Showing papers on "Metamaterial antenna published in 2016"
Patent•
14 Oct 2016
TL;DR: The metamaterial substrate can be less than 70 μm thick and buried into any PCB layer as mentioned in this paper, and can be used to create new electrical characteristics, properties and systems, sub-systems or component's specification not readily available with conventional circuit materials, substrates, and PCBs.
Abstract: This invention enables Frequency Selective Surface (“FSS”) and Artificial Magnetic Conductor (“AMC”) which exhibits Electromagnetic Band Gap (“EBG”) in any of the substrate's layer from a small and thin systems and sub-systems in package to a large-format PCBs. The metamaterial substrate may be integrated with electronic circuit components or buried in PCBs for circuit designs capable of transmitting, receiving and reflecting electromagnetic energy, altering electromagnetic properties of natural circuit materials, enhancing electrical characteristics of electrical components (such as filters, antennas, baluns, power dividers, transmission lines, amplifiers, power regulators, and printed circuits elements) in systems and sub-systems circuit designs. The metamaterial substrate creates new electrical characteristics, properties and systems, sub-systems or component's specification not readily available with conventional circuit materials, substrates, and PCBs. The metamaterial substrate can be less than 70 μm thick and buried into any PCB layer.
185 citations
TL;DR: In this paper, a single-feed microstrip antenna (CPMA) has a simple configuration but is hindered by a narrow, 3-dB axial ratio (AR) bandwidth.
Abstract: Wireless systems manufacturers desire a low-profile, wideband, circularly polarized (CP) antenna. Generally, a single-feed CP microstrip antenna (CPMA) has a simple configuration but is hindered by a narrow, 3-dB axial ratio (AR) bandwidth. The bandwidth of a multiple-feed CPMA can be enhanced but requires a complicated and larger feeding network. Many techniques have been employed to improve AR bandwidth, such as using dual-feed, network-based structures [1], stacked patches [2]?[3], array antennas with sequential feeding network [4], and multilayered structures [5]. However, these CP antennas are based on multiradiating patches or complicated feeding structures.
147 citations
TL;DR: In this paper, a high-gain broadband gradient refractive index (GRIN) planar lens fed by an antipodal exponential taper slot antenna (ATSA) is presented.
Abstract: The design, simulation, and measurement results of a high-gain broadband gradient refractive index (GRIN) planar lens fed by an antipodal exponential taper slot antenna (ATSA) are presented. As a constituent part of this lens, a novel nonresonant metamaterial unit cell, composed of bilayer triple rectangular rings, is proposed and its equivalent circuit model is developed and described. It is shown that, by utilizing this element, stronger capacitive couplings between adjacent metallic layers are realized resulting in a large refractive index variation of about 2.5, and hence, a thin lens with a thickness of $0.38\lambda_{0}$ , where $\lambda_{0}$ is the wavelength at 9.5 GHz. In addition, since the unit cell is designed to resonate at higher frequencies, its refractive index response is smoothly increased over a broad frequency range and this considerably enhances the operating bandwidth of the lens. The achieved measured results demonstrate a broad matching and $-3\;{\rm dB}$ gain bandwidths of 52% (7–12 GHz) and 65% (7–13.2 GHz), respectively. Furthermore, this lens offers a high aperture efficiency of 50% (21.2 dB gain) at the center frequency, and its sidelobe and cross-polarization levels are less than $-20\;{\rm dB}$ and $-26\;{\rm dB}$ across the entire matched band, respectively.
119 citations
TL;DR: In this article, a modified 2 × 2 and 3 × 3 series-fed patch antenna arrays with beam-steering capability are designed and fabricated for 28 GHz millimeter-wave applications.
