Modeling of fractal antennas

In this Master Thesis the characteristics of the chosen fractal microstrip antennas are investigated. For modeling has been used the structure of the square Serpinsky fractal curves. During the elaboration of this Master thesis the following steps were undertaken: 1) calculation and simulation of square microstrip antennа, 2) optimizing for obtaining the required characteristics on the frequency 2.5 GHz, 3) simulation and calculation of the second and third iteration of the Serpinsky fractal curves, 4) radiation patterns and intensity distribution of these antennas. In this Master’s Thesis the search for the optimal position of the port and fractal elements was conducted. These structures can be used in perspective for creation of antennas working at the same time in different frequency range.

Effective notch method assessment of misalignment for fatigue loaded welds

 The objective of this thesis work was to assess axial misalignment in fatigue loaded welds using the effective notch method. As a result, the fatigue behaviour of non-load carrying cruciform fillet welded joint under cyclic tensile loading has been studied. Various degrees of axial misalignment have been found in one series of non-load carrying cruciform fillet welded joints used in a laboratory investigation. As a result, it was important to carry out a comprehensive investigation since axial misalignment forms part of thequality of fatigue loaded structure and can reduce the fatigue strength. To extend the study, the correlation between fatigue strength and stress ratio, as well as stress concentration factor, were also studied. Moreover, a closer investigation of place of crack initiation and its dependence on weld sequence and imperfections of test specimen (angular distortion) was studied. For the fatigue class calculations, FEM (finite element method) and the effectivenotch approach are used. The addressed variable is the axial misalignment whichis introduce by modeling the entire joint. Fracture mechanics based calculations are also used and quantitatively compared with effective notch and experimental results.

Fractional slot permanent magnet synchronous motors for low speed applications

This study compares different rotor structures of permanent magnet motors with fractional slot windings. The surface mounted magnet and the embedded magnet rotor structures are studied. This thesis analyses the characteristics of a concentrated two-layer winding, each coil of which is wound around one tooth and which has a number of slots per pole and per phase less than one (q < 1). Compared to the integer slot winding, the fractional winding (q < 1) has shorter end windings and this, thereby, makes space as well as manufacturing cost saving possible. Several possible ways of winding a fractional slot machine with slots per pole and per phase lessthan one are examined. The winding factor and the winding harmonic components are calculated. The benefits attainable from a machine with concentrated windingsare considered. Rotor structures with surface magnets, radially embedded magnets and embedded magnets in V-position are discussed. The finite element method isused to solve the main values of the motors. The waveform of the induced electro motive force, the no-load and rated load torque ripple as well as the dynamic behavior of the current driven and voltage driven motor are solved. The results obtained from different finite element analyses are given. A simple analytic method to calculate fractional slot machines is introduced and the values are compared to the values obtained with the finite element analysis. Several different fractional slot machines are first designed by using the simple analytical methodand then computed by using the finite element method. All the motors are of thesame 225-frame size, and have an approximately same amount of magnet material, a same rated torque demand and a 400 - 420 rpm speed. An analysis of the computation results gives new information on the character of fractional slot machines.A fractional slot prototype machine with number 0.4 for the slots per pole and per phase, 45 kW output power and 420 rpm speed is constructed to verify the calculations. The measurement and the finite element method results are found to beequal.

Laajakaistainen Vivaldi-antennielementti

Diplomityössä suunniteltiin, rakennettiin ja mitattiin laajakaistainen antennielementti lineaariseen antenniryhmään. Elementti toimii mikroaaltoalueella, ja sen kaistanleveys on noin 4,8:1. Elementti koostuu kaksipuolisesta eksponentiaalisesti taperoidusta rakoantennista eli Vivaldi-antennista ja laajakaistaisesta siirtymästä liuskajohdosta kaksipuoliseen rakojohtoon. Elementin koko pienimmällä käyttötaajuudella on noin 0,31 lambda kertaa 0,34 lambda, josta antennitorven koko on vain noin 0,21 lambda kertaa 0,21 lambda. Elementti suunniteltiin HFSS-simulointiohjelman avulla ja rakennettiin kahdesta erillisestä piirilevystä puristamalla nämä yhteen alumiinisella kehyksellä. Mittauksilla varmistettiin elementin toiminta ja simulointien luotettavuus. Osoitettiin, että elementti voidaan suunnitella simulointiohjelman avulla ja rakentaa työssä käytetyllä tavalla. Osoitettiin myös, että tarvittavaa mitoitussimulointien määrää voidaan vähentää yhdistämällä erikseen mitoitetut rakoantenni ja siirtymä. Lisäksi simuloinnein osoitettiin, että elementti toimii myös ryhmässä ja että sen toimintaa voidaan parantaa kehyksen avulla.

