基于分时复用原理的多通道探地雷达时序控制模块设计及应用

为实现对隧道衬砌空洞和地质病害的无损、高效检测，基于分时复用原理，通过FPGA编程和时序电路设计实现一种瞬态脉冲型多通道探地雷达时序控制模块，并应用于多频多通道隧道病害检测探地雷达系统。该时序控制模块可以产生多路同频等相位差时钟，分时触发各个通道脉冲信号的单次收发，从时间上分离通道间串扰信号和有效雷达回波，实现探地雷达多频段多通道的高效工作。试验测试和实地验证结果表明： 该时序控制模块在脉冲重复频率为500 kHz时，能实现8通道雷达测试系统相邻通道间240 ns左右的触发时差，并在触发时差范围内保证观察时窗内雷达回波信号的稳定性； 同时，该模块也能应用于3频段6通道隧道病害检测探地雷达系统，并在距离介质分界面65 cm时反映出实际隧道预埋病害的深度和尺寸信息。

Design and Application of Multichannel Ground Penetrating Radar Timing Control Module Based on Time Division Multiplexing Principle

To achieve nondestructive and efficient detection of tunnel lining voids and geological diseases, a transient pulsed multichannel ground penetrating radar timing control module based on the principle of time division multiplexing is implemented through field programmable gate array programming and sequential circuit design and applied to multifrequency multichannel tunnel disease detection ground penetrating radar system. The proposed timing control module can generate multiple channels of clocks with the same frequency and equal phase difference to trigger a single transmission and reception of a narrow pulse source of each channel at different times, thereby separating the crosstalk signal between channels and the radar echo and resulting in an efficient system of multiband and multichannel ground penetrating radar. The experimental test and field verification results show the following: (1) When the repetition pulse frequency is 500 kHz, the proposed module can implement about 240 ns difference between the trigger time of adjacent channels of an eight channel radar test system. (2) This difference can ensure radar echo stability when the observation time is within the range of the trigger time difference. (3) The proposed module can also be applied to a three band six channel tunnel disease detection ground penetrating radar system and reflects the depth and size of the actual tunnel disease when it is 65 cm away from the medium interface.