Signal Calibration and Noise Reduction for Software-Defined Radio-Based GPR

This article studies signal calibration, frequency response estimation, and noise reduction for a software-defined radio (SDRadio)-based ground-penetrating radar (GPR). The radar signal generation utilizes the stepped frequency continuous wave (SFCW) method. The signal calibration takes advantage of the dual-channel structure of the SDRadio and solves the incoherent phase problem caused by phase mismatch between the local oscillators (LOs) in the transmitter and the receiver. The frequency response estimation involves two steps: First, the calibration measures the system's intrinsic frequency response. Then it measures the frequency response of the target under the ground surface. The noise effect at the receiver is reduced using the ridge regression method. For performance evaluation, outdoor and indoor experiments are conducted, which show that the GPR A-scan waveform and B-scan image qualities can be effectively improved. Compared with the traditional method, the signal-to-clutter ratio (SCR) of the A-scan waveform is improved by around 7 dB and that of the B-scan image is improved by around 13 dB.