. (#) Power consumption(Buffer) Total of two side buffer power-consumed. (Temperature variation) Table 3.3 Temperature variation of L-band current-reused VCO Temperature variation results -40 25 Turning Range Pout (dBm) Phase-Noise@100KHz (dBc/Hz) Phase-Noise@1MHz (dBc/Hz) Power consumption(core) # Power consumption(Buffer). 19.3%. 19.1%. 85 20%. -3.25. -2.6. -4.4. -104.62. -105.27. -102.97. -128.23. -128.71. -126.85. 2.556mW. 2.592mW. 2.718mW. 10.7mW. 10.6mW. 10.2mW. (#)Power consumption(Buffer) Total of two side buffer power-consumed. 40.

(52) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. (With interconnect line effect - Post Simulation) The interconnect lines impact circuits characteristics that maybe make circuit function fail without extracting interconnect line. Illustration Figure 3.7 slant lines was extracted interconnect lines and uses less and short interconnect lines in layout design that makes sure the circuit stable and decrease some don’t need parasitism. We used Agilent ADS Momentum to simulation this experiment.. Figure 3.7 Interconnect lines extraction of L-band current-reused VCO. 41.

(53) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. The post simulation is important work at RF circuit which has influence circuit characteristic. Shown in Figure 3.8 oscillation frequency at 1.6 Ghz and has -17.56 dBm 2nd harmonic error value. Figure 3.9 turning range is from 1.357 GHz to 1.626 Ghz. The phase noise 100 KHz and 1MHz offset are -107.67 dBc/hz and -128.332 dBc/hz respectively. The post/pre simulation specifications are shown in Table 3.4 and Table 3.5 reference of VCO comparability. Shown In Figure 3.11 and 3.12 are layout and microphotograph of VCO respectively.. 42.

(54) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Post-simulation results Transient Characteristics. Figure 3.8 Transient post-simulation of L-band current-reused VCO. Harmonic Characteristics Turning Range. Figure 3.9 Turning range post-simulation of L-band current-reused VCO. 43.

(55) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Phase-Noise：. Figure 3.10 Phase-noise post-simulation of L-band current-reused VCO. Table 3.4 L-band current-reused VCO Results of Post-simulation and pre-simulation Post- simulation. Per- simulation. Operation Voltage. 1.8 V. 1.8 V. Operating Frequency. 1.357GHz ~1.626GHz. 1.367GHz ~1.639GHz. Turning Range. 18.036%. 19.21%. Power consumption. (core). 1.85mW. 1.854mW. Power consumption. (Buffer). 7.51mW. 7.51mW. Pout.(dBm). -4.2. -4.375. Phase-Noise@100KHz (dBc/Hz). -107. -107. Phase-Noise@1MHz(dBc/Hz). -128. -128. #. (#)Power consumption(Buffer) Total of two side buffer power-consumed. 44.

(56) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Table 3.5 Reference of L-band current-reused VCO Results compare. [Ref.] supply Technol. Freq. Year voltage This Work [6]06’ Simulation.. [7]05’ Measurement. [8]03’ Measurement. [9]05’ Measurement. [10]06’ Measurement. [11]03’ Measurement. [12]07’ Measurement. [13]06’ Measurement. Turnin g Range. PDC (core). Phase-Noise @100KHz (dBm) (dBc/Hz) Pout.. Phase-Noise @1MHz (dBc/Hz). CMOS 19.21 1.854m 1.57G 0.18um % W. -4.3. -107. -128.38. 1V. CMOS 0.18um. 1.6G. N/A. 0.1mW. N/A. N/A. -121. 1.25V. CMOS 0.18um. 2G. N/A. 1mW. -7.4. -103. ~-121. 1.8V. 2V. CMOS 5GHz 0.18um. 36%. 80mW. -15. N/A. -85. 2V. SiGe BiCMO 2.5GH 20% S z 0.25-um. 32mW. -12. N/A. -115. 2.5v. BiCMO 3.9GH S 34% 11.2mW N/A z 0.25um. N/A. -121. 1V. CMOS 4.4Ghz 59% 0.13 µm. 3.0mW. N/A. N/A. -109. 1V. CMOS 0.18 µm. 2.4Ghz 4.7 N/A Ghz. 3.4mW. N/A. N/A. -122.42@2.4G -123.43@4.7G. N/A. -88.19. N/A. CMOS 0.35. 0.8V. ⎧m 3M2P N-Well. 1.5G. N/A. 9 mW (VCO + buffer). 45.

