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 paper proposes two innovative designs for the broadband and high-gain circularly polarized operation, a corner-truncated inverted -L patch antenna and a cylindrical-probe-fed circularly polarized patch antenna using a single probe feed. Next, the broad circularly polarized printed spiral strip antenna for 5 GHz WLAN operation is studied; we also proporse a compact dual-band circularly polarized antenna for GPS/ETC operation on vechicles. In addition, an experimental study of the nearly square circularly polarized microstrip antenna with a rectangular ground plane is presented. The CP antennas are greatly affected by the different side lengths of the rectangular ground plane. To compensate for this effect, the aspect ratio of the nearly square radiating patch should be increased with the increasing aspect ratio of the rectangular ground plane.

Owing to the need of high-directivity radiation in fix-point communication, this thesis designs the metamaterial with 4-fold rotational symmetric unitcells. Using their nearing-zero refractive index along two polarizations, we can get gain-enhanced antenna radomes and place them above dual- and circular-polarized antenna to verify our idea. It is known that the group delay variation in a communication system causes the degradation of symbol error rate, and positive group delay (GD) causes delay in signal propagation. Therefore, this research studies the negative group delay (NGD) behavior of metamaterial. Through analyzing the GD of metamaterial equivalent circuit caused by poles and zeros, we design a novel NGD bandpass circuit. Furthermore, this thesis develops graphic method for group delay investigatiion and study the relationship between NGD, loss and gain in order to simplify the design of GD compensation circuit.

In this thesis, I introduce two types of circularly polarized rectangular microstrip antennas at 2.44 GHz. First type has direct fed and the second has two inputs for fed. In first case is used a stub to make the frequency with minimum return loss and equal to the frequency with minimum axial ratio. In second case is use the power splitter to divide the wave in to two lines with phase shift 90° for feeding the patch. In this thesis is described, how to get the best results of Axial Ratio.

Práce je zaměřena na výzkum struktur založených na vlnovodu integrovaném do textilu (TIW). Pozornost je věnována elektrické charakterizaci textilních materiálů (textilní substráty, nitě), které jsou využívány při implementaci antén, rekonfigurovatelných a aktivních obvodů integrovaných do textilu. Práce se zabývá návrhem vícevrstvých přechodů mezi mikropáskovým vedením na konvenčním substrátu a vedeními integrovanými do textilu. Dále je prezentován koncept přepínače integrovaného do textilu. Přepínač je řízen vodivými sloupky, které vytvářejí otevřenou či zavřenou stěnu prostřednictvím stejnosměrně ovládaných PIN diod. Na závěr je formulována metodika návrhu kruhově polarizovaných antén integrovaných do textilu, jež jsou určeny pro práci v ISM pásmech až do 24 GHz. Všechny postupy návrhu byly ověřeny simulacemi a měřeními reálných vzorků, které byly vyrobeny sítotiskem stříbrnou polymerovou pastou. Polovodičové komponenty byly k obvodům přilepeny vodivým stříbrným lepidlem. Komponenty vyrobené sítotiskem byly porovnávány s referenčními strukturami, které byly realizovány pomocí samolepicí měděné fólie.