This thesis investigates the integration of planar antennas, such as Dielectric Resonator Antennas (DRAs) to the planar waveguide structure, specifically the Substrate Integrated Waveguide (SIW) for high radiation efficiency millimeter-wave (mm-wave) applications. The SIW is a low cost and low loss technology, since it almost keeps the guided wave inside the structure. Therefore, it is an excellent candidate feeding scheme compared to traditional planar (multi-conductor) structures, such as the Microstrip Line (MSL) and Co-planar Waveguide (CPW) for many planar antennas. It enhances the antenna???s overall radiation efficiency by minimizing the conduction loss, which dominates at the mm-wave frequency band. For this thesis, two different SIW-integrated DRA configurations operating at mm-wave frequency band are presented. The rectangular DRA is excited in its fundamental mode TE??11 for radiation through a narrow slot cut on the SIW broad wall. However, the coupling slot itself is excited by the SIW TE10 fundamental mode. In addition, the design guidelines, and a parametric study is also conducted on the proposed antenna parameters to investigate their impact on the antenna???s overall performance including the reflection coefficient and radiation pattern (gain). The results are provided within this thesis. The antenna is made of low cost and low loss materials that are available commercially. It is fabricated by using a novel and simple technique, which is compatible with the Printed Circuit Board (PCB) technology. The board is treated as multi-layers composed of the SIW-layer, and DRA element(s) layer, respectively. The fabricated antenna prototypes are tested to demonstrate their validity for real microwave/mm-wave applications. Their reflection coefficients and radiation patterns are measured, and the antenna shows a boresight gain of 5.51 dB and a radiation efficiency of more than 90 % over the operating frequency band of 33-40 GHz. Antenna arrays based on the SIW integrated DRA are investigated for high gain/radiation efficiency applications. Different array configurations such as, linear (series-fed and corporate-fed) and two-dimensional (2D) arrays are presented. The series-fed DRA array is characterized by a single SIW line loaded by DRA-slot pairs, whereas the SIW-power splitter is used to form the corporate-fed DRA array, when loaded by DRA-slot pairs. While the SIW hybrid-feeding scheme (series-feed combined with corporate-feed) is used to form 2D DRA arrays. In this design, the SIW-power splitter is used to split the power equally and in-phase among the sets (rows) of SIW series fed-DRA elements (columns). A simple and generic Transmission Line (T.L.) circuit model is proposed to simplify and expedite the antenna array design process. It is used to calculate the antenna reflection coefficient and radiation pattern (gain). The T.L. model does not take the mutual coupling between the DRA elements into account, since our study shows that its less than -20 dB over the operating bandwidth. However, it is useful and faster than full-wave solvers, such as HFSS, which consumes time and memory due to the huge generated mesh. The developed T.L. circuit model is used to design the antenna array and study the impact of its main designed parameters on the antenna performance. The developed antenna array T.L. model leads to a general design methodology (guidelines). It also allows for optimum array designs for a given set of performance requirements and to have more physical insight into the SIW technology based antenna systems for mm-wave bands. The designed antenna array samples are fabricated and tested within the operating frequency band 33-40 GHz. The series-fed antenna array shows a measured boresight gain of 11.70 dB, and high radiation efficiency, which is more than 90 % over an operating frequency band of 4%. Furthermore, the measured results are compared to these calculated by the proposed T.L. circuit model and full-wave solver. A good agreement between the measured and the HFSS results are observed, especially near the frequency at which the reflection coefficient is minimum. However, some deviation is noticed between the proposed circuit model and the measured results. This deviation is attributed to the discrete nature of the SIW structure that affects the Short Circuit (SC) performance (magnitude and phase), the T.L. lengths, and the mutual coupling between any two adjacent antenna elements. All these issues are handled efficiently and are taken into account by the full-wave solver. Therefore, the measured reflection coefficient agrees with that of the HFSS, except for a very small deviation, caused by the fabrication tolerances and measurement errors. However, the proposed T.L. circuit model is still valid and can easily predict and estimate the resonance behavior and the impedance bandwidth of the proposed antenna arrays in a very short time compared with the full-wave solver.

