The main purpose of this dissertation was to address key issues in the design and analysis of RF/microwave filters for wireless applications. Since RF/microwave filters are one of the bulkiest parts of communication systems, their miniaturization is one of the most important technological challenges for the development of compact transceivers. In this work, novel miniaturization techniques were investigated for single-band, dual-band, ultra-wideband and tunable bandpass filters. In single-band filters, the use of cross-shaped fractals in half-mode substrate-integrated-waveguide bandpass filters resulted in a 37 percent size reduction. A compact bandpass filter that occupies an area of 0.315 mm2 is implemented in 90-nm CMOS technology for 20 GHz applications. For dual-band filters, using half-mode substrate-integrated-waveguides resulted in a filter that is six times smaller than its full-mode counterpart. For ultra-wideband filters, using slow-wave capacitively-loaded coplanar-waveguides resulted in a filter with improved stopband performance and frequency notch, while being 25 percent smaller in size. A major part of this work also dealt with the concept of 'hybrid' RF MEMS tunable filters where packaged, off-the-shelf RF MEMS switches were used to implement high-performance tunable filters using substrate-integrated-waveguide technology. These 'hybrid' filters are very easily fabricated compared to current state-of-the-art RF MEMS tunable filters because they do not require a clean-room facility. Both the full-mode and half-mode substrate-integrated waveguide tunable filters reported in this work have the best Q-factors (93 - 132 and 75 - 140, respectively) compared to any 'hybrid' RF MEMS tunable filter reported in current literature. Also, the half-mode substrate-integrated waveguide tunable filter is 2.5 times smaller than its full-mode counterpart while having similar performance. This dissertation also presented detailed analytical and simulation-based studies of nonlinear noise phenomena induced by Brownian motion in all-pole RF MEMS tunable filters. Two independent mathematical methods are proposed to calculate phase noise in RF MEMS tunable filters: (1) pole-perturbation approach, and (2) admittance-approach. These methods are compared to each other and to harmonic balance noise simulations using the CAD-model of the RF MEMS switch. To account for the switch nonlinearity in the mathematical methods, a nonlinear nodal analysis technique for tunable filters is also presented. In summary, it is shown that output signal-to-noise ratio degradation due to Brownian motion is maximum for low fractional bandwidth, high order and high quality factor RF MEMS tunable filters. Finally, a self-sustained microwave platform to detect the dielectric constant of organic liquids is presented in this dissertation. The main idea is to use a voltage- controlled negative-resistance oscillator whose frequency of oscillation varies according to the organic liquid under test. To make the system self-sustained, the oscillator is embedded in a frequency synthesizer system, which is then digitally interfaced to a computer for calculation of dielectric constant. Such a system has potential uses in a variety of applications in medicine, agriculture and pharmaceuticals.

To increase capacity, lower latency, and boostdata rates, new higher gain antennas that can transmitmillimeter-waves are needed. Dielectric lens antennas arean attractive potential solution. The J1-project investigatedthe permittivity and losses of four 3D printing filamentsin four frequency bands, to better design a hyperboliclens antenna in the Ka-band with a WR-28 StandardGain Horn Antenna acting as a feed. To measure thedielectric filaments, the TRL calibration method wasevaluated in simulation and employed in measurementstogether with the NRW method for permittivity extraction.Shortcomings of these methods near resonant frequencieswere marginally analyzed in simulation, and the results ofthe processed measured permittivities were shown to havesignificant uncertainty in the loss tangent. Nevertheless thedatasheet specified<(r) =3 was shown to have meanrelative permittivity∗r= 3.53−0.13jin the Ka-band.Using the measurement data, a hyperbolic lens antennawas designed and optimized in simulation for the centerfrequency of the Ka-band at 33.25 GHz. The simulatedresults show an aperture efficiency of 36.2% and a gainof 30.4 dBi. / För att öka kapaciteten, sänka för- dröjningen samt höja datahastigheterna så behövs högre förstärkta antenner som kan transmittera millimetervågor. Här är dielektriska linsantenner en attraktiv, potentiell lösning. J1-projektet undersökte permittiviteten och förlusterna av fyra 3D-utskriftsfilament i fyra frekvensband, för att bättre designa en hyperbolisk linsantenn i Ka- bandet för en matande WR-28 “Standard Gain Horn Antenna”. För att kunna mäta de dielektriska filamenten så var TRL-kalibreringsmetoden utvärderad i simulering och nyttjad vid mätning tillsammans med NRW-metoden för att betsämma permittiviteten. Nackdelarna bakom dessa metoder nära resonanta frekvenser var marginellt analyserade i simulering och resultaten av de behandlade, mätta permittiviteterna visade sig ha märkbara osäker- heter i deras förlusttangens. Oavsett så blev medelvärdet på det uppmätta resultatet; av det databladsspecificerade materialet R (∈r) = 3; ∈*r = 3,53 -0,13j i Ka-bandet. Med hjälp av databladsspecifikationerna, så designades samt optimiserades en hyperbolisk linsantenn i simulering för Ka-bandets mittfrekvens på 33,25 GHz. De simulerade resultaten visar på en apertureffektivitet på 36,2% och en förstärkning på 30,4 dBi. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

<p>Коришћењем интердигиталног кондензатора и микроконтролера, систем за препознавање течности је имплементиран и испитан. Пермитивност течних узорака је коришћена као физичка особина на основу које се врши препознавање. Инвазивна и неинвазивна конфигурација сензора је израђена и испитана. Резултати указују на могућност развоја компактних, минијатурних уређаја за теренску употребу.</p> / <p>Korišćenjem interdigitalnog kondenzatora i mikrokontrolera, sistem za prepoznavanje tečnosti je implementiran i ispitan. Permitivnost tečnih uzoraka je korišćena kao fizička osobina na osnovu koje se vrši prepoznavanje. Invazivna i neinvazivna konfiguracija senzora je izrađena i ispitana. Rezultati ukazuju na mogućnost razvoja kompaktnih, minijaturnih uređaja za terensku upotrebu.</p> / <p>By using interdigital capacitor and a microcontroller, a system for liquid-type<br />recognition has been developed and examined. Permittivity of liquid samples<br />has been used as a physical property for recognition. Invasive and noninvasive<br />sensor configuration has been implemented and examined. Results<br />imply the possibility to develop compact, miniature, on-field devices.</p>