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

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.