metamaterials based radar antenna marketed for UAV sense and avoid

Echodyne’s Chief Technology Officer Tom Driscoll, left,
and CEO Eben Frankenberg, with their radar prototype in
an anechoic chamber for precise antenna measurements.
(Erika Schultz/The Seattle Times)

Bellevue company develops advanced radar system | The Seattle Times
Echodyne brings first metamaterials based radar antenna to market | 2015-12-07 | Microwave Journal

Echodyne Corp. announced limited availability of its first metamaterials electronically scanning array (MESA) for radar applications. Echodyne’s MESA makes high performance radar far easier to
deploy by lowering both the cost and weight by up to 10 or more times while decreasing the size of the antenna by up to 5 or more times over traditional electronically scanned arrays. The first product from Echodyne, a metamaterials electronically scanning array for X-band (MESA X-EVU) is now available for partners and integrators interested in evaluating MESA for radar systems in a variety of commercial markets including maritime, aviation, and surveillance/security among others.


Echodyne’s MESA X-EVU combines ultra-low C-SWAP (cost, size, weight, and power) with ultra-fast beam steering (sub-microsecond) in an electronically scanning array that can be integrated into new or existing radar systems.


Unlike conventional mechanical apertures which steer a radar beam using motorized gimbals, Echodyne’s MESA requires no moving parts to steer its beam. And unlike Phased Array radars or Active Electronically Scanning Array (AESA) radars that use complicated, expensive, and inefficient transmit/receive modules which include phase shifters, amplifiers, circulators, and low noise amplifiers behind every single antenna element, MESA uses a vastly simpler metamaterials architecture. The net effect of this simplified architecture is dramatically lower
cost, size, weight and power.

Specifications

Echodyne’s MESA-X-EVU operates at X-band and has a broad field of view (±50° in azimuth and ±45° in elevation) which it can scan very rapidly given its sub-microsecond beam switching speed.  The MESA-X-EVU subsystem includes the metamaterial array, the array control driver circuitry, and the beam steering computer. Fully assembled without packaging, the subsystem is a mere 50 x 18 x 2.5 cm with a total weight of only 1.4 kg. While this size and weight already demonstrates a vast
improvement over traditional electronically scanning arrays, Echodyne will be decreasing this even further as the company optimizes the technology for various implementations.  The aperture is  controlled through a simple USB 2.0 interface and requires only a single +12 DC source to operate. Integrators and radar manufacturers interested in evaluating MESA-X-EVU can connect their own Pulsed or FMCW transceivers through a single coax SMA port.

Related/Background:

• spendergast: Metamaterials for Radars and RCS Reduction 

•  Driscoll, T.; Urzhumov, Y.; Landy, N.; Basov, D.; Smith, D.R., "Dielectric metamaterials and composites in the age of 3D printing, and directional cloaking," in Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS), 2013 7th International Congress on , vol., no., pp.361-363, 16-21 Sept. 2013

• doi: 10.1109/MetaMaterials.2013.6809053
• Abstract: The rapid evolution of additive manufacturing techniques has the potential to revolutionize a wide range of fabrication-limited fields. In this article, we apply plastic additive manufacturing to the creation of radio-frequency electromagnetic devices, demonstrating a metamaterial-like unidirectional cloak. Enabling this all-dielectric cloak is a computational boundary-optimization design approach significantly different from traditional metamaterial design techniques. For a subset of applications, the new all-dielectric cloak proves to work as well as well as previous metal-inclusive designs.
