0www.nasa.gov

CLAS-ACT: Conformal, Lightweight Antennas for Aeronautical

Communications Technology PI: Mary Ann MeadorNASA Glenn Research Center

September 18-20 , 2018

Co-PI: James DowneyNASA Glenn Research Center

• ARMD Transformative Aeronautics Concepts Program

CONVERGENT AERONAUTICS SOLUTIONS PROJECT

https://ntrs.nasa.gov/search.jsp?R=20190001009 2020-07-02T23:06:23+00:00Z

Unmanned Air Systems (UAS) are increasing in use but range is mostly limited to line of sight

• Satellite Communication (SatCom) links would enable beyond line of sight (BLOS) coverage for UAS

• Currently only large UAS platforms can accommodate dish antennas

• Even so, they take up a lot of payload volume

• Smaller class UAS cannot accommodate SatCom Dish

• Solution: Conformal, Phased Array Antenna

1

ArticShark/Navmar Applied Sciences Corporation

Global Hawk/Northrop Grumman

•

NASA UAS that could be BLOS enabled by CLAS-ACT antenna (445-800 lb)

2

Range of UAS enabled by BLOS communications for coastal monitoring mission

L3 Viking 400

Navmar Tigershark XP

U.S. Navy/ NASA SIERRA

NASA (ASAB) Concept UAS

•

What we are trying to do

• Microwave antenna with high enough power for SatCom link

• Ultra low side lobesattenuated via electronic means to avoid interference with ground

• Built out of lightweight, low dielectric aerogels

• Conformal design to reduce drag and increase simplicity

3

Roll ·-

Broad-Side Direction \

1

Yaw

Radiation Pattern

•

End-Fire 1

- Direction

CLAS-ACT builds on aerogel antennas developed under Aero Seedling

4

8 element array shown in far-field range

• As much as double the gain and efficiency achieved depending on frequency

• 77 % lower density than same antenna array from conventional substrates!!

Award 2015

Scalable

EnhancedPerformance

20

16

12

4400

-----a-~1ex,.itm1nt ... . ... ~14:.:2tlttntl"l'lill'1 -&- Aietoge14X2eletn11n:iilt2 ---<>--Aertlgltl4J"2illllfflll"ll#3 .. .,.... ~14J.2..,..,li=.4 ~tl.if0d4.QIIN)J'rWII

4600 4000 5000

frequency, MHz

•

5200 4400 4600 4000 sooo S200

frequency, MHz

What difference will the CLAS-ACT antenna make?

5This will enable BLOS for small to medium UAS

CLAS-ACT antenna using electronic beamforming will reduce

interference to acceptable levels

Side lobes

Potential interference issues with ITU*

provisional Ku-band SatCom allocation for UAS

*International Telecommunication Union (ITU)

•

Goals and challenges

Challenge: Use phase array antenna beamforming to mitigate ground station interference for ITU compliance for UAS

Challenge: Fabricate a tightly integrated antenna system after inventing a more flexible form of the aerogel

Goal: Advance technologies for a Ku-band phased array antenna using an aerogel substrate to reduce SWaP(size weight and power) on UAS SatCom systems

Rigid aerogel

Broken antenna

6

- Proposed IT - O 8 . U Mask~a;td4no;.~:------- . m Dish Model (B Lat, 1 km altitud

Phased A essel) e rray beam 0 synthesis (49x49)

-80

50 100

Angle off Zenith (d eg)

Where we are now: Making the aerogels more conformable

7

Rigid polymer backbone 25 to 75 % flexible links included in polymer backbone

25 % of rigid links replaced by flexible links

1

•

Antenna Design Process

8

Circular Patch Element Triangular Lattice Sub-Array Conformal Prototype Array for Flight Test

Realized Gain Plot 1

120

-~ .o Minc-<Ul.46

•

1 20 •• • 5.%B(RealizedGainToto1I)

Making an Antenna Lightweight & Conformal

Phased array composition• Flexible aerogel layers (~3.3 mm) maximizes the benefits of the low dielectric constant• Thin multi-layer stack of higher dielectric materials for the feed network• Commercial transmit/receive (TR) chip modules provide electronic weighting of each element• 64 element sub-array to demonstrate feasibility of 500-2500 element full scale antenna• 50 % mass savings over conventional design

Stacked Patch Element2.5 mm Aerogel

0.8 mm Aerogel

Microwave Printed Circuit Board (PCB) Stack

~1 mm

T/R Module 9

•

r~✓-' Cli

{~- . IC2 II 2 ·

llilrf c2 L 1c15 1111[ lill!J _ 1~. S7 (,/,, ·C15

rrr 1 . s12 I ~-- · o

• Developed technique to align and bond the aerogel substrate with the radiating elements as well as a microstrip feed layer

• Tested in an anechoic chamber at Glenn Research Center (GRC)

10

First Antenna Array Prototype Tested •

iii' ~ C

0 - - - -'iii (.!)

