武汉电离层斜向返回探测系统波形发生器设计

针对传统电离层斜向返回探测雷达无法探测近距离电离层状态和可操作性差的缺点,为武汉电离层斜向返回探测系统 (Wuhan ionospheric oblique backscattering sounding system,WIOBSS)设计了一套新型波形发生器.该波形发生器采用等间隔收发探测体制,使WIOBSS不但能探测到大范围内的电离层状态,且能获得所用伪随机序列的最大增益性能.该波形发生器依据软件无线电思想,利用高性能现场可编程门阵列和数字上变频器,搭建了一个通用的硬件平台.该平台所有功能通过可编程软件实现,只要加载相应软件,就可以选择不同类型的伪随机序列,任意改变伪随机序列的长度和发射波形的占空比,从而满足不同电离层状态下的探测需求.该波形发生器采用PXI(peripheral component interconnect extensions for instruments)总线技术,设计成为一个小型化、高性价比的PXI模块.实验表明,采用该波形发生器的WIOBSS可清晰获得电离层垂直探测和斜向返回探测回波信息.

Design of the waveform generator for Wuhan ionospheric oblique backscattering sounding system

To overcome the problems that traditional ionospheric oblique backscattering sounding radar can not detect the ionospheric state in the vicinity and has poor operational performance, a new waveform generator was designed for Wuhan ionopheric oblique backscattering sounding system (WIOBSS). In this waveform generator, a new sounding system of transmission and reception in equal interval was utilized. With this new system, WIOBSS could detect the ionospheric state in a large range. The largest gain of applied pseudo-random sequence could be obtained as well. High performance field programmable gate array and digital upconverter were used to develop a general-purposed hardware platform. Furthermore, all functionalities are implemented with programmable software. Therefore, various pseudo-random sequences, the length of pseudo-random sequence and duty cycle could be achieved to meet the requirements in different ionospheric conditions by just loading appropriate software. This waveform generator also exploits merits of PXI ( peripheral component interconnect extensions for instruments) bus technology and was designed as a modular, compact and low-cost PXI-based system. The observations demonstrate that the echo of ionospheric vertical sounding and ionospheric oblique backscattering sounding had been obtained clearly by WIOBSS with this waveform generator.