Les métamatériaux sont des matériaux artificiels devenus très attractifs du fait de leurs propriétés électromagnétiques atypiques. Les structures CRLH (Composite Right Left-Handed) à ondes de fuite en particulier, permettent d’effectuer un balayage angulaire très important sur une large bande passante. Toutefois l’état de l’art montre qu’il faudrait un très grand nombre de cellules pour atteindre une efficacité de rayonnement acceptable. Vue la demande récurrente des nouveaux systèmes de transmission d’avoir des antennes de faible encombrement, il serait plus intéressant de trouver de nouvelles architectures d’antennes utilisant ces structures CRLH. L’objectif de la thèse est en premier lieu d’avoir une connaissance approfondie du comportement électromagnétique des structures CRLH. Afin de tirer profit de leurs propriétés électromagnétiques atypiques, de nouvelles architectures d’antennes inspirées des structures CRLH sont proposées. Ces nouvelles antennes permettent de réaliser différents types de diagrammes de rayonnement (large ouverture angulaire, faisceau étroit, double polarisation). Elles sont caractérisées grâce à une modélisation analytique qui aura été validée auparavant par la simulation électromagnétique. / Metamaterials are artificial structures with unusual electromagnetic properties. Composite Right-Left Handed (CRLH) radiating structures are very attractive antennas because of their scanning capability and wideband performances. However crlh lines must contain a large number of cells in order to have sufficient radiation efficiency. Due to the recurring request of having small antennas in new communication systems, new designs based on crlh structures must be found. The first objective of this thesis is to have full knowledge of electromagnetic properties of crlh structures. To take advantages of atypical electromagnetic behavior of CRLH structures, new CRLH based antennas designs are proposed. These new inspired antennas could produce different radiation patterns (with large beamwidth, narrow beam, double polarization). Analytical model, previously validated by electromagnetic simulator, is used to characterize the new proposed antennas.

