The Research Of Signal Acquisition And Processing Technology For Portable Laser Ceilometer

The cloud affects the safe take-off and landing of the aircraft.The height of the cloud base,one of the important parameters,is the basic requirement for meteorological support of aviation flight as a real-time and accurate observation of the height of the cloud base.At present,the commonly used cloud-height observation equipment on the ground is laser ceilometer.The laser ceilometer is divided into two types:ground-based fixed and hand-held portable.The development of hand-held portable laser ceilometer lags far behind that of fixed-based laser ceilometer.The traditional hand-held portable laser ceilometer's laser echo signal processing section uses analog circuit design to measure the height of the cloud base in a single-pulse counting operation.It is susceptible to noise and aerosol interference in the actual work.Inaccurate recognition of heights can easily cause "virtual measurement" and"missing test".To solve the problem that traditional portable laser ceilometer cannot accurately identify the height of cloud base,this paper proposes to install a high-speed data acquisition and processing system based on the combination of FPGA and ARM in the echo signal receiving and processing end of the traditional portable laser cloud toposcope.This system provides the on-chip system digital solution for the upgrade and improvement of the traditional portable laser ceilometer thanks to the advantages of data parallel processing of the highly integrated FPGA chip and the low power consumption and high performance of the ARM chip.The system uses FPGA to complete the digital sampling of the laser echo intensity information,and uses ARM to invert the multi-dimensional information of the echo intensity sampling data to achieve accurate measurement of the height of the cloud base.Aiming at the problem that laser echo signals are easily polluted by noise,an empirical mode decomposition algorithm based on autocorrelation and SG filtering is proposed to deal with the noisy signals.At the same time,in order to facilitate the measurement of the height of the cloud base in the field mobile environment,the system uses the GPS/Beidou dual-mode positioning module to monitor the corresponding geographical location information of the cloud for the first time on the portable laser cloud-height apparatus.The system hardware mainly includes a data acquisition module,a data buffer module,a data processing module,a data communication transmission module,a dual-mode positioning module,and a power supply module.The system software development is mainly completed by Quartus II and MDK5 development tools to achieve data acquisition,processing,storage and transmission functions.Finally,in order to facilitate the user's real-time and intuitive monitoring of information such as cloud height and cloud location,the system completes the software development of the upper computer software on the Visual Studio platform.The improved portable laser ceilometer and the ground-based fixed CHM 15K laser ceilometer were compared and tested.The test results of the two were relatively consistent.Finally,it was demonstrated that the system provided a reliable solution for the improvement and upgrade of the traditional portable laser ceilometer.