Nicolson-Ross-Weir Research Articles

Millimeter wave (220 GHz–330 GHz) characterizations of carbon nanotube films

A carbon nanotube (CNT) film on a substrate is characterized at millimeter waves (220 GHz−330 GHz) by metal rectangular waveguide scattering parameters (S-parameters) measurements. The anisotropy of the CNT film is investigated for different orientations of the on-substrate CNT film. The standard Nicolson–Ross–Weir (NRW) approach has been adopted to extract the complex permittivity (εr=ε′-jε″) and permeability (μr=μ′-jμ″) of the on-substrate CNT film from the measured S-parameters. The effective medium theory is then applied to remove the impact of the substrate and characterize the intrinsic CNT film. The observed frequency independent and anisotropic behaviors of the CNT film are very promising indicators that this material could be invaluable for a range of millimeter-wave applications.

Design of coaxial aircell fixture for the measurement of electromagnetic properties

Coaxial aircells are designed and fabricated to measure the electromagnetic properties of ferrite materials in the frequency range from 1 MHz to 3.6 GHz. These S-parameters are actually measured connecting the aircell to a vector network analyzer (VNA). The electromagnetic properties such as complex permittivity and complex permeability are extracted using Nicolson-Ross-Weir (NRW) method and also suitable air-gap corrections are made. To optimize the measured result and to estimate the error, the aircells are characterized in terms of their phase constant and resistivity of the aircell conductor. The measurements clearly showed that the electrical length is longer than the mechanical length of the aircell at all frequencies. The arithmetic mean of the resistivity of aircell which is of 7mm line size and 60mm length is about 66 nΩm. This paper presents a simple method by which the phase constant and resistivity of the aircell can be determined accurately. This is done with the transmission measurements made using a VNA.

Directive and Broadband 4-seg SRR Metamaterial Antennas

In this paper, a design of novel Mu Negative Group (MNG) 4segment SRR based microstrip patch antenna optimized for bandwidth, directivity and front to back lobe ratio has been presented. The microstrip patch antenna is designed using Ansoft HFSS version 13. Results were compared with MATLAB programming based on CAD formulas using equivalent circuit analysis of patch antenna. Nicolson Ross Weir (NRW) method has been used to retrieve the material parameters from transmission and reflection coefficient. Following this, a metamaterial-based-microstrip patch antenna has been designed. The unique shape proposed in this paper, gives remarkable enhancement in bandwidth by 30GHz, directivity by 2% and front to back lobe ratio by 9% but at cost of reducing antenna gain.

Extracting the dielectric constant of materials using ABC-based ANNs and NRW algorithms

ABSTRACTFive different Nicolson–Ross–Weir (NRW) extracting techniques are used to extract the dielectric constants of Teflon, Rexolite, Glass (borosilicate and soda-lime), Paper, and Ultralam 3850HT from S-parameters. The results of these extraction techniques are used to train the Artificial Neural Networks. In order to improve the accuracy of the results, the weights of ANNs are calculated using artificial bee colony estimation method. The results are compared with that obtained using NRW, Newton–Raphson, and genetic algorithm. The obtained results indicate that the proposed model gives good extracted parameters as compared with the previously published results.

Microwave Charecterization of Co-Doped Barium Hexaferrite Absorber Metarial

Co-doped BaFe11CoO19 barium hexaferrites were prepared with the standard sintering technique generally used for microwave absorber materials. In this work, XRD was used to identify the structure of the synthesized sample, vibrating sample magnetometer was used to obtain magnetic hysteresis loop of sample, and scanning electron microscopy was used to study its surface morphology. The complex permeability and complex permittivity were measured with an automated commercial measurement set up in the 18–26.5-GHz frequency range using the Nicolson-Ross-Weir (NRW) method. A domain wall resonance was detected around 19 GHz, and the maximum reflection loss value in the domain wall resonance region was found to be 18.3 dB, the minimum reflection loss value was found to be 14.5 dB. Co-doped BaFe11CoO19 barium hexaferrites seem to be a good candidate as a microwave absorber. The synthesis procedure and the measurement results are presented below.