(57) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Figure 3.11 Layout of L-band current-reused VCO. Figure 3.12 Microphotograph of L-band current-reused VCO. 46.

(58) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. 3.3.3 L-Band VCO Measurement Characteristic. In this section, we will discuss Measurement results. The Measurement results demonstrate the central oscillation signal of 1.49 GHz to be associated with the 269 MHz turning range and -125 dBc/Hz phase noise at 1 MHz offset. The power consumption of the VCO core is only 1.8 mW. The Measurement result evaluated by means of a figure of merit is about 186.11 dBc/Hz by equation (3.2). 2 ⎡⎛ ⎤ fm ⎞ ⎢ FOM = L { fm} + 10 log ⎜ ⎟ PDC ⎥ (3.2) ⎢⎝ fo ⎠ ⎥ ⎣ ⎦. Figure 3.13 Measurement Phase Noise result of L-band current-reused VCO. 47.

(59) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Figure 3.14 Measurement current result of L-band current-reused VCO. Figure 3.15 Measurement turning range result of L-band current-reused VCO. 48.

(60) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Figure 3.16 Measurement output power result of L-band current-reused VCO. Table 3.6 Results of simulation and Measurement Spec.. Simulation. Measurement Result. Voltage. 1.8 V. 1.8V. Current(core). 1.02mA. 1mA. Frequency. 1.357GHz ~1.626GHz. 1.24G~1.46G. Output-power Pout.(dBm). -4.2dBm. -3.37dBm. Power consumption (total). 1.85mW. 1.8mW. Turning Range. 18.04%. 16.30%. Phase-Noise@100KHz. -107.6. ~ -100. Phase-Noise@1MHz. -128.33. -123~-125.35. FOM. -189.91(1.836mW)@1M -186.11(1.8mW) @1M. Die Size. 1.36 X 1.29 mm. 49.

(61) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. 3.4 Design of Low-Power Current-Reused VCO for WiMAX FWA System The WiMAX FWA (Fixed Wireless Access) is fixed technology that didn’t like mobile application can use in pocket devices. But he has some advantage just like high transmission speed and high distance range. In this section, the VCO is application in IEEE 802.16e WMAX Fixed Wireless Access (FWA) under 2.50 ~ 2.69GHz.. 3.5 VCO Simulation and Measurements for WiMAX FWA 3.5.1 Design of Structure The main structure is the same for above L-band VCO. But we use source follower Buffer for some reason. Using source follower structure can get wide-band matching that can prevent manufacture processing variation and also influence buffer matching band variation than common source structure.. Figure 3.17 Schematic of the WiMAX FWA current-reused VCO with source follower output-buffers. 50.

(62) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. 3.5.2 WiMAX FWA VCO Simulation Characteristics. The study of circuit simulated, analyzed and extracted interconnect lines parasitic by Agilent-ADS software. The VCO core operates voltage, current, power-consumed, 1.5V and 4.1mA, 1.669mW respectively and output power is -5.9dBm and operation frequency 3.142GHz~3.839GHz turning range 19.954% phase-noise -126.3dBc/Hz at 1MHz offset frequency in pre-simulation. Shown in Figure 3.18 oscillation frequency at 3.1 Ghz and has -24.68 dBm 2nd harmonic error value. Figure 3.19 turning range is from 3.14 GHz to 3.83 Ghz. The phase noise 100 KHz and 1MHz offset are -104.65 dBc/hz and -126.309 dBc/hz respectively. The total specifications are shown in Table 3.7. In Table 3.8 and 3.9 are manufacture processing and temperature variation respectively. The simulation are little variation results that can be accepted. Shown in Figure 3.23 oscillation frequency at 3.36 Ghz and has -25.08 dBm 2nd harmonic error value. Figure 3.24 turning range is from 3.34 GHz to 3.91 Ghz. The phase noise 100 KHz and 1MHz offset are -101.17 dBc/hz and -123.46 dBc/hz respectively. In Table 3.11 and 3.12 are manufacture processing and temperature variation respectively.The post/pre simulation specifications are shown in Table 3.13 and Table 3.14 reference of VCO compare. Shown In Figure 3.26 and 3.27 are layout and microphotograph of VCO respectively.. 51.

