Showing papers on "Metamaterial antenna published in 2004"

Phased array metamaterial antenna system

Abstract: An efficient, low-loss, low sidelobe, high dynamic range phased-array radar antenna system is disclosed that uses metamaterials, which are manmade composite materials having a negative index of refraction, to create a biconcave lens architecture (instead of the aforementioned biconvex lens) for focusing the microwaves transmitted by the antenna. Accordingly, the sidelobes of the antenna are reduced. Attenuation across microstrip transmission lines may be reduced by using low loss transmission lines that are suspended above a ground plane a predetermined distance in a way such they are not in contact with a solid substrate. By suspending the microstrip transmission lines in this manner, dielectric signal loss is reduced significantly, thus resulting in a less-attenuated signal at its destination.

Metamaterial scanning lens antenna systems and methods

Abstract: The present invention is directed to systems and methods for radiating radar signals, communication signals, or other similar signals. In one embodiment, a system includes a controller that generates a control signal and an antenna coupled to the controller. The antenna includes a first component that generates at least one wave based on the generated control signal and a metamaterial lens positioned at some predefined focal length from the first component. The metamaterial lens directs the generated at least one wave.

Metamaterial exhibiting left-handed properties over multiple frequency bands

Abstract: We present experimental measurements at microwave frequencies of a double band left-handed metamaterial. The sample of metamaterial is composed of an extended version of the S-shaped resonators that exhibit simultaneously a negative permittivity and a negative permeability response at comparable frequencies. The experimental results clearly show that there exist two frequency bands where the refraction index is negative. The double left-handed passbands are due to the multiple capacitances and inductances induced in the structure, which can be further tuned to realize a metamaterial with multiple (more than two) left-handed frequency bands.

Stacked H-shaped microstrip patch antenna

Abstract: A small H-shaped microstrip patch antenna (MPA) with enhanced bandwidth is presented. The H-shaped antenna is first studied by a transmission line model and then is fully analyzed with a MoM code. A stacked patch configuration is proposed to increase the narrow bandwidth, radiation efficiency and directivity. The stacked H-shaped MPA is studied using Chu's fundamental limit for electrically small antennas.

Enhancement of evanescent waves in waveguides using metamaterials of negative permittivity and permeability

Abstract: Electromagnetic waves in waveguides consisting of metamaterials with negative permittivity and permeability are analyzed. It is found that metamaterials can enhance the intensity of the evanescent waves in the cladding without altering the propagation constant of the waveguide for both TE and TM modes. This is a unique property of metamaterials. The enhancement factor increases with the increasing of the thickness of the metamaterial and saturates when complete surface polaritons were established at the interface between the metamaterial and the cladding. The enhancement effect can improve the performance of evanescent-wave-based waveguide devices.

Design of a rectangular microstrip patch antenna at 1 GHz

Abstract: Low profile antennas support the operation of many modern communication systems. Microstrip patch antennas represent one family of compact antennas that offer a conformal nature and the capability of ready integration with a communication system's printed circuitry. In this research a rectangular microstrip patch antenna has been designed at 1 GHz. By using a transmission line model we demonstrated how one can accurately model and analyze the microstrip line inset fed rectangular patch antenna by using microwave office software. Our results showed very low return loss and VSWR which are typical parameters used to study the behaviour of antennas.

Defect modes and transmission properties of left-handed bandgap structures

Abstract: We analyze transmission of electromagnetic waves through a one-dimensional periodic layered structure consisting of slabs of a left-handed metamaterial and air. We derive the effective parameters of the metamaterial from a microscopic structure of wires and split-ring resonators possessing the left-handed characteristics in the microwave frequency range, and then study, by means of the transfer-matrix approach and the finite-difference time-domain numerical simulations, the transmission properties of this layered structure in a band gap associated with the zero averaged refractive index. By introducing defects, the transmission of such a structure can be made tunable, and we study the similarities and differences of the defects modes excited in two types of the band gaps.