~ -10 -~ - - Gain Phi (sim)

ro --Gain Phi (meas) E o -20 z -50 0 50

iii' Theta [dB)

~ 0 C 'iii <.!> -10 "O

-~ -20 - - Gain Theta (sim)

ro --Gain Theta (meas) E -30 0 z -50 0 50

Theta [dB]

Antenna Subarray Design for Fabrication• Flight prototype antenna circuit board design fabrication underway.• Anechoic chamber characterization planned late September

11

•

Placement of 8x8 Array on Aircraft

Null Steering of 8x8 Array

-80

-60

-40

-20

0

20

40

-180 -120 -60 0 60 120 180

Gai

n [d

Bi]

Theta [deg]

Phi = 0 deg, array centered

Phi = 0 deg, array off-center

Radius = 16 in.

-10 0 10 20 30 40 50 60 70 80 90

Elevation Angle (degrees)

-80

-60

-40

-20

0

Nor

mal

ized

Pow

er (d

B)

Elevation Cut (azimuth angle = 0.0°)

without nulling

with nulling

interference direction

-90 -45 0 45 90 135 180

Angle off Zenith (deg)

-70

-60

-50

-40

-30

-20

-10

0

Nor

mal

ized

Gai

n (d

B)

ITU proposed mask

Standard Beam, 22.7 dBi

Synthesized Beam, 21.6 dBi

-1

-0.5

-20

V

0

-1

0.5 -0.5

U

0

0.5

Gai

n (d

B)

11

0

20

Simulated performance of 64 element sub-array – Conformed to 16” radius– Antenna-aircraft coupling effects– Beam synthesis (with quantization) and null

steering methods to meet ITU mask

12

Antenna Pattern Simulations

~20 dB sidelobe

reduction

• r------------

c____ __ I

t..

Antenna Range testing – this Fall • Capture the expected performance of the array

including gain and beam steering pattern• Validate performance after environmental testing

(e.g. vibration)

Hanger Testing on a UAS - January• Capture installed antenna performance, including

fuselage/radome attenuation effects

Flight testing on a UAS - February• Capture antenna array performance and ground

interference at low elevation angles (5º to 25º) during a UAS flightAntenna Array Simulation and Testing Flow Diagram

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Planned Testing of the CLAS-ACT Antenna • Simulation Testing

Flight Test of CLAS-ACT Antenna on Global Hawk

• Working with Global Hawk team at Armstrong Flight Research Center (AFRC)

• Testing in restricted airspace around Edwards Air Force Base (AFB)

• Antenna will be mounted on simulated fuselage

– Designed and built at Langley Reseach Center (LaRC)

• Mockup placed under radome inside the Global Hawk

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•

New Portable Antenna Metrology System

• Developed at GRC to characterize antenna in-situ• Deployed robotic scanner to AFRC hanger

• Brought antenna range to aircraft• Results on NASA’s Ikhana aided ground station design

• Pre-flight testing of antenna on Global Hawk in Jan.

Collaborative robotic arm and laser tracker used to test antenna on UAS at AFRC

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Flight Testing on a UASMeasurement ground station (MGS) will capture antenna array performance and ground interference at low elevation angles (5º to 25º) during UAS flight• Aircraft will fly paths of varying altitude and constant range • Characterize installed antenna pattern• Real world feasibility assessment of side lobe reduction

Example Flight Passes for Measuring a Region of the Antenna Pattern 16

Challenge: ground stations sensitive enough to measure a signal specifically designed

to be very small

CLAS-ACT Antenna In-Flight Characterization

~ ~ MGS

1736km AGL

Indicates UAS passes required to characterize a ITU mask

region of interest

871km AGL

• - Proposed ITU Mask at 40° Lat, 1 km altitude --0.8 m Dish Model (Bessel) --Phased Array beam synthesis (49x49)

a~------~ ---------

• Ames Research Center (ARC) developed realistic flight paths for low elevation passes