(63) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. ( No manufacture processing variation and interconnect effect ) Transient Characteristics. Figure 3.18 Transient post-simulation of WiMAX FWA current-reused VCO. Harmonic Characteristics Turning Range. Figure 3.19 Turning range post-simulation of WiMAX FWA current-reused VCO. 52.

(64) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Phase-Noise：. Figure 3.20 Phase-noise post-simulation of WiMAX current-reused VCO Table 3.7 WiMAX FWA current-reused VCO of simulation specifications. #. Operation Voltage. 1.5 V. Operating Frequency. 3.142GHz ~3.839GHz. Turning Range. 19.954%. Power consumption. (core). 6.15mW. Power consumption. (Buffer). 1.669mW. Pout.(dBm). -5.9. Phase-Noise@100KHz (dBc/Hz). -104.6. Phase-Noise@1MHz(dBc/Hz). -126.3. (#) Power consumption(Buffer) Total of two side buffer power-consumed. 53.

(65) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. ( No manufacture processing variation and interconnect effect ). Table 3.8 Manufacture processing variation of WiMAX FWA current-reused VCO Manufacture processing variation results TT FF SS Turning Range(%) Pout (dBm) Phase-Noise@100KHz (dBc/Hz) Phase-Noise@1MHz (dBc/Hz). 19.9 -5.9 -104.5 -126.2. 19.5 -12 -104.6 -126.4. SF. 20.3 -11 -102.2 -125.2. 20.3 19.8 -9 -14 -104.8 -103.9 -126 -126.2. Table 3.9 Temperature variation of WiMAX FWA current-reused VCO Temperature variation results -25 25 Turning Range Pout (dBm) Phase-Noise@100KHz (dBc/Hz) Phase-Noise@1MHz (dBc/Hz). 20.6%. 19.9%. -5.5. -5.9. -106. -104.6. -127.7. -126. 54. FS. 85 19.3% -11 -102.7 -124.5.

(66) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. (With interconnect line effect - Post Simulation). Figure 3.21 Interconnect lines extraction of WiMAX FWA current-reused VCO. Figure 3.22 Interconnect lines extraction of WiMAX FWA current-reused VCO for layout. 55.

(67) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Post-simulation results Transient Characteristics. Figure 3.23 Transient post-simulation of WiMAX FWA current-reused VCO. Harmonic Characteristics Turning Range. Figure 3.24 Turning range post-simulation of WiMAX FWA current-reused VCO. 56.

(68) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Phase-Noise：. Figure 3.25 Phase-noise post-simulation of WiMAX FWA current-reused VCO. Table 3.10 Results of Post-simulation of WiMAX FWA. #. Operation Voltage. 1.5 V. Operating Frequency. 3.341GHz ~3.912GHz. Turning Range. 15.743%. Power consumption. (core). 5.95mW. Power consumption. (Buffer). 1.737mW. Pout.(dBm). -8.37. Phase-Noise@100KHz (dBc/Hz). -101.17. Phase-Noise@1MHz(dBc/Hz). -123.46. (#) Power consumption(Buffer) Total of two side buffer power-consumed. 57.

