Progress in Reflectarray Antenna Research: From Enhanced Frequency Features to Advanced Radia:on Capabili:es

Transcription

1 Progress n Reflectarray Antenna Research: From Enhanced Frequency Features to Advanced Rada:on Capabl:es Fan Yang Mcrowave and Antenna Insttute Electronc Engneerng Department Tsnghua Unversty

2 OUTLINE! v Introducton of reflectarray antennas v Reflectarray analyss and synthess methods v RA wth enhanced frequency features v RA wth advanced radaton capabltes v Conclusons

3 Antenna Classfcatons Low gan antenna 1. Gan < 10 db 2. Examples: * Dpole and loop * Mcrostrp and slot 3. Applcatons: cell phone laptop PDA WLAN etc. Mddle gan antenna < Gan < 20 db 2. Examples: * Horn antenna * Spral antenna 3. Applcatons: base statons antenna & EMC measurement Hgh gan antenna 1. Gan > 20 db 2. Examples: Reflector lens * Antenna array 3. Applcatons: space and satellte comm.

4 Images are from and Hgh Gan Antenna Development Parabolc Reflector New hgh-gan antennas Reflectarray o Smple well developed Ø Bulky lmted beam scan Mcrostrp Array o Low profle o Low mass o Easy to fabrcate o Easy for crcutry ntegraton o Element phase: ndvdual control o Low profle flexble beams Ø Power loss n the feed network o Beam-scannng reflectarrays o Amplfyng reflectarrays o Mult-beam reflectarrays o Contour-beam reflectarrays

5 Reflectarray Antennas Planar reflectng surface Feed antenna 1. R. E. Munson and H. Haddad Mcrostrp reflectarray for satellte communcaton and RCS enhancement and reducton U.S. patent August J. Huang Mcrostrp reflectarray antenna for the SCANSCAT radar applcaton JPLPublcaton No Nov D. M. Pozar and T. A. Metzler Analyss of a reflectarray antenna usng mcrostrp patches of varable sze Electroncs Letters Aprl 1993.

6 Phasng Elements n Reflectarrays Phase/tme delay lnes Varable element sze Element rotaton

7 Reflectarray Applcatons 3m aperture dual- frequency RA Integra:ve desgn of RA & solar panels JPL NASA 77GHz RA usng LC materal and LTCC technque GAC ESA

8 OUTLINE! v Introducton of reflectarray antennas v Reflectarray analyss and synthess methods v RA wth enhanced frequency features v RA wth advanced radaton capabltes v Conclusons

9 Reflectarrays Desgn Overvew Z q Desgn goals: R θ o rˆo Radaton patterns Beam drecton Y Drectvty φ o Gan and effcency r th element X Bandwdth Axal rato Ø Desgn parameters: Aperture sze D feed locaton f/d and feed pattern q value. Phase elements: patch rng dpole; substrate thckness & permttvty. Phasng approaches: varable sze element rotaton delay lnes.

10 Reflectarray Desgn Engne Analyss Tools Planar and Conformal Systems Radaton Analyss Array Theory Aperture Feld Full-wave Effcency Analyss Illumnaton effcency Spllover effcency Optmzaton Tools Phase-only Optmzatons Alternatng Projecton Method APM Partcle Swarm Optmzaton PSO M Measurement Tools Near-Feld Measurements Spectral NTFF Prncpal plane pattern cuts Mcrowave Holography Measured aperture felds for accurate smulatons Phase Error Analyss x 0 B x

11 Element Analyss Source Observaton Substrate Metal Patch Perodc Boundary Condtons Ground Plane FDTD model Full-wave analyss of unt cell: Ø Infnte array approach: n-house FDTD program Ansoft Desgner HFSS CST FEKO Ø Incdent angle phase range phase quantzaton quas-perodc

12 Effcency Analyss Aperture effcency η A :! A =! s!! t!! p!! o η η s - spll over η - llumna0on η t - taper η p - phase Spllover loss Effcency % η Illumnaton taper Z feed η s η a

13 Radaton Pattern Analyss Array theory approach Aperture feld method Full wave smula0on E uˆ E E M N = m= 1 n= 1 A mn uˆ = xˆ sn θ cos ϕ + ref x ref y m n Γ = m n Γ uˆ I r xx yx mn yˆ sn θ sn ϕ + zˆ cosθ Γ Γ xy yy E E nc x nc y m n. m n Radaton Pattern db Array Theory Aperture Feld co-pol Aperture Feld x-pol ! 1 degrees Radaton Pattern db Aperture Feld co-pol FEKO co-pol! FEKO x-pol ! degrees 1 50 Radaton Pattern db Measurement Smulaton α degrees 1

