新型互補式金氧半類比二階高頻濾波器之設計與分析及其在高階濾波器之應用

Abstract

新型互補式金氧半類比二階高頻濾波器之設計與分析及其在高階濾波器 之應用 學生：許恆壽 指導教授:吳重雨 博士國立交通大學電子工程系電 子研究所摘要 本論文提出並分析互補式金氧半(CMOS)特高頻(VHF)連 續性(continuous-time)電流以及電壓模式低通(lowpass)與帶通( bandpass)二階式(biquadratic)濾波器。配合上所提出之新型品質因素補 強電路(Q-enhancement circuits)，吾人可以構建高品質因素特高頻連續 性低通與帶通二階式濾波器，並以此二階式濾波器為基礎的構建模組，完 成電流模式(current-mode)連續性特高頻帶通階梯型(ladder)濾波器之組 建。所提出之特高頻連續性濾波器均已成功的利用0.8微米N型井互補式金 氧半技術完成電路的設計、模擬、與晶方研製。由量測研製之實驗性晶片 的結果成功的印證了濾波器的特性。 首先，吾人提出由可調式寬頻跨 阻放大器與跨導放大器組成之線性寬頻有限增益電流及電壓模式放大器， 並應用於特高頻連續性電流以及電壓模式濾波器之設計。當吾人將電晶體 的雜散電容列入考量，則此跨阻-跨導(跨導-跨阻)有限增益電流(電壓)放 大器可以直接視為特高頻電流(電壓)模式低通二階式濾波器。所提出之低 通二階式濾波器具有簡單之電路架構，因此佔用較小晶片面積並消耗較低 功率。而且高階特高頻低通濾波器的組建可經由直接串接低通二階式濾波 器來達成。此外，論文亦提出一新型品質因素補強電路。此品質因素補強 電路是由一可調式寬頻正增益電壓模式放大器與線性密勒電容構成，其目 的在於提升低通二階式濾波器之最大增益頻率(fM)與最大增益品質因素( QM)。實驗結果証實新型特高頻電流(電壓)模式低通二階式濾波器其最大 增益頻率之可調範圍由102百萬赫芝至148百萬赫芝(92百萬赫芝至142百萬 赫芝)、而最大增益品質因素之可調範圍由1.13至1.49(1.05至1.19)。所 測得之電流(電壓)模式低通二階式濾波器之最大信號準位為92 uArms(38.9 mVrms)，動態範圍為48.5分貝(50分貝)，當工作電壓為□.5 伏特時其消耗功率為21.8毫瓦(20毫瓦)。此外，經過品質因素補強電路的 作用後電流模式低通二階式濾波器之最大增益頻率可提升至186百萬赫芝 而最大增益品質因素更可高達18.5。所測得之最大信號準位為87.3 uArms ，動態範圍為46分貝，當工作電壓為□2.5伏特時其消耗功率為221.4毫瓦 。 其次，根據跨阻-電容二階帶通架構以及利用品質因素補強技術， 吾人構建特高頻電流模式高品質因素帶通二階式濾波器並以此為基礎細胞 元完成特高頻電流模式連續性帶通階梯型濾波器之組建。由帶通階梯型 RLC濾波器之原型出發並指定適當的狀態變數，帶通階梯型濾波器之狀態 方程式可皆以電流模式狀態變數來表示且改寫成具電流模式高品質因素帶 通二階函數之型式。因之，吾人可以利用電流模式高品質因素帶通二階式 濾波器為基本構建模組，完成電流模式連續性帶通階梯型濾波器之組建。 一個六階電流模式連續性帶通階梯型濾波器之實驗性晶片業已設計並完成 晶方研製。實驗結果顯示此六階電流模式連續性帶通階梯型濾波器之中心 頻率可高達48.4百萬赫芝，而所測得之最大信號準位為29.6 uArms，動態 範圍為48.3分貝。晶片面積為1.14平方毫米，當工作電壓為□.5伏特時其 消耗功率為73.3 mW/pole。 此外，結合跨阻-電容、跨阻-跨導架構以 及品質因素補強電路，吾人提出了一特高頻電流模式連續性高品質因素二 階式單元，用以執行帶通與低通濾波。同樣的，由具穿透零點之帶通階梯 型RLC濾波器之原型出發並指定適當的狀態變數，具穿透零點之帶通階梯 型濾波器之狀態方程式可皆以電流模式狀態變數來表示且具電流模式高品 質因素帶通二階函數、電流模式高品質因素低通二階函數、以及電流微分 函數之型式。因之，吾人可以利用電流模式高品質因素帶通二階式濾波器 、電流模式高品質因素低通二階式濾波器、以及電流式微分器為基本構建 模組，完成電流模式連續性具穿透零點之帶通階梯型濾波器之組建。一具 有70百萬赫芝之穿透零點且中心頻率在50百萬赫芝之帶通階梯型濾波器以 及一具有35百萬赫芝之穿透零點且中心頻率在50百萬赫芝之帶通階梯型濾 波器業已成功的設計並經由HSPICE驗證模擬之結果。由模擬結果顯示，所 提出之階梯型濾波器具有簡單電路架構、高中心頻率、以及低元件靈敏度 之特性。 最後，吾人提出簡單架構之寬頻有限增益電壓模式放大器並 應用於低電壓源、低功率特高頻連續性低通濾波器之設計。單端式與全平 衡式電路架構均列入設計考量。實驗結果顯示單端式(全平衡式)跨導-跨 阻式低通二階濾波器之最大增益頻率可高達237.4百萬赫芝(237.4百萬赫 芝)而最大增益品質因素為2.59(2.26)。當工作電壓為□1.25伏特時其消 耗功率為3.37毫瓦(9.44毫瓦)，最大信號準位為12.3 mVrms (84 mVrms) ，動態範圍為30分貝(48.5分貝)，且最大增益頻率之可調範圍大於35百萬 赫芝，而高階低通濾波器的組建可經由直接串接低通二階式濾波器來達成 。因將電晶體之雜散電容列入考量且所提出之電路中並沒有外加任何線性 電容，是以所提出之濾波器具Transistor-Only之特性而可以利用一般標 準數位金氧半製成技術加以研製。除此之外，由於電路架構之簡單性將佔 用較小之晶片面積且耗費較低功率。基於上述優點，所提出之濾波器符合 當今數位-類比混合式積體電路設計之趨勢以及關於低功率消耗之應用。 我們深信，吾人提出之電流與電壓模式特高頻連續性濾波器以及其設計技 術已為類比積體電路設計開創一可行之新領域。爾後，相關的研究發展將 持續進行。 ABSTRACT In this thesis, CMOS very high- frequency(VHF)continuous-time current and voltage-mode lowpass and bandpass biquadratic filters are proposed and analyzed. Combined with the proposed Q-enhancement circuits, the high-Q current-mode VHF biquadratic lowpass and bandpass filters can be constructed and used as the building blocks for the implementation of the current-mode continuous-time VHF bandpass ladder filters. The performances of these proposed VHF filters have been