• keywords: {dielectric materials;electromagnetic metamaterials;invisibility cloaks;optimisation;three-dimensional printing;3D printing;additive manufacturing techniques;all-dielectric cloak;computational boundary-optimization design approach;dielectric composites;dielectric metamaterials;directional cloaking;fabrication-limited field;metal-inclusive designs;metamaterial-like unidirectional cloak;plastic additive manufacturing;radio-frequency electromagnetic device creation;traditional metamaterial design techniques;Electromagnetics;Fabrication;Metamaterials;Scattering;Three-dimensional displays},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6809053&isnumber=6808931
• Sleasman, T.; Imani, M.F.; Xu, W.; Hunt, J.; Driscoll, T.; Reynolds, M.S.; Smith, D.R., "Waveguide-fed Tunable Metamaterial Element for Dynamic Apertures," in Antennas and Wireless Propagation Letters, IEEE , vol.PP, no.99, pp.1-1
• doi: 10.1109/LAWP.2015.2462818
• Abstract: We present the design of a tunable metamaterial element that can serve as the building block for a dynamically reconfigurable aperture. The element—a complimentary electric-LC (cELC) resonator—is patterned into the upper conductor of a microstrip transmission line, providing both a means of exciting the radiating metamaterial element as well as independent access for biasing circuitry. PIN diodes are connected across the capacitive gaps of the cELC and a DC bias current is used to switch the junction between conducting and insulating states. The leakage of RF signal through the bias line is mitigated by integration of a radial decoupling stub. The proposed design and operation of the element are demonstrated through full-wave electromagnetic simulations. We discuss the potential application of the cELC element as a building block for metamaterial apertures capable of dynamic beam-forming, imaging, or security screening applications.
• keywords: {Apertures;Arrays;Electromagnetic waveguides;Magnetic materials;Metamaterials;Microstrip;Resonant frequency;Aperture antennas;metamaterials;tunable circuits and devices},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7173427&isnumber=4357943
• Ebadi, S.; Driscoll, T.; Smith, D., "Visual illustrations of microwave holographic beamforming using a modulated surface-impedance metamaterial," in Antennas and Propagation Society International Symposium (APSURSI), 2013 IEEE , vol., no., pp.2343-2344, 7-13 July 2013
• doi: 10.1109/APS.2013.6711830
• Abstract: We demonstrate the use of a metamaterial to transition between a guided surface mode and a designed radiative aperture distribution. Plots of the field distribution at incremental distances removed from the aperture plane illustrate the transformation from the reference mode to the designed radiative aperture field - in this case a localized plane-wave mode which produces a pencil beam at one angle.
• keywords: {array signal processing;metamaterial antennas;microwave antenna arrays;microwave holography;microwave metamaterials;surface impedance;aperture plane;designed radiative aperture distribution;designed radiative aperture field;field distribution;guided surface mode;localized plane-wave mode;microwave holographic beamforming;modulated surface-impedance metamaterial;pencil beam;reference mode;Apertures;Impedance;Magnetic materials;Metamaterials;Microwave theory and techniques;Surface impedance;Surface waves},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6711830&isnumber=6710651
• Ebadi, S.; Landy, N.; Perque, M.; Driscoll, T.; Smith, D., "Wideband coaxial to substrate-integrated waveguide transition in a multilayer reconfigurable antenna configuration," in Antennas and Propagation Society International Symposium (APSURSI), 2014 IEEE , vol., no., pp.454-455, 6-11 July 2014
• doi: 10.1109/APS.2014.6904558
• Abstract: A low-profile, wideband transition between a coaxial waveguide and a substrate integrated waveguide (SIW) is presented in this paper. The transition is designed for a reconfigurable metamaterial antenna realized in multilayer Printed Circuit Board at X-band. The transition achieves S11 below -15dB across a bandwidth of 19%, making it attractive for many practical applications. Full wave simulation results will be presented along with subtle details of the fabrication such as effects of prepreg layers.