This thesis introduces, for the first time, Stepped Impedance Resonator (SIR) bandpass filters (BPF) based on Composite Right/Left-Handed (CRLH) transmission lines. In other words, a novel approach in design of BPFs for RF and microwave applications is successfully proposed and examined, which can serve both miniaturisation and performance enhancement purposes. In conducting this research, design, development and optimisation procedures and techniques for the proposed BPFs have been presented. Theoretical, numerical and experimental results have confirmed that these filters are capable of significantly reducing the size while maintaining the integrity of the filter performance; and in some cases, extensively enhancing the performance.Two λg/4-type CRLH SIRs are designed and characterised based on the available equations. ADS lumped-element equivalent circuit model and HFSS full-wave electromagnetic simulation, and measurement results prove that both CRLH SIRs surpassed their RH counterparts, in terms of both size and performance. Indeed, comparison of the first CRLH SIR with its RH counterpart revealed a 35% size (length) reduction. The second CRLH SIR design is measured to be 66% smaller than its RH counterpart and 14% smaller than the initial CRLH SIR. In addition, simulation and measurement results reveal that an intelligently designed CRLH SIR shows a better quality factor Q and input impedance |Zin| response, and provides higher design flexibility. Phase unwrapping and energy (current) flow analysis have been used to prove left-handedness of the CRLH SIRs. The concept is extended to propose multi-section (λg/2-type and tri-section SIRs) and tunable CRLH SIRs. Numerical analysis and obtained results show that the λg/2-type CRLH SIR benefits from a 45% size (length) reduction compared to its RH counterpart, and a better |Zin| response. The results obtained from the tri-section CRLH SIR (TSSIR), clearly show that the TSSIR is capable of relocating (and minimising) the multiple spurious resonance frequencies, while maintaining the same fundamental frequency f0. As such, no spurious frequency is observed before 8 GHz. Also, measurements indicated that the CRLH TSSIR is not only 30% smaller in length compared to its RH counterpart, it was even 28% smaller than a two-section RH SIR resonating at the same frequency of 2.5 GHz. In addition, the tuning capability of the ferrite CRLH SIR is illustrated when the operating frequency of the resonator is tuned from 5.1 GHz to 5.4 GHz, and 5.65 GHz for H0 = 2000, 2250, and 2500 Oe, respectively.These SIRs are then combined and configured to form two main categories of CRLH SIR bandpass filters: PCB filters based on RT Duroid and MMIC filters based on GaAs. In both filters, the homogeneity condition has been satisfied by ensuring that the longest length is much less than λg (in this case l = λg/12) for PCB-based filters and l = λg/14 for MMIC filters at the centre frequency of the filters. The first PCB-based CRLH SIR filter, which has been designed to operate at 2.75 GHz, is measured 24mm × 28mm. HFSS 3-D full-wave simulations and measurement results of this filter reveal that, with an insertion loss of -2.6dB and return loss of -21.5dB, the filter not only has a very good selectivity, but also is extremely efficient in extending the free-spurious stop-band, pushing the first spurious response to around 11 GHz (about 4×f0). The second PCB-based CRLH SIR filter has much smaller size, measuring overall filter dimensions of 6mm × 5.14mm. This filter also benefits from a smaller resonator size, improved overall coupling and a more controllable circuit. Theory, full-wave simulation and measurement results demonstrate that, with an insertion loss of -1dB and return loss of -34dB, the miniaturised CRLH SIR filter proves very successful as it was about 80% smaller in size compared to its RH counterpart with the same centre frequency, while maintaining the integrity of the filter performance. Moreover, the miniaturised CRLH SIR BPF is significantly more controllable in its dimensions and response due to the fact that more elementary parameters are available in the CRLH configuration.The MMIC CRLH SIR bandpass filters are then proposed with an emphasis on further size reduction with maintenance (or enhancement) of their transmission responses. As such, two classes of MMIC filters were designed: the first one is very small measuring 3.2mm × 3.4mm, with an insertion loss of -5.3dB at the centre frequency 3.1 GHz. The filter also shows good attenuation both before and after the passband with its first spurious frequency occurring at 13.52 GHz (i.e. > 4×f0). The second set of MMIC filters employed multilayer topology to reduce the filter size. It has been clearly shown that with an intelligent design, the size (dimension) limitations of the PCB-based filters have been overcome by using the MMIC technology, resulting in filters with significantly reduced sizes - design I: 1.32mm×3.35mm, and design II: 1.4mm × 1.5mm. It has also been observed that MMIC structures are generally exposed to inevitable losses, though steps can be taken to reduce such losses.

No description available.

In a communication system, the group delay variation (GDV) causes the distortion of signal and the degradation of symbol error rate. Usually, the compensation of group delay (GD) utilizing positive group delay (PGD) results in further propagation delay. Therefore, this research studies the negative group delay (NGD) behavior of metamaterial. Through analyzing the effects on GD caused by poles and zeros of circuit, the group delay circuit capable of switching between NGD and PGD is presented. Further, adjustable negative group delay circuits (NGDCs) are designed based on the concept of poles and zero. The NGD generated by NGDC is used to achieve the equalization of GD and recover the distorted signal in time domain. Additionally, owing to the limited frequency band of communication, a filter with high selectivity is required to utilize the available bandwidth. The character of left-handed metamaterial is applied to the design of filter for reducing the size and cost of traditional microstrip line filters with high selectivity. Under the balanced condition, composite right/left-handed (CRLH) transmission line behaves right- and left- handed characteristics in different frequency bands. Thus, a coplanar waveguide (CPW) filter with high selectivity, size reduction and low cost is presented utilizing such a CRLH structure.

No description available.

Yes / The paper demonstrates an effective technique to significantly enhance the bandwidth and radiation gain of an otherwise narrowband composite right/left-handed transmission-line (CRLH-TL) antenna using a non-Foster impedance matching circuit (NF-IMC) without affecting the antenna's stability. This is achieved by using the negative reactance of the NF-IMC to counteract the input capacitance of the antenna. Series capacitance of the CRLH-TL unit-cell is created by etching a dielectric spiral slot inside a rectangular microstrip patch that is grounded through a spiraled microstrip inductance. The overall size of the antenna, including the NF-IMC at its lowest operating frequency is 0.335λ0 × 0.137λ0 × 0.003λ0, where λ0 is the free-space wavelength at 1.4 GHz. The performance of the antenna was verified through actual measurements. The stable bandwidth of the antenna for |S11|≤ - 18 dB is greater than 1 GHz (1.4-2.45 GHz), which is significantly wider than the CRLH-TL antenna without the proposed impedance matching circuit. In addition, with the proposed technique the measured radiation gain and efficiency of the antenna are increased on average by 3.2 dBi and 31.5% over the operating frequency band. / This work is partially supported by RTI2018-095499-B-C31, Funded by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER,UE), and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