successfully designed and fabricated in 0.8 um CMOS N-well DPDM technology and the experimental chips have successfully been measured and verified the simulated characteristic. Firstly, the linear wideband finite-gain current and voltage-mode amplifiers constructed by tunable wideband transresistance (Rm) amplifier and (Gm) amplifier are proposed and applied to the design of VHF continuous-time current and voltage-mode filters.Considering the intrinsic capacitances of MOSFETS as filter elements, the Rm-Gm (Gm-Rm) finite-gain current(voltage) amplifier configuration can be regarded as VHF current (voltage)-mode biquadratic lowpass filter directly.The proposed biquadratic lowpass filters have simple structures and occupy small chip area and consume little power. Higher-order VHF lowpass filters can be realized by cascading the biquads directly. Moreover, a new Q-enhancement circuit which consists of a wideband tunable positive-gain voltage amplifier and a Miller capacitor is also proposed to enhance both maximum-gain frequency fM and maximum-gain quality factor QM of the VHF lowpass biquads. Experimental results successfully demonstrate capability of the proposed new filter implementation methods in realizing VHF current(voltage)-mode biquadratic lowpass filter with maximum-gain frequency fM tunable in the range of 102 MHz to 148 MHz (92 MHz to 142 MHz) whereas the maximum-gain quality factor QM tunable from 1.13 to 1.49 (1.05 to 1.19). The measured maximum signal level for voltage (current)-mode biquadratic lowpass is 38.9 mVrms(92 uArms) and dynamic range is 50 dB (48.5 dB) with the power dissipation to be 20 mW (21.8 mW) under □2.5 V power supply system. Moreover, after applying the Q- enhancement technique to the current-mode lowpass biquad,the maximum-gain frequency fM can be increased up to 186 MHz and the maximum-gain quality factor QM can be enhanced as high as 18.5. The measured maximum signal level for the current lowpass biquad with Q-enhance is 87.3 uArms and the dynamic range is 46 dB with the power dissipation 221.4 mW under □2.5 V power supply system. Secondly, based on the Rm-C biquadratic bandpass structure and Q-enhancement technique,the VHF current-mode high- Q bandpass biquadratic filter is constructed and applied as the basic building block for the realization of VHF current-mode bandpass ladder filter.Starting from the prototype of RLC bandpass ladder filter and assigning proper state variables, the state equations of the bandpass ladder filter can be represented all by current-mode state variable with form of high-Q current bandpass biquadratic function.Therefore,the current-mode continuous-time bandpass ladder filter can be implemented using current high-Q bandpass biquads as basic cells. Experimental chip of the 6-order current bandpass ladder filter has been designed and fabricated.Experimental results successfully demonstrated the current-mode bandpass ladder filter