An improved NRW method to extract electromagnetic parameters of metamaterials

ABSTRACTIn this article, an improved Nicolson–Ross–Weir (NRW) method has been developed to accurately retrieve electromagnetic parameters of metamaterials. By solving roots of higher degree for transmission term and applying first‐order approximation of Taylor's series to the resultant term, the accuracy of the proposed NRW method can be greatly improved. Combined with Kramers–Kronig (K‐K) relationship, the developed method can correctly solve the branch of the refractive index caused by complex exponential function and thus the proposed method is free from the limitation of the electric thickness of the measured materials. Numerical results including a single slab of fishnet structure and three slabs of wires and split‐ring resonators are given to show accuracy and efficiency of the proposed method. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:647–652, 2016

High performance terahertz antennas based on split ring resonator and thin wire metamaterial structures

ABSTRACTIn this letter, the left‐handed metamaterial (LH‐MTM) which has a negative refractive index (NRI) is employed to improve the performance of microstrip patch antenna. The LH‐MTM used in this work is a 3D periodic structure which consists of split ring resonators and thin wires (SRR/TW). The LH‐MTM is placed in front of the microstrip patch antenna and due to the NRI property of the LH‐MTM; the radiated electromagnetic beam size reduces which results in a highly focused beam. The proposed antenna has been designed and simulated using CST microwave studio and the MTM effective parameters are extracted from the s parameters by using Nicolson–Ross–Weir (NRW) algorithm. A parametric analysis has been performed to study the effects of the patch antenna and LT‐MTM lens separation and the size of the 3D LH‐MTM structure on the radiating properties and the impedance matching of the proposed antenna. For the experimental verification, the proposed antenna operating at 10 GHz is fabricated, the return loss and the gain for the proposed antenna with and without MTM are measured. Furthermore, the results show the antenna gain improved by 1.5 dB which validate the concept of beam focusing using NRI MTM structure, while the return loss and the bandwidth are slightly reduced. However, the idea has been extended to the terahertz frequency range by designing and simulating a 303 GHz antenna for heartbeat rate (HR) measurement. For 303 GHz patch antenna, the results demonstrate an improvement in the gain by 1.1 dB, in the bandwidth by 14.73 GHz, and in the return loss by 12.62 dB over their original values without MTM lens, while the beam size is slightly reduced. The simulation and experimental results investigated the idea of the beam focusing using NRI MTM for wide frequency ranges including microwaves and terahertz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:382–389, 2016

Electromagnetic properties of water on GHz frequencies for medicine tasks and metamaterial applications

In problems of modern radio physics and medicine it is important to know dielectric permittivity of liquids. Dispersion characteristics of water in UHF frequency band can be used to analyze the states of biological objects, and also to construct materials (metamanerials). The present work is intended to study the material properties of water in UHF frequency band based on two different techniques: Nicolson-Ross-Weir (NRW) [1] and the Active Nearfield Diagnostics [2].

Tunability of Triangular SRR and Wire Strip (TSRR-WS) Metamaterial at THz

This paper adumbrates a novel tunable metamaterial consisting of triangular split ring resonator (TSRR) and wire strip (WS) at THz frequency. Ansoft high frequency structure simulator (HFSS) has been used to design and analyse the metamaterial having Rogers RT/duroid 5870 (εr = 2.33) and FR4 (εr = 4.4) as substrate material. Nicolson Ross Weir (NRW) method has been used to retrieve the material parameters from transmission and reflection coefficient. 4% maximization has been obtained in the location of the negative region (or resonance frequency for permeability) by using FR4 with 0.75 μm instead of 1.25 μm as substrate thickness. In addition, 18% minimization has been achieved by using FR4 with 0.25 μm instead of RT/duroid 5870 substrate with the same thickness. Tunability has been proved by showing dependence of resonant frequency over the substrate thickness and substrate material.

Extraction of permittivity and permeability of low-loss fluids taking into account the impedance-mismatch and calibration reference-plane position

An improved Nicolson–Ross–Weir (NRW) algorithm is obtained by incorporating an impedance-mismatch factor and reference-plane-correction factors into the equations. Impedance mismatch and reference plane position are sources of error in the extraction of the permittivity and permeability of low-loss fluids. To apply the algorithm, a detailed model of the coaxial cell is developed for the calculation of the full scattering equations. The new model fits experimental data and reduces to the model commonly found in the literature for such cells. Measurements and simulations were carried out in the 300kHz to 3GHz frequency range.