Abstract: New modified 2 × 2 and 3 × 3 series-fed patch antenna arrays with beam-steering capability are designed and fabricated for 28-GHz millimeter-wave applications. In the designs, the patches are connected to each other continuously and in symmetric 2-D format using the high-impedance microstrip lines. In the first design, 3-D beam-scanning range of ± 25° and good radiation and impedance characteristics were attained by using only one phase shifter. In the second one, a new mechanism is introduced to reduce the number of the feed ports and the related phase shifters (from default number 2 N to the reduced number N + 1 in the serial feed (here N = 3) and then the cost, complexity, and size of the design. Here, good scanning performance of a range of ± 20°, acceptable sidelobe level, and gain of 15.6 dB are obtained. These features allow to use additional integrated circuits to improve the gain and performance. A comparison to the conventional array without modification is done. The measured and simulated results and discussions are presented.
113 citations
TL;DR: In this paper, a tunable metamaterial element that can serve as the building block for a dynamically reconfigurable aperture is presented, where the element is patterned into the upper conductor of a microstrip transmission line, providing both a means of exciting the radiating element as well as independent access for biasing circuitry.
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 beamforming, imaging, or security screening applications.
107 citations
TL;DR: In this article, 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.
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 to 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.
105 citations
TL;DR: In this article, a metamaterial superstrate is placed in between the elements of densely packed microstrip phased array and modified complementary split ring resonators are printed on the decoupling superstrate slab which caters for both surface and space wave effects.
Abstract: This paper reports on an effective mutual coupling suppression technique in which a metamaterial superstrate is placed in between the elements of densely packed microstrip phased array. Modified complementary split ring resonators are printed on the decoupling superstrate slab which caters for both surface and space wave effects. A detailed analysis of this proposed scheme is carried out on a low as well as on a high-permittivity substrate. Coupling suppression of 27 and 11 dB is achieved experimentally on the low- and high-permittivity substrates, respectively, with an element separation of $\lambda_{o}/8$ . The design is compact and easy to realize and it removes drawback of poor front-to-back ratio previously reported in other decoupling techniques. In addition to high-coupling suppression, the decoupling slab can be added or removed in real time which makes this technique versatile for various applications having stringent performance requirements.
103 citations
21 Mar 2016
TL;DR: Various parameters, for example the gain, S parameters, directivity and efficiency of the designed rectangular antenna are obtained from ADS Momentum.
Abstract: The purpose of this paper is to design a microstrip rectangular antenna in Advance Design System Momentum (ADS). The resonant frequency of antenna is 4.1GHz. The reflection coefficient is less than −10dB for a frequency range of 3.1GHz to 5.1 GHz. The proposed rectangular patch antenna has been devise using Glass Epoxy substrate (FR4) with dielectric constant (er = 4.4), loss tangent (tan δ) equal to 0.02. This rectangular patch is excited using transmission lines of particular length and width. Various parameters, for example the gain, S parameters, directivity and efficiency of the designed rectangular antenna are obtained from ADS Momentum.
95 citations
TL;DR: In this paper, a lumped element equivalent circuit is proposed and analyzed in detail for microstrip lines with pairs of complementary split-ring resonators (CSRRs), and a proof-of-concept of a differential sensor is proposed.
Abstract: This letter is focused on the modeling, analysis, and applications of microstrip lines loaded with pairs of electrically coupled complementary split-ring resonators (CSRRs). Typically, these epsilon-negative (ENG) metamaterial transmission lines are implemented by loading the line with a single CSRR (etched beneath the conductor strip) in the unit cell. This provides a stopband in the vicinity of the CSRR resonance. However, by loading the line with a pair of CSRRs per unit cell, it is possible to either implement a dual-band ENG transmission line (useful, for instance, as a dual-band notch filter), provided the CSRRs are tuned at different frequencies, or to design microwave sensors and comparators based on symmetry disruption (in this case by using identical CSRRs and by truncating symmetry by different means, e.g., asymmetric dielectric loading). The design of these CSRR-based structures requires an accurate circuit model able to describe the line, the resonators, and the different coupling mechanisms (i.e., line-to-resonator and inter-resonator coupling). Thus, a lumped element equivalent circuit is proposed and analyzed in detail. The model is validated by comparison to electromagnetic simulations and measurements. A proof-of-concept of a differential sensor for dielectric characterization is proposed. Finally, the similarities of these structures with coplanar waveguide transmission lines loaded with pairs of SRRs are pointed out.
