In recent high-speed digital circuits with pico-second rising/falling edges, it is reasonable to consider the power/ground planes as a dynamic electromagnetic system. The simultaneous switching noise (SSN) or ground bounce noise (GBN), resulting from the transient currents which flow between power/ground planes during the state transitions of the logic gates, has become a critical factor to degrade the signal integrity (SI) and power integrity (PI) in PCB or package design. In order to accurately perform overall system-level power integrity simulation, extracting the SPICE-compatible models with the resonant effect being considered in the power/ground planes and incorporating the model into the conventional circuit simulator, such as SPICE, is essential. In this thesis, a two-dimensional transmission line (2D-TL) model is proposed for constructing the SPICE-compatible model of the power/ground planes. Based on this model, the ground bounce noise for the BGA package mounted on a PCB can be efficiently evaluated. It is found that the behavior of GBN between the only package and package mounted on a PCB (hybrid structure) is obvious different. Then, we combine the SPICE-compatible model of the power/ground planes with decoupling capacitors to fast evaluate the behavior of GBN. It also has a good agreement between our model and the measured result. Adding decoupling capacitors between the power and ground planes is a typical way to suppress the GBN. However, they are not effective at the frequency higher than GHz due to their inherent lead inductance. In recent, a new method for eliminating the GBN at higher frequency is proposed by electromagnetic bandgap (EBG) structure with high impedance surface (HIS). Finally, we utilize 2D-TL model to fast analyze the behavior of the EBG, and combine decoupling capacitors with EBG structure to research the suppression of the GBN.

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.

The conventional mushroom-like Sievenpiper structure is re-visited in this thesis and a relationship is established between the dispersion and reflection phase characteristics of the structure. It is shown that the reflection phase frequency at which the structure behaves as a Perfect Magnetic Conductor (PMC) can be predicted for varying angles of incidence from the modal distribution in the dispersion diagrams and corresponds to the supported leaky modes within the light cone. A methodology to independently tune the location of the PMC frequency point with respect to the surface wave band-gap location is then presented. The influence of having said PMC frequency point located inside or outside the surface wave band-gap on a dipole radiation pattern is then studied numerically. It is demonstrated that the antenna exhibits a higher gain when the PMC frequency and band-gap coincide versus when they are separated. Two design cases are then presented for when the aforementioned properties coincide and are separated and a gain improvement of 1.2 dB is measured for the former case.

The conventional mushroom-like Sievenpiper structure is re-visited in this thesis and a relationship is established between the dispersion and reflection phase characteristics of the structure. It is shown that the reflection phase frequency at which the structure behaves as a Perfect Magnetic Conductor (PMC) can be predicted for varying angles of incidence from the modal distribution in the dispersion diagrams and corresponds to the supported leaky modes within the light cone. A methodology to independently tune the location of the PMC frequency point with respect to the surface wave band-gap location is then presented. The influence of having said PMC frequency point located inside or outside the surface wave band-gap on a dipole radiation pattern is then studied numerically. It is demonstrated that the antenna exhibits a higher gain when the PMC frequency and band-gap coincide versus when they are separated. Two design cases are then presented for when the aforementioned properties coincide and are separated and a gain improvement of 1.2 dB is measured for the former case.

Yes / This article presents a unique technique to enhance isolation between transmit/receive radiating elements in densely packed array antenna by embedding a metamaterial (MTM) electromagnetic bandgap (EMBG) structure in the space between the radiating elements to suppress surface currents that would otherwise contribute towards mutual coupling between the array elements. The proposed MTM-EMBG structure is a cross-shaped microstrip transmission line on which are imprinted two outward facing E-shaped slits. Unlike other MTM structures there is no short-circuit grounding using via-holes. With this approach, the maximum measured mutual coupling achieved is -60 dB @ 9.18 GHz between the transmit patches (#1 & #2) and receive patches (#3 & #4) in a four-element array antenna. Across the antenna’s measured operating frequency range of 9.12 to 9.96 GHz, the minimum measured isolation between each element of the array is 34.2 dB @ 9.48 GHz, and there is no degradation in radiation patterns. The average measured isolation over this frequency range is 47 dB. The results presented confirm the proposed technique is suitable in applications such as synthetic aperture radar (SAR) and multiple-input multiple-output (MIMO) systems. / H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E0/22936/1

Yes / A decoupling metamaterial (MTM) configuration based on fractal electromagnetic-bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely-packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal-shaped slots etched in each arm of the cross. The fractals are composed of four interconnected-`Y-shaped' slots that are separated with an inverted-`T-shaped' slot. The MTM-EMBG structure is placed between the individual patch antennas in a 2 × 2 antenna array. Measured results show the average inter-element isolation improvement in the frequency band of interest is 17, 37 and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for using metallic-via-holes. The proposed array covers the frequency range of 8-9.25 GHz for X-band applications, which corresponds to a fractional-bandwidth of 14.5%. With the proposed method the edge-to-edge gap between adjacent antenna elements can be reduced to 0.5λ 0 with no degradation in the antenna array's radiation gain pattern. Across the array's operating band, the measured gain varies between 4 and 7 dBi, and the radiation efficiency varies from 74.22 and 88.71%. The proposed method is applicable in the implementation of closely-packed patch antenna arrays used in SAR and MIMO systems. / Partially supported by 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.

