A new equivalent circuit of left-handed (LH) microstrip transmission line loaded with Complementary split-ring resonators (CSRRs) is presented. By adding the magnetic coupling into the equivalent circuit, the new equivalent circuit presents a more accurate cutoff frequency than the old one. The group delay of CSRRs applied with microstrip transmission line (TL) is also studied and analyzed into two cases which are passive CSRRs delay line and active CSRRs delay line. In the first case, the CSRRs TL is analyzed. The group delay can be varied and controlled via signal frequency which does not happen in a normal TL. In the active CSRRs delay line, the CSRRs loaded with TL is fixed. The diodes are added to the model between the strip and CSRRs. By observing a specific frequency at 2.03GHz after bias DC voltages from -10V to -20V, the group delay can be moved from 0.6ns to 5.6ns. A novel microstrip filter is presented by embedding CSRRs on the ground plane of microstrip filter. The filter characteristic is changed from a 300MHz narrowband to a 1GHz wideband as well as suppression the occurrence of previous higher spurious frequency at 3.9GHz. Moreover, a high rejection in the lower band and a low insertion loss of <1dB are achieved.Finally, it is shown that CSRRs applied with planar antenna can reduce the antenna size. The structure is formed by etching CSRRs on the ground side of the patch antenna. The meander line part is also added on the antenna patch to tune the operation frequency from 1.8GHz downward to 1.73GHz which can reduce the antenna size to 74% of conventional patch antennas. By using the previous antenna structure without meander line, this proposed antenna can be tuned for selecting the operation frequency, by embedding a diode connected the position between patch and ground. The results provide 350MHz tuning range with 35MHz bandwidth.

Metamaterials offer the freedom to tune the rich electromagnetic coupling between the constituent meta-atoms to tailor their collective electromagnetic response. Therefore, a comprehensive understanding of the nature of electromagnetic interactions between meta-atoms is necessary for novel metamaterial design, which is provided in the first part of this thesis. The subsequent work in the thesis applies the understanding from the first part to design and demonstrate novel one-dimensional metamaterials that overcome the limitations of metamaterials proposed in literature or exhibit electromagnetic responses not previously observed. Split-ring Resonators (SRRs) are a fundamental building block of many electromagnetic metamaterials. In the first part of the work in this thesis, it is shown that bianisotropic SRRs (with magneto-electric cross-polarisation) when in close proximity to each other, exhibit a rich coupling that involves both electric and magnetic interactions. The strength and nature of the coupling between two identical SRRs are studied experimentally and computationally as a function of their separation and relative orientation. The electric and magnetic couplings are characterised and it is found that, when SRRs are close enough to be in each other's near-field, the electric and magnetic couplings may either reinforce each other or act in opposition. At larger separations retardation effects become important. The findings on the electromagnetic interactions between bianisotropic resonators are next applied to developing a one-dimensional ultra-wideband backward-wave metamaterial waveguide. The key concept on which the metamaterial waveguide is built is electro-inductive wave propagation, which has emerged as an attractive solution for designing backward-wave supporting metamaterials. Stacked metasurfaces etched with complementary SRRs (CSRRs) have also been shown to exhibit a broadband negative dispersion. It is demonstrated through experiment and numerical modeling, that the operational bandwidth of a CSRR metamaterial waveguide can be improved by restricting the cross-polarisation effects in the constituent meta-atoms. The metamaterial waveguide constructed using the modified non-bianisotropic CSRRs are found to have a fractional bandwidth of 56.3\% which, based on a thorough search of relevant literature, is the broadest reported value for an electro-inductive metamaterial. A traditional coupled-dipole toy-model is presented as a tool to understand the field interactions in CSRR based metamaterials, and to explain the origin of their negative dispersion response. This metamaterial waveguide should be of assistance in the design of broadband backward-wave metamaterial devices, with enhanced electro-inductive waveguiding effects. In the final part of the thesis, a one-dimensional metamaterial prototype that permits simultaneous forward- and backward-wave propagation is designed. Such a metamaterial waveguide could act as a microwave analogue of nanoparticle chains that support electromagnetic energy transfer with a positive or a negative dispersion due to the excitation of their longitudinal or transverse dipole modes. The symmetry of the designed hybrid meta-atom permits the co-existence of two non-interfering resonances closely separated in frequency. It is experimentally and computationally shown that the metamaterial waveguide supports simultaneous non-interacting forward- and backward-wave propagation in an overlapping frequency band. The proposed metamaterial design should be suitable for realising bidirectional wireless power transfer applications.

