Metamaterial Transmission Lines Research Articles

DERIVATION AND GENERAL PROPERTIES OF ARTIFICIAL LOSSLESS BALANCED COMPOSITE RIGHT/LEFT-HANDED TRANSMISSION LINES OF ARBITRARY ORDER

A circuit theory-based approach for systematically deriving all possible lossless balanced composite right/left-handed transmission lines is described. To illustrate the usefulness of the proposed approach, novel artiflcial transmission line unit-cells with tri- and quad-band behaviour are proposed. It is shown that the number of right-handed or left-handed frequency bands exhibited by such transmission lines is determined by the order of its unit-cell. It is explained why artiflcial lossless balanced transmission lines exhibit a stop-band around each pole of their associated continuous transmission line that can not be closed up. Since this approach allows for the systematic derivation of such transmission line unit-cells of arbitrary order, multi-band components based on metamaterial transmission lines are envisaged.

A Compact Transmission-Line Metamaterial Antenna With Extended Bandwidth

A wideband and compact planar antenna is proposed using a doubly resonant transmission-line metamaterial (TL-MTM) structure. The antenna consists of two TL-MTM arms that resonate at different frequencies. Each arm comprises a microstrip transmission-line loaded with five spiral inductors and is well matched to 50 Omega through an embedded series meandered line. Each arm is designed to work as a single antenna at its own resonant frequency, determined by the loading spiral inductance, where a zero insertion phase occurs. A wideband antenna matching is enabled when these two resonances suitably merge together. A fabricated prototype has dimensions of lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> /4 times lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> /7 times lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> /29, yielding a vertical linear electric field polarization, and provides a 100-MHz bandwidth (-10 dB) with a measured radiation efficiency of 65.8% at 3.30 GHz.

Tunable bandpass filter based on capacitor-loaded metamaterial lines

A bandpass filter is constructed by loading a left-handed metamaterial transmission line with an additional shunt capacitor. The shunt capacitor provides more freedom to control the passband characteristics of the resulting metamaterial line. A bandpass filter is designed with a centre frequency that is tunable from 0.45 to 0.65 GHz.

Characterization of miniaturized metamaterial resonators coupled to planar transmission lines through parameter extraction

In this paper, a method for obtaining the electrical characteristics of metamaterial resonators coupled to planar transmission lines is proposed. This parameter extraction technique is based on the comparison between the measured (or full wave electromagnetic simulated) transmission and reflection characteristics of a host line loaded with such resonators and those obtained from its lumped element equivalent circuit model (previously reported by some of the authors). The resonant particles considered in this study are split ring resonators, spiral resonators, and other electrically small resonant particles based on two metal levels. The interest in this technique lies in the lack of analytical models providing the electrical parameters of several of the considered ultrasmall resonator topologies (due to their complexity). From the extracted parameters, it is concluded that the circuit models predict very accurately the frequency responses of the considered structures for the different resonators under study. There is an increasing interest in the synthesis of metamaterial transmission lines with extremely small unit cell size. In order to achieve dimensions close to (or even below) λg/100, it is imperative to use complex resonator topologies that combine broadside coupling and extremely elongated metallic strips (etched in different metal levels connected through vias). This justifies the proposed technique. Thus, this work is useful in aiding the synthesis of microwave components based on resonant type metamaterial transmission lines.

A Multilayer Compact Solid State Composite Right/Left-Handed Metamaterial Transmission Line

A multilayer fully integrated solid state composite right/left-handed metamaterial transmission line medium is presented. The left-handedness of the structure is validated by full electromagnetic wave simulation and experimental data. The measured results reveal that the bandwidth of the left-handedness of the transmission line medium is of 12.5 GHz, from 2.8 to 15.3 GHz. The reported multilayer structure consists of six left-handed unit cells and has a size of 1.81 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The super compactness of the structure makes it well suited for Si RF/MMIC applications.

