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Electronically-Tunable, Low Loss Microwave Thin-film Ferroelectric Phase-Shifter

Description:

TECHNOLOGY AREA(S): Electronics

OBJECTIVE: Design and development of low-loss and high-speed passive, analog, electronically-tunable microwave phase-shifter based on tunable thin-film ferroelectric (FE) materials for application in military and commercial communications systems operating in the frequency range of 1 - 12 GHz.

DESCRIPTION: Electronically-scanned antenna (ESA) systems based on phased-arrays are attractive for radar and on-the-move (OTM) communication systems providing advantages such as high-scan speeds, low control power, long-term reliability, high accuracy, and adaptive beam-forming [1,2]. These traits are advantageous, especially in the increasingly congested communications environments of modern warfare, where fast-changing operational environments require increasingly adaptive communication systems. Similarly, the demand for low-cost, high-frequency phase shifters is expected to increase in the commercial market to meet the growing demand for state-of-the-art transceivers designed for 5G communication. The congestion in the frequency spectrum, the need for highly power efficient operation, and the dangers of mutual interference are driving commercial networks to the exploitation of very agile narrow beams and dynamic null steering, mainly at base stations. Commercial vehicles such as boats and aircraft will have radar applications requiring steered beams. Military communication networks will have even greater requirements to mitigate the threats of detection, jamming, and interception in addition to the dangers of friendly interference. Furthermore, mobile military networks will not depend on stationary base stations, so they will require the dynamic steering of narrow beams at each network station. Military radars will be operating in this frequency range and will also require agile beam steering. A barrier to the use of phased array antennas in these applications is the system cost of the large number of phase shifters. Passive ESAs are composed of a large number of individual antenna elements, and are capable of electronically-controlled beam-forming and beam-steering by controlling the relative phase of the signal fed to each antenna element. The key component to passive ESAs is the electronically-tunable phase-shifter that adjusts the phase-angle of the signal arriving at an individual antenna element. In order to meet performance and cost requirements, high-performance phase-shifter components are needed that are both lightweight and compact, and the total phase variation needs to be 360 degrees to control an ESA with moderate bandwidth. Electronic phase-shifters tend to incur high insertion loss requiring active amplification; however, low-loss passive phase shifters are attractive since they are lower cost and require low power. Additionally, analog phase-shifters offer accurate phase control with continuously adjustable phase-shift, in contrast to digital phase-shifters that provide a discrete set of phase states controlled by phase-bits, and thus require a lower number of control voltages reducing the control-complexity [3]. Recent advances in the growth of tunable dielectrics and control of their domains demonstrate high intrinsic material Q values greater than 1000 [4-6] while maintaining high voltage tunabilities. These advances point to significant advances in affordable system capability due to the increased performance of tunable phase-shifters with high device Q values.

PHASE I: Ferroelectric material with intrinsic material Q’s over 1000 is within the current state-of-the-art [4-6]. Phase I of this topic will require the demonstration that the proposing company can grow and characterize high quality FE thin films with high intrinsic material Q and electronic tunability of 10:1 within an operating range of +/- 100 V and within the frequency range of 1-12 GHz. Design a FE phase shifter device structure using this material and show, by analysis or simulation, its feasibility for an electronically tuned phase shifter capable of continuous phase shift of 360 degrees in the frequency range of 1-12 GHz with low insertion loss (<6 dB) and tuning speeds of 0.5 microseconds. Develop and maintain contact with ARL (Army Research Laboratory) researchers for advice on materials measurement and application. Provide materials sample to ARL researchers for confirmation.

PHASE II: Develop a synergistic model that couples predictive materials design with phase shifter design and performance. Characterize the frequency dependent dielectric properties of the FE thin films, including permittivity, tunability, and dielectric loss, using basic test devices. Establish and demonstrate the low loss integration of the thin film FE material with the device structure and optimize the insertion loss and tunability. If the FE material will be metallized, demonstrate Q’s greater than 200 in MIM structures with 10:1 tunability with +/- 100 V tuning voltage. If the FE material will be used in a different device structure, demonstrate the low loss performance over the same tuning range. Demonstrate a phase shifter device capable of the metrics outlined above. Optimize the coupled device and FE material insertion loss and tunability, and a flat differential phase shift over the frequency range. Fully fabricate phase shifter prototypes ready for evaluation. Electrically characterize the phase shifter properties including S11 and S21 measurements over the frequency range. Deliver sample devices to the designated government laboratory for assessment and validation. Optimize the materials and device fabrication process for commercial scalability, considering the use of buffer layer or virtual substrate techniques for integration. Make contacts with communications and radar systems development offices such as CCDC C5ISR Center (Combat Capabilities Development Command Communications-Electronics Research, Development and Engineering Center)and industry systems providers to determine specific design parameters for a customer base. Develop a full commercialization plan to exploit these opportunities.

PHASE III: Develop components and circuits capable of meeting selected customer specifications for phase shifter circuits for applications in tactical radio and commercial wireless system handsets and radio systems. Describe specific military applications where the new technology will enable solution of specific problems. Provide a firm technology transition pathway for their developments (for example establish a production line for the fabrication of these circuits and components, produce the individual components for sale, or establish a licensing relationship with a company with a production capability). The path to commercialization is expected to first address radar and communications requirements for military and commercial systems, but is expected to expand into other wireless and electronic systems applications. Recommended transition paths are for mobile vehicular radio links via the Program Executive Office Command and Control or radars for the Program Executive Office Intelligence, Electronic Warfare, and Sensors. Significantly lowering the cost of the phased array antenna will bring the capability to use phased array systems to a much wider variety of military platforms, and therefore a greater market base. Commercial radio links and radars would be of interest to companies such as Lockheed Martin, Boeing, or Raytheon. Emerging 5G market will be explored for opportunities for further commercialization.

KEYWORDS: phase shifter, electronically tunable, ferroelectric, thin film

References:

G. Subramanyam, M.W. Cole, N.X. Sun, et al., “Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components”, Journal of Applied Physics, 114, 191301 (2013).; L.C. Sengupta and S. Sengupta, “Novel Ferroelectric Materials for Phased Array Antennas”, IEEE Transactions o Ultrasonics, Ferroelectrics, and Frequency Control, 44, 792 (1997); K. Khoder, M. Le Roy, and A. Perennec, “An All-Pass Topology to Design a 0-360o Continuous Phase Shifter with Low Insertion Loss and Constant Differential Phase Shift”, Proceedings of the 9th European Microwave Integrated Circuits Conference, 612 (2014); E. Mikheev, A.P. Kajdos, A.J. Hauser, and S. Stemmer, “Electric-field tunable BaxSr1-xTiO3 films with high figures of merit grown by molecular beam epitaxy”, Applied Physics Letters, 101, 252906 (2012); C.H. Lee, N.D. Orloff, T. Birol, et al., “Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics”, Nature, 502, 532-536 (2013); Z. Gu, S. Pandya, A. Samanta, et al., “Resonant domain-wall-enhanced tunable microwave ferroelectrics”, Nature, 560, 622-627 (2018); C.J.G. Meyers, C.R. Freeze, S. Stemmer, and R.A. York, “(Ba,Sr)TiO3 tunable capacitors with RF commutation quality factors exceeding 6000”, Applied Physics Letters, 109, 112902 (2016)

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