Many interesting ideas have emerged from research on electromagnetic eld interactions with di erent materials. Analyzing such interactions has extracted some essential proper- ties of the materials. For example, extracting constitutive parameters such as permittivity, permeability, and conductivity, clari es a material's behavior. In general, the electromag- netic eld interacts with materials either in the far- eld or near- eld of a source. This study focuses on the principle of near- eld microwave microscopy for detection purposes. Many studies have focused on the use of an electrically small resonator, such as a split-ring resonator (SRR) and a complementary split-ring resonator (CSRR), to act as a near- eld sensor for material characterization and detection. At the resonance frequency, the electric and magnetic energy densities are enhanced dramatically at certain locations in the resonator. Any disturbance of the eld around such a resonator with a material under test causes the resonance frequencies to exhibit a shift that is used as an indicator of the sensor sensitivity. In this thesis, a single CSRR is used as a sensing element for detecting cracks in metal surfaces. Many microwave techniques have been developed for crack detection. However, these techniques have at least one of the following drawbacks: working at high frequencies, measurement setup complexity and cost, and low sensitivity. The rst part of this thesis presents a new sensor based on the complementary split-ring resonator (CSRR) that is used to detect sub-millimeter surface cracks. The sensing mechanism is based on perturbing the electromagnetic eld around an electrically small resonator, thus initiating a shift in the resonance frequency. Investigation of the current distribution on a CSRR at the resonance frequency shows the critical location at which the enhanced energy is concentrated. In addition, the current distribution demonstrates the sensing element in the CSRR. The sensor is simple to fabricate and inexpensive, as it is etched-out in the ground plane of a microstrip-line using printed circuit board technology. The microstrip-line excites the CSRR by producing an electric eld perpendicular to the surface of the CSRR. The sensor exhibits a frequency shift of more than 240 MHz for a 200 m crack. In the second part of this thesis, the sensitivity of the sensor is increased by lling the same crack with a dielectric material such as silicon oil. While using CSRR to scan a block with 200 m wide and 2 mm depth dielectric lled crack, the resonance frequency of the sensor shifts 435 MHz more than a case scanning a solid aluminum. Finally, the total Inductance of a CSRR for miniaturizing purposes is increased using either lumped or distributed elements. In this thesis, the designs and the results are validated experimentally and numerically.

Many interesting ideas have emerged from research on electromagnetic eld interactions with di erent materials. Analyzing such interactions has extracted some essential proper- ties of the materials. For example, extracting constitutive parameters such as permittivity, permeability, and conductivity, clari es a material's behavior. In general, the electromag- netic eld interacts with materials either in the far- eld or near- eld of a source. This study focuses on the principle of near- eld microwave microscopy for detection purposes. Many studies have focused on the use of an electrically small resonator, such as a split-ring resonator (SRR) and a complementary split-ring resonator (CSRR), to act as a near- eld sensor for material characterization and detection. At the resonance frequency, the electric and magnetic energy densities are enhanced dramatically at certain locations in the resonator. Any disturbance of the eld around such a resonator with a material under test causes the resonance frequencies to exhibit a shift that is used as an indicator of the sensor sensitivity. In this thesis, a single CSRR is used as a sensing element for detecting cracks in metal surfaces. Many microwave techniques have been developed for crack detection. However, these techniques have at least one of the following drawbacks: working at high frequencies, measurement setup complexity and cost, and low sensitivity. The rst part of this thesis presents a new sensor based on the complementary split-ring resonator (CSRR) that is used to detect sub-millimeter surface cracks. The sensing mechanism is based on perturbing the electromagnetic eld around an electrically small resonator, thus initiating a shift in the resonance frequency. Investigation of the current distribution on a CSRR at the resonance frequency shows the critical location at which the enhanced energy is concentrated. In addition, the current distribution demonstrates the sensing element in the CSRR. The sensor is simple to fabricate and inexpensive, as it is etched-out in the ground plane of a microstrip-line using printed circuit board technology. The microstrip-line excites the CSRR by producing an electric eld perpendicular to the surface of the CSRR. The sensor exhibits a frequency shift of more than 240 MHz for a 200 m crack. In the second part of this thesis, the sensitivity of the sensor is increased by lling the same crack with a dielectric material such as silicon oil. While using CSRR to scan a block with 200 m wide and 2 mm depth dielectric lled crack, the resonance frequency of the sensor shifts 435 MHz more than a case scanning a solid aluminum. Finally, the total Inductance of a CSRR for miniaturizing purposes is increased using either lumped or distributed elements. In this thesis, the designs and the results are validated experimentally and numerically.

