Compact Metamaterials Induced Circuits and Functional Devices

In recent years, we have witnessed a rapid expansion of using metamaterials to manipulate light or electromagnetic (EM) wave in a subwavelength scale. Specially, metamaterials have a strict limitation on element dimension from effective medium theory with respect to photonic crystals and other planar structures such as frequency selective surface (FSS). In this chapter, we review our effort in exploring physics and working mechanisms for element miniaturization along with the resulting effects on element EM response. Based on these results, we afford some guidelines on how to design and employ these compact meta-atoms in engineering functional devices with high performances. We found that some specific types of planar fractal or meandered structures are particularly suitable to achieve element miniaturization. In what follows, we review our effort in Section 1 to explore novel theory and hybrid method in designing broadband and dual band planar devices. By using single or double such compact composite right-/left-handed (CRLH) atom, we show that many microwave/RF circuits, i.e., balun, rat-race coupler, power divider and diplexer, can be further reduced while without inducing much transmission loss from two perspectives of lumped and distributed CRLH TLs. In Section 2, we show that a more compact LH atom can be engineered by combining a fractal ring and a meandered thin line. Numerical and experimental results demonstrate that a subwavelength focusing is achieved in terms of smooth outgoing field and higher imaging resolution. Section 3 is devoted to a clocking device from the new concept of superscatterer illusions. To realize the required material parameters, we propose a new mechanism by combining both electric and magnetic particles in a composite meta-atom. Such deep subwavelength particles enable exact manipulation of material parameters and thus facilitate desirable illusion performances of a proof-of-concept sample constructed by 6408 gradually varying meta-atoms. Finally, we summarize our results in the last section

HIGH-PERFORMANCE PERIODIC ANTENNAS WITH HIGH ASPECT RATIO VERTICAL FEATURES AND LARGE INTERCELL CAPACITANCES FOR MICROWAVE APPLICATIONS

Modern communications systems are evolving rapidly to address the demand for data exchange, a fact which imposes stringent requirements on the design process of their RF and antenna front-ends. The most crucial pressure on the antenna front-end is the need for miniaturized design solutions while maintaining the desired radiation performance. To satisfy this need, this thesis presents innovative types of periodic antennas, including electromagnetic bandgap (EBG) antennas, which are distinguished in two respects. First, the periodic cells contain thick metal traces, contrary to the conventional thin-trace cells. Second, such thick traces contain very narrow gaps with very tall sidewalls, referred to as high aspect ratio (HAR) gaps. When such cells are used in the structure of the proposed periodic antennas, the high capacitance of HAR gaps decreases the resonance frequency, mitigates conduction loss, and thus, yields considerably small high efficiency antennas. For instance, one of the sample antenna designs with only two EBG cells offers a very small XYZ volume of 0.25λ×0.28λ×0.037λ with efficiency of 83%. Also, a circularly polarized HAR EBG antenna is presented which has a footprint as small as 0.26λ×0.29λ and efficiency as high as 94%. The main analysis method developed in this thesis is a combination of numerical and mathematical analyses and is referred to as HFSS/Bloch method. The numerical part of this method is conducted using a High Frequency Structure Simulator (HFSS), and the mathematical part is based on the classic Bloch theory. The HFSS/Bloch method acts as the mainstay of the thesis and all designs are built upon the insight provided by this method. A circuit model using transmission line (TL) theory is also developed for some of the unit cells and antennas. The HFSS/Bloch perspective results in a HAR EBG TL with radiation properties, a fragment of which (2 to 6 cells) is introduced as a novel antenna, the self-excited EBG resonator antenna (SE-EBG-RA). Open (OC) and short circuited (SC) versions of this antenna are studied and the inherently smaller size of the SC version is demonstrated. Moreover, the possibility of employing the SE-EBG-RA as the element of a series-fed array structure is investigated and some sample high-efficiency, flat array antennas are rendered. A microstrip antenna is also developed, the structure of which is composed of 3×3 unit cells and shows fast-wave behaviors. Most antenna designs are resonant in nature; however, in one case, a low-profile efficient leaky-wave antenna with scanning radiation pattern is proposed. Several antenna prototypes are fabricated and tested to validate the analyses and designs. As the structures are based on tall metal traces, two relevant fabrication methods are considered, including CNC machining and deep X-ray lithography (DXRL). Hands-on experiments provide an outlook of possible future DXRL fabricated SE-EBG-RAs

