Abstract: Remote recovery of acoustic signals from passive sources is provided. Wideband radars, such as ultra-wideband (UWB) radars can detect minute surface displacements for vibrometry applications. Embodiments described herein remotely sense sound and recover acoustic signals from vibrating sources using radars. Early research in this domain only demonstrated single sound source recovery using narrowband millimeter wave radars in direct line-of-sight scenarios. Instead, by using wideband radars (e.g., X band UWB radars), multiple sources separated in ranges are observed and their signals isolated and recovered. Additionally, the see-through ability of microwave signals is leveraged to extend this technology to surveillance of targets obstructed by barriers. Blind surveillance is achieved by reconstructing audio from a passive object which is merely in proximity of the sound source using clever radar and audio processing techniques.

Abstract: Constant information ranging for dynamic spectrum access in a joint positioning-communications system is provided. Embodiments described herein provide a simultaneous positioning, navigation, timing, and communications system that cooperatively executes multiple radio frequency (RF) services. A constant-information ranging (CIR) strategy or algorithm is defined that maintains constant information learned about an incoherent moving target by modulating a revisit interval to minimize the number of interactions. This significantly reduces spectral congestion and offers a control mechanism to dynamically manage spectral access. The CIR algorithm is validated in a simulation environment where a 91% reduction in spectral access for a particular flight path is observed while maintaining a 3-centimeter (cm) precision in ranging.

Abstract: Hybrid in-situ and signal of opportunity (SoOP) calibration for antenna arrays is provided. Deployment of aircraft antennae is redesigned to support multiple services with shared physical elements that conform to the exterior of an aircraft to mitigate drag. Conformal arrays are, however, susceptible to structural changes in the fuselage that manifest as pointing errors and side lobe degradation. Embodiments provide an online calibration algorithm that leverages cooperative satellites in direct line-of-sight of a radio frequency (RF) device with an antenna array (e.g., an aircraft with a conformal antenna array) to optimally steer beams. These external calibration sources supplement an in-situ source mounted on a common platform with the antenna array (e.g., placed on the aircraft's tail). Models are established for potential sources of mismatch and the hybrid calibration method is demonstrated via simulations.

Abstract: Position information estimation in a distributed radio frequency (RF) communications system is provided. Embodiments disclosed herein facilitate high-precision estimations of positions, orientations, velocities, and acceleration of network nodes in a distributed RF network. The distributed RF communications system incorporates a series of estimation processes which makes it susceptible to propagation of errors. To ensure robustness of the distributed RF communications system, relative positions of network nodes are tracked by iteratively tracking parameters used for estimating position information. Some embodiments take advantage of Kalman filtering algorithms by leveraging principles directed by physics. At every network node, several filtering algorithms can be employed to synchronize clocks, track delay between multiple-input multiple-output (MIMO) antennas and estimate position and orientation of other network nodes.

Abstract: Position information estimation in a distributed radio frequency (RF) communications system is provided. Embodiments disclosed herein facilitate high-precision estimations of positions, orientations, velocities, and acceleration of network nodes in a distributed RF network (e.g., including base stations and vehicles, such as aircraft or unmanned aerial systems (UASs)). Modern radio systems must adapt to limited spectral access by reducing spectrum demand and increasing operational efficiency. In this regard, an RF system is provided which simultaneously performs positioning and communications tasks. This system specifically addresses the issue of spectral congestion by employing an extremely efficient positioning strategy and using a joint waveform that simultaneously enables both tasks. This efficiency in turn supports more users in a given frequency allocation.