Array antennas, and more specifically phased array antennas, are widely used in radar detection and communication systems because of their excellent beam scanning ability and simple control. Generally speaking, the scanning function can be realized in two ways: mechanically or electronically. Mechanical steering is done by rotating the whole structure, so there is a certain delay. The electronic scanning is done by controlling the relative relationship between the input signals of different array elements. Electronical scanning is then faster and easy to integrate with other circuits, which makes it an interesting solution to these applications. However, the disadvantage of electronic steering is that the scanning angle range is limited, which is generally within the range of ±60° . Beyond this range, the performance of the antenna will decrease considerably. One way to improve the antenna gain or expand the scanning range of the array antenna is to combine the array antenna with a dielectric radome. This thesis mainly studies how to adjust the shape of the dielectric radome with a center frequency of 28GHz to expand the beam scanning range of the two-dimensional array composed of rectangular waveguide ports. The inner and outer profiles of the dielectric lens follows the conics equation, and the shape of the lens can be controlled by adjusting different parameters. In this thesis, I adjust the lens shape according to three different objectives: 1. Increase the gain of the array antenna at the small scanning angle (0° ∼ 30°). The adjusted lens model increases the gain in this range by about 0.5 dBi; 2. Improve the gain of the array antenna at the large scanning angle (60° ∼ 80°). The final lens model increases the gain of the array antenna at the scanning angle of 70° and 80° by about 0.5 dBi and 1 dBi respectively; and 3. Improve the directivity of the array antenna in the range of 0° ∼ 70° . The final dielectric lens model improves the directivity in the broadside direction by about 1 dBi, and increases about 0.6 dBi when the scanning angle is 60° ; / Arrayantenner, och mer specifikt fasantenner, används ofta i radardetekterings- och kommunikationssystem på grund av deras utmärkta strålskanningsförmåga och enkla kontroll. Generellt kan skanningsfunktionen realiseras på två sätt: mekaniskt eller elektroniskt. Mekanisk styrning görs genom att rotera hela strukturen, så det finns en viss fördröjning. Den elektroniska skanningen görs genom att styra det relativa förhållandet mellan ingångssignalerna för olika arrayelement. Elektronisk skanning är då snabbare och lätt att integrera med andra kretsar, vilket gör det till en intressant lösning för dessa applikationer. Nackdelen med elektronisk styrning är dock att skanningsvinkeln är begränsad, vanligtvis mindre än ±60°. Utöver detta område kommer antennens prestanda att minska avsevärt. Ett sätt att förbättra antennförstärkningen eller utöka antennens skanningsområde är att kombinera arrayantennen med en dielektrisk radom. Denna avhandling studerar huvudsakligen hur man justerar formen på den dielektriska radomen med en centerfrekvens på 28GHz för att utöka strålskanningsområdet för den tvådimensionella array bestående av rektangulära vågledarportar. Den dielektriska linsens inre och yttre form följer konekvationen, och linsens form kan kontrolleras genom att justera olika parametrar. I denna avhandling justerar jag linsens form enligt tre olika mål: 1. Öka förstärkningen av antennen vid den lilla skanningsvinkeln (0° ∼ 30°). Den justerade linsmodellen ökar förstärkningen i detta område med cirka 0.5 dBi; 2. Förbättra förstärkningen av antennen vid den stora skanningsvinkeln (60° ∼ 80° ). Den slutliga modellen på linsen ökar förstärkningen av antennen i skanningsvinkeln 70° och 80° med cirka 0.5 dBi respektive 1 dBi; och 3. Förbättra riktigheten hos antennen i intervallet 0° ∼ 70°. Den slutliga dielektriska linsmodellen förbättrar riktningen i breddriktningen med ca 1 dBi, och ökar ca 0.6 dBi när skanningsvinkeln är 60°;