90 citations
TL;DR: In this paper, a dual-beam microstrip leaky-wave antenna is proposed to steer two symmetrical side beams simultaneously by sweeping the operating frequency, where the second higher order mode of the microstrip is excited.
Abstract: Wideband microstrip leaky-wave antennas (LWAs) that radiate two symmetrical side beams are described. The two beams are steered simultaneously by sweeping the operating frequency. To achieve this, the second higher order mode of the microstrip is excited. Two electric field nulls are created between the microstrip and the ground plane using via arrays to suppress lower order modes. To test the concept, one of the antenna designs was prototyped. The prototyped antenna is capable of steering two symmetrical beams within a range of 37° when frequency is swept between 6.92 and 8.75 GHz. The measured peak gain of the antenna is 12.7 dBi and the variation of gain from 6.92 to 8.75 GHz is 3.1 dB. The measured 10-dB return loss bandwidth is 23%, which is very large for a dual-beam microstrip LWA. Such a wide impedance bandwidth is essential to achieve beam scanning over a wide angular range by sweeping frequency. Another advantage is that this single-layer antenna is easy to fabricate.
79 citations
TL;DR: A meaningful comparative study where all commonly used feed mechanisms such as coaxial probe, microstrip line, and rectangular aperture for both antennas operating near the same frequency is considered, indicating relative advantages and disadvantages.
Abstract: Microstrip patches and dielectric resonators (DRs) are two low-profile variants of modern microwave and wireless antennas. However, the DR antenna (DRA) is relatively new and still passing through the stages of development. Both variants are quite similar in terms of performance and characteristics. This article focuses on a meaningful comparative study where we have considered all commonly used feed mechanisms such as coaxial probe, microstrip line, and rectangular aperture for both antennas operating near the same frequency. Circular geometry, i.e., cylindrical DRA (CDRA) and circular microstrip patch antenna (CMPA), have been chosen, and a systematic investigation based on thorough experiments has been executed. Multiple sets of prototypes have been fabricated and measured at 4 GHz. All available data have been furnished and compared, indicating relative advantages and disadvantages. This comparative study should provide qualitative and quantitative instructions to a designer for choosing the right element and corresponding feed based on design requirement and feasibility.
TL;DR: In this article, a magnetoelectric dipole antenna with magnetic metamaterial loading is presented, which exhibits an impedance bandwidth of 44% ranging from 1.7 to 2.67 GHz and boresight gain of about 8.5 dBi.
Abstract: This communication presents a novel miniaturized magnetoelectric dipole antenna by introducing magnetic metamaterial loading. The proposed antenna, excited by a $\Gamma $ -shaped probe, consists of a planar electric dipole and a quarter-wave shorted patch antenna. To miniaturize the antenna, the metamaterial loading is fully arranged inside the shorted patch antenna and the matching portion of the $\Gamma $ -shaped probe. The loading is formed by a stack of modified rectangular split-ring resonators, which are placed very closely in parallel. With the presence of the metamaterials, the effective permeability of the substrate is increased, and therefore the antenna finds a significant size reduction. Most importantly, the impedance and radiation characteristics of the antenna are not compromised too much. The antenna loaded with metamaterials exhibits an impedance bandwidth of 44% ranging from 1.7 to 2.67 GHz and a boresight gain of about 8.5 dBi. The volume size is reduced by 48% when compared with the original design having an impedance bandwidth of 47%.
TL;DR: An electrically controllable square-loop metamaterial based on vanadium dioxide (VO2) thin film was proposed in the terahertz frequency regime to perform roles not only as a resonator but also as a micro-heater for the electrical control of the VO2.