Design of Multiband PIFA loaded with Split Ring Resonator

In this paper, a multiband planar inverted-F antenna (PIFA) with high gain and appreciable bandwidth at the resonant frequencies is designed using metamaterial concept. The proposed PIFA without metamaterial is designed to resonate at 7.46 GHz with return loss of -23.71 dB and gain value 5.41 dBi. The designed antenna is having maximum possible bandwidth of 361.8 MHz. The proposed PIFA with split ring resonator (SRR) loading resonates at multiple frequencies i.e. 5.60 GHz, 6.68 GHz, 7.98 GHz, 8.44 GHz and 9.42 GHz. Return loss at 5.60 GHz is -22.48 dB and gain is 7.10 dBi. At 6.68 GHz return loss is -34.55 dB and gain is 7.68 dBi. Return loss is -30.4 dB at 7.98 GHz and gain is 4.21 dBi. At 8.44 GHz return loss is -15.23 dB and gain is 4.04 dBi. Return loss and gain values at 9.42 GHz is -16.88 dB and 4.77 dBi respectively. After loading with metamaterial maximum bandwidth observed is of 736 MHz. Metamaterial loading has shown to increase the number of resonant frequencies of reference antenna with bandwidth and gain enhancement. It also had an impact on the antenna performance in terms of the return loss improvement and size reduction. Nicolson-Ross-Weir (NRW) method has been employed for verifying metamaterial characteristics of SRR. Design is simulated using HFSS Software.

Effective Electromagnetic Parameters of Metamaterial Transmission Line Loaded With Asymmetric Unit Cells

In this paper, we propose the generalized extraction procedure for retrieval of the effective constitutive parameters for a metamaterial transmission line loaded with asymmetric unit cells. The asymmetric unit cell is replaced with a transmission line immersed in equivalent bianisotropic medium described by effective parameters e, μ, and Zc, and bianisotropic parameters u and η. The proposed retrieval procedure is applied to novel dual-band unit cells and compared with the standard Nicolson-Ross-Weir (NRW) method that is originally developed for the symmetric unit cell and then extended to the asymmetric one using the averaged value of reflection coefficients. It has been shown that, in case of pronounced asymmetry, the NRW method gives only the exact value of refraction, but effective permittivity and permeability are considerably different from the exact values since they are calculated by means of the approximate value of characteristic impedance.

Amelioration of rectangular microstrip patch antenna characterstics by incorporating it with double-Negative left-handed inspired metamaterial in L-band

With the numerous increases in the use of microwave frequencies in communication applications, certain antenna potential characteristics should be an integral part of the design process. For example, GPS, WLAN are all applications that share common potential characteristics requirement in their antenna. A “FRAMED SQUARE RINGS” double negative inspired metamaterial structure was introduced as a cover to the rectangular microstrip patch antenna at a height of 3.2 mm from the ground plane, operating at 1.95 GHz. The results showed that the proposed metamaterial cover, effectively improves the patch antenna’s gain and bandwidth. The complex permittivity and permeability of the proposed structure has been extracted by Nicolson-Ross-Weir (NRW) approach. The outcomes of this work open the possibility to use the proposed structure as a miniaturized and flexible antenna in L-Band for wireless communication applications.

DESIGN AND CHARACTERIZATION OF COMPACT MICROSTRIP PATCH ANTENNA USING “SPLIT RING” SHAPED METAMATERIAL STRUCTURE

Authors analyzed and explored asignificant concept of micro-strip patch antennaconfigured by double negative left handedmetamaterial which have dielectric permittivity &magnetic permeability both negative simultaneously.Basic aim of this paper is to explain thegeneral properties of rectangular micro-strippatch antenna with metamaterial structure likereturn loss, bandwidth, directivity and gain. Inthis paper authors have compared the return loss,bandwidth & gain of the micro-strip patchantenna at a frequency of 2GHz and height of 3.2mm from the ground plane with “SPLIT RING”Shaped double negative left-handed metamaterial.It has been observed that the return loss hasimproved by 20dB. The complex permittivity andpermeability of the proposed structure has beenextracted by Nicolson-Ross-Weir (NRW)approach. DOI: http://dx.doi.org/10.11591/ijece.v2i5.788 Full Text: PDF

Ewald method for 3D periodic dyadic Green's functions and complex modes in composite materials made of spherical particles under the dual dipole approximation

We derive the Ewald representation for the dyadic periodic Green's functions to represent the electromagnetic field in a three dimensional (3D) periodic array of electric and magnetic dipoles. Then we use the developed theory to analyze the modes with real and complex wave number in a 3D periodic lattice of lead telluride (PbTe) microspheres at infrared frequencies and in a 3D periodic lattice of titanium dioxide (TiO2) microspheres at millimeter waves. Each microsphere is equivalently modeled with both an electric and a magnetic dipole, via a method here called the dual dipole approximation (DDA). The 3D lattices exhibit first a magnetic‐induced then an electric‐induced feature determined by microsphere magnetic and electric resonances. The DDA wave number results are compared to the ones computed with single electric or single magnetic dipole approximation and to the ones retrieved by using the Nicolson‐Ross‐Weir (NRW) retrieval method from reflection and transmission of finite thickness slabs computed by a full‐wave simulation. It is shown that the DDA method is in very good agreement with NRW, in contrast to the previously reported single dipole approximation methods that fail to predict one of the two features (either electric or magnetic). A mode with transverse polarization is found to be dominant and able to propagate inside the lattice, and therefore the composite material can be treated as a homogeneous one with effective refractive index. This is obtained by adopting five different retrieval procedures for each lattice, and their agreement or disagreement is discussed.

