Integration Of High-q Filters With Highly Efficient Antennas

The integration of high-quality (Q)-factor 3-D filters with highly efficient antennas is addressed in this dissertation. Integration of filters and antennas into inseparable units eliminates the transitions between the otherwise separate structures resulting in more compact and efficient systems. The compact, highly efficient integrated 3-D filter/antenna systems, enabled by the techniques developed herein, allow for the realization of integrated RF front ends with significantly- reduced form factors. Integration of cavity filters with slot antennas in a single planar substrate is first demonstrated. Due to the high Q factor of cavity resonators, the efficiency of the integrated filter/antenna system is found to be the same as that of a reference filter with the same filtering characteristics. This means a near 100% efficient slot antenna is achieved within this integrated filter/antenna system. To further reduce the footprint of the integrated systems, vertically integrated filter/antenna systems are developed. We then demonstrate the integration of cavity filters with aperture antenna structures which enable larger bandwidths compared with slot antennas. The enhanced bandwidths are made possible through the excitation and radiation of surface waves. To obtain omnidirectional radiation patterns , we integrate cavity filters with monopole antennas. Finally, the integration of filters with patch antennas is addressed. Unlike the other filter/antenna integration examples presented, in which the antenna is utilized as an equivalent load, the patch antenna provides an additional pole in the filtering function. The presented techniques in this dissertation can be applied for filter/antenna integration in all microwave, and millimeter-wave frequency region

New design approach of antennas with integrated coupled resonator filters

In the majority of microwave receiving and transmitting systems, a requirement is to have a filter immediately adjacent to the antenna or antenna array. This thesis presents a new methodology for antenna design where a filter is either fully or partially integrated with the antenna elements. The design of this antenna-filter follows the well-established coupled-resonator filter design theory, in which each resonator can not only be used as a filter element but also as a radiator. In order to verify the concept, a two-port bandpass filter designed using dipole antennas is the first work in this thesis to verify the use of dipole antennas as resonators. The coupling matrix has been used to obtain the filter response. One port antenna-filters made out of one, two and three dipoles. The method has also been utilised to implement X-band waveguide components which consist of an antenna-filter, antenna power divider and an antenna-diplexer. The calculation, simulation and measurement results are in good agreement. These proposed components has been designed, simulated, fabricated and measured. They have provided verification of the method, showing the antenna and filter theories and can be applied to miniaturise these components for use in the wireless communication and radar systems

Frequency-agile filtering antennas for S-band and X-band applications

Multi-functional, highly flexible, and tightly integrated Radio-Frequency Front-Ends (RFFEs) are at the forefront of the current developments to improve the performance of next-generation wireless RF systems. In the past decade, filtering antennas, or filtennas, have emerged as a potential solution to minimize the Radio-frequency system's cost and complexity while maximizing performance in a highly integrated module. The RF co-design approach of combining the filtering and radiation functionalities into a single unit is beneficial for improving a system's Signal-to-Noise (SNR) performance while limiting interference in a congested frequency spectrum. Furthermore, frequency-agile filtennas can enhance an RF system's adaptation to changing radio environments. The work presented in this thesis utilizes conventional bandpass filter synthesis techniques to enhance the performance of tunable filtennas for next-generation RFFEs. By using high-$Q$ Evanescent-mode (EVA-mode) cavity resonators and highly efficient slot antennas, multiple filtenna designs are demonstrated. First, the building blocks of the filtennas are individually developed. A novel Evanescent-mode Cavity-Backed Slot Antenna (ECBSA) with contactless capacitive tuning is designed for radiation functionality. Long-range external linear actuators are deployed to tune the critical gap size of the cavity. Experimental results of the antenna demonstrate a high power-handling capacity and wide tuning from 1.7 GHz to 2.6 GHz (40\%). The ECBSA is then integrated with a contactless-tuned EVA-mode resonator to form a 2nd-order tunable filtenna. The fabricated filtenna demonstrates frequency tuning from 2-2.6 GHz (26\%), with a peak realized gain ranging from 2.7~dB to 5.2~dB. The filtenna showed excellent tuning reliability due to the deployed closed-loop monitoring system and exhibits state-of-the-art performance in the class of tunable cavity-based filtennas. The frequency scalability of the tunable filtenna is next investigated in the X-band (8-12~GHz) frequency regime. A new filtenna structure and tuning scheme is conceptualized by incorporating varactor diodes on a novel superstrate-loaded cavity-backed slot antenna. The performance trade-offs and loss analysis is completed by analyzing the resistive losses associated with tuning varactors. In addition, a new technique is proposed to estimate a varactor's quality factor for high-frequency applications. The proposed method does not require any calibration or de-embedding processes. The varactor-$Q$ estimation technique can effectively estimate the bias and frequency-dependent varactor quality factor for any reconfigurable RF application