• keywords: {broadband antennas;coaxial waveguides;metamaterial antennas;printed circuits;substrate integrated waveguides;waveguide antennas;waveguide transitions;SIW;X-band;full wave simulation;low-profile wideband transition;multilayer printed circuit board;multilayer reconfigurable antenna configuration;prepreg layer effect;reconfigurable metamaterial antenna;wideband coaxial to substrate-integrated waveguide transition;Antennas;Nonhomogeneous media;Radio frequency;Substrates;Waveguide transitions;Wideband},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6904558&isnumber=6904322
• Machado, M.; Ebadi, S.; Driscoll, T.; Smith, D., "Experimental improvement of birefringence and response time in Liquid Crystals using surface preparation of polyimide at 20GHz," in Microwave Symposium (IMS), 2014 IEEE MTT-S International , vol., no., pp.1-4, 1-6 June 2014
• doi: 10.1109/MWSYM.2014.6848609
• Abstract: This paper presents an experimental study analyzing the effects of surface treated Polyimide (PI) on dielectric anisotropy and response time of Liquid Crystal (LC) in an In-Plane Switching (IPS) cell design. A Co-Planar Waveguide (CPW) transmission line is used as an in-plane interrogation architecture, with a layer of LC enclosed on top of the CPW. By applying different surface preparations of PI, we are able to derive an optimum condition to maximize birefringence and minimize response times at 20 GHz. Measured phase change is increased from 28 deg to 72 deg for the same length of the CPW line. At the same time, measurement results show that fall time is decreased from 9.32 s down to 4.1 s. These improvements will facilitate realization of LC in microwave devices in need of fast and tunable materials.
• keywords: {birefringence;coplanar waveguides;liquid crystal polymers;birefringence;co-planar waveguide transmission line;dielectric anisotropy;frequency 20 GHz;in-plane interrogation architecture;in-plane switching cell design;liquid crystals;microwave devices;polyimide;response time;surface preparation;time 4.1 s;time 9.32 s;Face;Frequency measurement;Gaskets;Integrated optics;Optical sensors;Liquid crystal;in-plane switching;polyimide;response time;switching speed},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6848609&isnumber=6847849
• Mallik, A.; Kundu, S.; Goni, M.O., "Gain and SAR improvement of a conventional patch antenna using a novel Pi-shaped DNG metamaterial," in Electrical Information and Communication Technology (EICT), 2013 International Conference on , vol., no., pp.1-6, 13-15 Feb. 2014
• doi: 10.1109/EICT.2014.6777862
• Abstract: Conventional microstrip patch antennas have several advantages such as low profile, light weight and low cost over the others, but lag behind in some criterion such as low gain and high SAR, where using metamaterials can be a possible solution. In this paper, a, antenna system is proposed where an S-shaped planar antenna, operating at frequencies of 11 GHz and 13 GHz, uses a Pi-shaped double negative metamaterial array, designed in CST, to improve its gain and SAR. In this system, metamaterial array is applied not as an antenna, but as an associating device for the planar antenna. This array can be implemented on a printed circuit board while maintaining a specific distance from the patch antenna. The gain of the antenna system is enhanced by 6.063 dB at 11 GHz (Increase of 1088.5%) and 3.77 dB at 13 GHz (Increase of 83.4%). The metamaterial array is placed between the antenna and a human-head model which clearly reduces the SAR by 1.379 W/kg at 11 GHz (Decrease of 99.99%) and 1.774 W/kg at 13 GHz (Decrease of 99.66%). This system is applicable for any X and K_u band applications such as satellite and Radar communications, where high gain and directivity is required. The negligible SAR value announces its capability of being used in any portable communication device where human-safety is a major concern.