In the lower millimetre-wave frequency range, Substrate Integrated Waveguide (SIW) circuits have emerged as a reasonable compromise between rectangular waveguide and standard microstrip technologies. They are formed by a top- and bottom-metalized substrate and two arrays of plated or riveted holes (via holes) to replace the vertical metallic walls in conventional rectangular waveguide. Although many passive components known from traditional waveguide technology have been fabricated in SIW, one of the main challenges is to integrate active components with typical coaxial-type interfaces within the SIW environment. Therefore, the work presented in this dissertation focuses on new broadband transitions from SIW to other planar transmission-line technologies such as microstrip coplanar waveguide, coplanar strip line, slot line and coupled microstrips. Several of the new transitions are prototyped and experimentally verified. Two of these transitions are then used to integrate a low noise amplifier within SIW input and output ports. The measurements of fabricated SIW amplifier prototypes show very promising performance and clearly demonstrate successful integrations of active components within SIW. Finally, one of the new SIW-to-coplanar-waveguide transitions is employed as an interface to an SIW-based antenna, thus demonstrating the principle of connectivity of SIW to all currently used planar circuit technologies. / Graduate

Abstract The main objective of this thesis was to research the integration of novel materials and fabrication processes into Low Temperature Co-fired Ceramic (LTCC) technology; enabling fabrication of Radio Frequency (RF) and microwave components with advanced performance. The research focuses on two specific integration cases, which divide the thesis into two sections: the integration of tunable dielectric structures and the integration of air filled waveguides. The first section of the thesis describes the development and characterization of low sintering temperature Barium Strontium Titanate (BST) thick film paste. Sintering temperature of BST is decreased from approximately 1350 °C down to 900 °C by lithium doping and pre-reaction of the doped composition. This allows the co-sintering of the developed BST paste with commercial LTCC materials. Additionally two integration techniques to embed tunable components in an LTCC substrate using the developed BST paste are also presented and the electrical performance of the components is evaluated. The highest measured tunability value was 44% with a bias field of 5.7 V/µm. The permittivity of the films varied between 790 and 190, and the loss tangent varied between 0.004 and 0.005, all measured unbiased at 10 kHz. The developed LTCC compatible BST paste and the presented integration techniques for tunable components have not been previously published. In the second section of the thesis, a fabrication method for the LTCC integrated air-filled rectangular waveguides with solid metallic walls is presented. The fabrication method is described in detail and implemented in a set of waveguides used for characterization. A total loss of 0.1–0.2 dB/mm was measured over a frequency band of 140–200 GHz. The electrical performance of the waveguides is evaluated and their use demonstrated in an integrated LTCC antenna operating at 160 GHz.

An ever-increasing demand for wider bandwidths in communication, radar, and imaging systems has emerged. In order to facilitate this growing demand, progressive research into millimeter-wave technologies has become vital in achieving next generation networks such as 5G. Being cost effective and easy to manufacture, Substrate Integrated Waveguide (SIW) circuits have been demonstrated as a viable candidate for high-frequency applications due to their low-loss, high quality-factor, and high power-handling capabilities.Research on beam-forming networks, specifically the Butler matrix, has demonstrated powerful beam-steering capabilities through the use of passive component networks. Through these clever configurations, a cost effective and robust option is available for us to use. In order to further millimeter-wave research in this area, this thesis presents a modified configuration of the Butler Matrix in SIW that is physically reconfigurable; by separating the Butler matrix from the antenna array at a pre-selected point, the array can be easily interchanged with other 1-Dimensional,and 2-Dimensional slot antenna arrays. Although this system does not fall under the rigorous definitions of Reconfigurable Antennas, it should be noted that the interchangeability of 1 and 2 dimensional arrays is not typically expressed in Butler matrix configurations. Design and simulations are carried out in CST Microwave Studio to inspect individual components as well as system characteristics. Circuit prototypes are then manufactured and tested in an anechoic chamber to validate simulation results and the design approach. / Graduate / 2020-07-17