Abstract: An electrically controllable square-loop metamaterial based on vanadium dioxide (VO2) thin film was proposed in the terahertz frequency regime. The square-loop shaped metamaterial was adopted to perform roles not only as a resonator but also as a micro-heater for the electrical control of the VO2. A dual-resonant square-loop structure was designed to realize band-pass characteristics in the desired frequency band. The measured Q-factors of the basic and scaled-down metamaterials fabricated on VO2 thin films were 2.22 and 1.61 at the center frequencies of 0.44 and 1.14 THz in the passbands, respectively. The transmittances of the proposed metamaterial were successfully controlled by applying a bias voltage without an external heater. The measured transmittance on-off ratios of the metamaterials were over 40 at the center frequencies in the passbands. In the future, electrically controllable terahertz metamaterial based on VO2 metamaterial could be employed as high-performance active filters or sensors.
TL;DR: In this article, a light-weight antenna with E-shaped slits and inductive microstrip lines grounded using metallic via-holes has been proposed to achieve a peak gain and radiation efficiency of 4.45 dBi and 85.8%, respectively, at 2.76 GHz.
Abstract: This study presents the empirical results of a low-profile light-weight antenna based on a periodic array of the complementary artificial magnetic conductor metamaterial structure, which is realised by loading the antenna with E-shaped slits and inductive microstrip lines grounded using metallic via-holes. The finalised prototype antenna operates over a broadband of 0.41–4.1 GHz, which corresponds to a fractional bandwidth of 165.84%, and has dimensions of 40 × 35 × 1.6 mm3 or 0.054λ 0 × 0.047λ 0 × 0.0021λ 0, where λ 0 is free-space wavelength at operating frequency of 410 MHz. The finalised antenna has a peak gain and radiation efficiency of 4.45 dBi and 85.8%, respectively, at 2.76 GHz. At the lower operating frequency of 410 MHz, the gain and radiation efficiency are 1.05 dBi and 32.5%, respectively, which is normally highly challenging to realise with very small antennas. The planar nature of antenna enables easy integration with wireless transceivers.
TL;DR: In this paper, two closely spaced printed meander line antennas (MLAs) are developed by using metamaterial loading techniques with reduced mutual coupling, which showed significant size reduction and less mutual coupling compared to similar arrays on conventional substrates.
Abstract: Two closely spaced printed meander line antennas (MLAs) are developed by using metamaterial loading techniques with reduced mutual coupling. The antenna array built on the metamaterial substrate showed significant size reduction and less mutual coupling compared to similar arrays on conventional substrates. Demonstrated to have left-handed magnetic characteristics, the methodology uses elliptical split-ring resonators (E-SRRs) placed horizontally between the patch and the ground plane with a row of the same type between antenna elements. Measured return loss of the printed antenna with this technique is less than $-{\hbox {10}}~\hbox{dB}$ from 5.1-5.9 GHz which covers the IEEE 802.11a (5.15-5.35 GHz and 5.47-5.725 GHz) American standard and HIPPER LAN/2 (5.15-5.35 GHz and 5.725-5.825 GHz) European standard. Also this antenna has an omnidirectional radiation pattern, high gain, and very good pattern stability over the operating band. It is shown to have great impact on the antenna performance enhancement in terms of high efficiency, low voltage standing wave ratio, good bandwidth and less mutual coupling between two antennas with a very close separation of about ${\hbox {0.073}}{\lambda _0}$ . Experimental data show a reasonably good agreement between the simulation and measured results.
TL;DR: In this article, the authors present an analysis of a slotted waveguide antenna (SWA) whose directivity has been enhanced by using metamaterial parasitic elements, and apply an adapted form of the discrete dipole approximation (DDA) as a modeling tool and verify the accuracy and versatility of this method for different configurations, including matched and shorted SWAs, with and without parasitic elements.
