Antenne a metasuperfice modulata Potenziale applicativo per lo spazio

Toward a revolution in antennas?

Overview

Modulated metasurface antennas are undoubtedly a new area of development in the antenna field.

The European Space Agency is active in this area since many years and this presentation focuses on the following points:

• Background

• Motivations

• Current status

• Perspectives

Historical background

1. Oliner seminal work (1959)

2. Holographic antennasa. Checcacci, P.; Russo, V.; Scheggi, A., “Holographic antennas”, IEEE Trans.

Antennas Propag., Volume: 18 , Issue: 6, Year: 1970 , Page(s): 811 – 813

b. Iizuka, K.; Mizusawa, M.; Urasaki, S.; Ushigome, H., “Volume-type holographicantenna”, IEEE Trans. Antennas Propag., Volume: 23 , Issue: 6, Year: 1975, Page(s): 807 – 810

3. Frequency sensitive surfaces

4. Photonic bandgap structures

5. Metamaterials

Holographic antennas

Checcacci (1970) Iizuka (1975) Elsherbiny (2004)

Università di Siena (2006-2010)

May years after Oliner’swork, some application of its idea to antennas started to surface.

Current R&D landscape

• USA

Sievenpiper, Colburn (UCSD), Grbic (Umich), Smith (Duke)

Mostly concentrated on electronic scanning with -pixel control, large number of patents

• Europe

Maci, Martini, Caminita - Università di SienaVecchi, Matekovitz - Politecnico di TorinoFreni – Università di FirenzeDe Vita – IDS Ingegeneria dei SistemiCasaletti - Université de Paris 6Sauleau, Ettorre - Université de RennesGomez, Tornero - Universidad Politécnica de CartagenaRajo Iglesias - Universidad Carlos Terciero MadridNeto, Lombard - Technische Universiteit DelftLuukkonen, Treviakov - TKK Helsinki Sabbadini, Minatti – ESA-ESTEC

Patent US20120194399

Key motivations: strategic

The space sector appears to be lowering its growth rate, while global competition increases as the offer from emerging countries grows.

As a consequence, the need for cost reduction to maintain European Industry competitiveness becomes stronger and stronger.

An increase in modularity and design reusability, without compromising performances is therefore very desirable.

Key motivations: programmatic

Matematerials and metasurfaceshave been the object of extensive research over past decades.

Today, the application of (modulated) metasurfaces to antennas is quickly gaining momentum and the application potential appears to be large.

Conjugate-Matched Metasurface AntennasThe trend toward miniaturisation to reduce mass and envelop (and cost) for a same type of mission is strong.Antennas are a well known and somewhat distressing example of the opposite tendency.Yet, the challenge to at leastsave mass and reduce cost isthere needs to be answered.

Key motivations: technologic

Conjugate-Matched Metasurface Antennas• Use sub-wavelength features to gain control of surface

impedance at antenna boundaries• Exploit the added freedom for improved solutions

The modulated metasurface answer

ESA Technology developments

A number of activities have produced promising results so far other sare being started

1. Innovative Planar Highly Directive Antenna Based on Artificial SurfacesLEO X-band Data downlink (IDS, UniSi, UniFi)

2. Scalable low-mass low-envelope high-to-very-high gain antennaScience and Exploration HGA X-ban (IDS, UniSi, TASI)

3. Shared aperture reflector antennaShaped-reflector antenna enhancement (Ticra, UniSi)

4. Biomass calibration radar transponder assessmentStudy of a metasurface-enhanced array solution (ESA, Wave Up, UniSi)

5. Beam shaping by surface impedance controlTelecom antenna solutions using curved metasurfaces (UniSi, IDS, MVI, Ticra)

6. Thin metasurface lensesStudy of metasurface lenses to enhance reflector antennas (UniSi, Wave Up, ESA)

X-band data downlink from LEO

Isoflux pattern: uniform power density at the Earth surface.

Bandwidth: 8.5-8.7 GHz.

Polarization: circular.

Cross polar: lower than -6dB.

X-band isoflux CP antenna prototype

Performances

Antenna plane

Feeding line plane

Ground plane

Sectoral-beam version

Re-using the same basic design…

High-gain antennas

Very similar behaviour and two very different technologies

The strong gain reduction is due to the high losses of dielectric used for the second antenna (ABS !)

Array enhancement

Reduce complexity by replacing the tapered portion of an array for very low-sidelobe and cross-polar with a metasurface

0 0.5 1 1.5 2 2.5 3 3.5 40

0.2

0.4

0.6

0.8

1

1.2

1.4

/Lambda

Aperture Distribution

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90-60

-50

-40

-30

-20

-10

0

10

20

30

[Deg]

dBi

Directivity

Aperture distribution

Antenna directivity

-0.04

-0.02

0

0.02

0.04

-0.02

0

0.02

0123

x 10-3

Severe beam degradations!

MetaReflector concept

A metasurface reduces scan aberrations by improving beam collimation

Correction of aberrations

Initial design obtained with ray optics approximation

Enhanced avionics antennas

Miniaturised X-band TT&C antenna25×25×33 mm (ESA study)

Pattern control and interference reduction

Improved beam shape

The use of a metasurface allows a better control of the antenna pattern adding very little complexity.

Metasurfing and meta-lenses

Use metasurface to guide the surface wave or to shape a space wave

adding further freedom.

Many applications can be envisaged:

• Taper control in FSS reflectors

• Beam formers

• Improved radome performances

• RF-Enhanced thermal blankets

A robust design methodology

A complete design procedure has been developed and validated covering all steps from initial sizing to accurate performance assessment and a patent application filed by ESA.

