基于FPGA的时间域航空电磁多波脉冲发射电路控制设计

Design of FPGA-based time-domain airborne electromagnetic multi-wave pulse transmitting circuit control

时间域航空电磁法是航空地球物理领域重要的技术方法,具有大深度探测能力,为实现大探测深度兼顾浅层分辨能力,需要研发一种多波脉冲发射装置,能够同时发射大电流半正弦波和快速关断小峰值电流梯形波。该文利用现场可编程门阵列(Field Programmable Gate Array,FPGA)作为硬件平台,采用硬件描述语言(Verilog),通过脉冲频率调制或脉宽调制方式来精确控制发射电流的波形、频率和脉宽,从而实现数字化控制,产生精度高、可控性强的多路数字驱动信号。与传统的半正弦波发射电路相比,其主波发射脉冲由两个1/4正弦波组成,上升沿和下降沿的时长和陡度可以通过程序独立调节,副波发射脉冲为快速关断沿的小幅值梯形脉冲,通过实测试验验证了该文方法的可行性,能够满足深地与近地表探测的要求。

Time-domain airborne electromagnetic is an important technical method in the field of airborne geophysics. It has large-depth exploration capabilities. In order to achieve large exploration depths and shallow resolution capabilities,it is necessary to develop a multi-wave pulse transmitter that can simultaneously transmit large current half-sine waves and quickly turn off the small peak current trapezoidal wave. This paper uses Field Programmable Gate Array(FPGA) as the hardware platform,and adopts the hardware description language(Verilog) to precisely control the waveform,frequency and pulse width of the transmit current through pulse frequency modulation or pulse width modulation. Realize digital control,produce high-precision,controllable multi-channel digital drive signals. Compared with the traditional half sine wave transmitting circuit,the main wave transmitting pulse is composed of two1/4 sine waves. The duration and steepness of the rising edge and the falling edge can be adjusted independently through the program,and the secondary wave transmitting pulse is quickly turned off. The small amplitude trapezoidal pulse along the edge. The feasibility of the method in this paper is verified through the actual test,and it can meet the requirements of deep and near-surface exploration.