Real-time, Pseudo Real-time and Stroboscopic Sampling in Time-Domain GPRs

GPR performance rapidly decreases with time propagation depending on soil characteristics, thus the dynamic range of the system plays a key role in subsurface visibility. Dynamic range mainly depends on Analog-to-Digital Converter (ADC) number of bits and receiver sampling efficiency, but it can be increased by averaging multiple traces (under the condition of uncorrelated external noise). Most time-domain GPRs use stroboscopic sampling to collect high bandwidth signals and this limits the averaging factor. Therefore, high-speed ADCs are very attractive for time-domain GPRs as they enable a large stacking factor. However, the low number of significant bits limits the Signal-to-Noise Ratio (SNR) or renders this advantage negligible. A further alternative is pseudo real-time sampling which combines fast ADCs with trace averaging; in this case, multiple samples are acquired from each radar trace by shifting the sampling trigger, and then re-assembled by a logic circuit.