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In recent years, there has been increasing interest in microwave direction-of-arrival (MW-DOA) estimation due to wide applications in the military and commercial areas, such as electronic warfare, wireless communications, and wireless localization. DOA information can be used to minimize the signal power of the interference while maximizing the power of the desired signal, improving the performance of the system.
Use of photonic devices in MW-DOA circuits has become more prevalent due to their wide bandwidths (BWs), the low-attenuation losses associated with fiber-optic cables, immunity to electromagnetic interference, and the ability to implement true time delay lines. The revolution in MW photonics has rendered new techniques for generating MW signals, photonic signal processing including MW delay line filters for beamforming applications, and photonic analog-to-digital converters. But, wideband optical technology may have it’s greatest near-term impact in direction finding (DF) and digital receiver architectures.
Pushing the utility of optical technology in DOA estimation, Navy researchers have developed a preprocessing technique – robust symmetrical number system (RSNS) – to yield a high spatial resolution, wide frequency bandwidth, wide field of view, with a minimum number array elements, and a short array baseline length. These benefits are derived from a multi-element wideband DF array (for optical down conversion) with RSNS preprocessing combined with a dual-electrode Mach-Zehnder modulator.
- Fine angular resolution using a much smaller array size than is typically required for linear arrays employing super-resolution signal processing techniques
- The use of RSNS preprocessing obtains an unambiguous DOA
- The photonic DF array with RSNS preprocessing can monitor a wide BW to determine the DOA of pulsed emitters
- US patent 9,590,740 available for license
- Simulation and experimental testing results available
- Potential for collaboration with Navy researchers