Crosstalk-Based Calibration for High Accuracy Ranging Using Software-Defined Radios

High-accuracy ranging measurements require precise knowledge of systematic delays caused by latencies in the hardware system. In this work, a calibration procedure for estimating such delays using intrinsic crosstalk between the transmit and receive hardware internal to a Software-Defined Radio (SDR) is presented. Since the crosstalk contains a distorted and attenuated version of the transmitted waveform, the signal received on the receiver channel is processed using a matched-filter to increase the processing gain; the delay between transmission is reception of the crosstalk signal provides an estimate of the intrinsic delays in the system. Since the internal latency is generally static after the hardware is initialized, such a calibration may only need to be performed once at system startup. The approach is demonstrated using SDR hardware and shows centimeter-level delay accuracies for waveforms of 7 ms length and 500 kHz bandwidth.