Abstract: We present an analysis of a slotted waveguide antenna (SWA) whose directivity has been enhanced by using metamaterial parasitic elements. We apply an adapted form of the discrete dipole approximation (DDA) as a modeling tool and verify the accuracy and versatility of this method for different configurations, including matched and shorted SWAs, and with and without parasitic elements. The results presented in this letter demonstrate the capabilities of the DDA for the fast and accurate simulation of aperture antennas composed of small radiators, and its further application for the design of complex metamaterial structures.
TL;DR: It is demonstrated that a tiny direct-current voltage of 6V can arise a shift of double-negativity pass band by 40% bandwidth, which exhibits that it is an easily controlled and highly tunable acoustic metamaterial, and furthermore, the meetamaterial marginally causes electromagnetic interference to the surroundings.
Abstract: With the advance of the research on acoustic metamaterials, the limits of passive metamaterials have been observed, which prompts the studies concerning actively tunable metamaterials with adjustable characteristic frequency bands. In this work, we present a tunable acoustic metamaterial with double-negativity composed of periodical membranes and side holes, in which the double-negativity pass band can be controlled by an external direct-current voltage. The tension and stiffness of the periodically arranged membranes are actively controlled by electromagnets producing additional stresses, and thus, the transmission and phase velocity of the metamaterial can be adjusted by the driving voltage of the electromagnets. It is demonstrated that a tiny direct-current voltage of 6V can arise a shift of double-negativity pass band by 40% bandwidth, which exhibits that it is an easily controlled and highly tunable acoustic metamaterial, and furthermore, the metamaterial marginally causes electromagnetic interference to the surroundings.
TL;DR: The proposed tunable metamaterial resonator may be used to realize reconfigurable microwave circuits such as reflection/transmission filters, antennas, and sensors, and for achieving flexibility in many other microwave circuits.
Abstract: In this brief, we designed, constructed, and analyzed a frequency-tunable metamaterial resonator. The proposed design consists of an S-shaped resonator, a ground frame, and a feeding transmission line. First, the structure is designed as a nontunable resonator and then tunability is achieved by employing varactor diodes. In order to verify and demonstrate its tunable metamaterial properties, reflection and transmission parameters, group delay, electric and magnetic field distributions, and permittivity and permeability at each tuned frequency were analyzed. Simulation and measured results agree well and show that a high transmission and reflection peak occurs at each resonance frequency that may be tuned with the applied control voltage. Therefore, the proposed tunable metamaterial resonator may be used to realize reconfigurable microwave circuits such as reflection/transmission filters, antennas, and sensors, and for achieving flexibility in many other microwave circuits.
TL;DR: This work presents a complete feedback control approach that enables adaptive control of the radiation pattern for the electronically scanned metamaterial antenna that is robust to measurement noise and is able to continuously optimize performance throughout changing environmental conditions and antenna characteristics.
Abstract: Robust, continuous, and software-defined beam pattern control of holographic metamaterial antennas is necessary to realize the potential of these low-power-consumption, thin, lightweight, inexpensive antennas for consumer usage of satellite communication. We present a complete feedback control approach that enables adaptive control of the radiation pattern for the electronically scanned metamaterial antenna that is robust to measurement noise and is able to continuously optimize performance throughout changing environmental conditions and antenna characteristics. The physical size, weight, and cost advantages of the metamaterial antenna make it an attractive technology when paired with robust and adaptive on-board software strategies to optimize antenna performance and self-tune for various environmental conditions.
TL;DR: The metamaterial element is an electrically-small, complimentary electric-LC (cELC) resonator designed to exhibit large radiated power while maintaining low ohmic losses in a waveguide-fed metasurface antennas.
Abstract: We present a metamaterial element designed as an efficient radiator for waveguide-fed metasurface antennas. The metamaterial element is an electrically-small, complimentary electric-LC (cELC) resonator designed to exhibit large radiated power while maintaining low ohmic losses. The shape of the element is tapered to simultaneously achieve broadband operation and suppression of cross polarization radiation. Full-wave numerical studies at the K-band are conducted to examine its performance when etched into a microstrip line. In this configuration, the element shows a radiation efficiency of 90.2% and a fractional bandwidth of 8.7%. To investigate the potential benefits of the proposed element in two-dimensional platforms, the radiative characteristics of the element are calculated when the element is embedded in a dielectric-filled parallel-plate waveguide. This efficient metamaterial element has potential application as a building block for metasurface devices used in imaging, sensing, wireless power transfer, and wireless communication systems.
