N142-114 TITLE: Spectrum Monitoring Payload for ScanEagle Unmanned Aerial Vehicle

TECHNOLOGY AREAS: Air Platform, Sensors, Battlespace

ACQUISITION PROGRAM: PMW-120

RESTRICTION ON PERFORMANCE BY FOREIGN NATIONALS: This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120-130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign nationals may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign national who is not in one of the above two categories, the proposal may be rejected.

OBJECTIVE: Develop instrument package (including antenna system) for ScanEagle unmanned aerial vehicle (UAV) that facilitates sampling the electromagnetic (EM) field from emitters of opportunity in the 100 MHz–10 GHz range.

DESCRIPTION: A variety of tools exist to estimate EM propagation. Nonetheless, the processing chain (weather models, EM propagation models, etc.) does not produce an estimate of the state of the EM propagation environment that is coherent in time and space with the true environment. ONR 322 MM and PMW-120 investments have resulted in the development of a variety of techniques for inference of the characteristics of the propagation medium from sampling of the EM Field via shipboard radars and communications, processes referred to as refractivity-from-clutter (RFC) [1, 2] and refractivity-from-radio (RFR). [3, 4] Efforts are underway as well to fuse these new forms of data with background fields of atmospheric refractivity generated by numerical weather prediction models. A significant gap in the EM field measurements is that the Navy normally lacks high-quality observations (e.g., accurate measurements of power normalized for the effect of antenna patterns, etc.) at altitudes above those associated with shipboard antennas.

The objective of this research is to enable operational forces to capture measurements of the EM field for this kind of processing at heights through and then above the marine atmospheric boundary layer (MABL). Successful execution of this SBIR topic would support a proof-of-concept demonstration for a spectrum monitoring capability for the ScanEagle unmanned aerial vehicle (UAV). The ScanEagle is already employed for carrying meteorological (as well as other) payloads. Functionally, the spectrum monitoring capability would do the same thing a desk-top spectrum analyzer would do if controlled by a computer to measure received power for a dozen or so targeted signals of opportunity.
There are two significant challenges though. One challenge is that the size weight and power (SWaP) characteristics of a desk-top spectrum analyzer are an order of magnitude off from meeting the requirements for being a ScanEagle payload. A second challenge is development of an antenna subsystem that is able to negate the effects of the 3-D pattern of the antenna elements across a broad frequency range. For example, the designer may opt for using a number of glue-on or tape-on patch antenna elements on the wings and fuselage of the ScanEagle; the sampling and signal processing strategy might include random phase and amplitude offsets in the addition of the array element signals. Again, the goal is minimizing the variability induced by the complex nature of the antenna pattern, not to maximize the gain per se. A related goal is that the signal processing is not overly dependent upon the antenna placement; i.e., the displacement of an antenna element by a small amount (e.g., 1") would not have an adverse impact on the performance of the system.

The offeror will design a spectrum monitoring capability that possesses the following attributes:
• Functionally similar to a spectrum monitoring capability that would be achieved using a computer-controlled spectrum analyzer.
• Insomuch as possible, utilize Standard Commands for Programmable Instruments (SCPI) for loading mission configuration.
• Have size, weight and power (SWaP) characteristics that are compatible with the ScanEagle UAV.
• Designs who's SWaP allows concurrent operation of meteorological payloads or integrates a low SWaP meteorological payload including an appropriate humidity sensor in order to calculate observed modified refractivity profiles is considered a bonus.
• Have sensitivity approaching that of high-end desk-top units.
• Withstand up to 24 hours immersion in salt water.
• Interface with UAV GPS and navigation system to appropriately tag EM power measurements.
• Antennas are part of the design. The antenna subsystem must largely negate the effects of the direction of the EM field relative to the aircraft’s orientation.
• Addresses bandwidth conservation for payload data (i.e., data transferred to ground station during mission).

The trade-space for the development should take advantage of the following:
• Ultra-fast sampling is not required; a nominal target is sampling power at 10 center frequencies each minute.
• The frequency range is 100 MHz to 10 GHz.
• Frequencies higher than 10 GHz is considered a bonus.
• Performance throughout frequency range does not have to be uniform as long as it is known.
• The ability to measure phase information and angle-of-arrival is considered a bonus.
• On-board versus on-ground processing of signals.

PHASE I: Define and develop a concept for a Spectrum Monitoring Payload System for ScanEagle Unmanned Aerial Vehicle that can meet the performance requirements and the SWaP constraints listed in the description.
• Systematically explore the trade space for the monitoring package payload and the antenna subsystem.
• Evaluate components and explain the rationale for the associated design decisions (i.e., low-noise amplifier, modification of off-the-shelf gear, etc.).
• Show how the design will minimize SWaP.
• Provide a detailed description of the data and power interfaces to the ScanEagle.
• Provide a detailed description of the antenna system.

PHASE II: Produce a prototype package that works with a ScanEagle UAV. This will be an all-up system whose spectrum monitoring plan is configured by users before the mission. The package will be installable in a UAV, and utilize the UAV's onboard connections. The antennas for the package shall be assessed to ensure acceptability for installation.

PHASE III: The spectrum monitoring payload will be productized as an enhancement to the Airborne LIDAR package that is the subject of a Technology Transition Agreement between NAVOCEANO and PMW-120. The productization shall include:
• Addressing performance issues identified in Phase II.
• Improving SWaP to facilitate simultaneous use with Airborne LIDAR.
• Design changes to reduce manufacturing and maintenance costs.
• Documentation to support use by naval operational personnel.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Telecom industry could use technology to lower cost of field measurements used in antenna site studies.

REFERENCES:
1. Karimian, Ali, Caglar Yardim, Tracy Haack, Peter Gerstoft, William S. Hodgkiss, and Ted Rogers, Towards assimilation of atmospheric surface layer using weather prediction and radar clutter observations, AMS Journal of Applied Meteorology and Climatology, 52, 2013.

2. Karimian, Ali, Caglar Yardim, Peter Gerstoft, William S. Hodgkiss, and Amalia E. Barrios, Refractivity Estimation from Sea Clutter: An Invited Review, Radio Science, 2011.

3. Peter Gerstoft, Donald F. Gingras, Member, L. Ted Rogers, and William S. Hodgkiss, "Estimation of Radio Refractivity Structure Using Matched-Field Array Processing", IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 48, No. 3, March 2000.

4. Rogers, L.T., "Likelihood Estimation of Tropospheric Duct Parameters from Horizontal Propagation Measurements," Radio Science, (32) 1, 1997.

KEYWORDS: Spectrum; propagation; unmanned; payload; swap; telemetry

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