Several possible implementations

Besides the ones shown so far, several other implementation options exists, ranging from fully metallic to purely dielectric structures and all their possible combinations.

Also combinations with variable materials, e.g. nematic crystals are known to be in principle feasible.

While at least for on-board solutions, the simplest solutions remain the most promising, wide-range exploration is useful to fully assess the potential.

Pin bed Printed elements

Modulated dielectric Multi-layer grid

More possibilities…

A.J. Martinez-Ros, J.L. Gomez-Tornero, G. Goussetis - IEEE AP

Not really a metasurface: a metaline ?

A rough technology map

1 10 100 f (GHz)

0.1

1

Size(m)

2“Printed circuit”

Filled honeycomb

Shaped dielectricMetal-only

Interwoven dielectrics

3D printing

Sandwich technologies

Optical technologies

Other potential applications

Radio links

TVROBase stations

Medical

Main achievement (so far)

The feasibility of a new flexible antenna technology has been demonstrated.

The first examples offer ultra-thin and lightweight solutions with performances comparable to existing ones.

Open issues

Needless to say there are several open issues, but more important there a few known limitations:

• Multiband structures are not easy to obtain

• Aperture efficiency is as yet suboptimal

• Design procedure implementation limited to printed structures

• Design optimisation tools have limited reach owing to complexity

Value for space applications

Modulated metasurfaces antennas:

• Are applicable to several antenna architectures

• Result in products based on already available technologies

• Have a potential for performance improvement in several area• Direct pattern and polarisation control• Low-envelope, low-complexity, low-mass alternative in many cases• First design and performance estimate very close to final solution

• Allow single-qualification multiple-missions customisable antennas• The same basic design can be used for many antenna patterns• A small range of antennas could cover common space-systems needs• Only RF testing required, plus possibly a delta-qualification

• Are amenable to dynamic re-configuration…

Metasurface Antennas in Space

Several applications of modulated metasurface antennas are conceivable in the space sector, for instance:

Space segment

• LEO Data downlink, mainly for Earth Observation – feasibility proven• HGA for Science and Exploration missions – under development• Aperture sharing for shaped reflector antennas for Telecomms - started• Compact “reflector antennas”, mainly TLC (EO, Science, Expl.) - started• Horns and beam formers (TLC, EO) – started (horns)• Beam-shaping frequency or polarisation selective screens (TLC)• SAR antenna panels, Sounder antennas (EO)• Navigation transmit antennas (NAV)

Ground segment

• Narrow-beam satellite ground terminals (portable and mobile)• TVRO • GNSS high-end receivers

Configuration mapping

Metasurface configuration

Applications

Science EO Telecom Navigation

Flat panel fed in plane (holographic) HGA PDHT Payload Tx antenna

Array SAR Payload

Lens antennas Radar Payload

Integrated in thermal blanket LGA TT&C

Reflector antenna Radar Payload

Panel with metasurface feeder MGA Terminal Rx antenna

Curved panel fed in plane PDHT Terminal

Horn with metasurface walls (also outside) MGA Payload

Metasurface cup with (metasurface) feeder MGA Terminal

Helix equivalent MGA TT&C TT&C

Conical/cylindrical antenna MGA TT&C

Bicone equivalent TT&C

Faceted antenna HGA

Cradle-like array SAR Payload

Lens-based BFN Payload

ESA activities

0102 0304 05 06 070809 101112

201101 02 0304 0506 07 0809 1011 12

20120102 030405 06070809 1011 12

201301 02 0304 05 0607 08091011 12

20140102 030405 06 070809 101112

2015

Running In TRP Plan In ARTES Plan Fund request

Low mass and volume X-band HGA for Exploration

Innovative Planar Highly Directive Antenna Based on Artificial

Surfaces

Meta-reflectors

Assessment of Metasurface

Antenna Configuration,

Technology and Implementation

Meta-horns

Antennas based on metasurface facets

Antennas based on (highly) curved metasurfaces

Shared aperture reflector antenna

Beam shaping by surface impedance control

Scalable low-mass low-envelope high-to-very-high gain antenna

Conjugate-Matching Antenna Design Tool

Metasurface Characterisation Methodology

In GSTP Plan In other plans

0102 030405 06 070809 101112

2016

Engineering model of X-band HGA for Exploration

Engineering model of isoflux antenna for LEO

0102 0304 05 06 070809 101112

2017

Low-complexity data downlink antenna

AMC/Metamaterial Antennas for Broadband Connectivity

Beam-scanning metasurface antennas(Internal research fellowship)

Metasurface Antenna Potential and Tecnhology Assessment (Internal work)

Conjugate-Matched Metasurface Enhanced Array

Meta-lenses

Completed Intended

Thin Metasurface Lenses (external Post-doc)

Meta-arrays

Other related research areas at ESA

The Agency is also actively pursuing technology developments in neighbouring areas, like:

• Artificial Magnetic Conductors in antennas

• Millimiter-wave metamaterial lenses (multilayer metasurfaces)

• Active surfaces (uniform metasurfaces with active elements)

• Metamaterial waveguides

Conclusions

It is possible todesign the boundary condition at

the antenna surfaceinstead of

adjusting the antenna shape to exploit a fixed boundary condition

leading to significant advantages

fatti non foste a viver come bruti,ma per seguir virtute e canoscenzaD.Alighieri, La Divina commedia, Inferno, Canto 26°, 119:120