• -5 degree to -25 degree negative elevation wrt aircraft wing

• Input to Northrup Grumman to produce Final Mission Plan

Main Lobe

4th side lobe

3rd side lobe

3-D Antenna Pattern

• Sensitivity analyses – Wind effects on flight path and antenna

measurements– Dynamic noise floor analysis– Position uncertainty effects on antenna

measurements

Proposed Flight Test Plan for Global Hawk

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•

CLAS-ACT Team• James Downey• Bryan Schoenholz• Marie Piasecki• Bushara Dosa• Peter Slater• Seth Waldstein• Anne Mackenzie• Bill Fredericks• Scott Kenner• Ray Rhew• Mark Cagle• Jeremy Smith• Andy Gutierrez

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• Patricia Martinez• Ricardo Arteaga• Kelly Snapp• Rick Alena• Aaron Cohen• Baochau Nguyen• Stephanie Vivod• Haiquan Guo• Jessica Cashman• Rocco Viggiano• Marcos Pantoja• Kevin Cavicchi• Dan Oldham

•

Backup

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Conformal Lightweight Antenna Systems for Aeronautical Communication Technologies (CLAS-ACT)

• Lead Center & Partner Centers: GRC, LaRC, ARC, AFRC• External Collaborators: University of Akron• Aeronautics Barrier to Overcome: Reduce sidelobes to meet

requirements for provisional Ku band use for UAS for Beyond Line of Site Communications

• ARMD Strategic Thrusts and associated Outcome(s) addressed:– Thrust 1: Safe, Efficient Growth in Global Operations

• BLOS enabled conformable antennas for UAS will transform NAS through NextGen technologies

– Thrust 3. Ultra-efficient commercial vehicles• Improved vehicle efficiency through reduced weight and drag

– Thrust 6: Assured autonomy for aviation transformation• Enable continuous, system-wide information connectivity supporting autonomous operations

• Idea/Concept: Antennas which enable beyond line of sight (BLOS) command and control for UAS to take advantage of newly assigned provisional Ku-bands for UAS; Unique antenna designs to avoid interference with ground; Unconventional substrates to reduce weight; Conformal designs to reduce drag

• Feasibility Assessment: Demonstrate conformability of aerogel substrates and feasibility of fabrication; Demonstrate high directivity antenna with reduced sidelobes using beamforming

• Feasibility Assessment Criteria: 20 dB reduction is sidelobes; 1 m bend radius of aerogel • Duration of Execution & total full-cost: 2.5 years & $3.5 M

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Approach to more flexible aerogels

• Utilize aliphatic diamines to replace 25 to 75 mol % of aromatic diamine

• Goal is – More bendable aerogels in 2-3 mm thicknesses– Lowest dielectric constant – Best mechanical properties– Best moisture resistance

• Three different aliphatic diamines studied• Modeled data from three studies to make

comparison among them and come up with optimum formulation(s)

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H2N

O

NH2

O

NH2H2N

H2NNH2

1,3-Bis(4-aminophenoxy)neopentane (BAPN)

1,5-diamino-2-methylpentane (DAMP)

1,12-diaminododecane (DADD)

H2N NH2

2,2'-Dimethylbenzidine (DMBZ)

vs.

O

H2N NH2

4,4'-oxydianiline (ODA)

•

Antenna Pattern CalculationsRadiation Pattern for an 8x8 Array on A/C, Half Cylinder Approximation for A/C Body

Placement of 8x8 Array on Aircraft

Null Steering of 8x8 Array to Avoid Interference 50x50 Array Pattern With a 2° Beam Width, Cylindrical Approximation for A/C Body

Array layout on cylindrical platform, 16- in. radius.

X

Z Y

Normalized power pattern in two planes.

-80

-60

-40

-20

0

20

40

-180 -120 -60 0 60 120 180

Gai

n [d

Bi]

Theta [deg]

Phi = 0 deg, array centered

Phi = 0 deg, array off-center

Array layout on half-cylinder platform, 16- in. radius

3-D Gain pattern

Radius = 16 in.

