Chromatographic Signal Modulation Optimization And Hardware Implementation

With the development of science and technology, people have a further requirement for the quality of life. But in recent years, food safety problem and environment pollution problem is increasingly prominent, and how to accurately detect unhealthy food or the pollution in air and water become an urgent need to solve the problem. Therefore, as far as possible to obtain higher resolution plays an indispensable role. Sigma Delta modulator using the noise shaping technology, will move noise into the outside of the signal bandwidth. It greatly increases the signal-to-noise ratio and accurately gets the weak signal features. Then it could accurately response the detected signals, so as to avoid unnecessary accidents. Therefore, the theory and application of Sigma Delta modulator has received the widespread attention.In this paper, we will design a high precision to detect liquid substance liquid chromatography based on the Xilinx FPGA XC3S1200E. This paper firstly summarizes the basic theory of digital to analog converter and the basic parameters and indexes of converters. Then the paper introduces the Sigma Delta modulator which involves some technology theory, for example Oversampling technique, Noise Shaping technique and Dynamic Mismatch Element technique. Then we analyze the relationship of the stability and the topology of the modulator. According to the characteristics of the liquid chromatographic signal, this paper designs overall architecture of the modulator. System use SIMULINK to make simulation and realize the various modules of the modulator with Verilog HDL.The system simulation shows that when an oversampling rate is8, the SNR reaches128dB with the1Hz sine signal input, when a sampling rate is16, it is148dB. According to the verification of the system, it could ensure stability and the measurement accuracy, also be measured continuously.