Research And Design Of High-speed Analog Low-pass Filter Circuit

Based on the basic principles of analog filters, the development of optimized elliptic filter group delay characteristics, and high-speed circuit modules for transconductance are presented, then completed a cross of G_m-C and switch-current filter of the study design and analysis of the discussion.Based on the study of G_m-C filter, the importance of transconductor circuit is found in it, and high speed transconductor is designed based on this. In the terms of bad characteristic of elliptic filter, a optimized group delay circuit is designed. Based on the good performance of high speed of current-switch filter, principle analysis and circuit design are also presented. Two kinds of basic cell circuit and simulation are built based on the elliptic low-pass filter.When has not optimized group circuit, G_m-C filter's SFDR is 61dB, cut-off frequency is 160.3MHz and group delay is 65ns. In the opposite, the filter's SFDR is 57dB, cut-off frequency is 160.9MHz and group delay is 11ns. Based on the simulation results, adding elliptic filter balanced delay correction filter circuit group delay characteristics, and will not affect the level before the amplitude and frequency characteristics to optimize overall filter performance.Switching current filter is discrete-time signal processing, which is input signal sampling and maintain current, the current through the switch integrator on the current signal processing is the final discrete-time filter output signal. According to system design and simulation of Cadence, SI filter is up to 62 dB SFDR, filter cut-off frequency of 161.6 MHz, and 24ns group delay.Based on the elliptical filter, the establishment of two low-pass filter integrity of the basic unit circuits and circuit simulation are built up for these two filters .In ensuring the same rate under the conditions, SI filter can significantly reduce the output signal distortion.Combine these filters, in ensuring the same rate under the conditions of SI filter can significantly reduce output signal distortion. The basic cell architectures implemented in these filters are also presented. To improve the filter, some of the cell architectures have to be designed carefully. The details of those cells are described. Transconductance is a practical, common-mode feedback operational amplifier circuit modules and circuit design of the findings and Cadence simulation results.This paper is based on the design of high-speed wireless communications systems in the reconstruction DAC waveform applications. The results achieved in the relevant applications in the larger reference value. So this research will be to promote and improve the internal high-speed analog low-pass filter study.