Generalized Model for Multiband Metamaterial Transmission Lines

In this letter, a generalized circuit model valid for the description of composite right/left handed metamaterial transmission lines with an arbitrary number of bands is presented for the first time. The model is a T- or pi-circuit where the series branch is composed of parallel connected series resonators, and the shunt branch consists on series connected parallel resonant tanks. It is demonstrated that any arbitrary T- or pi-circuit exhibiting alternate left-handed and right-handed bands can be expressed in the form of the proposed circuit. This justifies the consideration of the circuit as a generalized model of multiband metamaterial transmission lines.

CRLH metamaterial leaky-wave and resonant antennas

Composite right-/left-handed (CRLH) transmission-line (TL) metamaterials, with their rich dispersion and fundamental right-/left-hand duality, represent a paradigm shift in electromagnetics engineering and, in particular, for antennas. This paper presents an overview of the most practical leaky-wave and resonant CRLH antennas, which all exhibit functionalities or/and performance superior to prior state of the art. The leaky-wave antennas provide full-space dynamic scanning capability, with fan beams, conical beams in uni-planar configurations, pencil beams without any complex feeding network, and actively shaped beams based on the concept of aperture digitization. The resonant antennas offer alternative properties and a solution to beam-squinting when no scanning is required, including multi-band (dual/tri-band) operation, zeroth-order high efficiency, high directivity, and planar electric and magnetic monopole radiators.

Study and realisation of dual-composite right/left-handed coplanar waveguide metamaterial in MMIC technology

A novel realisable dual composite right/left-handed (D-CRLH) coplanar waveguide (CPW) transmission line (TL) in GaAs MMIC technology demonstrated by theoretical analysis and experimental results is presented. A D-CRLH TL is the dual of the conventional CRLH TL in the sense that it consists of series LC parallel tanks and shunt LC series tanks. However, an ideal D-CRLH TL cannot be realised because of unavoidable parasitic effects. The measured results indicated that a real D-CRLH TL exhibits a fundamentally different frequency response at higher frequency band in that a real D-CRLH TL cannot provide unlimited left handed (LH) bandwidth. Instead, it has triple bands; right-handed (RH) passband at lower frequencies (DC-2.9 GHz), LH passband at intermediate frequencies (5.1–14.3 GHz) and RH passband at higher frequencies (above 14.3 GHz). The reported fully integrated D-CRLH CPW TL metamaterial has a very compact size of 2.2 mm2 which leads to a small loss 1.5 dB within 3 dB LH passband.

Doubly Tuned Metamaterial Transmission Lines Based on Complementary Split-Ring Resonators

In this article, tuning is applied to metamaterial transmission lines loaded with complementary split-ring resonators. Specifically, a double-tuning scheme is proposed, where one semiconductor varactor diode is placed between the inner and outer metallic regions of the complementary split-ring resonator, whereas the second varactor diode is placed in series with the host line above the position of the complementary split-ring resonator. By tuning the former varactor, we can tailor the electrical characteristics of the complementary split-ring resonator. By using the second varactor as a switch, we can choose operation of the structure as a left-handed or as a negative permittivity structure. The result is a reconfigurable/tunable filtering structure that can be used as notch filter or narrow band-pass filter. A prototype device has been designed and fabricated.

Metamaterial filters: A review

In this paper, a review on metamaterial filters is presented. Several filters based on resonant-type composite right/left-handed metamaterial transmission lines are revised. The different results presented show the application possibilities of such structures in the design of filters with different bandwidths and performances. Some results based on other approaches are also shown.

Experimental Verification of Overcoming the Diffraction Limit with a Volumetric Veselago-Pendry Transmission-Line Lens

A fully printed Veselago-Pendry lens (isotropic n=-1, epsilon(r)=-1, mu(r)=-1) is presented which is based on transmission-line metamaterials. The lens is constructed in a parallel-plate environment at 1.569 GHz and without any embedded sources and achieves a resolution better than the diffraction limit (full width half power of 0.235 lambda). Because the lens is low loss (<0.3 dB per unit cell), the focused fields are dominated by the evanescent components which dictates that subwavelength tightening of the beam is achieved only in the transverse and not the longitudinal direction. The demonstrated lens is quarter-wavelength thick thus allowing ample "working distance" between the subject/image and the lens.