Antenna System Design for 5G and Beyond – A Modal Approach

Antennas are one of the key components that empower a new generation of wireless technologies, such as 5G and new radar systems. It has been shown that antenna design strategies based on modal theories represent a powerful systematic approach to design practical antenna systems with high performance. In this thesis, several innovative multi-antenna systems are proposed for wireless applications in different frequency bands: from sub-6 GHz to millimeter-wave (mm-wave) bands. The thesis consists of an overview (Part I) and six scientific papers published in peer-reviewed international journals (Part II). Part I provides the overall framework of the thesis work: It presents the background and motivation for the problems at hand, the fundamental modal theories utilized to address these problems, as well as subject-specific research challenges. Brief conclusions and future outlook are also provided. The included papers of Part II can be divided into two tracks with different 5G and beyond wireless applications, both aiming for higher data rates.In the first track, Papers [I] to [IV] investigate different aspects of antenna system design for smart-phone application. Since Long Term Evolution (LTE) (so-called 3.5G) was deployed in 2009, mobile communication systems have utilized multiple-input multiple-output antenna technology (MIMO) technology to increase the spectral efficiency of the transmission channel and provide higher data rates in existing and new sub-6 GHz bands. However, MIMO requires multi-antennas at both the base stations and the user equipment (mainly smartphones) and it is very challenging to implement sub-6 GHz multi-antennas within the limited space of smartphones. This points to the need for innovative design strategies. The theory of characteristic modes (TCM) is one type of modal theory in the antenna community, which has been shown to be a versatile tool to analyze the inherent resonance properties of an arbitrarily shaped radiating structure. Characteristic modes (CMs) have the useful property of their fields being orthogonal over both the source region and the sphere at infinity. This property makes TCM uniquely suited for electrically compact MIMO antenna design.In the second track, Papers [V]-[VI] investigate new integrated antenna arrays and subarrays for the two wireless applications, which are both implemented in a higher part of the mm-wave frequency range (i.e. E-band). Furthermore, a newly developed high resolution multi-layer “Any-Layer” PCB technology is investigated to realize antenna-in-package solutions for these mmwave antenna system designs. High gain and high efficiency antennas are essential for high-speed wireless point-to-point communication systems. To meet these requirements, Paper [V] proposes directive multilayer substrate integrated waveguide (SIW) cavity-backed slot antenna array and subarray. As a background, the microwave community has already shown the benefits of modal theory in the design and analysis of closed structures like waveguides and cavities. Higher-order cavity modes are used in the antenna array design process to facilitate lower loss, simpler feeding network, and lower sensitivity to fabrication errors, which are favorable for E-band communication systems. However, waveguide/cavity modes are confined to fields within the guided media and can only help to design special types of antennas that contain those structures. As an example of the versatility of TCM, Paper [VI] shows that apart from smartphone antenna designs proposed in Papers [I]-[IV], TCM can alsobe used to find the desirable modes of the linear antenna arrays. Furthermore, apart from E-band communications, the proposed series-fed patch array topology in Paper [VI] is a good candidate for application in 79 GHz MIMO automotive radar due to its low cost, compact size, ability to suppress surface waves, as well as relatively wide impedance and flat-gain bandwidths

Advanced High Efficiency Architectures for Next Generation Wireless Communications