A High Gain & Wide Band Rectangular Microstrip Patch Antenna loaded with �Interconnected SRR� Metamaterial Structure

Communication applications require wide band and highly directive planner antennas. For such requirement this work deals with the analysis and simulation of a rectangular microstrip patch antenna loaded with INTERCONNECTED SRR metamaterial structure at a height of 3.2mm from the ground plane. The work also investigates the potential properties of the proposed metamaterial structure. The proposed Antenna is designed at a operating frequency of 2.75GHz to meet S-Band (2-4GHz) applications. By loading Interconnected SRR metamaterial structure with the rectangular patch antenna at a height of 3.2mm, the antennas bandwidth is found to be increased up to 378MHz and return loss is reduced to -42.2dB i.e. the potential properties like return loss, bandwidth, directivity and total efficiency of the proposed antenna increases to a great extent in comparison to the rectangular patch antenna alone. Double Negative properties of metamaterial have been proved by Nicolson-Ross-weir (NRW) method.

Effective electromagnetic parameters of left-handed coplanar waveguide transmission lines

This paper presents a kind of wideband, low-loss left handed transmission line (LHTL). It is composed of a parallel meander inductance and a serial cutting capacitor based on the coplanar waveguide (CPW) transmission line (TL). A better method of parameter extraction is formulated based on a more accurate Nicolson–Ross–Weir (NRW) approach. According to medium theory, the complex effective parameters of permittivity and permeability have been extracted from transmission and reflection scattering matrix. Through extracting the β parameter of the CPW TL, the characteristics of LHTL have been verified. The effective bandwidth is about 100% from 11 GHz to 21 GHz with low loss.

A Stepwise Nicolson–Ross–Weir-Based Material Parameter Extraction Method

Approaches of automated evaluation of electromagnetic material parameters have received a lot of attention in the literature. Among others, one method is to retrieve the material parameters from the reflection and transmission measurements of the sample material. Compared to other methods, this is a rather wideband method, but suffers from an intrinsic limitation related to the electrical thickness of the measured material. In this letter, we propose a novel way to overcome this limitation. Although being based on the classical Nicolson-Ross-Weir (NRW) technique, the proposed extraction technique does not involve any branch seeking and is therefore capable of extracting material parameters from samples thicker than λ/2, a measure that would otherwise cause problems in the NRW extraction technique. The proposed derivative of the NRW extraction technique is then used to study the effect of thermal noise on the extracted material parameters.

Boundary Effects on the Determination of Metamaterial Parameters From Normal Incidence Reflection and Transmission Measurements

A method is described for the determination of the effective electromagnetic parameters of a metamaterial based only on external measurements or simulations, taking boundary effects at the interfaces between a conventional material and metamaterial into account. Plane-wave reflection and transmission coefficients at the interfaces are regarded as additional unknowns to be determined, rather than explicitly dependent on the material parameters. Our technique is thus analogous to the line-reflect-line (LRL) calibration method in microwave measurements. The refractive index can be determined from S-parameters for two samples of different thickness. The effective wave impedance requires the additional assumption that generalized sheet transition conditions (GSTCs) account for the boundary effects. Expressions for the bulk permittivity and permeability then follow easily. Our method is validated by comparison with the results using the Nicolson-Ross-Weir (NRW) for determining properties of an ordinary material measured in a coaxial line. Utilizing S-parameters obtained from 3-D full wave simulations, we test the method on magnetodielectric metamaterials. We compare the results from our method and the conventional one that does not consider boundary effects. Moreover, it is shown that results from our method are consistent under changes in reference plane location, whereas the results from other methods are not.

Reliable method for material characterisation using quasi-optical free-space measurement in W-band

An extension to the Nicolson–Ross–Weir (NRW) algorithm to retrieve complex permittivity and permeability from both reflection and transmission coefficients is presented. This new numerical retrieval approach solves the phase ambiguity problem associated with the NRW algorithm. A free-space quasi-optical two-port measurement setup is employed to obtain the scattering parameters of different samples in the W-band frequency range. The results of different samples with various thicknesses are presented. The advantages and limitations of the method are also discussed.