A two-dimensional isotropic metamaterials formed by crossed split-ring resonators (CSRRs) are studied in this paper. The effective characteristic parameters of this media are determined by quasi-static Lorentz theory. The induced current distributions of a single CSRR at the resonant frequency are presented. Moreover, the dependence of the resonant frequency on the dimensions of single CSRR and the spaces of the array are also discussed. / Singapore-MIT Alliance (SMA)

The study of optical phenomena related to the strong electromagnetic response of noble metals (silver (Ag) and gold (Au) being most popular) over the last couple of decades has led to the emergence of a fast growing research area called plasmonics named after 'surface plasmons' which are electron density waves that propagate along the interface of a metal and a dielectric medium. Surface plasmons are formed by the coupling of light to the electrons on the metal surface subject to the fulfillment of certain physical conditions and they are bound to the metal surface. Depending on whether the metallic medium is a continuous film or a structure having dimensions less than or comparable to the wavelength of the exciting light, propagating or localized surface plasmons can be excited. The structure can be either a hole or an arbitrary pattern in a metal film, or a metallic particle. An array of subwavelength structures can behave as an effective homogeneous medium to incident light and this is the basis of a new class of media known as metamaterials. Metallic metamaterials enable one to engineer the electromagnetic response to  incident light and provide unconventional optical properties like negative refractive index as one prominent example. Metamaterials exhibiting negative index (also called negative index materials (NIMs)) open the door for super resolution imaging  and development of invisibility cloaks. However, the only problem affecting the utilization of plasmonic media to their fullest potential is the intrinsic loss of the metal, and it becomes a major issue especially at visible-near infrared (NIR) frequencies. The frequency of the surface plasmon is the same as that of the exciting light but its wavelength could be as short as that of X-rays. This property allows light of a given optical frequency to be conned into very small volumes via subwave lengthmetallic structures, that can be used to develop ecient sensors, solar cells, antennas and ultrasensitive molecular detectors to name a few applications. Also, interaction of surface plasmons excited in two or more metallic subwavelength structures in close proximity inuences the far-eld optical properties of the overall coupled system. Some eects of plasmonic interaction in certain coupled particles include polarization conversion, optical activity and transmission spectra mimicking electromagnetically-induced transparency (EIT) as observed in gas based atomicsy stems. In this thesis, we mainly focus on the optical properties of square arrays of certain plasmonic structures popularly researched in the last decade. The structures considered are as follows: (1) subwavelength holes of a composite hole-shape providing superior near-eld enhancement such as two intersecting circles (called' double hole') in an optically thick Au/Ag lm, (2) double layer shnets, (3) subwavelength U-shaped particles and (4) rectangular bars. The entire work is based on electromagnetic simulations using time and frequency domain methods. Au/Ag lms with periodic subwavelength holes provide extraordinarily high transmission of light at certain wavelengths much larger than the dimension of the perforations or holes. The spectral positions of the maxima depend on the shape of the hole and the intra-hole medium, thereby making such lms function as a refractive index sensor in the transmission mode. The sensing performance of the double-hole geometry is analyzed in detail and compared to rectangular holes. Fishnet metamaterials are highly preferred when it comes to constructing a NIM at optical frequencies. A shnet design that theoretically oers a negative refractive index with least losses at telecommunication wavelengths (1.4 1.5 microns) is presented. U-shaped subwavelength metallic particles, in particular single-slit split-ring resonators (SSRRs), provide a large negative response to the magnetic eld of light at a specic resonance frequency. The spectral positions of the structural resonances of the U-shaped particle can be found from its array far field transmission spectrum at normal incidence. An effort is made to clarify our understanding of these resonances with the help of localized surface plasmon modes excited in the overall particle. From an application point of view, it is found that a planar square array of SSRRs eectively functions as an optical half-wave waveplate at the main resonance frequency by creating a polarization in transmission that is orthogonal to that of incident light. A similar waveplate eect can be obtained purely by exploiting the near-eld interaction of dierently oriented neighbouring SSRRs. The physical reasons behind polarization conversion in dierent SSRR-array systems are discussed. A rectangular metallic bar having its dipolar resonance in the visible-NIR is called a nanoantenna, owing to its physical length in the order of nanometers. The excitation of localized surface plasmons, metal dispersion and the geometry of the rectangular nanoantenna make an analytical estimation of the physical length of the antenna from the desired dipolar resonance dicult. A practical map of simulated resonance values corresponding to a variation in geometrical parameters of Au bar is presented. A square array of a coupled plasmonic system comprising of three nanoantennas provides a net transmission response that mimicks the EIT effect. The high transmission spectral window possesses a peculiar dispersion profile that enables light with frequencies in that region to be slowed down. Two popular designs of such plasmonic EIT systems are numerically characterized and compared. / <p>QC 20121017</p>