This thesis deals with the design of lens antennas for automotive radar in 77 GHz bandwidth. The work explains methods of designing waveguides as well as horn antennas and dielectric lens. A simulation of three designed horn antennas is performed in CST Microwave Studio. Antennas with spherical and hyperbolical lens are simulated as well and subsequently optimized for maximal gain. The thesis also investigates effects of the lens permittivity on its properties. Furthermore, the work deals with a design of an antenna system with minimalized antenna coupling. Nylon, ABS and photopolymer lens are designed and compared afterwards. ABS and photopolymer lens were produced by 3D print

With the rise of high frequency communication systems such as 5G, new types of antennas has to be developed in order to meet the new requirements. In recent years, lens antennas made of periodic structures has been shown to have desirable performance when increasing operational frequency without increasing the size of the antennas. One way of manufacturing the lenses for the antennas are with 3D printers loaded with dielectrics with specified permittivity. This project group studied the process of designing and manufacturing a flat Maxwell fish eye lens at 5 GHz with a bandwidth of 3.5 GHz to 6 GHz. The resulting design is a lens based on a periodic configuration of cuboid unit cells made from dielectrics which consisted of a hole. By choosing the ratio of dielectric and holes in the unit cells, each part of the lens could be tuned to achieve a specific effective refractive index required for realising the Maxwell fish eye lens.

[pt] Este trabalho tem como objetivo aplicar uma técnica de síntese ótica de lentes dielétricas circularmente simétricas, que são iluminadas por uma fonte pontual com diagrama circularmente simétrico. A interface da lente (interface do dielétrico-ar) será modelada utilizando as aproximações da Ótica Geométrica e da Física Ótica. Da Ótica Geométrica, o controle da densidade de potência em campo distante é obtido pela aplicação de conservação de energia no interior dos tubos de raios que emergem do centro de fase da fonte e a determinação da direção dos raios que emergem da superfície do dielétrico é obtida através da aplicação da Lei de Snell para os raios incidentes na interface. Da Física Ótica, é possível obter as correntes elétrica e magnética na superfície externa da lente para determinar o campo radiado na integração dessas correntes pela superfície a partir da suposição de que as dimensões da lente e da curvatura da interface sejam muito maiores que um comprimento de onda no espaço livre. Devido a simetria circular, simplificações na formulação e nos esquemas numéricos para a solução serão apresentadas, resultando em técnica de projeto mais eficientes. A descrição da superfície da interface da lente é obtida através de técnica numérica. / [en] This work aims to apply a technique of optical synthesis of symmetrically circular dielectric lenses, which are illuminated by a point source with a symmetrically circular diagram. The lens interface (dielectric-air interface) will be modeled using the approximations of Geometric Optics and Physical Optics. From Geometric Optics, control of the power density in the far field is obtained by applying energy conservation inside the ray tubes that emerge from the phase center of the source and the determination of the direction of the rays emerging from the dielectric surface is obtained through the application of Snell’s law for the incident rays at the interface. From Physical Optics, it is possible to obtain the electric and magnetic currents on the external surface of the lens to determine the radiated field in the integration of these currents along the surface assuming that the lens dimensions and interface curvature are much larger than a wavelength in free space. Due to circular symmetry, simplifications in formulation and numerical schemes for the solution will be presented, resulting in a more efficient design technique. The description of the lens interface surface is obtained through numerical technique.

This master´s thesis is focused on the ways of possible realisation of the directive horn antenna with suppressed side lobes in the frequency bands 71-76 GHz and 81-86 GHz. In this thesis a detailed research of the feasible options including parameters comparison and assessment of pros and cons of the particular solutions has been performed. Among the specified technical requirements, the emphasis has been placed on the manufacturing options and low cost availability of the materials applicable for the given antenna. The main part of the thesis deals with the conical horn antenna loaded with a hyperbolic dielectric lens, further the antenna with flat dielectric lens based on a transmitarray and also the integrated elliptical lens antenna. The following part of the thesis deals with the possibilities of characterizing the properties of the dielectric material of the lens.