14 Reflectarray Desgn Roadmap Element desgn System desgn Element type Beam drecton Gan GEA: Aperture sze feed locaton Element parameters Phase compensaton RA: Aperture felds Prototype & measurement RA: Far feld Comparson: Patterns Drectvty Gan Axal Rato Bandwdth

15 OUTLINE! v Introducton of reflectarray antennas v Reflectarray analyss and synthess methods v RA wth enhanced frequency features Ø Broadband reflectarrays Ø Mult-band reflectarrays v RA wth advanced radaton capabltes v Conclusons

16 Bandwdth of Reflectarrays q Prnted reflectarray has an nherent narrow bandwdth. q Bandwdth of a mcrostrp reflectarray s lmted prmarly by two factors. 1 Bandwdth of Elements o A mcorstrp patch element generally has a bandwdth of about 3 to 5 %. 2 Dfferental Spatal Phase Delay at the desgn frequency Δ s = N + dλ as frequency changes Δ s = N + d λ + Δλ where N s an nteger dλ s the compensated phase

17 Bandwdth Enhancement Methods Element bandwdth Wdeband phase synthess 9.5% 4.8% 5.8% 7.6% 10.9% 16.3%

18 Broadband Sub-λ RA: Freq. Behavor Γ degrees λ/2 elements λ/3 elements λ/4 elements Phase Error degrees λ/2 elements λ/3 elements λ/4 elements Frequency GHz Frequency GHz λ/2 desgn λ/4 desgn

19 Broadband Sub-λ RA: Prototypes λ/2 element spacng array λ/3 element spacng array 848 patches 1941 patches Crcular aperture D = nch = 32 GHz Materal 20 ml Rogers 5880 ε r =2.2 substrate wth 0.5 ounce claddng

20 Broadband Sub-λ RA: Patterns 32 GHz Gan db λ/2 array λ/3 array Smulaton Measurement

21 Broadband Sub-λ RA: Gan & BW λ/2 array: The 1 db gan bandwdth s 8.03% GHz to GHz λ/3 array: The 1 db gan bandwdth s 10.94% GHz to GHz

22 Sngle-Layer Tr-Band RA: Geometry Element geometry: 1. Ka band 32 GHz: v Crcular rng for CP v Use angular rotaton technque for phase compensaton 2. C band 7.1 GHz: v Cross dpole for reversed CP v Adjust the dpole sze for phase compensaton 3. X band 8.4 GHz: v Splt square loop for CP v Change slot postons for phase compensaton Prnted on a sngle layer h = 62 ml ε r =2.33.

23 Sngle-Layer Tr-Band RA: Prototype A crcular reflectarray wth a dameter of meter ncludng: 692 cross dpoles at C band 7.1 GHz 685 square rngs at X band 8.4 GHz crcular rngs at Ka band 32 GHz

24 Sngle Layer Tr-Band RA: Results Ka band 32 GHz X band 8.4 GHz C band 7.1 GHz Peak Gan db Center Frequency f c -1 db Bandwdth % η f c % Ka X C

25 OUTLINE! v Introducton of reflectarray antennas v Reflectarray analyss and synthess methods v RA wth enhanced frequency features v RA wth advanced radaton capabltes Ø Mult-beam reflectarrays Ø Beam scannng reflectarrays v Conclusons

26 Advanced Radaton Performance of RA An mportant feature of RA: Reflecton phase of each element can be ndvdually adjusted è abundance of desgn freedom. Ø Advanced radaton propertes: Multple beams from a sngle feed; Contoured beam pattern or shaped beam pattern; Wde beam scannng angles.

27 Drect Methods for MBRA Desgn Geometrcal Approach The reflectarray surface s dvded nto N sub-arrays each radatng a beam n a gven drecton. Dsadvantage: q Hgh sde-lobe levels q Gan reducton and beam wdenng Problem: Sub-Arrays wth Smaller Apertures Superposton Approach = = N n y x j n R n e y x A y x E 1 φ The feld on the reflectarray surface Number of beams = = N n y x j Feed R n e y x A y x E 1 φ 1 1 = N n y x j e φ n Problem: Ampltude Error Dsadvantage: q Reduced gan due to sde-lobes q Hgh sde-lobe levels = = N n y x j Feed n e y x A y x 1 φ φ

28 Alternatng Projecton Method APM q APM or ntersecton approach s a robust local optmzaton search that s well suted for optmzaton of large array antennas. q An teratve process that searches for the ntersecton between two sets. O.M. Bucc G. Mazzarella and G. Panarello Reconfgurable arrays by phase-only control IEEE Trans. Antennas Propag. vol. 39 no. 7 pp July < > = v u M v u F v u F v u F v u M v u M v u F v u M v u F v u M v u F v u F v u F v u M v u F P L L U L U U M x 0 x B M