Phased array antennas, capable of controlling the direction of their radiated beam, are demanded by many conventional as well as modern systems. Applications such as automotive collision avoidance radar, inter-satellite communication links and future man-portable satellite communication on move services require reconfigurable beam systems with stress on mobility and cost effectiveness. Microwave phase shifters are key components of phased antenna arrays. A phase shifter is a device that controls the phase of the signal passing through it. Among the technologies used to realize this device, traditional ferrite waveguide phase shifters offer the best performance. However, they are bulky and difficult to integrate with other system components. Recently, ferrite material has been introduced in Low Temperature Co-fired Ceramic (LTCC) multilayer packaging technology. This enables the integration of ferrite based components with other microwave circuitry in a compact, light-weight and mass producible package. Additionally, the recent concept of Substrate Integrated Waveguide (SIW) allowed realization of synthesized rectangular waveguide-like structures in planar and multilayer substrates. These SIW structures have been shown to maintain the merits of conventional rectangular waveguides such as low loss and high power handling capabilities while being planar and easily integrable with other components. Implementing SIW structures inside a multilayer ferrite LTCC package enables monolithic integration of phase shifters and phased arrays representing a true System on Package (SoP) solution. It is the objective of this thesis to pursue realizing efficient integrated phase shifters and phased arrays combining the above mentioned technologies, namely Ferrite LTCC and SIW. In this work, a novel SIW phase shifter in ferrite LTCC package is designed, fabricated and tested. The device is able to operate reciprocally as well as non-reciprocally. Demonstrating a measured maximum reciprocal phase shift of 132o and maximum non-reciprocal shift of 118o at 12 GHz. Additionally a slotted SIW antenna is designed and integrated with the phase shifter in an array format, demonstrating a beam scanning of ± 15o. The design is highly suitable for mobile automotive radars and satellite communications systems.

Yes / A novel 50μm Silicon-based on-chip antenna is presented that combines metamaterial (MTM) and substrate integrated waveguide (SIW) technologies for integration in THz circuits operating from 0.28 to 0.30 THz. The antenna structure comprises a square patch antenna implemented on a Silicon substrate with a ground-plane. Embedded diagonally in the patch are two T-shaped slots and the edges of the patch is short-circuited to the ground-plane with metal vias, which convert the structure into a substrate integrated waveguide. This structure reduces loss resulting from surface waves and Silicon dielectric substrate. The modes in the structure can be excited through two coaxial ports connected to the patch from the underside of the Silicon substrate. The proposed antenna structure is essentially transformed to exhibit metamaterial properties by realizing two T-shaped slots, which enlarges the effective aperture area of the miniature antenna and significantly enhances its impedance bandwidth and radiation characteristics between 0.28 THz to 0.3 THz. It has an average gain and efficiency of 4.5dBi and 65%, respectively. In addition, it is a self-isolated structure with high isolation of better than 30dB between the two ports. The on-chip antenna has dimensions of 800×800×60 μm3. / 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

