The Design Of Fourteen Order Switched Capacitor Bandpass Filter With Tunable Bandwidt

This topic is about the design of filter processing analog signal.This paper introduced the related knowledge from the typical continuous time structure,first introduced the switch capacitor circuit work,according to the analysis of switched capacitor circuits and filter non ideal factors which were to be discussed,get a more practical solution,finally proposed the feasible scheme of bandpass structure: according to the bandwidth of the bandpass filter to realize the continuous adjustable requirements,but also to achieve the desired attenuation speed,select the appropriate structure of the reference band ripple and other technical indicators,from these core parameters to determine the cascade form to achieve fourteen order band-pass filter.The determination of the structure requires feasibility verification.For system level modeling in Matlab,determine the structure of the high pass filter section and low-pass filter part,get the corresponding transfer function,all coefficients are obtained using the form of code,and optimize.The overall design is a differential input differential output that allows the output range to be two times larger than the single ended form,and is more visible in suppressing the common mode noise of the entire filter.To explore the non ideal factors mainly focus on the following points: first,the switch resistor thermal noise introduced in the system,affecting the signal transmission,the deterioration in band ripple;secondly,the capacitance and the layout design of the simulation parameters do not match,resulting in the actual filter transfer function changes;finally,the actual operational limited gain,bandwidth and slew rate constraints,work performance and the accuracy of this will affect the integrator.A switched capacitor bandpass filter with fourteen order is constructed in order to achieve the stopband attenuation rate of 60 dB per octave.After get the global optimization coefficient and verified by Matlab according to the transistor level design of the filter,the transistor level circuit design and Simulation of the 0.35 um process is Huahong Cadence environment,finally get the layout structure of the overall design,the post layout simulation,verify the correctness of the design from theory to implementation.The simulation results show that the gain in the passband is 64.81 dB,and the rising and falling stopband attenuation rates are 59.64 dB,each octave and 61.23 dB per octave,the ripple within the band is minimum,as low as 75 mdB,which meets the design requirements.After the completion of the layout,the simulation is carried out to verify that the passband frequency signal can be fully adopted.