Abstract: 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.

Key words: tunnel disease detection, sixchannel groundpenetrating radar, timing control module, timedivision multiplexing