Yes / Empirical results of an electrically small printed monopole antenna is described with fractional bandwidth of 185% (115 MHz–2.90 GHz) for return-loss better than 10 dB, peak gain and radiation efficiency at 1.45 GHz of 2.35 dBi and 78.8%, respectively. The antenna geometry can be approximated to a back-to-back triangular shaped patch structure that is excited through a common feed-line with a meander-line T-shape divider. The truncated ground-plane includes a central stub located underneath the feed-line. The impedance bandwidth of the antenna is enhanced with the inclusion of meander-line slots in the patch and four double split-ring resonators on the underside of the radiating patches. The antenna radiates approximately omnidirectionally to provide coverage over a large part of VHF, whole of UHF, entire of L-band and some parts of S-band. The antenna has dimensions of 48.32×43.72×0.8 mm3, which is corresponding with the electrical size of 0.235λ_0×0.211λ_0×0.003λ_0, where λ_0 is free-space wavelength at 1.45 GHz. The proposed low-profile low-cost antenna is suitable for application in wideband wireless communications systems. / H2020-MSCA-ITN-2016 SECRET-722424 and UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1

In recent years, there has been an increasing interest on left handed metamaterials because of their possible innovative applications. The pioneer study introducing such materials was brought out by V. G. Veselago in 1968 [1]. In his work, Veselago proposed a medium having simultaneously negative electric permittivity and magnetic permeability and investigated its electromagnetic characteristics. He found out that the electric field, magnetic field and the propagation vector form a left handed triplet, thus named such materials as &ldquo / Left Handed Materials&rdquo / . Despite the significance of Veselago&rsquo / s inferences, the metamaterial theory stayed dormant for nearly 30 years. Towards the end of 1990s, the physically realizable left handed materials were built as the combination of two periodical structures / Split Ring Resonators (SRRs) and metallic thin wire arrays [4-5]. In this thesis, electrical and magnetic characteristics of the left handed metamaterials are theoretically investigated by using the analytical models for their permittivity and permeability functions with respect to frequency. For this purpose, first, two basic metamaterial structures / the Split Ring Resonators and Thin Metallic Wire Arrays are studied individually and their electrical and magnetic characteristics are examined. Finally, the composite left handed structure containing both SRRs and thin wires is studied to investigate the resulting simultaneous resonance properties and to estimate their overall effective permeability and permittivity functions.