With the trends of fast edge rates, high clock frequencies, and low voltage levels for the high-speed digital computer systems, the ground bounce noise (GBN) or simultaneously switching noise (SSN) on the power/ground planes is becoming one of the major challenges for designing the high-speed circuits. In order to analyze the impact of the GBN on signal integrity (SI) and electromagnetic interference (EMI), an accurate and efficient modeling approach that considers the active devices and passive interconnects is required. This thesis focuses on two points. One is developing modeling approaches for analyzing the GBN effects, and the other is proposing solutions to reduce it. First, based on the FDTD algorithm several efficient modeling approaches including equivalent current-source method (ECSM), Kirchoff surface integral representation (KSIR), and slot-corrected 2D-FDTD are developed. After that, a power/ground-planes design for efficiently eliminating the GBN in high-speed digital circuits is proposed by using low-period coplanar electromagnetic bandgap (LPC-EBG) structure. Its extinctive behaviors of low radiation and broadband suppression of the GBN is demonstrated numerically and experimentally. Good agreements are seen.

This thesis focuses on the modeling and solutions of the simultaneous switching noise (SSN) problems in the power delivery networks (PDN) of high-speed digital circuit packages. An efficient numerical approach based on two-dimension (2D) finite-difference time-domain (FDTD) method combined with the lumped circuit model of the interconnection is proposed to model the PDN of a package and PCB. Based on this approach, the mechanism of noise coupling between package and PCB can be analyzed. In addition, a novel photonic crystal power layer (PCPL) design for the PDN of the package or PCB is proposed to suppress the SSN. The periodic High-Dk material is embedded into the substrate layer between the power and ground planes. Both modeling and measurement demonstrate the PCPL can form a wide stopband well with excellent suppression of the SSN propagation in the substrate and the corresponding electromagnetic interference (EMI).

In the first part of the thesis, the 2-D structures in stratified media are analyzed using an efficient MoM technique. The method is used to optimize transmitted or reflected electric fields from the 2-D structures. The genetic algorithm is used in the optimization process. In the second part a 3-D MoM technique is implemented to analyze multilayered structures with periodically implanted material blocks. Using the method, the dispersion and reflection characteristics of the structure are calculated for different configurations. The results are compared with the results found in the literature and it is seen that they are in good agreement. Asymptotic Waveform Evaluation (AWE) technique is utilized to obtain the Pade approximation of the solution in terms of frequency. The high order derivatives that are required by the AWE technique are calculated through Automatic Differentiation technique. Using the AWE method, the dispersion diagram and reflection characteristics of the periodic structures are obtained in a shorter time. The results are compared with the ones obtained through direct calculation and it is seen that they are in perfect agreement. The reflection coefficients that are obtained from the 3-D MoM procedure are used to calculate Green&rsquo / s functions that approximate electric field of an infinitesimal dipole on the periodically implanted substrate. Using the calculated Green&rsquo / s functions and the spectral domain MoM procedure, dispersion characteristics of a microstrip line on the periodically implanted substrate are obtained.

abstract: Flexibility, reconfigurability and wearability technologies for antenna designs are presented, investigated and merged in this work. Prior to the design of these radiating elements, a study is conducted on several flexible substrates and how to fabricate flexible devices. Furthermore, the integration of active devices into the flexible substrates is also investigated. A new approach of designing inkjet-printed flexible reconfigurable antennas, based on the concept of printed slot elements, is proposed. An alternate technique to reconfigure the folded slot antenna is also reported. The proposed radiator works for both Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The flexible reconfigurable antenna is also redesigned to resonate at both (2.4/5.2 GHz) for WLAN devices and its Multiple-Input Multiple-Output (MIMO) configuration is reported. Two orthogonal elements are used to form the MIMO antenna system for better isolation. The wearability of the proposed flexible reconfigurable radiator is also discussed. Since wearable antennas operate close to the human body, which is considered as a lossy tissue, an isolation between the radiating elements and human body is required to improve the radiation characteristics and to reduce the Specific Absorption Rate (SAR). The proposed antenna is redesigned on an Artificial Magnetic Conductor (AMC) surface that also functions as a ground plane to isolate the radiator from the human body. To examine its performance as a body-worn device, it is measured at different positions on the human body. Furthermore, simulations show that the SAR level is reduced when using the AMC surface. The proposed wearable antenna works for both Wireless Body Area Network (WBAN) and WiMAX body-worn wireless devices. Electromagnetic bandgap (EBG) structures are used to suppress surface wave propagation in printed antennas. However, due to the presence of vias, not all of them can be utilized in flexible radiators. Thus, a Perforated High Impedance Surface (PHIS) is proposed which suppresses the surface waves without the need of vias, and it also serves as a ground plane for flexible antennas. The surface wave suppression and the antenna applications of the proposed PHIS surface are discussed. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017