-10 0 10 20 30 40 50 60 70 80 90

Elevation Angle (degrees)

-80

-60

-40

-20

0

Nor

mal

ized

Pow

er (d

B)

Elevation Cut (azimuth angle = 0.0°)

without nulling

with nulling

interference direction

-~-· .... ~~·

fo l.i.1 Ci.}m [tlB1l

DimtlMlon Matrix U~t

......... ,..,._, ~49(-l 6'.'i,9'-i ,jjS,0,e-3

!OCH

0

;;,- -20 :2.

" 3 ·40 fr_

] -60 g ~ -80

-100

·180

• I

- FFl Gain Phi = 0 deg - FF 2 Gain Phi = 90 Deg

-120 -60 0

Theta [deg]

60 120 180

Antenna Fabrication in progressAntenna Design

Fabrication

Control Design

Control Circuit Fabrication

Splitting Network

TR Module

Multi Layer Bonding

+ ~ -~~

4 -

-

Radome made out of polymer film for

protection and to allow standard fabrication

TR Modules (heat producing electronics)

RF Signal Feed Thru (may be many points) '-....

Antenna Mounting Surface

/ /4 ,........,J--1

Mounting Plate

• Antenna Elements (Cu)

-- Power and Control ' Feed Thru (may be

~any points)

RF Absorber?

Optional component

' shelf

"'- Support Arms

Effect of aliphatic diamine content on modulus

• Modulus is effected by the increase in density as aliphatic content increases

• DMBZ backbone has higher modulus than ODA even at lower density

• Picture shows DMBZ with 25% BAPN

24

10

100

8.0

8.59.0

9.510.0

3040506070

Mod

ulus

, MPa

Polym

er co

nc., w

t%

Aliphatic diamine, mol%

BAPN/ODA BAPN/DMBZ

10

100

8.0

8.59.0

9.510.0

3040506070

Mod

ulus

, MPa

Polym

er co

nc., w

t%

Aliphatic diamine, mol%

DAMP/ODA DAMP/DMBZ

10

100

8.0

8.59.0

9.510.0

3040506070

Mod

ulus

, MPa

Polym

er co

nc., w

t%

Aliphatic diamine, mol%

DADD/ODA DADD/DMBZ

H2N

O

NH2

O

NH2H2NH2N

NH2

Density, g/cm30.09 0.2 0.3 0.40.1

Mod

ulus

, MP

a

1

10

100

25 % BAPN w/DMBZ25 % BAPN w/ODA75% BAPN w/DMBZ75 % BAPN w/ODA

H2N

O

NH2

O •

High Data Rate Satellite Communications for 500 lbs. MTOW Class UAS

• 500 lbs. MTOW class UAS cannot accommodate a satellite dish antenna due to system weight and volume Ku band 48” dish antenna and associated communications equipment weight is 168 lbs. as fitted

to Global Hawk.

• Iridium satellite systems offer global reach and are compact and light enough for Group 3 UAS A single iridium channel is only 2.4. kb/s per channel; useful for command and control but

generally insufficient bandwidth for most sensor data Note that Iridium NEXT will support up to 1.4 Mbps

• For these reasons most Group 3 UAS are operated within line of site (LOS) of a ground station LOS is 150 km for an aircraft at 5000 ft. altitude assuming a ground station antenna height of 10 m

• CLAS-ACT enables Group 3 UAS to accommodate an antenna that supports high data rate (~25 Mb/s) communications via geostationary satellites, enabling beyond line-of-site operations with real time sensor-data monitoring

Note: D.O.D. UAS Group 3 is 55 lbs. to 1320 lbs.25

•

UAS for CLAS-ACT

• There are very few UAS currently available in the flight regime between relatively small (10 lb. payload) and very large (1500 lb. payload)

• The lack of medium sized UAVs is likely due to restrictive regulations and because many of the potential missions can be performed with manned aircraft Current FAA regulations require a Certificate of Authorization (COA) to fly UAVs over

55lbs. beyond visual range within the region of jurisdiction of the FAA Currently, a COA is very unlikely to be granted for flying a large UAV over populated

regions It is often expedient to use a manned aircraft, rather than obtain a COA even though

using a manned aircraft is potentially more expensive and restricted in endurance to a maximum of 12 hours or so

In the future, advanced autonomy that includes sense and avoid, plus proven very high reliability is expected to allow operation of all sizes of UAVs within the NAS

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•

UAVs for CLAS-ACT

L3 Viking 400No longer in production but NASA has several available for science missions

Dimensions Weights PerformanceWingspan 20 ft. MTOW 540 lbs. Range 560 nmiLength 15 ft. Payload 100 lbs. Endurance 8 hWing Area 43.7 ft2 Sat Comm Airspeed 70 ktsAspect Ratio Empty Weight 337 lbs. Altitude 15,000 ft.Engine Size 36 HP Fuel Weight 150 lbs.