• keywords: {metamaterial antennas;microstrip antennas;microwave antenna arrays;planar antennas;printed circuits;CST;Ku band applications;Pi-shaped DNG metamaterial;Pi-shaped double negative metamaterial array;S-shaped planar antenna;SAR improvement;X band applications;frequency 11 GHz;frequency 13 GHz;gain improvement;human-head model;microstrip patch antennas;portable communication device;printed circuit board;radar communications;satellite;Antenna arrays;Arrays;Gain;Metamaterials;Patch antennas;Synthetic aperture radar;Double negative metamaterial;farfield gain;microstrip patch antenna;specific absorption rate;sub-wavelength structure},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6777862&isnumber=6777807
• Liu, Y.; Hao, Y.; Li, K.; Gong, S., "Radar Cross Section Reduction of a Microstrip Antenna Based on Polarization Conversion Metamaterial," in Antennas and Wireless Propagation Letters, IEEE , vol.PP, no.99, pp.1-1
• doi: 10.1109/LAWP.2015.2430363
• Abstract: A novel method aimed at reducing radar cross section (RCS) under incident waves with both x- and y-polarizations, with the radiation characteristics of the antenna preserved, is presented and investigated. The goal is accomplished by the implementation of the polarization conversion metamaterial (PCM) and the principle of passive cancellation. As a test case, a microstrip patch antenna is simulated and experimentally measured to demonstrate the proposed strategy for dramatic radar cross section reduction (RCSR). Results exhibit that in-band RCSR is as much as 16 dB compared with the reference antenna. In addition, the PCM has a contribution to a maximum RCSR value of 14 dB out of the operating band. With significant RCSR and unobvious effect on the radiation performance of the antenna, the proposed method has a wide application for the design of other antennas with a requirement of RCS control.
• keywords: {Antenna measurements;Metamaterials;Microstrip;Microstrip antennas;Phase change materials;Radar cross-sections;Microstrip antenna;polarization conversion metamaterial (PCM).;radar cross section reduction},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7102711&isnumber=4357943
• Chen, Xi; Huifeng Ma; Xinmi Yang; Qiang Cheng; Jiang, Wei Xiang; Cui, Tie Jun, "X-band high directivity lens antenna realized by gradient index metamaterials," in Microwave Conference, 2009. APMC 2009. Asia Pacific , vol., no., pp.793-797, 7-10 Dec. 2009
• doi: 10.1109/APMC.2009.5384269
• Abstract: This paper presents the theoretical modeling and prototype demonstration of broadband, low loss, and dual polarization capability of a gradient index metamaterial lens using multilayer microstrip square ring arrays. Microstrip closed square ring elements of variable size are distributed on the planar substrate to satisfy the radial gradient index function and axial impedance match layer configuration of the lens, which is designed to transform spherical wave-front into planar wave-front and minimize reflection loss. A prototype gradient index lens antenna composed of multilayer of CSR arrays and a PEC horn are modeled and simulated. The simulation results shows that the prototype lens antenna maintain low return loss and high directivity over X-band. These results demonstrate the feasibility of such a light weight slab metamaterial lens for broadband and high directivity antenna application, such as in radar and communication system.
• keywords: {gradient index optics;horn antennas;impedance matching;lens antennas;metamaterials;polarisation;CSR array multilayer;PEC horn antenna;X-band high directivity lens antenna;axial impedance match layer;dual polarization capability;gradient index metamaterial;multilayer microstrip square ring arrays;planar wavefront;reflection loss minimization;spherical wavefront transformation;Broadband antennas;Impedance;Lenses;Metamaterials;Microstrip antenna arrays;Nonhomogeneous media;Polarization;Prototypes;Radar antennas;Virtual prototyping;Closed Square Ring;Dual Polarization;Gradient Index Lens;High Directivity;Impedance Match Layer;Lens Antenna;broadband Metamaterials},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5384269&isnumber=5384114
• Crepin, T.; Martel, C.; Gabard, B.; Boust, F.; Loecker, C.; Bertuch, T.; Martinaud, J.-P.; Dousset, T.; Marcotegui, J.A.; Rodriguez-Ulibarri, P.; Beruete, M.; Maci, S., "Blind spot mitigation in phased array antenna using metamaterials," in Radar Conference (Radar), 2014 International , vol., no., pp.1-4, 13-17 Oct. 2014
• doi: 10.1109/RADAR.2014.7060390
• Abstract: In this work, a metaradome based on a fakir's bed of nails is designed and tested in order to suppress the blind directions of a 100-element antenna array. The antenna is a microstrip array designed to operate in X-band. The fakir's bed metamaterial-like was first approximated using analytical formulas before a full-wave numerical optimization. Experimental results are exposed and confronted to numerical results. They show a significant reduction of the blind spot subsequent to the metaradome addition.