with center frequency f0 up to 48.4 MHz. The measured maximum signal level for the current bandpass ladder filter is 29.6 uArms and the dynamic range is 48.3 dB. The chip area is 1.14 mm2 and the power dissipation is 73.3 mW/pole for □.5 V power supply system. Moreover, combining the Rm-C and Rm-Gm structures with Q-enhancement circuits, the VHF current-mode continuous-time high-Q biquadratic section which performs bandpass and lowpass filtering is proposed. Similarly,starting from the prototype of RLC ladder filter with transmission zero and assigning proper state variables, it is shown that state equations of the current-mode bandpass ladder filter with transmission zero can be represented all by current state variables and rewritten in form of high-Q lowpass biquadratic, high-Q bandpass biquadratic, and current differential functions. Thus, the proposed current-mode bandpass ladder filter with transmission zero can be implemented using current high-Q bandpass biquads,high-Q lowpass biquads,and current-mode differentiators as basic cells.The current-mode bandpass ladder filter of f0 up to 50 MHz with a transmission zero f0z as high as 70 MHz and the current bandpass ladder filter of f0 up to 50 MHz with a transmission zero f0z located at 35 MHz have been successfully designed and simulated by HSPICE. From the simulation , it is shown that the proposed filters have simple structures, high center frequencies, and low component sensitivities. Finally, for the design of low voltage low power VHF continuous-time lowpass filters,simple-structur ed wideband finite-gain voltage amplifiers are proposed. Both single-ended and fully-balanced topologies have been developed.Experimental results have successfully shown that the fM of the single-stage (fully-balanced) Gm-Rm lowpass biquad can be as high as 237.4 MHz (237.4 MHz) with the maximum-gain quality factor QM to be 2.59(2.26) for 1.25 V power supply voltage. The power consumption is 3.37 mW (9.44 mW), the maximum signal level is 12.3 mVrms (84 mVrms), and the dynamic range is 30 dB (48.5 dB). The maximum-gain frequency fM of the fabricated VHF Gm-Rm lowpass filters can be tuned in a range larger than 35 MHz. Moreover, higher-order VHF lowpass filter can be implemented by cascading biquads directly.Since intrinsic capacitor are considered as filter elements and not any linear capacitor added in the proposed filters,the filters are transistor-only and can be implemented using standard digital VLSI process. The simplicity in circuit structure result in small chip area and low power consumptions.These beneficial characteristics make the proposed VHF filters suitable for integrated mixed-mode circuit design and low power applications. It is believed that the proposed current and voltage-mode VHF continuous-time filters and their design methodology offer new design scope and feasibility for analog ICs. Further research will be conducted in the future.