This thesis focuses mostly on investigating different potential applications of meta-transmission line (TL), particularly composite right/left handed (CRLH) TL, and analyzing some new phenomena and applications of meta-TL, mostly left-handed (LH) TL. Realization principle will also be studied.   First, the fundamental electromagnetic properties of propagation in the presence of left-handed material (LHM) are illustrated. The transmission line approach for LHM design is described together with a brief review of the transmission line theory. As a generalized model for LHM TL, CRLH TL provides very unique phase response, such as dual-band operation, bandwidth enhancement, nonlinear dispersion, and the existence of critical frequency with zero phase velocity. Based on these properties, some novel applications of the existing CRLH transmission lines are then given, including a notch filter, a diplexer, a broadband phase shifter, a broadband balun, and a dual band rat-ring coupler. In the design of notch filters and diplexers, CRLH TL shunt stub is utilized to provide high frequency selectivity due to the existence of critical frequency with zero phase velocity. The proposed wideband Wilkinson balun, which comprises of one section of conventional transmission lines and one section of CRLH-TL, is shown to have a 180°±10° bandwidth of 2.12 GHz centered at 1.5 GHz. In the analysis of the dual band rat-ring couplers, a generalized formulation of the requirements about impedances and electrical length of the branches are derived, and as an example, a compact dual-band rat-race coupler is designed utilizing the balanced CRLH TL. Furthermore, a low pass filter is also proposed and designed based on a single (epsilon) negative coplanar waveguide (CPW).Various principles to realize meta-transmission lines are investigated. The main conclusions are listed below:Ÿ         Dual composite right/left handed (D-CRLH) transmission line, which is the dual structure of conventional CRLH TL, shows opposite handedness in the high frequencies and low frequencies with CRLH TL. Meanwhile, in the practical implementation, D-CRLH TL always shows a sharp stopband. A notch filter and a dual-band balun are designed based on D-CRLH TL. Ÿ         The lattice type transmission line (LT-TL) shows the same magnitude response with the conventional right-handed (RH) TL, but a constant phase difference in the phase response over a wide frequency band. A wideband rat-race coupler is proposed as an application of the LT-TL. Ÿ         Finger-shorted interdigital capacitors (FSIDCs) are analyzed and it is shown that FSIDC alone can act as a left-handed transmission line. The value of the reactive elements (inductors and capacitors) in the equivalent circuit model is determined by the dimensions of FSIDC. The relationship between them is analyzed.Later, transmission line loaded with negative-impedance-converted inductors and capacitors is illustrated as the first non-dispersive LH transmission line. The design of a negative series impedance converter is given in detail and a wideband power divider is designed as a potential application of the newly proposed meta-transmission lines in is also given. The final part of the thesis focuses on the study of microstrip lines loaded with complementary split ring resonators (SRRs). An equivalent circuit is made for this structure. The circuit model is verified by the experimental results of cases with different periodic lengths. Thereafter, a meander line split ring resonator (MLSRR) is presented. It shows dual band property and the miniature prototypes of complementary MLSRR loaded transmission lines are fabricated. By comparing the resonance frequencies of complementary MLSRR and multiple SRR, it is shown that the complementary MLSRR is very compact. C-MLSRR is applied in rejecting unnecessary frequencies in the ultra wideband antennas. / QC 20100720