• keywords: {antenna phased arrays;interference suppression;metamaterial antennas;microstrip antenna arrays;radomes;X-band;blind spot mitigation;fakir bed metamaterial;full-wave numerical optimization;metaradome;microstrip antenna array;phased array antenna;Antenna arrays;Antenna measurements;Antenna radiation patterns;Arrays;Gratings;Metamaterials;antenna array;metamaterial;scan blindness},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7060390&isnumber=7060235
• Barka, A.; Gobin, V.; Roux, F.X., "FETI domain decomposition method for the electromagnetic characterization of meta materials and antenna arrays," in Antennas and Propagation (EUCAP), 2012 6th European Conference on , vol., no., pp.2658-2659, 26-30 March 2012
• doi: 10.1109/EuCAP.2012.6206159
• Abstract: Design of artificial materials or radiating element mock-up need a specific effort for full wave modeling. Due to the heterogeneity of the structure, Finite Element Method is chosen. A high performance solver based on FETI Method is developed and applied to an X band EBG material.
• keywords: {antenna arrays;antenna radiation patterns;finite element analysis;metamaterial antennas;FETI domain decomposition method;X band EBG material;antenna arrays;artificial materials;dual-primal finite element tearing and interconnecting;finite element method;full wave modeling;metamaterial electromagnetic characterization;radiating element mock-up;Antenna arrays;Finite element methods;Magnetic materials;Mathematical model;Metamaterials;Periodic structures;FETI algoritm;Finite Element;metamaterial},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6206159&isnumber=6205804
• Forati, E.; Hanson, G., "A novel epsilon-near-zero total internal reflection antenna to form radar sum and difference patterns," in Antennas and Propagation Society International Symposium (APSURSI), 2013 IEEE , vol., no., pp.1520-1521, 7-13 July 2013
• doi: 10.1109/APS.2013.6711419
• Abstract: A novel geometry is proposed to achieve sum and difference patterns using a monopole antenna as the feed. This geometry consists of a dielectric flare with an embedded uniaxial wire medium acting as an ENZ material. Beams are formed via total internal reflection, but by placing two metallic plates on two side walls of the flare, sum and difference patterns can be interchanged. Physics of the structure are discussed and its radiation pattern, gain and input impedance are calculated by full wave simulation. The antenna is chosen to operate at x band and can be easily fabricated.
• keywords: {antenna radiation patterns;metamaterial antennas;monopole antennas;radar antennas;antenna feed;dielectric flare;epsilon-near-zero total internal reflection antenna;monopole antenna;radar difference pattern;radar sum pattern;Dielectrics;Geometry;Impedance;Materials;Radar;Radar antennas;Wires},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6711419&isnumber=6710651
• Madany, Y.M.; Elkamchouchi, H.M.; Miligy, A.F., "TE10 transmission enhancement for X-band guided waves using multi-mode metamaterial array and multi-mode extractor-converter structures," in Microwave and Millimeter Wave Technology (ICMMT), 2012 International Conference on , vol.5, no., pp.1-4, 5-8 May 2012
• doi: 10.1109/ICMMT.2012.6230436
• Abstract: In this paper, guided waves with enhancement TE₁₀ transmission using multi-mode metamaterial array and multimode extractor-converter structures have been introduced and analyzed using the full 3D electromagnetic field inside a structure based on the finite element method. The proposed structure presents TE₁₀ enhancement transmission coefficient ratio up to 35.3 through different varieties of metamaterial array, mode extractor-converter structures and combined together compared to the conventional guided waves. The proposed structure characteristics such as metamaterial S-parameter retrieval results, the magnitude of electric field and transmission ratio for different cases are obtained to demonstrate the performance.