TL;DR: In this paper, an engineered novel tunable dual-band metamaterial antenna based on stacked split ring resonator (SRR) array is presented for global positioning satellite applications.
Abstract: An engineered novel tunable dual-band metamaterial antenna based on stacked split ring resonator (SRR) array is presented. The μ-negative SRR array present at two sublayers of stacked microstrip patch antenna substrate adds tuning capability to the antenna with marginal trade-off between antenna gain and cross-polarization. If the size of resonator element is considerably smaller than resonance wavelength, ideally lesser than λ/10, the resonator would support the resonating mode of antenna. Compact SRR array embedded in radiator facilitate the antenna tuning to intended allocated spectrum of L5- and S-band frequencies without modifying external dimensions of patch antenna, which in turn helps the satellite payload design. The variations in SRR array dimensions and inter-element spacing are subsequently utilized to maintain the antenna gain and voltage-standing wave ratio. The proposed design of inset fed antenna, matched at 50 Ω, was validated by experimental results and it is suitable for global positioning satellite applications.
TL;DR: In this article, a multifunctional $1 \times 4$ phased array antenna employing wideband frequency agile microstrip patches with simultaneous polarization reconfiguration has been designed and experimentally verified.
Abstract: A novel multifunctional $1 \times 4$ phased array antenna employing wideband frequency agile microstrip patches with simultaneous polarization reconfiguration has been designed and experimentally verified. Each radiating element consists of a circular microstrip patch connected to an annular microstrip ring via four varactor diodes for achieving frequency agility between 1.5 and 2.4 GHz (frequency agility bandwidth $\approx 46$ %, $S_{11} \leq -10$ dB). Employing two feed points per radiator enables switching among four polarization senses (two linear and two circular polarizations) using a polarization feed network (PFN). For realizing beam steering, the optimum amplitude and phase excitation coefficients for each radiating element were calculated using projection matrix method based on active element pattern, which is then applied to each corresponding radiating element using programmable digital phase shifters, low noise amplifiers, and attenuators arranged in a beam forming network. Measurement shows ±52° beam peak steering at 1.5 GHz and ±28° beam peak steering at 2.4 GHz based on 3 dB gain variation criteria for both the linear and circular polarizations. The simulated and measured results agree reasonably well.
TL;DR: In this paper, a wideband and unidirectional loop antenna with mu-negative (MNG) unit cells is presented, which achieves a wide fractional bandwidth of 52% from 0.64 to 1.1 GHz with a measured peak front-to-back-ratio and gain of 13 dB and 4.8 dBi.
Abstract: The theory, design, analysis, and verification of a wideband and unidirectional loop antenna loaded with mu-negative (MNG) metamaterial unit cells is presented. It is shown that by nonperiodic positioning of MNG unit cells on the loop structure, the amplitude of the surface current can be modified in a desired section of the loop, and hence, unidirectional radiation is achievable at the mu-zero resonance frequency. Moreover, it is demonstrated that as a result of the capacitive MNG loading, a 90° phase difference occurs between the vertical arms of the loop. Therefore, its radiation mechanism can be characterized as an array of two dipole antennas positioned a quarter wavelength apart, thus creating unidirectional radiation. To further improve the performance of the antennas, a quarter-wavelength strip is located in the vicinity of the loop to act as a resonator and director at higher frequencies. With the proposed structure, the final design is at least 50% smaller, in terms of the occupied area, than recent antenna designs of conventional loops, MNG loaded loops, and loop–dipole composite antennas. It also achieves a wide fractional bandwidth of 52% from 0.64 to 1.1 GHz, which is 50% wider than recent MNG metamaterial unit cell loaded loops, with a measured peak front-to-back-ratio and gain of 13 dB and 4.8 dBi, respectively.