Navmar Tigershark XP Long Range

Navmar claim beyond line-of-sight capable. Variants of this UAV are widely used by the D.O.D.

Dimensions Weights PerformanceWingspan 30 ft. MTOW 800 lbs. Range 1200 nmiLength Payload 150 lbs. Endurance 15 hWing Area Sat Comm Airspeed 80 ktsAspect Ratio Empty Weight Altitude 20,000 ft.Engine Size Fuel Weight 180 lbs.

U.S. Navy/ NASA SIERRA

Experimental aircraft, limited availability. Presumably additional aircraft could be built.

Dimensions Weights PerformanceWingspan 20 ft. MTOW 445 lbs. Range 600 nmiLength 12 ft. Payload 100 lbs. Endurance 10 hWing Area Sat Comm Airspeed 60 ktsAspect Ratio Empty Weight Altitude 12,000 ft.Engine Size Fuel Weight

NASA (ASAB) Concept UAV This is a conventional design powered by a small diesel engine

Dimensions Weights PerformanceWingspan 30 ft. MTOW 500 lbs. Range 1530 nmiLength 16 ft. Payload 50 lbs. Endurance 28 hWing Area 62.5 ft2 Sat Comm 75 lbs. Airspeed 55 ktsAspect Ratio 15 Empty Weight 275 lbs. Altitude 20,000 ft.Engine Size 50 HP Fuel Weight 100 lbs.

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Missions for 500 lbs. Class UAVs

• There are many potential missions for medium sized UAVs; one example is coastal monitoring Harmful algae blooms TurbidityWater temperature (input for weather forecasting) Pollution, e.g. oil spills Photogrammetry, to monitor erosion over time Disaster assistance, hurricanes Marine life monitoring (e.g. whales, turtles) Safety and security (Coastguard reconnaissance)

• Instrument package (weight < 50 lbs.) Hyperspectral imager High definition video and still camera Thermal camera Data processing computer Data storage

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GT study: CLAS-ACT Benefits Summary

• Increased responsiveness: ability to quickly and effectively communicate with aircraft

• Airspace management: quickly and easily redirect UAVs to prevent accidents

• Increased efficiency, communication, and coverage in swarm applications

• Vehicle health and performance monitoring

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Source: Development of Cloud-Based UAV Monitoring and Management System

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GT study: Some examples of UAV mission types and impact from CLAS-ACT antenna

Relative Score

Mission Examples CLAS-ACT benefits summary

First Responder and Emergency Support

•Search and rescue• Fire fighting• Medical assistance• Supplies delivery

• Recognition of situation changes• Remotely providing help and support (supplies and instructions)

Disaster relief • Rapid response• Rescue assistance• Disaster modeling

• Visualize and locate site and severity of disaster• Instant situation updates in harmful environments• Independence from ground-based systems that may be damaged

Scientific •Volcano measurement•Species monitoring•Fishing and oceanic•Extreme environments

• Real time data gathering• Fast and accurate responder• Minimal human risk and interaction

Package delivery •Mail•Commercial and private delivery

• Real-time tracking• Fast and accurate redirection

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• • ~

•

GT study: Surface area, drag, weight of CLAS-ACT antenna

• Surface area– Assuming a steady 30°bank angle turn the

required area increases by 15% to 0.29 m2(3.11 ft2)

– Smallest size UAV (ThunderB) has a wing area >6x larger than this (~2 m2)

• Drag– Thickness of 1 cm– Will require a ramp to ensure lift not affected– Estimated drag increase <1% if applied to

entire wing of smallest vehicle• Weight

– For required area the weight is 0.87 kg (1.9 lb)– Smallest UAV has a payload of ~8.8 lb

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http://www.bluebird-uav.com/wp-content/uploads/2014/07/SpyLite-GDT-710x375.jpg

•