Electronically-controlled metamaterial-based transmission line as a continuous-scanning leaky-wave antenna

Abstract: An electronically-controlled metamaterial-based transmission line (TL) is demonstrated for the first time and applied to a continuous-scanning leaky-wave (LW) antenna. This transmission line is a composite right/left-handed (CRLH) microstrip structure incorporating varactor diodes for fixed-frequency voltage-controlled operation. The CRLH structure is rigorously analyzed in terms of the equivalent circuit models and dispersion diagrams. The TL behaviour is verified by way of its application as a LW antenna which is experimentally demonstrated. The antenna, operated at the fixed frequency of 3.1 GHz, exhibits the capability of continuous scanning from backward to forward angles over a range of 77/spl deg/ (from -41/spl deg/ to +36/spl deg/), with efficient broadside radiation, by varying the varactors bias voltages from 15V to 0V (5V at broadside).

Lumped element models of double negative metamaterial-based transmission lines

Abstract: Realizations of double negative (DNG) metamaterials using lumped element representations of lossless and lossy transmission lines are reported. Double negative media are artificial materials in which the permittivity and permeability are both negative. Analytical and numerical results for a variety of transmission line network representations explain how they can exhibit low-pass, high-pass, and band-pass dispersion characteristics when a DNG medium is produced in a specified frequency region of interest. Detailed dispersion properties of these various configurations are given. Comparisons with previous formulations are provided. It is shown conclusively that the DNG metamaterials occur only when the overall equivalent transmission line per-unit-length impedance is capacitive and the overall equivalent transmission line per-unit-length admittance is inductive. A convenient categorization of the possible DNG medium designs in transmission line constructs or more complex 2-D or 3-D inclusion based structures thus is provided.

Leaky-wave radiation from planar negative-refractive-index transmission-line metamaterials

Abstract: This paper examines the radiation properties of one- and two-dimensional transmission-line negative-refractive-index (NRI) metamaterial antennas, and highlights the critical features of their dispersion characteristics as they pertain to leaky-wave radiation. This permits an explanation of the mechanisms with which backward, broadside or forward beams can be obtained from NRI transmission-line metamaterials. This discussion is supported by numerical simulations as well as by experimental results.

Low-profile design of dual-frequency and dual-polarised triangular microstrip antennas

Abstract: A single-feed triangular microstrip patch antenna that can be operated at two distinct resonant modes is proposed. The two resonant modes can radiate an omnidirectional dipole-like pattern with linear polarisation and a broadside pattern with circular polarisation, respectively. To achieve the required frequency ratio of the two operating frequency bands, several designs of the proposed antennas with different substrate thickness and patch sizes are studied. In addition, these designs can easily obtain a 50 Ω input impedance without any additional matching circuit. Details of the antenna design and obtained performance are presented.

Transmission line model design formula for microstrip antennas with slots

Abstract: A technique, based on the transmission line model, for the analysis of a rectangular microstrip antenna, in which more than one slot have been embedded in its non-radiating edges, is presented. Using this method, the number and the dimensions of the slots in a microstrip antenna can be calculated, in order to get a desired lower resonant frequency from a much smaller patch than the initial rectangular one.

The nature of radiation from leaky waves on single- and double-negative metamaterial grounded slabs

Abstract: In this work we investigate the dispersion and radiation properties of leaky waves on metamaterial grounded slabs. A simple analysis of the dispersion equation of TE and TM waves supported by such structures reveals that leaky waves of only the proper type exist when double-negative metamaterials are employed, while proper or improper leaky waves exist in single-negative grounded slabs, depending both on which constitutive parameter is negative and on TE or TM polarization. Numerical results on specific structures are provided that illustrate the backward nature of radiation from the proper leaky waves and show the behaviour of the frequency scan through broadside as the metamaterial layer changes its constitutive parameters.

A novel high-efficiency rectenna for 35GHz wireless power transmission

Abstract: Rectenna is one of the keys to microwave power transmission; microstrip patch antenna is very suitable to such places as microwave plane and high platform Aiming at the low efficiency of ordinary theory and method, a new theory was introduced and a 35GHz square patch rectenna was designed, it decreased the difficulty of design and increased the efficiency of system The results of simulations reveal that the conversion efficiency of system reached to 52% and proves its feasibility and higher efficiency

Transmission characteristics of deformed split-ring resonators

Abstract: A metallic-microstructure composite, which is comprised of deformed-split-ring resonators (DSRRs) and wires, is shown to preserve the transmission characteristics of a left-handed metamaterial, implying the simultaneously negative values of effective permeability and permittivity, as well as a wider bandwidth of resonance. Furthermore, the DSRR is so designed that it minimizes the size of the unit cell for fabrication, which is favorable for the implementation of left-handed metamaterial in near infrared region.