TL;DR: In this article, a novel metamaterial rectifying surface (MRS) for electromagnetic energy capture and rectification with high harvesting efficiency is presented, which is fabricated on a three-layer printed circuit board, which comprises an array of periodic metammaterial particles in the shape of mirrored split rings, a metal ground, and integrated rectifiers employing Schottky diodes.
Abstract: A novel metamaterial rectifying surface (MRS) for electromagnetic energy capture and rectification with high harvesting efficiency is presented. It is fabricated on a three-layer printed circuit board, which comprises an array of periodic metamaterial particles in the shape of mirrored split rings, a metal ground, and integrated rectifiers employing Schottky diodes. Perfect impedance matching is engineered at two interfaces, i.e. one between free space and the surface, and the other between the metamaterial particles and the rectifiers, which are connected through optimally positioned vias. Therefore, the incident electromagnetic power is captured with almost no reflection by the metamaterial particles, then channeled maximally to the rectifiers, and finally converted to direct current efficiently. Moreover, the rectifiers are behind the metal ground, avoiding the disturbance of high power incident electromagnetic waves. Such a MRS working at 2.45 GHz is designed, manufactured and measured, achieving a ha...
TL;DR: In this article, a 3x4 array of high refractive-index metamaterial (HRIM) unit cells is used to tilt the main beam by +30 degrees with respect to the end-fire direction.
Abstract: Elevation-plane beam tilting is demonstrated for a printed dipole antenna operating over 57–64 GHz. This is achieved using a 3x4 array of high refractive-index metamaterial (HRIM) unit cells. The unit cell comprises a modified H-shaped structure with stub loading to control the refractive index of the unit cell over a finite frequency range. Integration of the 3x4 array in the H-plane of a dipole antenna is shown to deflect the main beam by +30 degrees with respect to the endfire direction over 57–64 GHz. In addition, the proposed technique provides 5 dB gain enhancement.
TL;DR: In this article, a small metasurface (MS) lens was proposed to enhance the boresight gain of antennas, which has a circular-shaped substrate with a diameter of only $1 ε ε, where ε is the wavelength at the operating frequency of 4.5 GHz in free space, and identical patterns of unit cells having rectangular-ring shapes printed on both sides.
Abstract: This article presents the design of a small metasurface (MS) lens to enhance the boresight gain of antennas. The MS lens has a circular-shaped substrate with a diameter of only $1\lambda_{0},$ where $\lambda_{0}$ is the wavelength at the operating frequency of 4.5 GHz in free space, and identical patterns of unit cells having rectangular-ring shapes printed on both sides. The rectangular-ring unit cells have a constant width along the x-axis direction and varying lengths following the gradient index (GRIN) function along the y-axis direction. This results in the MS lens having a decreasing refractive index in the x-axis direction. The refractive index of the MS lens is analyzed using a computer simulation and compared with that of an ideal lens. The small MS lens is placed at a distance of $\lambda_{0}/2$ from a source antenna to form a small MS lens antenna (SMLA) for boresight gain enhancement. Two types of planar antenna, a planar slot and patch antennas, are used for studies as the source antenna using computer simulation and measurement. The simulated and measured results agree well. The results show that the small MS lens can effectively reduce the main beamwidths and, thus, enhance the boresight gain of both source antennas by more than 5 dB.
TL;DR: In this paper, an S-band compact metamaterial microwave source is proposed, which is based on a rectangular output coupler and a new all-metal metammaterial slow-wave structure.