• keywords: {S-parameters;electromagnetic fields;finite element analysis;metamaterials;microwave frequency convertors;ridge waveguides;S-parameter retrieval;TE₁₀ enhancement transmission coefficient ratio;X-band guided waves;electric field magnitude;finite element method;full 3D electromagnetic field;multimode extractor-converter structures;multimode metamaterial array;rectangular waveguide;unit cell symmetrical ridge ring-stubbed line structure;Arrays;Educational institutions;Electric fields;Electromagnetic waveguides;Metamaterials;Radar;Radar antennas},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6230436&isnumber=6230355
• Liangliang Liu; Zhuo Li; Bingzheng Xu; Jian Yan; Pingping Ning; Changqing Gu, "A high-efficiency rectangular waveguide to domino plasmonic waveguide converter in X-band," in Antennas and Propagation (APCAP), 2014 3rd Asia-Pacific Conference on , vol., no., pp.974-977, 26-29 July 2014
• doi: 10.1109/APCAP.2014.6992666
• Abstract: A rectangular waveguide (RW) to domino plas-monic waveguide (DPW) converter in X-band (8.2-12.4GHz), which is based on the high-efficiency conversion between guided waves and domino plasmon polaritons (DPPs), is proposed in this work. A matching transition composed by gradient domino arrays and flaring upper wall to match the wave number and impedance between the RW and DPW has been presented and designed. Simulated results on the S-parameters and near-field distributions show excellent transmission performance between the RW and DPW in the X-band. The proposed plasmonic metamaterial can find potential applications in advanced plasmonic integrated devices and circuits in the microwave and THz frequencies.
• keywords: {metamaterials;rectangular waveguides;X-band;advanced plasmonic integrated devices;domino plasmonic waveguide converter;frequency 8.2 GHz to 12.4 GHz;gradient domino arrays;high-efficiency rectangular waveguide;plasmonic metamaterial;Dispersion;Microwave circuits;Optical surface waves;Periodic structures;Plasmons;Surface impedance;Surface waves;domino plasmon polaritons;guided waves;high-efficiency conversion;rectangular waveguide},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6992666&isnumber=6992393
• Noor, A.; Hu, Z., "Metamaterial dual polarised resistive hilbert curve array radar absorber," in Microwaves, Antennas & Propagation, IET , vol.4, no.6, pp.667-673, June 2010
• doi: 10.1049/iet-map.2009.0047
• Abstract: A novel thin metamaterial wideband radar absorber, formed by two layers of resistive Hilbert curve arrays, is analysed numerically, revealing a reduction in monostatic radar cross section (RCS) of more than 10 dB from 8 to 18.8 GHz (81 fractional bandwidth) for E_x and 9.1-20.7-GHz (78- fractional bandwidth) for E_y polarisations, respectively. These bandwidths are significantly wider than those reported so far for space filling curve array-based absorbers. Furthermore, the structure has thickness of only 0.11λ to 0.24λ at lowest and highest frequencies, respectively. The lateral dimensions are only 0.13λ to 0.3λ per unit cell at lowest and highest frequencies, respectively, which is several times smaller than that of recently reported circuit analogue absorbers operating in the similar frequency band. The significance of smaller lateral dimensions is that the proposed structure can suppress diffraction effects.
