Design Of High Order Switch Capacitor Bandpass Filter With Passband Tunable

With the rapid progress of integrated circuit technology,analog active filters widely used in traditional signal processing fields cannot meet the needs of designers due to their low accuracy,poor linearity,and large noise.Switched-capacitor filters are gradually entering the researchers' sight.Switched-capacitor filters have the characteristics of simple structure,easy integration,and high precision,which have attracted the attention of more and more designers.This subject is to design a high order switched capacitor bandpass filter chip with passband tunable,which can be used in Doppler positioning signal interface circuit.The subject first deduces the basic working principle of the switched capacitor basic circuits.,and explains the advantages of the switched capacitor circuits compared with the traditional analog circuits.The equivalent model of the Z-domain of the switched capacitor circuits are given to facilitate the subsequent analysis and design.Then the structure of the high-order filter,the analysis of the biquad structure and the derivation of the transfer function are introduced,and the non-ideal factors in the switched-capacitor circuit are analyzed.Then according to the design index,use Matlab/Simulink to design the filter,including parameters and models.Modeling and simulation through Simulink,prove that the design meets the requirements.Finally,the circuit and layout design of the filter are completed using Hua Hong 0.35 ?m CMOS process.The design uses a fully differential structure to take the advantage of it.The designed sub-modules include: fully differential amplifiers,two-phase non-overlapping clocks,reference blocks,and biquad structures.For layout design,IO,PAD,Sealring,etc,should also be added to complete the overall layout design,and on this basis,DRC,LVS,and post-simulation of the layout are completed as well.The switched capacitor bandpass filter layout area designed for this subject is 2650?m×2950?m.The post-simulation results show that the designed filter's passband can be adjusted from 2KHz to 200 KHz by changing the input clock frequency.The overall passband ripple is around 0.3d B.The high-pass transition band attenuation is-76 d B/octave,and the low-pass transition band attenuation is-84 d B/octave.The high order switched capacitor bandpass filter with passband tunable designed in this subject is correct and the performance meets the design specifications.