The magnetic tunability of ferrites has been studied and applied on many electric components for working in various frequency bands. Filters or resonators loaded by ferrites can thus work for different frequency requirements by tunning external biasing field. However, filters or resonators built by traditional waveguides are large in size. And for tunning with biasing field below the ferroresonance point, dissipation in ferrites will increase rapidly if the working frequency is near the ferroresonance zone. It leads to the drop of Q values of resonators and the tuning range is limited to stay away from ferroresonance. For the filter, remaining high Q values in wide frequency tuning range is the base of good performance and tunability. In industry, demands of cost reduction and integration encourage the miniaturization of electric components. It is always challenging but attractive to find solutions compromising size, performance, and implement ability. In this project, investigation for possible solutions of magnetic bias tunable filter is made and their comparisons are presented. Analysis and simulation are made to a specific ferrites-loaded substrate integrated waveguide resonator. With homogeneous below-resonance biased field, results in the reference are reached again and analyzed. With biasing filed above the ferroresonance, higher Q values and smaller size can be achieved and the drop of Q is avoided. A magnet structure is designed to study how the resonator works in inhomogeneous biasing filed. Biasing of below-resonance field is achieved with the magnets structure, though the performance is not good as homogeneous biasing case. A 3-order filter is then built based on the resonator working in the below-resonance bias. It’s a band-pass filter and tunable. A magnet structure is also built and simulated for the filter to verify its feasibility. / Magnetisk avstämning av ferriter har studerats och applicerats på många elektriska komponenter för arbete i olika frekvensband. Filter eller resonatorer lastade av ferriter kan därmed fungera för olika frekvenskrav genom att tuna externt biasing fält. Filtren eller resonatorerna byggda av traditionella vågledare är dock stora i storlek. Och för tunning med biasing field under ferroresonanspunkten, kommer avledning i ferriter att öka snabbt om arbetsfrekvensen är nära ferroresonanszonen. Det leder till sänkning av Q-värden för resonatorer och inställningsområdet är begränsat för att hålla sig borta från ferroresonans. För filtret är kvarvarande höga Q-värden i brett frekvensinställningsområde grunden för god prestanda och avstämning. Inom industrin uppmuntrar krav på kostnadsminskning och integration till miniatyrisering av elektriska komponenter. Det är alltid utmanande men attraktivt att hitta lösningar som kompromissar med storlek, prestanda och implementerbarhet. I detta projekt undersöks möjliga lösningar av magnetiskt bias tunable filter och deras jämförelser presenteras. Analys och simulering görs till en specifik ferritbelastad substratintegrerad vågledarresonator. Med homogent vinkelfält under resonans nås resultaten i referensen igen och analyseras. Med biasing arkiverad över ferroresonansen, högre Q-värden och mindre storlek kan uppnås och fallet av Q undviks. En magnetstruktur är utformad för att studera hur resonatorn fungerar i inhomogen biasing fil. Biasing av nedanstående resonansfält uppnås med magnetens struktur, men prestandan är inte bra som homogen biasing fall. Ett 3-ordningsfilter byggs sedan baserat på resonatorn som arbetar i nedanstående resonans bias. Det är ett bandpassfilter och kan justeras. En magnetstruktur byggs och simuleras också för filtret för att verifiera dess genomförbarhet.

Due to high demand for planar structures with low loss, a considerable amount of research has been done to the design of substrate integrated waveguide (SIW) components in the mm-wave and microwave range. SIW has many advantages in comparison to conventional waveguides and microstrip lines, such as compact and planar structure, ease of fabrication, low radiation loss, high power handling ability and low cost which makes it a very promising technology for current and future systems operating in K-band and above. Therefore, all the work presented in this dissertation focuses on SIW technology. Five di erent antenna systems are proposed to verify the advantages of using SIW technology. First, a novel K-band end- re SIW circularly polarized (CP) antenna system on a single layer printed-circuit board is proposed. A high gain SIW H-plane horn and a Vivaldi antenna are developed to produce two orthogonal polarizations in the plane of the substrate. CP antennas have become very popular because of their unique characteristics and their applications in satellites, radars and wireless communications. Second, a K-band front-end system for tracking applications is presented. The circuit comprises an antenna array of two Vivaldi antennas, a frequency-selective power combiner, and two frequency-selective SIW crossovers, which eliminate the need for subsequent ltering. The integration of monopulse systems in planar, printed circuit SIW technology combined with the added bene ts of ltering functions is of great importance to the antennas and propagation community. Third, a phased array antenna system consisting of 24 radiating element is designed as feed system for reflector antennas in radio astronomy applications. A Ku-band antipodal dipole antenna with wide bandwidth, low cross-polarization and wide beamwidth is suggested as the radiating element. Forth, four di erent right-angled power dividers including in-phase and out-of-phase dividers as feed systems for antenna arrays are introduced. TE10 - to - TEq0 mode transducers are used for obtaining two, three, and four output dividers with phase control ability at K- and Ka-band. This feature is practical, for instance, when designing tracking systems since they are employed to obtain controllable phase distributions over the output ports. Fifth, a Ku-band beam steering antenna system which is applicable to use for wireless communications, radar systems, and also 5G applications is proposed. This antenna system uses variable reflection-type phase shifters which electrically steer the beam over a 50-degree scan range. Therefore, the SIW technology's reliability and also promising behavior in the microwave frequency range is proven for di erent applications. / Graduate