Synthesis of waveguide antenna arrays using the coupling matrix approach

With the rapid development in communication systems recently, improvements in components of the systems such as antennas and bandpass filters are continuously required to provide improved performance. High gain, wide bandwidth, and small size are the properties of antennas which are demanded in many modern applications, and achieving these simultaneously is a challenge. This thesis presents a new design approach to address this challenge. The coupling matrix is an approach used to represent the circuits made of coupled resonators such as filters and multiplexers. The approach has been utilised here to integrate a single resonator-based antenna with an n$^t$$^h$ order filter. The integrated component is capable of providing a controllable bandwidth and introduces the filtering functionality. The approach is further developed in order to integrate bandpass filters with N×N resonator-based antenna arrays. This is to increase the gain of the array as well. Six novel components have been fabricated for the purpose of validation. This thesis also looks at a 300 GHz communication system which is proposed at The University of Birmingham with the objective to build a 10 metre indoor communication link. A 300 GHz (8×8) waveguide antenna array has been designed and fabricated for the system

Silicon-Based Terahertz Circuits and Systems

The Terahertz frequency range, often referred to as the `Terahertz' gap, lies wedged between microwave at the lower end and infrared at the higher end of the spectrum, occupying frequencies between 0.3-3.0 THz. For a long time, applications in THz frequencies had been limited to astronomy and chemical sciences, but with advancement in THz technology in recent years, it has shown great promise in a wide range of applications ranging from disease diagnostics, non-invasive early skin cancer detection, label-free DNA sequencing to security screening for concealed weapons and contraband detection, global environmental monitoring, nondestructive quality control and ultra-fast wireless communication. Up until recently, the terahertz frequency range has been mostly addressed by high mobility compound III-V processes, expensive nonlinear optics, or cryogenically cooled quantum cascade lasers. A low cost, room temperature alternative can enable the development of such a wide array of applications, not currently accessible due to cost and size limitations. In this thesis, we will discuss our approach towards development of integrated terahertz technology in silicon-based processes. In the spirit of academic research, we will address frequencies close to 0.3 THz as 'Terahertz'. In this thesis, we address both fronts of integrated THz systems in silicon: THz power generation, radiation and transmitter systems, and THz signal detection and receiver systems. THz power generation in silicon-based integrated circuit technology is challenging due to lower carrier mobility, lower cut-o frequencies compared to compound III-V processes, lower breakdown voltages and lossy passives. Radiation from silicon chip is also challenging due to lossy substrates and high dielectric constant of silicon. In this work, we propose novel ways of combining circuit and electromagnetic techniques in a holistic design approach, which can overcome limitations of conventional block-by-block or partitioned design methodology, in order to generate high-frequency signals above the classical definition of cut-off frequencies (ƒt/ƒmax). We demonstrate this design philosophy in an active electromagnetic structure, which we call Distributed Active Radiator. It is inspired by an Inverse Maxwellian approach, where instead of using classical circuit and electromagnetic blocks to generate and radiate THz frequencies, we formulate surface (metal) currents in silicon chip for a desired THz field prole and develop active means of controlling different harmonic currents to perform signal generation, frequency multiplication, radiation and lossless filtering, simultaneously in a compact footprint. By removing the articial boundaries between circuits, electromagnetics and antenna, we open ourselves to a broader design space. This enabled us to demonstrate the rst 1 mW Eective-isotropic-radiated-power(EIRP) THz (0.29 THz) source in CMOS with total radiated power being three orders of magnitude more than previously demonstrated. We also proposed a near-field synchronization mechanism, which is a scalable method of realizing large arrays of synchronized autonomous radiating sources in silicon. We also demonstrate the first THz CMOS array with digitally controlled beam-scanning in 2D space with radiated output EIRP of nearly 10 mW at 0.28 THz. On the receiver side, we use a similar electronics and electromagnetics co-design approach to realize a 4x4 pixel integrated silicon Terahertz camera demonstrating to the best of our knowledge, the most sensitive silicon THz detector array without using post-processing, silicon lens or high-resistivity substrate options (NEP &lt; 10 pW &#8730; Hz at 0.26 THz). We put the 16 pixel silicon THz camera together with the CMOS DAR THz power generation arrays and demonstrated, for the first time, an all silicon THz imaging system with a CMOS source.</p

Analysis and design of metamaterial-inspired microwave structures and antenna applications