A dual-polarized stacked microstrip antenna subarray for X-band SAR application

Abstract: The design and testing of an X-band stacked microstrip antenna subarray for dual-polarization applications are introduced. The radiation element is excited by two approaches separately for the orthogonal polarization operation, one of which is the coplanar microstrip line, while the other is through an H-shaped slot. The measured results of S-parameters and radiation patterns of the array are presented, showing a bandwidth of 20% for VSWR/spl les/1.5 and good radiation characteristics.

An enhanced cavity model for microstrip antennas

Abstract: An enhanced cavity model for analyzing microstrip patch antenna is presented. The predicted resonant frequency and resonant resistance of the antenna are in good agreement with measured data. Theoretical results of the enhanced model are also compared with some commonly used models to determine their range of validity. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 520 -523, 2004; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/mop.20022

Artificial magnetic conductors for low-profile resonant cavity antennas

Abstract: We present the application of artificial magnetic conductor (AMC) ground planes to low-profile resonant cavity antennas. Our novel high-gain microstrip patch antenna has a partially reflective surface (PRS) superstrate and an AMC is utilised as ground plane to reduce the antenna profile. The antenna is studied using a resonant cavity model with the microstrip patch source internal to the cavity. The antennas are formed by the ground plane and a metallodielectric electromagnetic band gap (MEBG) array that acts as a PRS. The profile of the antenna is reduced to half by virtue of employing the AMC ground plane instead of a PEC one.

Metamaterial microstrip backward couplers for fully planar fabrication techniques

Abstract: A novel approach to obtain metamaterials in microwave planar circuit technology compatible with fully planar fabrication techniques is described. Microstrip lines with dual split ring resonators (SRRs) etched on the ground plane along with series capacitive gaps in the upper conductor strip are considered. The occurrence of left-handed (metamaterial) wave propagation in such media is demonstrated. Then, a metamaterial coupler made of a regular microstrip line and a left-handed microstrip line is examined. Co-directional traveling waves result in contra-directional Poynting vectors on the lines thus leading to power being coupled backwards. Backward coupling much tighter than that achievable with traditional (also backward) /spl lambda//4-couplers of the same inter-line distance is reported.

Operation of a periodic structure for a microstrip line over a large frequency band

Abstract: The operation of a microstrip transmission line with periodically-etched circles in the ground plane is investigated. The operation of the structure as a leaky-wave antenna is of particular interest. The structure is studied over a large frequency range, using finite-difference time-domain (FDTD) simulations.

Codirectional coupler and power divider mixed microstrip and metamaterials with lumped-elements L-C

Abstract: A coupled-line backward coupler and a power divider, composed of the conventional microstrip line and the composite left-handed line with lumped-elements L-C, are presented The coupler exhibits arbitrary coupling level and broad bandwidth The power divider shows multi-ports, different coupling level output The theoretical circuit-model simulated results are demonstrated by experiments Both a 3-dB coupler and a trisecting power divider are demonstrated experimentally

Directive metamaterial antenna using high impedance surface

Abstract: /spl lambda//2 is the minimum length along the propagating direction to support a cavity mode Here we show experimentally that metamaterial cavity formed by a high impedance surface (HIS) and an electrically responded surface can make a dipole highly directive 3dB angular width is less than 30/spl deg/ Thickness of the cavity is much less than /spl lambda//4 at working wavelength with return loss up to -40dB This study is of great potential in realizing subwavelength antenna with high directivity in the future

Design of dual-polarized microstrip patch antennas with excellent polarization purity

Abstract: The work presents a new dual-polarized microstrip patch antenna fed by double slot-coupled feeds of 180/spl deg/ phase shift and a coplanar microstrip feed The simulated and measured results show that this antenna achieves a high isolation (<-41 dB) across the entire operating frequency and low cross-polarization level (<-30 dB)