• keywords: {Hilbert spaces;antenna arrays;metamaterials;radar antennas;radar cross-sections;bandwidth 8 GHz to 18.8 GHz;bandwidth 9.1 GHz to 20.7 GHz;circuit analogue absorbers;metamaterial dual polarised radar absorber;monostatic radar cross section;resistive Hilbert curve array radar absorber;space filling curve array-based absorbers;thin metamaterial wideband radar absorber},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5487340&isnumber=5487338
• Abadi, S.M.A.M.H.; Ghaemi, K.; Behdad, N., "Ultra-wideband, true-time-delay, metamaterial-based reflectarray antenna," in Radio Science Meeting (Joint with AP-S Symposium), 2014 USNC-URSI , vol., no., pp.100-100, 6-11 July 2014
• doi: 10.1109/USNC-URSI.2014.6955482
• Abstract: Summary form only given. With the recent progress in the areas of periodic structures and metamaterials, numerous innovative designs of reflectarray antenna systems have been reported as potential replacements of parabolic antennas. Reflectarrays have also found applications in at phased arrays that are used for many high-gain antenna applications such as satellite communications and radar systems. Reflectarray antennas are generally composed of locally-periodic structures with unit cells that act as spatial phase shifters or spatial time-delay units. These unit cells are commonly implemented from resonant building blocks (e.g. patch antennas). Such reflectarrays suffer from relatively small bandwidths and tend to be highly dispersive. Moreover, in situations where reflectarrays are fed with multiple feed antennas to achieve a multi-beam aperture, the sensitivity of the responses of these spatial phase shifters to the angle of incidence of the electromagnetic wave can seriously deteriorate the response of the structure. Hence, in applications where signals with instantaneously broad bandwidths are used, reflectarray antennas free of chromatic aberration must be employed. In this paper, we propose a new technique for designing low-profile, ultrawideband, and true-time-delay (TTD) reflectarray antennas. Such an antenna is composed of numerous spatial time delay units (TDU) distributed over a planar surface that provides a desired time delay over a wide frequency range. Each spatial TDU is a unit cell of appropriately designed miniaturized-element frequency selective surfaces (MEFSSs) composed entirely of non-resonant constituting elements. A prototype of the proposed TTD reflectarray with focal length to aperture diameter ratio (f/D) of 1 is designed to operate at a center frequency of 10 GHz. The designed structure is a low-profile structure with an overall thickness of 4.78 mm (or equivalently 0.16λ_o where λ_o is the free space - avelength at the center frequency of operation), and uses spatial TDU with the dimensions of 6.5 mm x 6.5 mm (≈ 0.22λ_o x 0.22λ_o). The antenna gain at the center frequency is 28.4 dB, and the frequency range within which the gain does not vary more than 4 dB is 7-13 GHz (a relative gain bandwidth of 60%). The side lobe level (SLL) remains below -12 dB across the band when it is illuminated under normal incidence angle. Also, because of the sub-wavelength feature of each TDU as well as its small overall thickness, the reflectarray demonstrate a scanning performance in a wide field of view of ±45^o, which comes at the expense of slight degradation of the SLL. Details of the design of the structure as well as the measurement results of the fabricated prototype will be presented and discussed at the symposium.
• keywords: {antenna feeds;antenna phased arrays;aperture antennas;frequency selective surfaces;metamaterial antennas;microwave phase shifters;multibeam antennas;reflectarray antennas;ultra wideband antennas;MEFSSs;SLL;TDU;TTD;angle of incidence wave;antenna phased arrays;chromatic aberration;electromagnetic wave;focal length to aperture diameter ratio;frequency 7 GHz to 13 GHz;gain 28.4 dB;high-gain antenna;locally-periodic structures;low-profile reflectarray antennas;metamaterial-based reflectarray antenna;miniaturized-element frequency selective surfaces;multibeam aperture antenna;multiple feed antennas;nonresonant constituting elements;parabolic antennas;periodic structures;planar surface;reflectarray antenna system designs;resonant building blocks;scanning performance;side lobe level;size 4.78 mm;spatial phase shifters;spatial time delay units;sub-wavelength feature;true-time-delay reflectarray antenna;ultrawideband reflectarray antenna;unit cells;Gain;Phase shifters;Phased arrays;Radar antennas;Ultra wideband antennas},
• URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6955482&isnumber=6955372