Novel metamaterial and metamaterial-inspired structures and microwave/antenna applications thereof are proposed and studied in this thesis. Motivated by the challenge of extending the applicability of metamaterial structures into practical microwave solutions, the underlying objective of this thesis has been the design of low-cost, easily fabricated and deployable metamaterial-related devices and the development of computational tools for the analysis of those. For this purpose, metamaterials composed of tightly coupled resonators are chosen for the synthesis of artificial transmission lines and enabling antenna applications. Specifically, fully-printed double spiral resonators are employed as modular elements for the design of tightly coupled resonators arrays. After thoroughly investigating the properties of such resonators, they are used for the synthesis of artificial lines in either grounded or non-grounded configurations. In the first case, the supported backward waves are exploited for the design of microstrip-based filtering/diplexing devices and series-fed antenna arrays. In the second case, the effective properties of such structures are employed for the design of a novel class of self-resonant, low-profile folded monopoles, exhibiting low mutual coupling and robust radiating properties. Such monopoles are, in turn, used for the synthesis of different sub-wavelength antenna arrays, such as superdirective arrays. Finally, an in-home periodic FDTD-based computational tool is developed and optimized for the efficient and rigorous analysis of planar, metamaterial-based, high-gain antennas.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Advanced direct metal 3D printed passive components for wireless communications and satellite applications

This thesis presents the design of advanced microwave passive filters, antennas, and antenna arrays using direct metal 3D printing technology. These work all incorporate the printing technology into the RF component design process, demonstrating the potential possibilities of direct metal 3D printing in the investigation and fabrication of passive microwave components with irregular shapes but attractive features. This thesis's works involved an extensive frequency range that starts with investigating S-band filters and then extends to C-band and Ku-band filters and antennas design. It is well known that in S- and C- band radio frequency (RF) applications that miniaturization is a critical factor for RF devices besides high performances. For this reason, the first project in this thesis proposed a novel compact waveguide loaded air slots resonator for designing inline bandpass filters. As a result, the designed filters not only have a smaller size than coaxial ones but also have controllable transmission zeros with inline structures. Since the air slots resonator is loaded inside the cavity, it is difficult to fabricate by conventional methods, but accessible by 3D printing technique with appropriate self-support structures. The fabrication quality was reflected by the mechanical and RF property measurements, which first demonstrated the advantage of using 3D printing technique to fabricate components with complex structures. The second project presents a compact high-Q fan-shaped folded waveguide resonator, which is applied to successfully design one C-band filter and filtering antenna. High performance RF properties and easy-to-print structures are always considered together. Accordingly, this work proposed and validated novel slots cross negative coupling topology of the filter and novel filtering antenna theory. Also, each of the designed components has better self-supported structures that can be printed with only two pieces, which highly reduced assembly processes and errors. Furthermore, the RF properties from measurement results further demonstrated that the reliability of the metal 3D printing technology for C-band RF applications. The concepts of the third project are extended from the second project but replaces the folded waveguide resonator with a metal strong coupling resonator (MSCR). The MSCR allows for even further compact dimensions while maintaining a high Q value of over 1000. It also allows producing mixed electrical-magnetic coupling by the curving coupling metal pairs intentionally. Except for the desired RF properties, the designed filter based on the MSCR can be printed as a whole even with complex inner circuits structures. Furthermore, the MSCR was integrated with the helical antenna using the proposed theory presented in the second project. Although the helical antenna belongs to the electrical-small antenna, the designed filtering antenna still has a high transmission efficiency of more than 95% and a 6 dBi realized gain concerning its less than quarter-wavelength. In addition, the filtering antenna has five helical radiation elements and one filter prototype but was printed with only three pieces, which showed the advantages of the direct metal 3D printing technology again. The fourth and the last project introduces a Ku-band slots antenna array application based on the sine corrugated waveguide resonator. Similar to previous projects, advanced RF performances were pursued in this project, in addition to demonstrating the use of 3D printing technology to fabricate compact and specific structures. The designed antenna array achieved a higher gain, wider band, and more simple feeding networks. The mode analysis method based on the EM software CST was applied to guide the design since no related formulas were available. The designed model was printed with two pieces and was measured thoroughly. The measured surface roughness, in-band responses, and radiation patterns showed promising results for the sine corrugated waveguide and 3D printing technology in satellite applications. In general, this thesis researched and proved the reliability and advantages of direct metal 3D printing technology in designing and fabricating advanced microwave passive components below the Ku-band. It should be mentioned that the designed passive components in this thesis can be easily re-designed/re-configured and applied on the 5G wireless base station and satellite communication systems

