This study focuses on developing an extremely low C-SWaP radar sensing solution for single target tracking over a marine environment. The radar system-on-chip (SoC) Utilizes ultra-wideband (UWB) low-probability of intercept (LPI) and low-probability of detection (LPD), which provides a networked, range-based tracking solution when combined with an active phased array antenna. A key innovation of the technical implementation is range extension utilizing digital delay-line triggering, which synchronizes multiple SoC ICs to sample arbitrary ranges simultaneously.
Using ultra-wideband (UWB) impulse radar for detecting and tracking fast-moving small targets over the ocean surface has been considered before with limited applications. The challenges of deploying such radar sensors on small, unmanned marine platforms are addressed in this study. The first challenge is the stringent size and weight requirement to allow a tracking radar sensor to be fitted into the payload of a small unmanned surface vehicle (USV). For the first time, we implemented a design that is based on a single chip UWB radar sensor operating at X-band, which effectively achieves the size and weight requirement for a small USV payload. The second challenge is range extension and range ambiguity resolution. With the UWB radar operating various high-PRF modes, we developed a novel approach that stitches together range profiles from multiple PRFs, to extend the effective non-ambiguous range at the cost of scan speed. The third challenge is developing a lowcost, ultra-wideband planar antenna and front-end, which is also part of the USV payload and needs to be able to perform either sector scanning, or even electronic scanning, with a very low profile. We have successfully designed and implemented one such antenna using a dipole array design. By integrating the solutions into a complete system, we have performed a series of lab and outdoor tests of the UWB radar sensor and obtained some promising target data. Simulations are also being developed for testing the potential target signatures and tracking effectiveness of moving targets over ocean surface clutter environments.
There is a significant need for portable, low-cost, and multi-functional ground and airborne radars. In some applications, the goal is to integrate multiple functions within a limited and constrained frequency band. For other applications, however, the challenge is how to support multiple missions that have been associated with separated frequency bands. This study considers the feasibility of two possible solutions for multifunction radar: the multi-band, agile frequency diversity radar, and a broad-band, common radar aperture. For either of the solutions, the goal is to find the optimal architectures and enabling technologies that support the integration of the following mission requirements: (1) automatic precise landing support, (2) counter-threat detection (such as counter-drone) in ground and airborne operations, (3) 3Daltitude- finding, (4) portable local weather surveillance. We investigated the basic requirements of each of these missions and summarized the trade analysis results. Next, we investigated the current enabling technologies for two proposed aperture options, especially regarding the design of radiating elements. Multiple antenna element designs were studied, which show promise for meeting multi-band or broadband aperture needs. A simulation verification based on the Phased Array System Simulator (PASIM) technology, which was jointly developed with MathWorks, is introduced. The simulation serves as a method to evaluate the quality of performance (QoP) of different radar missions that can be achieved with specific architectures. We investigated a mixed-signal transceiver and GPU-enabled backend software system that allows for the parallel execution of multiple radar missions through the same aperture.
Electronically scanned phased array antennas have been in use for many years for such applications as search and surveillance, tracking, and remote sensing. They offer fast beam switching and multi-beam operation, but are subject to scan blindness due to the effects of mutual coupling between elements. Scan blindness is an undesirable decrease in array gain at specific frequencies and angles. The blindness comes about when the array structure is capable of supporting a forced surface wave model. A novel substrate will be investigated which may eliminate scan blindness by cutting off these surface wave modes. Researchers have been investigating the properties of a periodic dielectric structure exhibiting a photonic bandgap since 1987. This photonic bandgap structure prevents electromagnetic propagation in any direction (in two dimensions for the 2D structure). The geometries examined have been two and three-dimensionally periodic with lattice structures typically being triangular or rectangular. The investigation of the photonic bandgap structures had been confined to theory until about 1994 when researchers constructed and characterized the properties of a finite 2D structure. Recently, researchers have suggested using the photonic bandgap structure as a substrate. This paper investigates the use of a photonic bandgap substrate, PBGS, to reject the surface wave and eliminate scan blindness. To support the theory, experimental data will be presented comparing the scan performance of an array on a PBGS and an array on a conventional homogeneous substrate.
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