Yes / This paper presents a novel on-chip antenna using standard CMOS-technology based on metasurface implemented on two-layers polyimide substrates with a thickness of 500 μm. The aluminium ground-plane with thickness of 3 μm is sandwiched between the two-layers. Concentric dielectric-rings are etched in the ground-plane under the radiation patches implemented on the top-layer. The radiation patches comprise concentric metal-rings that are arranged in a 3 × 3 matrix. The antennas are excited by coupling electromagnetic energy through the gaps of the concentric dielectric-rings in the ground-plane using a microstrip feedline created on the bottom polyimide-layer. The open-ended feedline is split in three-branches that are aligned under the radiation elements to couple the maximum energy. In this structure, the concentric metal-rings essentially act as series left-handed capacitances CL that extend the effective aperture area of the antenna without affecting its dimensions, and the concentric dielectric rings etched in the ground-plane act as shunt left-handed inductors LL, which suppress the surface-waves and reduce the substrates losses that leads to improved bandwidth and radiation properties. The overall structure behaves like a metasurface that is shown to exhibit a very large bandwidth of 0.350–0.385 THz with an average radiation gain and efficiency of 8.15dBi and 65.71%, respectively. It has dimensions of 6 × 6 × 1 mm3 that makes it suitable for on-chip implementation. / This work is partially supported by RTI2018-095499-B-C31, Funded by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER,UE), and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and the fnancial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1. / Research Development Fund Publication Prize Award winner, March 2020

Yes / A feasibility study of a novel configuration for a super-wide impedance planar antenna is presented based on a 2 × 2 microstrip patch antenna (MPA) using CST Microwave Studio. The antenna comprises a symmetrical arrangement of four-square patches that are interconnected to each other with cross-shaped high impedance microstrip lines. The antenna array is excited through a single feedline connected to one of the patches. The proposed antenna array configuration overcomes the main drawback of conventional MPA with a narrow bandwidth that is typically <5%. The antenna exhibits a super-wide frequency bandwidth from 20 GHz to 120 GHz for S11 < −15 dB, which corresponds to a fractional bandwidth of 142.85%. The antenna’s performance of bandwidth, impedance match, and radiation gain were enhanced by etching slots on the patches. With the inclusion of the slot, the maximum radiation gain and efficiency of the MPA increased to 15.11 dBi and 85.79% at 80 GHz, which showed an improvement of 2.58 dBi and 12.54%, respectively. The dimension of each patch antenna was 4.3 × 5.3 mm2 . The results showed that the proposed MPA is useful for various existing and emerging communication systems such as ultra-wideband (UWB) communications, RFID systems, massive multiple-output multiple-input (MIMO) for 5G, and radar systems. / This work was partially supported by the Innovation Program under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

Yes / In this review paper, a comprehensive study on the concept, theory, and applications of composite right/left-handed transmission lines (CRLH-TLs) by considering their use in antenna system designs have been provided. It is shown that CRLH-TLs with negative permittivity (ε <; 0) and negative permeability (μ <; 0) have unique properties that do not occur naturally. Therefore, they are referred to as artificial structures called “metamaterials”. These artificial structures include series left-handed (LH) capacitances (C L ), shunt LH inductances (L L ), series right-handed (RH) inductances (LR), and shunt RH capacitances (CR) that are realized by slots or interdigital capacitors, stubs or via-holes, unwanted current flowing on the surface, and gap distance between the surface and ground-plane, respectively. In the most cases, it is also shown that structures based on CRLH metamaterial-TLs are superior than their conventional alternatives, since they have smaller dimensions, lower-profile, wider bandwidth, better radiation patterns, higher gain and efficiency, which make them easier and more cost-effective to manufacture and mass produce. Hence, a broad range of metamaterial-based design possibilities are introduced to highlight the improvement of the performance parameters that are rare and not often discussed in available literature. Therefore, this survey provides a wide overview of key early-stage concepts of metematerial-based designs as a thorough reference for specialist antennas and microwave circuits designers. To analyze the critical features of metamaterial theory and concept, several examples are used. Comparisons on the basis of physical size, bandwidth, materials, gain, efficiency, and radiation patterns are made for all the examples that are based on CRLH metamaterialTLs. As revealed in all the metematerial design examples, foot-print area decrement is an important issue of study that have a strong impact for the enlargement of the next generation wireless communication systems. / This work was supported in part by the Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER, UE) under Grant RTI2018-095499-B-C31, in part by the Innovation Programme under Grant H2020-MSCA-ITN-2016 SECRET-722424, and in part by the financial support from the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/E022936/1.