Time shift and phase offset estimation for lightweight multichannel SDR receiver

The use of small and low-power general-purpose Software Defined Radio (SDR) receivers seems to be a very attractive solution in the context of moving platform for multichannel RF signal acquisition, required in Passive Coherent Location (PCL), passive SAR, and digital beamforming. These receivers, however, are designed mainly for single-channel operation and additional hardware components and software algorithms are required to perform coherent signal acquisition. A simple calibration procedure for time shifts and phase offsets, based on cross-correlation between the signals with superimposed training sequences, has been already presented as a solution. However, the results of processing the real signals acquired in the field have shown that this simple method cannot be applied in case of receiving strong signals from the antennas due to misleading phase offset estimates. In this paper, we propose a more advanced algorithm of estimation that employs matched filtering. This method has been validated by processing hours of four-channel recordings with DAB, DVB-T, and FM broadcast signals prepared for PCL processing.