L'abstract è presente nell'allegato / the abstract is in the attachmen

ANALYSIS AND DESIGN OF ANTENNA PROBES FOR DETECTION / IMAGING APPLICATIONS

Analysis and Design of Antenna Probes for Detection / Imaging Applications Ayman Elboushi, Ph.D. Concordia University. As a result of increasing international terrorist threats, the need for an efficient inspecting tool has become urgent. Not only for seeing through wall applications, but also to be employed as a safe human body scanner at public places such as airports and borders. The usage of microwave and millimeter wave antennas and systems for detection / imaging applications is currently of increasing research interest targeting the enhancement of different security systems. There are many challenges facing researchers in order to develop such systems. One of the challenges is the proper design of a low cost, reduced size and efficient antenna probe to work as a scanning sensor. In this thesis, two different technology choices of antenna probes for the feasibility of constructing detection / imaging systems are investigated. The first one covers the Ultra Wide Band (UWB) range (3.1 GHz to 10.6 GHz), while the second operates over the Millimeter-Wave (MMW) range. In addition to the development of several antenna probes, two detection / imaging systems are demonstrated and showed reasonably accurate detection results. Three different UWB monopole antenna prototypes, with different radiator shapes (circular, crescent and elliptical) have been introduced. These antennas are designed using a standard printed circuit board (PCB) process to work as probing sensors in a proposed UWB detection / imaging system. In order to enhance the resolution and the detection accuracy of the probe, 4-element Balanced Antipodal Vivaldi Antenna (BAVA) array fed by 1-to-4 UWB modified Wilkinson power divider has been developed. Some successful experiments have been conducted using the proposed UWB detection / imaging system combined with the fabricated antenna probes to detect the presence of a gap between two walls made of different material types, to evaluate the gap width and to estimate the size and exact location of a hidden target between the walls. The second research theme of this thesis is to develop small-sized, light-weight and high gain MMW scanning antenna probes. For the realization of such probes, several gain enhancement techniques have been adopted, including hybridization and a multi-element array principle. Several high-gain hybrid antennas have been designed, fabricated and tested. For demonstration purposes, experiments have been carried out for detecting and imaging a small metallic coin under the jeans layer of a three-layer target emulating a human body’s covering layers. A performance comparison between a standard metallic MMW horn and hybrid microstrip patch/conical horn antenna has been made. The proposed reduced size antenna sensor shows increased efficiency compared with the bulky horn antenna. Resolution enhancement of the reconstructed image of the hidden target is implemented using a new triple-antenna MMW sensor. The triple-antenna sensor consists of three adjacent microstrip patch / conical horn antennas separated by 1.5 wavelengths at the center frequency for coupling reduction between these elements. The middle element of the sensor is used for monitoring the time domain back-reflected signal from the target under inspection, while the side elements are used for monitoring the scattered signals. By the aid of a special signal processing algorithm, an enhanced image of the concealed object can be obtained by combining the three readings of each point in the area under study. The proposed system shows a great ability for detecting a hidden target and enhances the reconstructed image resolution

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

Realization Limits of Impulse-Radio UWB Indoor Localization Systems

In this work, the realization limits of an impulse-based Ultra-Wideband (UWB) localization system for indoor applications have been thoroughly investigated and verified by measurements. The analysis spans from the position calculation algorithms, through hardware realization and modeling, up to the localization experiments conducted in realistic scenarios. The main focus was put on identification and characterization of limiting factors as well as developing methods to overcome them

