基于FPGA的高性能电离层测高仪数控系统设计

Design of Digital Control System for High-performance Ionosonde Based on FPGA

为建立天地一体化电磁观测系统,实现电离层等的实时准确观测,为地震机理的研究与地震预报工作提供科学有效的数据,提出了一种高性能电离层测高仪数控系统设计方案将应用于电磁卫星的地面同步验证系统中,给出了数控系统的时序控制单元、发射单元和接收单元等的具体实现.在收发延迟可变的雷达时序控制下,发射单元利用直接数字合成技术产生1~30 MHz的脉冲信号,40位类巴克码对脉冲信号进行二进制相位调制编码,随后交替发射正交极化波;接收单元利用高速模数转换器实现信号的数字化,采用FPGA技术进行下变频处理.本数控系统的设计可直接获取回波信号的极化信息,高度分辨率为1.5 km,探测周期小于2 min.实验结果表明,该数控系统方案切实可行.

This paper presents a high-performance ionosonde’s digital control system design scheme,which is consisted of timing control unit,transmitting unit and receiving unit.This system is employed in electromagnetic synchronization verification system on the ground to establish integrated electromagnetic observation systems of heaven and earth with the electromagnetic satellite,to realize real-time accurate observation of the ionosphere,and to provide scientific and effective data for the study of earthquake mechanism and earthquake prediction.Under the radar timing control with variable transmission and reception delay,the transmitting unit uses Digital Frequency Synthesis(DDS)technology to generate pulse signals with the frequency range is 1 MHz to 30 MHz.The pulse signal is encoded by the 40-bit quasi-Barker codes in binary phase shift keying modulation,and orthogonally polarized waves are transmitted alternately by the antenna.The analog-to-digital conversion of the receiving unit is realized by a high-speed Analog-to-Digital Converter(ADC),and the Digital Down-Conversion(DDC)is carried out by the Field Programmable Gate Array(FPGA)technology.The polarization information of the echo signal can be caught by the ionosonde.The height resolution of the ionosonde is 1.5 km,the detection period of the ionosonde is less than 2 min.The verification results show that the digital control system scheme is feasible.