Circuit-Theoretic Physics-Based Antenna Synthesis and Design Techniques for Next-Generation Wireless Devices

Performance levels expected from future-generation wireless networks and sensor systems are beyond the capabilities of current radio technologies. To realize information capacities much higher than those achievable through existing time and/or frequency coding techniques, an antenna system must exploit the spatial characteristics of the medium in an intelligent and adaptive manner. This means that such system needs to incorporate integrated multi-element antennas with controlled and adjustable performances. The antenna configuration should also be highly miniaturized and integrated with circuits around it in order to meet the rigorous requirements of size, weight, and cost. A solid understanding of the underlying physics of the antenna function is, and has always been, the key to a successful design. In a typical antenna design process, the designer starts with a simple conceptual model, based on a given volume/space to be occupied by the antenna. The design cycle is completed by the antenna performing its function over a range of frequencies in some complex scenarios, i.e., packaged into a compact device, handled in different operational environments, and possibly implanted inside a human/animal body. From the conceptual model to the actual working device, a large variety of design approaches and steps exist. These approaches may be viewed as simulation-driven steps, experimental-based ones, or a hybrid of both. In any of these approaches, a typical design involves a large amount of parametric/optimization steps. It is no wonder, then, that due to the many uncertainties and ‘unknowns’ in the antenna problem, a final working design is usually an evolved version of an initial implementation that comes to fruition only after a considerable amount of effort and time spent on “unsuccessful” prototypes. In general, the circuit/filter community has enjoyed a better design experience than that of the antenna community. Designing a filter network to meet specific bandwidth and insertion loss is a fairly well-defined procedure, from the conceptual stages to the actual realization. In view of the aforementioned, this work focuses on attempting to unveil some of the uncertainties associated with the general antenna design problem through adapting key features from the circuit/filter theory. Some of the adapted features include a group delay method for the design of antennas with a pre-defined impedance bandwidth, inverter-based modeling for the synthesis of small-sized wideband antennas, and an Eigen-based technique to realize multi-band/multi-feed antennas, tunable antennas, and high sensitivity sensor antennas. By utilizing the proposed approaches in the context of this research, the design cycle for practical antennas should be significantly simplified along with various physical limitations clarified, all of which translates to reduced time, effort, and cost in product development.4 month

Impedance Transformers

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Metamaterials for Decoupling Antennas and Electromagnetic Systems

This research focuses on the development of engineered materials, also known as meta- materials, with desirable effective constitutive parameters: electric permittivity (epsilon) and magnetic permeability (mu) to decouple antennas and noise mitigation from electromagnetic systems. An interesting phenomenon of strong relevance to a wide range of problems, where electromagnetic interference is of concern, is the elimination of propagation when one of the constitutive parameters is negative. In such a scenario, transmission of electromagnetic energy would cease, and hence the coupling between radiating systems is reduced. In the first part of this dissertation, novel electromagnetic artificial media have been developed to alleviate the problem of mutual coupling between high-profile and ow-profile antenna systems. The developed design configurations are numerically simulated, and experimentally validated. In the mutual coupling problem between high-profile antennas, a decoupling layer based on artificial magnetic materials (AMM) has been developed and placed between highly-coupled monopole antenna elements spaced by less than Lambda/6, where Lambda is the operating wavelength of the radiating elements. The decoupling layer not only provides high mutual coupling suppression (more than 20-dB) but also maintains good impedance matching and low correlation between the antenna elements suitable for use in Multiple-Input Multiple-Output (MIMO) communication systems. In the mutual coupling problem between low-profile antennas, novel sub-wavelength complementary split-ring resonators (CSRRs) are developed to decouple microstrip patch antenna elements. The proposed design con figuration has the advantage of low-cost production and maintaining the pro file of the antenna system unchanged without the need for extra layers. Using the designed structure, a 10-dB reduction in the mutual coupling between two patch antennas has been achieved. The second part of this dissertation utilizes electromagnetic artificial media for noise mitigation and reduction of undesirable electromagnetic radiation from high-speed printed-circuit boards (PCBs) and modern electronic enclosures with openings (apertures). Numerical results based on the developed design configurations are presented, discussed, and compared with measurements. To alleviate the problem of simultaneous switching noise (SSN) in high-speed microprocessors and personal computers, a novel technique based on cascaded CSRRs has been proposed. The proposed design has achieved a wideband suppression of SSN and maintained a robust signal integrity performance. A novel use of electromagnetic bandgap (EBG) structures has been proposed to mitigate undesirable electromagnetic radiation from enclosures with openings. By using ribbon of EBG surfaces, a significant suppression of electromagnetic radiation from openings has been achieved