Broadband Via-Free Microstrip Balun Using Metamaterial Transmission Lines

A novel metamaterial broadband microstrip balun design is proposed. The broadband balun consists of a pair of identical metamaterial transmission lines. In the odd mode, a virtual ground is formed between the symmetric plane. The odd mode is allowed while the even mode is rejected. No vias are required to realize the shunt inductors of the metamaterial lines, and no power divider is used. Baluns with good performance can be achieved. In this letter, two baluns are fabricated and measured. For the balun with seven units, the output amplitude difference is less than 0.7 dB, and the differential phase is 181deg plusmn 3deg from 1.6 to 3.6 GHz, while the input return loss is greater than 10 dB.

Fast and accurate simulations of transmission-line metamaterials using transmission-matrix method

Recently, two-dimensional (2D) periodically L and C loaded transmission-line (TL) networks have been applied to represent metamaterials. The commercial Agilent's Advanced Design System (ADS) is a commonly-used tool to simulate the TL metamaterials. However, it takes a lot of time to set up the TL network and perform numerical simulations using ADS, making the metamaterial analysis inefficient, especially for large-scale TL networks. In this paper, we propose transmission-matrix method (TMM) to simulate and analyze the TL-network metamaterials efficiently. Compared to the ADS commercial software, TMM provides nearly the same simulation results for the same networks. However, the model-process and simulation time has been greatly reduced. The proposed TMM can serve as an efficient tool to study the TL-network metamaterials.PACS Codes:41.20.Jb

Broadband VCO using electronically controlled metamaterial transmission line based on varactor‐loaded split‐ring resonator

AbstractIn this article, the broadband voltage‐controlled oscillator (VCO) using electronically controlled metamaterial transmission line based on varactor‐loaded split‐ring resonator (VLSRR) is presented. It is demonstrated that VLSRR coupled to microstrip line can lead to metamaterial transmission line with tuning capability. The negative effective permeability is realized by the VLSRR in a narrow band above the resonant frequency. The bias of VLSRR is controlled by the varactor diodes. The phase noise of VCO is −108.84 to −106.84 dBc/Hz at 100 kHz in the tuning range, 5.407–5.84 GHz. The figure of merit (FOM) called power‐frequency‐tuning‐normalized (PFTN) is 20.144 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1078–1082, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23305

Improved circuit model for left-handed lines loaded with split ring resonators

In this letter, an improved lumped element equivalent circuit model for left-handed lines based on split ring resonators (SRRs) is presented and discussed. It is rigorously demonstrated that although the previously accepted circuit model of these metamaterial transmission lines (a π circuit) provides a good description of device behavior, its electrical parameters do not actually describe the physics of the structure. Conversely, the parameters of the improved equivalent circuit model are representative of the different elements of the structure, including the SRRs, the shunt inductive elements and the host line. It is also shown that the proposed model can be transformed to a π model which is formally identical to the previous reported model of SRR-based left-handed lines. With this transformation, the main relevant characteristics of these left-handed lines are perfectly interpreted.

Modelling metamaterial transmission lines: a review and recent developments

AbstractThis review paper is devoted to the discussion and comparison of the lumped element equivalent circuit models of the different types of metamaterial transmission lines that have been proposed so far, namely the CL-loaded lines, and those lines based on the resonant type approach. The latter category comprises both artificial lines loaded with split ring resonators (SRRs), or related topologies, and metamaterial transmission lines based on complementary split ring resonators (CSRRs). It will be the main aim of this paper to clearly justify the circuit elements of the models (and link such elements to the line physics and topology), to compare the different lines to the light of these models, and to point out the advantages and drawbacks of the different metamaterial transmission lines. As long as metamaterial transmission lines are exhaustively used for the design of compact microwave and millimeter wave components with improved performance and/or based on new functionalities, and their synthesis is based on the lumped element equivalent circuits, this paper is of actual interest for RF/microwave engineers and in general to those readers involved in metamaterial research and applications.