Designing of statically loaded sheet metal structures

The goal of this thesis is to give information to machine designers about how to design and size sheet metal structures and joints. Generally, the designing object is to lighten structures. To design structures that are light and can carry loads more effectively, designers have to be updated of new manufacturing techniques and new designing methods and criterions. With knowledge of this thesis, a designer can recognize objects and methods plus how and where it is possible to apply these new more effectively load carrying structures. The thesis gives answers to questions of corrosion and material planning, goes into joint types and manufacturing techniques of sheet metal structures. One of the main issues is to develop designers world of ideas to design right kind of products with new lasertechniques.

DFM(A)- aspects for a horn antenna design

In this paper aspects of design for manufacturability and assembly (DFMA) are applied to the design of coaxially fed standard gain horn antenna for 1.70 - 2.60 GHz. Possibilities to utilize cross-technological approach method is examined. Methods of DFMA for laser processing are covered and practical design guides and methods are developed. Antenna construction for easy manufacturing and specialized performance is shown. Required dimensions and tolerances are discussed and suitable materials for laser processing are selected.

Microwave Slot Transmission Line Filled with Ferroelectric and Ferromagnetic Layers

Now when the technology is fast developing it is very important to investigate new hybrid structures. One way is to use ferrite ferroelectric layered structures. Theoretical and experimental investigation of such structures was made. These structures have advantages of both layers and it is possible to tune the behavior of this structure by external electric and magnetic field. But these structures have some disadvantages connected with presence of thick ferroelectric layer. One way to overcome this problem is to use slotline. So this is another new way to create hybrid ferrite ferroelectric structures, but it is needed to create new theory and find experimental proof that the behavior of these structures can be tuned with external magnetic and electric fields.

Antenna Design for Contactless IC Card Applications

Contactless integrated circuit cards are one form of application of radio frequency identification. They are used in applications such as access control, identification, and payment in public transport. The contactless IC cards are passive which means that both the data and the energy are transferred to the card without contact using inductive coupling. Antenna design and optimization of the design for contactless IC cards defined by ISO/IEC14443 is studied. The basic operation principles of contactless system are presented and the structure of contactless IC card is illustrated. The structure was divided between the contactless chip and the antenna. The operation of the antenna was covered in depth and the parameters affecting to the performance of the antenna were presented. Also the different antenna technologies and connection technologies were provided. The antenna design process with the parameters and the design tools isillustrated and optimization of the design is studied. To make the design process more ideal a target of development was discovered, which was the implementation of test application. The optimization of the antenna design was presented based on the optimization criteria defined in this study. The solution for the implementation of these criteria and the effect of each criterion was found. For enhancing the performance of the antenna a focus for future study was proposed.

Hindsgavl slot

kuv., 15 x 22 cm

Unequal Teeth Widths for Torque Ripple Reduction in Permanent Magnet Synchronous Machines With Fractional-Slot Non-Overlapping Windings

Permanent magnet synchronous machines with fractional-slot non-overlapping windings (FSPMSM), also known as tooth-coil winding permanent magnet synchronous machines (TCW PMSM), have been under intensive research during the latest decade. There are many optimization routines explained and implemented in the literature in order to improve the characteristics of this machine type. This paper introduces a new technique for torque ripple minimization in TCW PMSM. The source of torque harmonics is also described. The low order torque harmonics can be harmful for a variety of applications, such as direct drive wind generators, direct drive light vehicle electrical motors, and for some high precision servo applications. The reduction of the torque ripple harmonics with the lowest orders (6th and 12th) is realized by machine geometry optimization technique using finite element analysis (FEA). The presented optimization technique includes the stator geometry adjustment in TCW PMSMs with rotor surface permanent magnets and with rotor embedded permanent magnets. Influence of the permanent magnet skewing on the torque ripple reduction and cogging torque elimination was also investigated. It was implemented separately and together with the stator optimization technique. As a result, the reduction of some torque ripple harmonics was attained.

Antenna feed design for omnidirectional broadband antenna

This thesis is about development broadband feed for two-mirror antenna system that match following requirements: beamwidth from 45 to 90 degrees at -3 dB level, circular polarization, absence of radiation to the lower hemisphere area. Literature review was done in the areas of the UWB antennas creation. During the work attempts were made to create a feed in a form of the quad ridged horn and "eleven" antennas. The latter is introduced as the most effective feed among all antennas discussed in thesis. Radiation patterns and other results for "eleven" antenna were obtained. Results were saved as far field sources and placed slightly below focal point into the two-mirror antenna system, because phase center of the “eleven” antenna is predominantly shifted upwards. Directivity patterns for the two-mirror system were obtained and the conclusions about the work results have been made