No / In this paper, a compact microstrip band-pass filter (BPF) covering the 3.4 to 3.8 GHz spectrum bandwidth for 5G wireless communications is presented. The planar filter uses three resonators, each terminated by a via to hole ground at one end and a capacitor at the other end with 50 Ω transmission line impedances for input and output terminals. The coupling between the lines is adjusted to resonate at the centre frequency with third-order band-pass Butterworth properties. The proposed combline filter is designed on an alumina substrate with a relative dielectric constant of 9.8 and a very small size of 9×5×1.2 mm3. The proposed filter is simulated and optimized using CST microwave studio software. / European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424, UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1

Nowadays, demands for fully integrated and miniaturized RFIC (Radio Frequency Integrated Circuits) have increased in wireless microwave communication system. Passive components such as coupler, divider and filters are always fabricated in outside of ICs due to their bulky sizes, which have been a great barrier to a realization of a fully integrated design. To solve this problem, miniaturization of passive components is one of the big issues at the present time. This paper shows the development of two important microwave passive components, quadrature hybrid and rat-race couplers for LTE lower (698 -960 MHz) and higher (1.71 - 2.70 GHz) frequency bands, which are obtained by replacing quarter-wave (λ/4) transmission line of a conventional coupler by their equivalent coupled line, resulting in significant size reduction. The miniaturized quadrature and rat race couplers are designed and fabricated with a Rogers 4360 substrate as a platform in producing significantly reduction. The design is validated by electromagnetic simulation and measurement. The size of the implemented quadrature hybrid coupler is 30 × 26.8 mm^2 and 14.9 × 12.5 mm^2, which are 82.60 % and 69.03% compared to the conventional couplers for lower and higher frequency band respectively. And, 55.5 × 27.9 mm^2 and 19.2 × 14.8 mm^2 for rat race coupler, which are 79.69 % and 62.35 % compared to the conventional coupler for lower and higher frequency band, respectively. Also, the reflection coefficient and the isolation are as good as conventional one and coupling procedure is similar or better than it.

Directional couplers are passive components in radio frequency (RF) engineering and have a broad set of applications. With the scope of how a directional coupler can be implemented in a design, it is important to have specified goals in mind when designing a coupler, for the component to be precise and behave in a desired way. Different design variations also have benefits and disadvantages, and in this project several variations of couplers were investigated. The limiting factors in this project were the rather small area to work with, combined with the design requirements. This is ultimately what made the design approach unique and the reason for using an iterative process in a simulation software, where conventional methods of designing could not be used. Out of the different designs that were tested, two directional couplers on the RO4350B substrate with a gap of 0.34 mm between the transmission lines fulfilled every design parameter except the one regarding the coupling factor. There are three notable conclusions that were drawn. The first is that all directivity compensation methods that were evaluated are valid after optimizing relevant parameters. Some methods could be combined to have an even greater effect, such as the soldermask and wiggly line methods. The second is that ground vias can affect the directivity of a directional coupler substantially. Designing a coplanar waveguide coupler can also have benefits in respect to the given design requirements in this project. Thirdly, a lossy material such as FR4 could be used and still achieve the design parameters at these frequencies.

Le but de ce travail était de développer des filtres passe-bande RF dans la technologie de PCB, avec trois objectifs principaux. Le premier objectif était de développer des formules de synthèse tosimplify la procédure de conception du filtre. Le deuxième était de parvenir à un rejet wideout bande sans modifier les caractéristiques de la bande de filtrage. Le troisième objectif est de contrôler la fréquence centrale du filtre en utilisant diode varicap. / The purpose of this work was to develop RF bandpass filters in PCB technology,with three main objectives. The first objective was to develop synthesis formulas tosimplify the design procedure of the filter. The second was to achieve wideout-of-band rejection without modifying the in-band filtering characteristics. Thethird objective was to control the center frequency of the filter by using varactordiode.The bandpass filter topology treated in this thesis is based on Stub-LoadedResonators (SLR). The main features of this filter topology were treated. Equivalentcircuits based on J-inverters and susceptance parameters were derived. Based onthese equivalent circuits, synthesis formulas were developed. Simulations werepresented to validate the synthesis theory. For a proof-of-concept, third orderstripline bandpass filters were designed and fabricated based on this synthesis.Analysis technique using odd- and even- mode was achieved on the SLR. Thusresonance odd- and even-mode conditions were derived. These conditions aim toeasily control the first spurious frequency. Moreover, to go further in improving theout-of-band rejection a new technique, called “U corner structure”, was developedand design rules were derived. Based on these design rules an extended out-of-bandrejection was achieved without any modification in the passband and by maintainingthe compactness of the filter. A first spurious frequency was localized at up to ninetimes the working frequency in the case of the Parallel-coupled Stub-Loadedresonator (PC-SLR) filter. Also, by applying this technique into the classicalparallel-coupled filter the first and second spurious frequencies were rejected. Toaddress the issue of tunable filters, the SLRs were correctly loaded by variablecapacitors (varactor diode). The center frequency of the PC-SLR filter was easilycontrolled by maintaining a large out-of-band rejection.

This thesis presents novel radio frequency microelectromechanical (RF MEMS) circuits based on the three-dimensional (3-D) micromachined coplanar transmission lines whose geometry is re-configured by integrated microelectromechanical actuators. Two types of novel RF MEMS devices are proposed. The first is a concept of MEMS capacitors tuneable in multiple discrete and well-defined steps, implemented by in-plane moving of the ground side-walls of a 3-D micromachined coplanar waveguide transmission line. The MEMS actuators are completely embedded in the ground layer of the transmission line, and fabricated using a single-mask silicon-on-insulator (SOI) RF MEMS fabrication process. The resulting device achieves low insertion loss, a very high quality factor, high reliability, high linearity and high self actuation robustness. The second type introduces two novel concepts of area efficient, ultra-wideband, MEMS-reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. The coupling is achieved by tuning both the ground and the signal line coupling, obtaining a large tuneable coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity over a very large bandwidth. This thesis also presents for the first time on RF nonlinearity analysis of complex multi-device RF MEMS circuits. Closed-form analytical formulas for the IIP3 of MEMS multi-device circuit concepts are derived. A nonlinearity analysis, based on these formulas and on  measured device parameters, is performed for different circuit concepts and compared to the simulation results of multi-device  conlinear electromechanical circuit models. The degradation of the overall circuit nonlinearity with increasing number of device stages is investigated. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a highest overall IIP3 for the whole circuit.The thesis further investigates un-patterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip inductances. The approach used is to increase the thickness of the ferromagnetic material without increasing its conductivity, by using multilayer NiFe and AlN sandwich structure. This suppresses the induced currents very effectively and at the same time increases the ferromagnetic resonance, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. The so far highest permeability values above 1 GHz for on-chip integrated un-patterned NiFe layers were achieved. / <p>QC 20140328</p>