Data Acquisition System Design Of High-precision Linear-polarimeter

In recently, with the development of science and technology, as a remote sensing instrument, sunphotometer can detect aerosol optical thickness and distinguish the atmospheric microphysical properties, it has important applications in the field of remote sensing. Polarimeter can obtain more information dimensions, high precision polarization detection, so it becomes a direction of development of solar radiation meteradvantages. To meet the high-precision polarimeter polarization measurement requirements, the instrument system design puts forward new demands, specifically, it mainly for electronics has a large dynamic range, good linearity along with low system noise. Therefore, the design of a high-precision polarization radiometer data acquisition system has important implications for the development of the instrument.In this paper, based on high-precision linear-polarimeter working principle and application requirements. Aiming at shortcoming of high resistance feedback resistor noise, poor stability and low degree of integration of the traditional polarization radiometer data acquisition system which uses the transimpedance amplification method to obtain a weak signal, the research on high-precision linear-polarization radiometer data acquisition system has been carried out. The important circuit parameters of the instrument have been analyzed. Besides, a noise model for micro current acquisition mode and the SNR formula have been established. Finally, it is concluded that in the case of less demanding sampling frequency using capacitance intergration method measurement method has low noise and higher SNR. The new method overcomes the problems of traditional polarization radiometer data acquisition system such as low intergration, poor stability, small SNR and other issues.Based on the above analysis and research, then replies the high-precision linear-polarimeter data acquisition system needs and program design, uses a digital integrated chip DDC112 translate the direct photosensor signal to a 20bit digital signal and read it by a FPGA microprocessor bases on capacitive intergration. Also the circuit design and performance of the high-precision linear-polarimeter data acquisition system have been tested to verify the rationality of the design. The test results show that:the data acquisition system with high dynamic range response, equivalent noise radiance ideal, conventional aerosol detection band SNR is greater than or equal to 127, the typical surface detection band SNR is greater than or equal to 147, the stability of the instrument superior linearity of is better than 1%, the degree of linear polarization measurement accuracy is better than 0.5%, to instrument design specifications.