(69) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. (With manufacture processing variation and interconnect effect) Table 3.11 Manufacture processing variation with interconnect effect of WiMAX FWA current-reused VCO Manufacture processing variation results TT FF SS Turning Range(%) Pout (dBm) Phase-Noise@100KHz (dBc/Hz) Phase-Noise@1MHz (dBc/Hz). 15.74 -8.37 -101.2 -123.5. 15.25 -4.6 -100.8 -123. 16 -13 -100.7 -123.3. SF. FS. 16 -6.7 -101.3 -123.2. 15.4 -9.3 -101 -123.5. Table 3.12 Temperature variation with interconnect effect of L-band current-reused VCO Temperature variation results -25 25 Turning Range Pout (dBm). 20.6%. Phase-Noise@100KHz (dBc/Hz) Phase-Noise@1MHz (dBc/Hz). 19.9%. -10.6. -7.6. -102.3. -101.2. -124.4. -123.5. 85 19.3% -12. -110.7 -130.6. Table 3.13 Results of Post-simulation and pre-simulation Post-Simulation. Pre- Simulation. Operation Voltage. 1.5 V. 1.5 V. Operating Frequency. 3.341GHz ~3.912GHz. 3.142GHz ~3.839GHz. Turning Range. 15.743%. 19.954%. Power consumption. (core). 5.95mW. 6.15mW. Power consumption. (Buffer). 1.737mW. 1.669mW. Pout.(dBm). -8.37. -5.9. Phase-Noise@100KHz (dBc/Hz). -101.17. -104.6. Phase-Noise@1MHz(dBc/Hz). -123.46. -126.3. #. (#) Power consumption(Buffer) Total of two side buffer power-consumed. 58.

(70) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Table 3.14 reference of WiMAX FWA current-reused VCO Results compare. Ref.. supply. Technol.. Freq.. CMOS 0.18um. 3.4Ghz. 15.74% 5.95. 1.2V. CMOS 90-nm. 5.6Ghz. 9.50%. 1V. CMOS 90-nm. 1.75Ghz. 1.25V. CMOS 0.18um. 1V. voltage. This Work 1.5V [14] Measurement. [15] Measurement. [6]ref. Measurement. [7] Simulation. [10] Measurement. [16] Measurement. [17] Measurement. [8] Measurement. [9] Measurement. Phase-Noise Phase-Noise PDC Turning Pout. @100KHz @1MHz (mW) Range (dBc/Hz) (core) (dBm) (dBc/Hz) -8.37. -101.17. -123.46. 0.52. -3. N/A. -112. 4%. 5.54. -6. N/A. -107. 2G. N/A. 1. -7.4. -103. ~-121. CMOS 0.18um. 1.6G. N/A. 0.1. N/A. N/A. -121. 2.5v. BiCMOS 0.25um. 3.9GHz. 34%. 11.2. N/A. N/A. -121. 1.8V. CMOS 0.18 µm. 5.32Ghz. 264 MHz. 5.71 -12.85. -88. -116.1. 1V. CMOS 0.18um. 2.42GHz. 1.70%. 4.6. N/A. -112. -134. 2V. CMOS 0.18um. 5GHz. 36%. 80. -15. N/A. -85. 2V. SiGe BiCMOS 0.25-um. 2.5GHz. 20%. 32. -12. N/A. -115. 59.

(71) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Figure 3.26 Layout of WiMAX FWA current-reused VCO. Figure 3.27 Microphotograph of WiMAX FWA current-reused VCO. 60.

(72) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. 3.5.3 WiMAX FWA VCO Measurement Characteristics In this section, The Measurement results demonstrate that central oscillation signal of 3.2 GHz with the 500 MHz turning range, 2.82 to 3.35 GHz but in this case. We got some VCO steady problem in phase-noise. we will discuss late, About power-consumption which we trade-off between power-consumption and phase-noise. Usually we hope to get as low phase-noise as possible. So we expense some power-consumption to get lower phase-noise and the VCO core is about 6.15 mW.. (a). 61.

