Detection and Ranging Beyond the Canonical Resolution Limit

Abstract: The canonical range resolution limit in radar, sonar, and lidar systems is found to be a special case of a more general resolution limit. The general limit indicates that it is possible to surpass the canonical limit in moderate (of order unity) signal-to-noise ratio (SNR) environments by using the signal amplitude and phase information. The canonical limit only considers the bandwidth of the received signal without considering how SNR affects the range resolution. Details present in the signal amplitude, such as attenuation and geometric spreading, can act as additional sources of range information. Previous studies have taken advantage of the relationship between target distance and signal amplitude or phase to achieve higher resolution ranging, and often employ unusual transmit waveforms for this purpose. These methods each provide distinct bounds on range resolution, rather than a unified bound applicable across different systems and applications. We apply ideas from information theory to determine a general lower bound to the smallest resolvable range bin size and corresponding target strength measurements.