Abstract: In this paper, we present an S-band compact metamaterial microwave source, which is based on a rectangular output coupler and a new all-metal metamaterial slow-wave structure that has been proposed previously. Due to the reversed Cherenkov radiation of the metamaterial, this metamaterial microwave source can be considered as a new sort of backward wave oscillators (BWOs). The S-band metamaterial microwave source has been further studied and analyzed by using Ansoft HFSS and CST Particle studio particle-in-cell solver. The simulated results show that the electronic efficiency of this S-band metamaterial microwave source can go up to 90% with the peak output power of 4.5 MW. When compared with conventional BWOs, it has obvious advantages such as miniaturization and high electronic efficiency.
TL;DR: In this paper, the authors presented a novel 434 MHz applicator design based on a metamaterial zeroth order mode resonator, which is used to build larger array congurations.
Abstract: 2 Abstract |Current microwave hyperthermia applicators are not well suited for uniform heating of large tissue regions. The objective of this research is to identify an optimal microwave antenna array for clinical use in hyperthermia treatment of cancer. For this aim we present a novel 434 MHz applicator design based on a metamaterial zeroth order mode resonator, which is used to build larger array congurations. These applicators are designed to effectively heat large areas extending deep below the body surface and in this work they are characterized with numerical simulations in a homogenous muscle tissue model. Their performance is evaluated using three metrics: radiation pattern-based Effective Field Size (EFS), temperature distribution-bas Therapeutic Thermal Area (TTA), and Therapeutic Thermal Volume (TTV) reaching 41{45 ◦ C. For 2 � 2 and 2 � 3 array congurations, the EFS reaching > 25% of maximum SAR in the 3.5 cm deep plane is 100% and 91% of the array aperture area, respectively. The corresponding TTA for these arrays is 95% and 86%, respectively; and the TTV attaining > 41 ◦ C is over 85% of the aperture area to a depth of over 3 cm in muscle, using
TL;DR: In this article, the authors proposed and studied numerically a tunable and reconfigurable metamaterial based on coupled split-ring resonators (SRRs) and plasma discharges, which couples the magnetic-electric response of the SRR structure with the electric response of a controllable plasma slab discharge.
Abstract: We propose and study numerically a tunable and reconfigurable metamaterial based on coupled split-ring resonators (SRRs) and plasma discharges. The metamaterial couples the magnetic-electric response of the SRR structure with the electric response of a controllable plasma slab discharge that occupies a volume of the metamaterial. Because the electric response of a plasma depends on its constitutive parameters (electron density and collision frequency), the plasma-based metamaterial is tunable and active. Using three-dimensional numerical simulations, we analyze the coupled plasma-SRR metamaterial in terms of transmittance, performing parametric studies on the effects of electron density, collisional frequency, and the position of the plasma slab with respect to the SRR array. We find that the resonance frequency can be controlled by the plasma position or the plasma-to-collision frequency ratio, while transmittance is highly dependent on the latter.
TL;DR: In this article, an ultrathin (subwavelength) hierarchy multi-slit metamaterial with simultaneous negative effective density and negative compressibility is proposed to absorb sound over a wide frequency range.
Abstract: An ultrathin (subwavelength) hierarchy multi-slit metamaterial with simultaneous negative effective density and negative compressibility is proposed to absorb sound over a wide frequency range. Different from conventional acoustic metamaterials having only negative real parts of acoustic parameters, the imaginary parts of effective density and compressibility are both negative for the proposed metamaterial, which result in superior viscous and thermal dissipation of sound energy. By combining the slit theory of sound absorption with the double porosity theory for porous media, a theoreticalmodel is developed to investigate the sound absorption performance of the metamaterial. To verify the model, a finite element model is established to calculate the effective density, compressibility, and sound absorption of the metamaterial. It is theoretically and numerically confirmed that, upon introducing micro-slits into the meso-slits matrix, the multi-slit metamaterial possesses indeed negative imaginary parts of effective density and compressibility. The influence of micro-slits on the acoustical performance of the metamaterial is analyzed in the context of its specific surface area and static flow resistivity. This work shows great potential of multi-slit metamaterials in noise control applications that require both small volume and small weight of sound-absorbing materials.