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development

Subarray-Based Multibeam Antenna Frontend for Millimeter-Wave Hybrid Beamforming

With the paradigm shift from sub-6 GHz to millimeter-wave (mm-Wave) for wireless communications, beamforming becomes essential for mm-Wave access points to mitigate losses. Due to the small wavelength, a compact circuit could accommodate a large number of antenna elements. This favors the principle of beamforming to achieve high array-gain and spatial resolution through a large-scale N × M array. For such antenna frontends, full-digital beamforming circuitry requires N × M RF chains, which is unfeasible and energy inefficient. Likewise, a higher-order mm-Wave analog beamforming network is highly lossy to generate N × M beams. Hybrid beamforming addresses this dilemma by partitioning the beamforming between the analog and digital domains appropriately. For this purpose, the antenna frontend needs to be segmented into subarrays, such that the subarray-based analog beamspace patterns are digitally processed rather than processing element patterns individually. Thus, hybrid beamforming requires a suitable subarray-based N × M multibeam antenna frontend. In this thesis, a study of the subarray antennas is presented for hybrid beamforming operation. A simplified model is considered in which the analog beam-switching is performed in the azimuth plane (H-plane) and the digital beamspace beamforming in the elevation plane (V-plane). This is to reduce the number of RF chains as well as to achieve fine-tuned digital beam-steering in V-plane along with predefined analog switched-beams in H-plane. In this research work, the frequency band of 28 – 32 GHz is considered for prototyping purposes. For practical use at mm-Wave, the microstrip line technology is augmented with the perfect magnetic conductor (PMC) packaging. The fixed-beam and switched-beam subarrays with an order of n × m = 1 × 4, 2 × 2, and 4 × 4 are investigated. A dual-polarized aperture-coupled magneto-electric dipole antenna is designed as a single element with 20% bandwidth, ports' isolation better than 35 dB, cross-polarization less than -25 dB, and gain of 8 dBi. Using this element, a fixed-beam 4 × 4 dual-polarized subarray is designed that maintains a bandwidth of 16.7% at 30 GHz with a maximum gain of 19.3 dBi and symmetrical radiation patterns. The fixed-beam limitation of the 2n × 2m subarray leads to building the efficient switched-beam subarray antennas for hybrid beamforming. For this purpose, a 2 × 2 dual-polarized analog beamforming network is designed for 28-32 GHz. Two identical PMC packaged microstrip line networks, one for each polarization, are designed on a single substrate surface. However, to be processed for beamspace digital beamforming, this topology exhibits physical layout and array factor problems. Thus, further designs are investigated to meet the hybrid beamforming frontend requirements. To this end, as switched-beam subarrays for hybrid beamforming, two PMC packaged 4 × 4 Butler matrices are presented with a longitudinal layout and a folded layout for the end-fire and broadside radiation characteristics, respectively. The former design achieves a 5 GHz (28-33 GHz) bandwidth with return loss and isolation, both better than 15 dB. At 30 GHz, the insertion loss is 0.8 ± 0.3 dB, and antenna-ports' phase distributions are ±45° and ±135°. E-plane-flared horn antennas terminate the Butler matrix antenna-ports as a linear array. The double-ridge gap waveguide horn antenna is designed to reduce the scan loss within a subarray environment. The H-plane fan-beam switching covers ±42° with a maximum gain of 11.7 and 11.2 dBi for the inner (1R) and outer (2R) radiation beams. The latter novel topology of the folded Butler matrix is laid out for a compact tiled planar antenna frontend to accommodate a beamforming network beneath the antenna array's physical footprints. As compared to the conventional longitudinal layout, the size is reduced by more than 50 %. The PCB aperture-coupled antenna elements are integrated within the PMC packaged environment for a broadside radiation characteristic. The folded Butler matrix and antenna element are designed for a bandwidth of 4 GHz (28-32 GHz). The single antenna element's directivity is 5.22 dBi; whereas, for a 1 × 4 switched-beam subarray antenna, the directivities are 11.1 dBi and 10.6 dBi for 1R and 2R beams, respectively. Using Butler matrices-based 1 × 4 switched-beam subarrays, two types of multibeam antenna frontends with order N × M = 4 × 4 are constructed. Post-processing for the digital beamforming is applied over the subarray-based analog beamspaces. The first hybrid beamforming model maintains a scan range of ± 42o in the H-plane and ± 28o in the V-plane with BV × BH = 3 × 4 = 12 beams. Similarly, the second model maintains a scan range of ± 38o in the H-plane and ± 40o in the V-plane with BV × BH = 4 × 4 = 16 beams. As compared to full-analog two-dimensional (2-D) beamforming, these models are capable of fine-tuned beam-steering in the V-plane because the complex beamforming coefficients are not fixed but calculated digitally. Furthermore, compared to full-digital 2-D beamforming, it reduces the number of active RF chains from N × M to N