(73) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. (b) Figure 3.28 Measurement result of WiMAX FWA current-reused VCO spectrum (a) Normal state (b) frequency per 2 by divider. Show illustration 3.28 (a) (b) and 3.29, we can see very dirty spectrum in Figure 3.28(a) (b) that occurred acute of signal frequency and the target frequency variation form 0.5M~1MHz. So we can’t get stable frequency to Measurement phase-noise during our Measurement. By above reason, we conjecture that due to we used too long-length interconnect to connect body to Vbody PAD(ref. figure 3.26) which pass through and too close inductance , signal output line and inductance Guard.-Ring that made much noise-signal coupling to capacitor to MOS’s body and direct influence circuits. Show Figure.3.29 that result to show no frequency locked and instrument can’t find real center carrier frequency to plot normal tendency of phase-noise.. 62.

(74) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Figure 3.29 Measurement phase-noise-instable result of WiMAX FWA current-reused VCO. Figure 3.30 Measurement turning range result of WiMAX FWA current-reused VCO. 63.

(75) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Figure 3.31 Measurement Vtune V.S. current result of WiMAX FWA current-reused VCO. Figure 3.32 Measurement output power result of WiMAX FWA current-reused VCO. 64.

(76) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Show Figure 3.31 and 3.32 VCO Vtune V.S. current /output power (dBm) respectively that had very close result with simulation. Table 3.15 Simulation and Measurement results of WiMAX FWA VCO Simulation. Measurement. Spec.. Result. Voltage. 1.5 V. 1.5V. Current(core). 3.96mA. 4.1mA. Frequency. 3.341~3.912GHz. 2.82G-3.35G. Output power_Pout.(dBm). -8.37dBm. -8 ~ -10dBm. Power consumption (total). 5.53mW. 6.15mW. Turning Range. 15.74%. 16.73%. Phase-Noise@100KHz. -101.17. - X (instable). Phase-Noise@1MHz. -123.46. - X(instable). FOM. -187.56_1M_3.91G -186.19_1M_3.34G. - X(instable). Die Size. 1.13 X 1.05 mm. 3.6 Discussion and Summary Two different bands Current-Reused Configuration of VCO are introduced in this chapter. In above sections, the Current-Reused Configuration can use one path current to get half power-consumed that difference than convention VCO [6] two path currents. In the phase-noise characteristic, we optimize inductance Q factor and find the maximum value that. 65.

(77) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. not only can got most sharp spectrum but also got good phase-noise. The Low-Power CMOS Voltage-controlled oscillator (VCO) had built by current-reused configuration with Output-Buffer fabricate by TSMC 0.18μm mixed signal/RF 1P6M process. A Good performance was Measurement with this design. The VCO circuit resonator was application on 1.24G~1.46G and 2.82G-3.35G 2.21~2.39 GHz respectively, the turning voltage two VCO both bias voltage between 0 to 1.8 V, Output power -3.37dBm and -8dBm and phase-noise -125.35 dBc/Hz at 1-MHz offset frequency(L-band). The power consumption of the VCO (core) only 1.8mW at 1.2V and 6.15mW at 1.5V voltage supply.. MOS body. 1. Interconnect line of Vbody 3. 2. Figure 3.33 Discusser layout of WiMAX FWA current-reused VCO. 66.

(78) Chapter 3 Design of Low-Power Current-Reused CMOS VCO. Three fail reasons are shown in Figure 3.33. The fail resins we conclude are unsuitable position of interconnection line. In our comment, that reason 1(square_no.1): VCO output signal coupling to Vbody interconnect line and noise pass through into P-MOS capacitor. Reason 2(square_no.2): The inductance Guard-Ring connects to ground not average in this case and Guard-Ring is use M1 connect to ground, our body interconnect line also the same that. So noise very easy coupling to there. Reason 3(square_no.3): This is M1 to M6 coupling capacitance. In this case, we neglect that effect in parasite extraction at EM-simulation and that by reason 1 and 2 maybe output signal and guard-ring noise also coupling to LC resonator. Form above reasons, instable and shift frequency maybe by that. Therefore, above Noise Current experiment prove our problem point at this issue.It is shown in Figure 3.34. It is injected 50 μ A current noise into body pad.. Figure 3.34 Noise Current experiment for proving instable oscillation. 67.