Characterizing Multipath Delays in Antenna Array and Synthetic Aperture Radar Systems

Technology

This technology enables a receiving wireless node to measure the relative delay of different OFDM signal paths resolved using antenna arrays or synthetic aperture radar techniques. This is achieved by leveraging the fact that a delay in the time domain of an OFDM signal path translates to a rotation in phase of the received signal, across OFDM subcarriers. This indicates that the slope of the phase of a received OFDM channel measured across subcarriers captures the delay of this signal in the time-domain, and therefore, measuring the difference in these slopes can provide the relative delay between two OFDM signal paths. This approach is particularly advantageous given that a small delay in time, even less than one OFDM time sample (i.e., the time corresponding to a single sample at the OFDM receiver) can still be measured based on the difference in slopes.  

Problem Addressed

SAR is a technique in which successive pulses of radio waves are transmitted from a transceiver to “illuminate” a target scene, and the echo of each pulse is received and recorded at the transceiver. Localization of radio frequency reflectors or transmitters may be complicated by the presence of reflecting structures that cause there to be multiple paths from a target object to a receiver. The Inventors have developed a technology that enables identifying the relative delays of different paths of a signal measured by an OFDM wireless receiver from a wireless transmitter, using SAR techniques for applications in localization, gesture sensing or imaging, to identify the line-of-sight path, or to analyze possible sources of multipath in the environment.  

Advantages

• Solution can be extended to other frequency division technologies (e.g., FDM) where the wireless channel is available at the receiver across independent frequencies