This thesis presents the first fully tunable substrate integrated waveguide (SIW) filter implemented with PIN diodes and RF MEMS switches. The methodology for tuning SIW filters is explained in detail and is used to create three separate designs. Each SIW cavity is tuned by perturbing via posts connecting or disconnecting to/from the cavity's top metal layer. In order to separate the biasing network from the SIW filter, a three-layer PCB is fabricated using Rogers RT/duroid substrates. The first tunable design utilizes the Philips BAP55L PIN diode. This two-pole filter provides six frequency states ranging from 1.55 GHz to 2.0 GHz. Fractional bandwidth ranges from 2.3 percent – 3.0 percent with insertion loss and return loss better than 5.4 dB and 14 dB respectively for all frequency tuning states. The second tunable design utilizes the Radant RMSW-100 MEMS switch, providing six states ranging from 1.65 GHz to 2.1 GHz. Fractional bandwidth for this filter varies from 2.5 percent - 3.0 percent with insertion loss and return loss better than 12.4 dB and 16 dB respectively for all states. The third design utilizes the OMRON 2SMES-01 RF MEMS relay, providing fourteen states ranging from 1.19 GHz to 1.58 GHz. Fractional bandwidth ranges from 3.6 percent - 4.4 percent with insertion loss and return loss better than 4.1 dB and 15 dB respectively for all frequency states. Two of the three designs (Philips PIN diode and OMRON MEMS) produced good results validating the new SIW filter tuning methodology. Finally, to illustrate the advantage of microstrip planar structures integrated with SIW structures, low pass filters (LPFs) are implemented along the input and output microstrip-to-SIW transition regions of the tunable SIW filter. With minimal change to the overall filter size, this provides spurious suppression for the additional resonant modes inherently present in waveguide structures. The implemented design utilizes the same OMRON MEMS tunable SIW filter specifications. This two-pole tunable filter provides the same performance as the previous OMRON MEMS design with exception to an added 0.7 dB insertion loss and spurious suppression of -28 dB up to 4.0 GHz for all frequency tuning states.

Microwave filters play key roles in controlling the frequency response at specific locations of any communications, radar, or test system. Microwave resonators provide the frequency selective building blocks necessary for filter design. Reconfigurable/ tunable microwave resonators have facilitated the design of tunable filters. Recently, MEMS based tuning mechanisms developed widely tunable resonators maintaining high Q; however, limit in the number of reconfiguration states. This thesis proposes a fluidic-reconfigurable Xband SIW resonator capable of continuous tunability across the reconfiguration range. A dielectric post of fluidic dispersions with variable material properties embedded in a two inductive post static SIW resonator defines the tuning mechanism. The development of an analytical closed-form expression for the resonant frequency and Q across reconfiguration, a circuit model, and full-wave simulation predicts the tunable performance with estimated material properties of the fluidic dispersion. Measured data on an initial tunable SIW resonator design showed good reconfiguration performance but more losses than expected which could potentially be explained from the discovery of a major design error not associated with the resonator itself. A second tunable SIW resonator designed and fabricated proves the material properties of the fluidic dispersions contain more losses than estimated and hinder the resonators performance. By comparing simulated and measured data new estimates for the material properties of the fluidic dispersion are proposed which agree with trends in recent literature. Low-loss fluidic dispersions will enable a significant performance increase in the current tunable SIW resonator. Two low-cost material measurement systems are designed to expedite research efforts in finding low-loss microwave fluidics. Both systems accurately compute dielectric constant but not loss tangents. The initial systems provide necessary first steps in the design of future highly accurate material measurement systems.