Made available in DSpace on 2014-12-17T14:55:19Z (GMT). No. of bitstreams: 1 MarinaldoPSN_TESE.pdf: 2731148 bytes, checksum: 7c2caa3355d4d42f0702baf0d147bf97 (MD5) Previous issue date: 2014-04-25 / Universidade Federal do Rio Grande do Norte / Metamaterials have attracted a great attention in recent years mostly due to their electromagnetic properties not found in nature. Since metamaterials began to be synthesized by the insertion of artificially manufactured inclusions in a medium specified host , it provides the researcher a broad collection of independent parameters such as the electromagnetic properties of the material host. In this work was presents an investigation of the unique properties of Split Ring Resonators and compounds metamaterials was performed. We presents a theoretical and numerical analysis , using the full-wave formalism by applying the Transverse Transmission Line - LTT method for the radiation characteristics of a rectangular microstrip antenna using metamaterial substrate, as is successfully demonstrated the practical use of these structures in antennas. We experimentally confirmed that composite metamaterial can improved the performance of the structures considered in this thesis / Os metamateriais tem atra?do uma grande aten??o nas ?ltimas d?cadas, principalmente devido as suas propriedades eletromagn?ticas n?o encontradas na natureza. Desde que os metamateriais passaram a ser sintetizados atrav?s da inser??o de inclus?es artificialmente fabricadas num meio hospedeiro especificado, isto propicia ao pesquisador uma larga cole??o de par?metros independentes, tais como as propriedades eletromagn?ticas do material hospedeiro. Neste trabalho foi realizada uma investiga??o das propriedades ?nicas dos Ressoadores em Anel Partido (Split Ring Ressonators - SRR) e dos metamateriais compostos. Apresentou-se uma an?lise te?rica e num?rico-computacional, utilizando o formalismo de onda completa atrav?s da aplica??o do m?todo da Linha de Transmiss?o Transversa LTT, para as caracter?sticas ressonantes de uma antena de microfita com patch retangular utilizando substrato metamaterial, assim como ? demonstrado com sucesso ? utiliza??o pr?tica dessas estruturas em antenas. Esta utiliza??o pr?tica ? confirmada experimentalmente

The rise of connected devices and the internet of things has increased the need for systems capable of transmitting high frequency signals wirelessly. An important part of these systems are the filters. Filters remove signals within unwanted frequency ranges. These filters can be implemented using e.g. periodic structures. In this article, we present a design for such a filter that aims to have a stopband between 3-6 [GHz] using square complementary split ring resonators (CSRR) on a substrate integrated waveguide (SIW). The design is based on a dimensional parametric study. An alternative design based on circular CSRR's is also presented and discussed. The design is validated using a commercially available software and a novel method simulating higher order of modes (HOM). The novel simulation method is shown to be advantageous due to its ability to evaluate the attenuation coefficient of a periodic filter. Additionally, a quadratic CSRR structure was shown to have a larger stopband and a similar attenuation coefficient when compared to circular CSRR structure when applied on a SIW. Furthermore, an impedance matching structure for the both CSRR filters were designed and both filters were simulated. / Förekomsten av uppkopplade enheter och användandet av sakernas internet har ökat behovet av system som kan sända högfrekventa signaler trådlöst. En viktig del av dessa system är filter, som eliminerar signaler inom oönskade frekvensband. Dessa filter kan implementeras med periodiska strukturer. I denna rapport presenterar vi en design för ett sådant filter med ett stoppband mellan 3-6 [GHz] som använder sig av kvadratiska "complementary split ring resonators" (CSRR) på en "substrate integrated waveguide" (SIW). Designen är baserad på en geometrisk parametrisk studie. En alternativ design som använder sig av cirkulära CSSRs presenteras och diskuteras. Den föreslagna designen valideras med en kommersiellt tillgänglig och en egenframställd metod vid namn "higher order of modes" (HOM) metoden. Den egenframställda simulationsmetoden visas vara fördelaktig då den är kapabel att evaluera filtrets attenuationskoefficient. Utöver detta visas att en design baserad på kvadratiska CSRRs vara fördelaktig då den genererar ett större stoppband och liknande attenuationskoefficient jämfört med den cirkulära CSSR designen vid tillämpning på en SIW. Fortsättningsvis presenteras en matchande struktur för båda filter varpå båda kompletta filter simuleras. / Kandidatexjobb i elektroteknik 2022, KTH, Stockholm