TECHNOLOGY AREAS: Sensors, Electronics, Battlespace

ACQUISITION PROGRAM: PMA-290, PEO(T), PEO(W), PMA-231, PMA-265

OBJECTIVE: Develop innovative large tunable time delay technology in microwave domain radar and communication systems using advanced fiber-optic true time delay (TTD) beam forming networks.

DESCRIPTION: Photonics and microwave technologies offer new opportunities for accurately controlling thousands of array elements as well as the wide bandwidth of shared aperture antennas. Photonics technologies are providing an interconnect solution for future airborne phased array radar antennas where bandwidth, EMI immunity, size and weight requirements are becoming increasingly difficult, if not impossible, to meet using conventional electrical interconnect methods.

Phased array antennas offer many advantages including no physical movement, accurate beam pointing, increased scan flexibility in two dimensions, precise phased array element amplitude and phase, low sidelobes, and reduced power consumption and weight. The implementation of large tunable time delays in the microwave domain is quite complex, resulting in bulky and heavy beamforming networks. The use of optics has been proposed to alleviate these problems in the microwave domain since fiber-optics offer low weight, immunity to electromagnetic interference, and true time delay (TTD) capability. However, the attenuating effects of optical solutions have made TTD solutions impractical to implement.

Recent commercial and DARPA supported efforts are developing low loss photonic switches for the telecommunications and military market. A new approach to optical switching using 3D micro electrical mechanical systems (MEMS) integrated on silicon VLSI chip is making this possible. Photonic switched true time delay (TTD) beam forming networks are needed to control the myriad of array elements while handling the broad bandwidth required of a shared antenna. Efficient elemental vector summation (in the receive mode) or distribution (in the transmit mode) must be obtained independent of frequency and angle. Proposed TTD solutions must demonstrate several bit accuracy which supports >1000 antenna elements within a minimal volume (<0.1 m3), require less than 100 W of power, and exhibit environmental ruggedness over an approximate -40 to 100�C range. TTD beamforming systems have recently been demonstrated using wavelength-division multiplexing (WDM) fiber-optics, photolithographically defined ultra-low-loss polymeric waveguides and wavelength tunable optical modules (OPLL), among others. This system should be able to operate at much higher frequencies with a reduced cost compared to existing systems.

PHASE I: Determine the feasibility of a true time delay (TTD) technology scalable to thousands of elements and capable of multi-beam formation. Take into account bandwidth, precise phased array element amplitude and phase, ease of packaging, package size and power, and environmental ruggedness over the �40 to 100�C temperature range. Include error detection and correction technology as needed.

PHASE II: Develop and fabricate a packaged testbed to demonstrate a true time delay (TTD) unit meeting the specifications above. Include aircraft representative fiber optic cable plant interconnect technology into the characterization testbed.

PHASE III: Transition the True Time Delay (TTD) Beam Forming Network for use in next generation phased array radar and electronic warfare systems.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The research under this program could extend beyond military radar systems to commercial radar systems and networks. Further, the effort here to reduce the size and weight even gives a competitive advantage in the commercial telecommunications marketplace.

REFERENCES:
1. Foshee, J., Colegrove, Y. Tang, Z. Shi, X. Zhang, and S. Tang, "Switched optical polymeric waveguide true-time-delay lines for wideband photonics phased array antennas," Proc. SPIE 5356, p. 65�73, 2004.

2. Howard R. Rideout, Joe S. Seregelyi, and Jianping Yao, "A True Time Delay Beamforming System Incorporating a Wavelength Tunable Optical Phase-Lock Loop," Journal of Lightwave Technology, Vol. 25, Issue 7, p. 1761-1770, 2007.

3. Howley, B., Wang, X., Chen, M. and Chen, R. "Reconfigurable Delay Time Polymer Planar Lightwave Circuit for an X-band Phased-Array Antenna Demonstration," Journal of Lightwave Technology, Vol. 25, Issue 3, pp. 883-890.

KEYWORDS: True Time Delay (TTD); Beam Forming Network; Shared Aperture Antennas; Next Generation Phased Array Radar; Electronic Warfare Systems; Fiber Optics

TPOC: (301)342-9102
2nd TPOC: (301)342-9824