A. Rennings

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.

Extended composite right/left-handed (E-CRLH) metamaterial and its application as quadband quarter-wavelength transmission line

A novel extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structure, constituted by the combination of the conventional CRLH (C- CRLH) and the recently introduced dual CRLH (D-CRLH) prototypes, is proposed. This E-CRLH metamaterial is characterized by eight LC parameters (four C-CRLH and four D-CRLH parameters), which allow unprecedented diversity in the manipulation of the dispersion relation of the resulting TL structure. In particular, an E-CRLH TL metamaterial, under an extended balance condition, exhibits two frequencies of infinite wavelength propagation. In addition, the E-CRLH is intrinsically a quadband (arbitrary quadruplet of frequencies) structure. The latter property is exploited here into the design of a quadband quarter- wavelength transformer, and may be applied in principle to any TL-based microwave component.

Composite right/left-handed /spl lambda/-resonator ring antenna for dual-frequency operation

A novel ring structure operating as a dual-frequency resonating antenna is presented. The ring analysis and design is based on the concept of the composite right/left-handed transmission line (CRLH TL), with the particularity that the ends of the line are connected together so as to form a closed loop. As in the case of conventional ring resonators, multiples of full wavelength (n/spl lambda/) field distributions are supported. The key feature of the proposed resonator is that an identical field distribution along the ring is achieved at two different operating frequencies. This phenomenon is due to the dual nature of the CRLH dispersion characteristic. The lower operating frequency corresponds to the /spl lambda/ mode in the left-handed (LH, backward wave, /spl beta/<0) range, while the higher resonance frequency corresponds to the /spl lambda/ mode in the right-handed (RH, forward wave, /spl beta/>0) range. The main benefit of having the same field distribution is that identical performances (radiation, polarization and matching) are achieved at each of the two frequencies. The proposed antenna structure has been simulated with commercial MoM/FEM tools and validated with measurements on fabricated prototypes.

Pencil-Beam Full-Space Scanning 2D CRLH Leaky-Wave Antenna Array

A novel pencil-beam, full-space scanning 2D composite right/left-handed (CRLH) transmission line (TL) leaky-wave antenna (LWA) array is proposed. The proposed array achieves the same performance of conventional phase array antennas in a simpler manner. Moreover, array elements are fed by a CRLH infinite-wavelength series power divider and therefore the separation between array elements and the number of array element can be extended arbitrary. The CRLH series power divider eliminates the requirement of complex and high loss feeding networks commonly found in conventional arrays. Experimental results of each system components are presented along with analytical and simulation results of the complete array system.

Enlarged half-wavelength resonator antenna with enhanced gain

A concept of gain enhancement by radiation aperture enlargement has been presented. The nonlinear dispersion relation of a CRLH TL has been used to enlarge the antenna length keeping the resonance frequency nearly constant. It has been shown that the gain is strongly dependent on the size of the radiation aperture. This fact supports the idea that the x-component of the electric field in the interdigital capacitors of the unit cells is the main contribution to the radiation aperture and is also in agreement with the far-field polarization. A maximum gain of 10.7 has been reached for the largest antenna with 18 unit cells.

Dual mode zeroth order ring resonator with tuning capability and selective mode excitation

A novel ring configuration supporting two orthogonal unique zeroth order modes is presented. The analysis and the design of this ring are based on the artificially engineered composite right left handed (CRLH) transmission lines. A CRLH transmission line exhibits unusual and more diverse propagation characteristics. In the dispersion diagram a lower left hand (LH) and a higher right hand (RH) frequency range is separated by a propagation band gap. This band gap is confined by two zero phase origins (/spl beta/=0), associated with an infinite guided wavelength at non-zero frequencies. Using the CRLH-TL in a ring configuration with connected ends, both zero phase origins along with their corresponding frequencies form a valid resonance mode. One zeroth order mode comes with a constant transmission line voltage, a so-called voltage mode, while the transmission line current is zero. The other zeroth order mode is referred to as current mode and operates at resonance with a constant transmission line current and zero voltage along the resonator line. A simple tuning technique for the voltage modes resonance frequency is addressed. Different feeding strategies to excite both zeroth order modes simultaneously in a one port device as well as decoupled two port selective mode feeding (either voltage or current mode) are discussed.

Ultra-Compact Power Splitter Based on Coupled Surface Plasmons

A novel power splitter based on coupled surface plasmons (SPs) is proposed for optical frequency applications. This power divider is an ultra-compact forward or co-directional coupling device. A specific SiO2-Ag-SiO2 685-THz design is demonstrated by full-wave analysis, where a coupling length of only 36 nm and an overall dimension of around 500 nm is achieved. The underlying principle of coupled SPs may lead to various novel nanoscale optical devices.

A novel clustered dielectric cubes metamaterial (CDC-MTM)

We investigate here a nonmetallic metamaterial (MTM) made of clustered dielectric cubes, where left-handed (LH) bands are generated by antisymmetric modes producing plasmonic artificial magnetic dipoles alternating with electric dipoles, so as to generate negative refractive index (NRI) characteristics. This structure bears some similarity with the metallic nanopillar pairs made of gold introduced in A.N. Grigorenko (2005) for magnetic activity at visible frequencies

A low-profile antenna solution for mobile phones with GSM, UMTS and WLAN operation

A novel low-profile antenna solution for mobile communication devices consisting of a first antenna for EGSM and DCS, a second dual-band antenna for the Tx and Rx bands of UMTS and a third antenna for standards operating in the ISM 2.4 GHz and 5 GHz frequency bands (WLAN and Bluetooth) is presented in this paper. Our antenna concept is based on a dual-layer approach. The /spl lambda//4 resonances of the radiators on top and bottom layer are used to form a dual-band resonator antenna. The main advantage of the proposed structure is the very low profile of the antenna with no additional height above the substrate. This might be an issue for other multi-band antennas based on a folded planar inverted-F antenna (PIFA). In the future devices for mobile communication become even smaller than today. A minimal height (flatness) of these products is a design criteria. Our printed antenna arrangement is an ideal candidate for those applications. The performance of the antenna test board has been simulated using commercial FDTD/FEM software tools. These simulation results have been validated with measurements on a fabricated prototypes.

Stable and Efficient Time-Domain Simulation of Metamaterials with an Extended Equivalent Circuit (EEC) Graded Mesh FDTD

A stable and efficient extended equivalent circuit (EEC) graded mesh FDTD scheme for composite right/left-handed (CRLH) metamaterials (MTMs) is presented along with a novel stability criterion based on a Lyapunov-type energy function. This criterion is firstly derived for a purely right-handed (PRH) medium, where it has been found to be advantageous compared to the Courant condition for highly non-uniform meshes, which are quite common in practice. Moreover, this criterion was extended to the cases of epsilon-negative (ENG), mu-negative (MNG) and CRLH MTMs, for which no stability condition was available so far. As an illustration of the EEC FDTD scheme, a spatial-frequencies quasi-optical diplexer principle is proposed