A Broadband Quadrature Power Splitter Using Metamaterial Transmission Line

A broadband quadrature power splitter (QPS) is developed using the metamaterial transmission line (MM TL). It consists of a Wilkinson power divider and two phase-adjusting TLs, namely a MM TL and a microstrip (MS). The slope of the phase-response curve of the MM TL is synthesized to be the same as that of the MS along with the 90deg phase increment at two design frequencies. Hence, the broadband quadrature phase difference over the desired frequency range can be obtained. In this letter, the QPS is developed at the center frequency of 2 GHz. Over the frequency range of 1.1-3.5 GHz, an amplitude imbalance of less than 0.9 dB and a phase error of less than plusmn5deg have been experimentally demonstrated.

Guided-Wave Propagation Characteristics of Fully-Integrated Coplanar-Waveguide Metamaterials with Distributed Loading

Transmission line metamaterials on coplanar waveguide with series-capacitive and shunt-inductive distributed loading in periodical intervals are characterized using our developed fullwave self-calibrated method of moments. Firstly, the two effective per-unit-length transmission parameters, i. e., complex propagation constant and characteristic impedance, are numerically extracted. The results provide a straightforward insight into the forward- and backward-wave propagation characteristics in several distinctive bands, including the left- and right-handed stop-bands and passbands. In particular, it is demonstrated that in the whole left-handed passband, the propagation constant has purely negative phase constant while the characteristic impedance has only positive real quantity. Next, varied left- and right-handed passbands are studied in terms of lower/higher cut-off frequencies based on ideal equivalent circuit model and practical distributed CPW elements, respectively. Of particular importance, the left-handed and right-handed passbands find to be able to be directly connected with a seamless bandgap under the condition that normalized inductance and capacitance of loaded CPW inductive and capacitive elements become exactly the same with each other. Finally, the 9-cell metamaterial circuits on CPW with actual 50Ω feed lines are designed and implemented for experimental validation on the derived per-unit-length parameters.

Varactor-Loaded Complementary Split Ring Resonators (VLCSRR) and Their Application to Tunable Metamaterial Transmission Lines

In this letter, the varactor-loaded complementary split ring resonator (VLCSRR) is presented for the first time. This particle is the dual counterpart of the varactor-loaded split ring resonator (VLSRR), which was introduced previously by some of the authors. Thanks to the presence of the varactor diodes, the electrical characteristics of the particle can be electronically tuned. Thus, by loading a microstrip line with VLCSRRs, the structure exhibits a tunable rejection band which is attributed to the negative effective permittivity provided by the particle. It is also shown in this letter that by adding a gap to the structure, the rejection band is switched to a tunable pass band with left handed wave propagation. Due to the topology of the complementary split rings resonators, the insertion and polarization of the diode varactors is not straightforward. These aspects are discussed in the letter. A circuit model for the VLCSRR is proposed. From parameter extraction and comparison between simulation of the circuit model and experiment good agreement is obtained.

Novel miniaturized planar left-handed metamaterial transmission lines verified by the backward wave property

Based on the technique of reducing working frequency of split ring resonators (SRR)，this paper presents a miniaturized left-handed metamaterial transmission line unit，and retrieves the effective permittivity and permeability parameters from the transmission and reflection data. To verify the presence of the left-handed frequency band，3D numerical simulation is conducted to an array of left-handed metamaterials including eight units，which demonstrates that the left-handed metamaterial microstrip line can support unique backward wave property very well. Compared with conventional left-handed microstrip lines，this structure has been reduced by 60% in electrical sizes，and would be more convenient for fabrication in applications as miniaturized planar circuit components.