29 A Symmetrc MBRA APM Method 0-5 Measured Quad-Beam Smulated Quad-Beam Smulated Sngle-Beam Radaton Pattern db Measured gan 25.3 db θ degrees 0-5 Measured Quad-Beam Smulated Quad-Beam Radaton Pattern db θ degrees P. Nayer F. Yang and A. Z. Elsherben Desgn of a sngle-feed quad-beam reflectarray antenna IEEE Trans. Antennas Propag. vol. 60 no. 2 pp Feb

30 Partcle Swarm Optmzaton PSO q A powerful global optmzaton method developed by Kennedy and Eberhart n q A stochastc evolutonary optmzaton technque based on the movement and ntellgence of swarms. q It s comparable n performance wth other stochastc optmzatons such as genetc algorthm GA wth the added advantage that PSO s much smpler to mplement. Very large number of elements What s the challenge? e.g. ~ 1000 element array 400 partcles teratons 1. J. Kennedy and R. C. Eberhart Partcle swarm optmzaton n Proc. IEEE Conf. Neural Networks IV Pscataway NJ mllon ftness evaluatons 2. J. Robnson and Y. Rahmat-Sam Partcle swarm optmzaton n electromagnetcs IEEE Trans. Antennas Propag. vol. 52 no. 2 pp Feb D. W. Boernger and D. H. Werner Partcle swarm optmzaton versus genetc algorthms for phased array synthess IEEE Trans. Antennas Propag. vol. 52 no. 3 pp Mar

31 An Asymmetrc MBRA PSO Method 1 Smulaton -2 1 Measurement v 0-8 v u Measurement u

32 Beam Scannng Reflectarray Antenna The phase on the reflectarray aperture can be changed to scan the beam φ x y = k0d + φr x y Z rˆo spatal delay control θ o Y element phase control Feed Dsplacement The phase center of the feed s moved to scan the beam r φ o th element X Aperture Phase Tunng The phase of RA elements s changed to scan the beam Hybrd Desgn Improve system performance Reduce system cost

33 B-Focal Beam Scannng RA Ø Tradtonal parabolc RA: Ø B-focal desgn concept: Gan db θ degrees - xz-plane

34 Reflectarray Optmzatons Radaton Pattern db Radaton Pattern db Conventonal Desgn Bfocal Desgn θ degrees Bfocal Desgn PSO Desgn PSO θ degrees MOPSO Radaton Pattern db Radaton Pattern db θ degrees PSO MOPSO PSO MOPSO Slght ncrease n SLL ~2dB Beam at + 10 Sgnfcant mprovement n SLL Beam at θ degrees

35 BSRA Prototypes & Measurements Parabolc PSO B-Focal MOPSO 32GHz D=160mm 848 patch elements Smulatons Measured Parabolc B-focal MOPSO PSO 20 Gan Gan db Gan db db θ degrees degrees θ degrees degrees

36 Infrared & THz Reflectarrays Loss at hgh frequency! Delectrc reflectarray

37 Conformal Reflectarray Z û Observaton drecton r f û o Man beam drecton X mn th element Y For D/R c = 1 the gan loss n the conformal desgns are: Concave desgn 0.1 db Convex desgn 0.6 db Inkjet slver prntng on flexble materal: Kapton

38 OUTLINE! v Introducton of reflectarray antennas v Reflectarray analyss and synthess methods v RA wth enhanced frequency features v RA wth advanced radaton capabltes v Conclusons

39 Conclusons The prnted reflectarray s a new genera:on of hgh gan antenna and ts mul:tude of capabl:es wll encourage con:nuous development and exc:ng applca:ons n the future John Huang Analyss desgn and measurement technques RA wth wdeband and mult-band features RA wth mult-beam and beam-scannng operatons New fronters: nfrared & THz RA conformal RA Exctng applcatons n space exploraton satellte communcatons radar remote sensng

40 Acknowledgements Ø Thanks to the project collaborators: Colleagues: Students: A. Elsherben J. Huang Y. Rahmat- Sam G. Boreman H. Xn S. Xu A. Yu Y. Km B. Devreddy T. Elsherben P. Nayer Y. Mao A. Abdelrahman F. Guo W. An S. Cheng X. Lu Ø Thanks to the project sponsors: NASA: MSSGC EPSCoR Natonal Scence Foundaton NSF Chnese Hgh-Tech Research and Development Plan

41 Thanks! Questons?