Browsing by Subject "Power electronics."

Now showing 1 - 4 of 4

Open Access
High power high efficiency microwave power amplifier design using Class-E topology
(2010) Coşkun, Akif Alperen
Power consumption is a major problem in wireless technology. Since power ampli- fier is one of the most power consuming element, efficiency of the power amplifier should be optimized. Switching amplifiers typically offer very high efficiency. As the frequency increases, the efficiency drops. Class-E is a switching amplifier which is suitable for microwave frequencies. It attains a very high efficiency with proper voltage and current characteristics. Different techniques to obtain these characteristics are possible. In this work, we implement a 38 dBm power amplifier at 2 GHz. Different methods are examined to obtain a high efficiency behavior. We obtained a power added efficiency of 60%.
Open Access
New techniques to design performance improved power dividers and directional couplers using the new scattering parameter relations
(2015) Taş, Vahdettin
Wide bandwidth provides with several benefits in RF applications such as enabling high data rates for communication applications, enhancing the multi tread avoiding capabilities of the jamming systems, improving the effectiveness of spread spectrum techniques. Operation in a wide bandwidth requires either broadband components or multiple narrow band components together with sophisticated multiplexing methods. There are several trivial methods to increase the bandwidth of the RF components. For instance the bandwidth of a power divider can be increased by increasing the number of sections which directly increases the insertion loss and circuit size, burdening a big trade off for the designer. The methods avoiding such a trade off are life savers in most of the applications. Such methods require new design approaches. This work aims to develop such methods with a special focus on improving the bandwidth and performance of the power dividers and directional couplers. We derive new scattering parameter relations and show that the relations require tricky design guidelines. S-parameter relations for a number of power divider types and directional coupler schemes are investigated. The derived equations have significant usages. One of the equations is used to design the optimal isolation network for the Wilkinson power divider. A number of equations imply a reduction in the number of the optimization parameters in the design of n-section or n-way dividers. Another equation is used to increase the directivity of microstrip directional couplers in a wide bandwidth. Experimental results are presented verifying the theoretical work.
Open Access
Silicon carbide high voltage devices
(2011) Kazar, Özgür
Open Access
Ultra wideband tapered power combiner/divider
(2014) Ünlü, Okan
Many typologies like the designs of Wilkinson Power Divider and Gysel Power Divider have been worked and improved through the years. Each design targets a higher bandwidth, a better isolation and a higher power handling capacity or smaller size. The basic analysis of every structure begins with the even mode and the odd mode models. The tapered lines are ultra wideband matching structures that are used to match real impedances. The only limitation of tapered line is the size, which has to be the half wavelength of the lower frequency limit. The tapered lines do not have any upper frequency cut-off. Because of the limitations in sizes, tapered lines have not been able to be used very commonly. The proposed new topology has a new taper topology with a single capacitor at the input side to decrease the lower frequency limit of the tapered line. The even mode structure of the proposed power divider/combiner is constructed of these improved tapered lines. In the odd mode analysis, the N section Wilkinson power divider/combiner design has been used. In order to determine the isolation resistor values, four different methods have been proposed. The proposed structure uses the surface resistive materials to implement these resistors. It has been observed that continuity of the isolation resistors between transmission lines causes some loss in the even mode. In order to solve this problem, the width of the resistors should be as small as possible to prevent the even mode loss.