FDTD analysis of microstrip patch antenna covered by plasma

Abstract: A microstrip inset-fed patch antenna covered by plasma layer is simulated by using the (FD)/sup 2/ TD formulation Expressions of calculating the coefficients in the electric field update equation for plasma are presented in detail Computational examples illustrate that the resonant frequency of the patch antenna covered by plasma layer is changed The curves presented may be useful when introducing appropriate corrections in the design of the microstrip patch antennas that are subjected to a plasma environment

Beam scanning characteristics of microstrip triangular array antenna on normally biased NiAl ferrite

Abstract: A conventional 4/spl times/4 planar microstrip equilateral triangular array antenna (METAA) is designed on a NiAl biased ferrite substrate in the C-band (5 GHz) region. The antenna shows tunability in resonant frequency, bandwidth, and efficiency and radiation conductance on application of an external magnetic field normal to the plane of the array geometry. The radar cross section (RCS) characteristics, especially the resonance behavior of the array with various bias conditions, are studied and compared to the case of an unbiased ferrite. It is investigated that the RCS can be moved with respect to frequency by changing the magnetic bias field. It is also found that magnetic losses affect the RCS at resonance significantly.

A compact quadruple crossed-dipole microstrip antenna designed for dual frequency and beam scanning operation

Abstract: A synthesis of a compact crossed-dipole microstrip antenna is introduced. An attempt is made to include most of the operating characteristics required in modern communication systems. The antenna is composed of four crossed dipoles, forming a 2×2 element planar array that radiates an elliptically polarized field, operates in the ranges from 1.8 GHz to 1.9 GHz (DCS) and from 2.5 GHz to 2.8 GHz (UMTS) and has a satisfactory power gain. The feeding of interconnected dipoles is obtained using folded microstrip lines that minimize the size of the structure and also the parasitic radiation. The overall array has eight probe-fed ports. Their suitable phase excitation can drive the antenna to produce patterns with a maximum value in the desired directions.

Network analysis of aperture-coupled cavity-fed microstrip patch antenna

Abstract: The paper presents a general theory for the analysis of an aperture-coupled cavity-fed microstrip patch-antenna to develop a simple but accurate equivalent circuit model. The developed equivalent circuit consists of ideal transformers, admittance elements, and transmission lines. These circuit element values are computed by applying the complex power concept, the Fourier transform and series representation, and the spectral-domain immittance approach. The input impedance of the antenna is calculated and compared with the published data. Good agreements validate the simplicity and accuracy of the developed equivalent circuit model.

Leaky-Wave Radiation from a Two-Dimensional Negative-Refractive-Index Transmission-Line Metamaterial

Abstract: A two-dimensional transmission-line negative-refractive-index (NRI) metamaterial exhibits pencil-beam radiation that can be scanned from approximately -30° (backward radiation) to +30° (forward radiation) over a 150MHz frequency range about 2.4GHz. A novel feeding technique interfaces the metamaterial antenna with a positive-refractive-index (PRI) medium excited by a shorted vertical dipole, which, at frequencies approaching the stopband edges, establishes a nearly uniform phase distribution over the metamaterial aperture via the refractive index contrast between the two media. INTRODUCTION Following the original experimental verification of negative refraction by Shelby et al.(1) using a microwave metamaterial comprising wires and split-ring resonators, the periodically L-C loaded transmission-line based planar metamaterial has successfully demonstrated focusing of a cylindrical wave (2-3) by virtue of a negative refractive index (NRI), and more recently, has verified that the diffraction limit can be overcome using such materials (4-5), as was suggested by Pendry (6). The radiative properties of a one-dimensional CPW-based transmission-line metamaterial have also been examined in (7), in which it was experimentally verified that such a line can produce backward leaky-wave fan-beam radiation from the fundamental spatial harmonic with low cross-polarization levels. A similar TL approach was followed by Itoh and Caloz and led to interesting structures and circuits (8). In this paper, we reveal the radiative properties of a two-dimensional transmission-line NRI metamaterial aperture antenna that produces pencil-beam radiation that can be frequency scanned from -30° (backward wave radiation) to +30° (forward wave radiation) over a 150MHz frequency range about 2.4 GHz. A novel feeding technique interfaces the metamaterial antenna with a positive-refractive-index (PRI) medium excited by a shorted vertical dipole, which establishes a nearly uniform phase distribution over the metamaterial aperture via the refractive index contrast between the two media.