Hakan P. Partal

An experimental study of high precision TOA based UWB positioning systems

An ultra-wide band (UWB) localization study by developing a Time-of-Arrival (TOA) algorithm is presented and experimentally verified. The technique and test setup presented in this work offers an easy to understand localization method utilizing the UWB technology. The challenges in designing UWB RF hardware and creating an effective algorithm for the UWB system have been overcome resulting in an accurate location estimation. The proposed system is promising to achieve high precision location estimation system.

Radiation from a circular loop in the presence of spherically symmetric conducting or dielectric objects

The problem of electromagnetic radiation from a circular loop antenna of radius a, carrying a current I is considered. The loop may be radiating in the presence of one or more of the following objects: a centrally located dielectric or perfectly conducting sphere of radius b a and outer radius d, a perfectly conducting spherically symmetric cap at radius b, and another such cap at radius d. Typically geometric structures considered are shown. It is demonstrated how the presence of the sphere, shell, and caps can change and direct the radiation pattern of the loop.

High frequency modeling and impedance matching of power transformers for PLC applications

Over recent years Smart Grid communication applications in different frequency bands have been developed and used in the power utility industry. These applications consist of relay protection communication for high voltage equipment and distribution automation systems. Some research thus far has been focused on the modeling of power distribution lines in the medium to low voltage range. This paper will analyze the transmission of high frequency signals at MHz level thru a transformer and offer modeling techniques to better optimize the efficiency of the signals. This research contains a multidisciplinary approach to the power transformers for increased communication efficiency by designing matching networks in power lines. The objective of this paper is to help research in this particular topic and use this article as a starting point for future research in modeling of high frequency transformers for power line communication applications.

The Exact Analytical Solution for Large Circular Loops Radiating Around a Dielectric Coated Conducting Sphere

In this paper, the electromagnetic field of electrically large circular loop antennas, with different radii and different nonuniform current values, around a dielectric coated conducting sphere is considered. One or more loop antennas are located on the outer surface of a spherical dielectric shell covering a conducting sphere. Eigenfunction series solutions for the field are assumed in two regions. The current distribution on the wire loop, driven by a voltage source, is determined by Fourier series expansion and all necessary harmonics are taken into account. Exact analytical field expressions in closed forms are derived and field patterns are plotted. The antenna model and formulation presented in this paper offer exact analytical solutions to several loop antenna problems.

The Usage of Dielectric Resonator Filters in Microwave Frequency Synthesizers

Microwave frequency synthesizers in the presence of dielectric resonator filters are presented in this paper. Various types of microwave filters are discussed depend on applications. Dielectric resonators are considered next to microstrip filters because of great benefits for the filter applications. A specific design example is given to focus on the usage of the dielectric resonators and filters

Radiation from loops next to a sphere in a radome

Radiation from multiple circular loop antennas of different radii and of different current values is considered. Parallel circular loops lie on an imaginary spherical surface of radius a. A conducting or dielectric sphere of radius b<a and a dielectric shell of inner radius c>a and of outer radius d could be placed around the loops. The circular loops are parallel to the xy-plane and their centers are on the z-axis. The centers of the sphere and the dielectric shell are both at the origin. Eigenfunction series solutions are assumed in different regions of the problem. The unknown coefficients are computed by enforcing boundary conditions at the interfaces of these different regions.

An UWB high-q bandpass filter with wide rejection band using defected ground structures

In this paper, an ultra-wideband microstrip bandpass filter (BPF) which operates from 2 GHz to 4.7 GHz, with high selectivity and wide rejection band is presented and experimentally verified. The filter is composed of microstrip lines with shorted stubs acting as a high pass filter (HPF) on top side and dumbbell shaped defected ground structures (DGSs) on bottom side acting as a low pass filter (LPF). The seventh order high pass filter structures and three dumbbell shaped DGS resonators combined on a single layer microstrip substrate are optimized using microwave circuit and electromagnetic (EM) simulation tools to obtain the ultra-wideband bandpass filter. The designed compact filter has 0.9 dB max insertion loss in-band, no harmonics are observed up to and above 12 GHz and finally, it has a good selectivity. The designed hybrid circuit is a production friendly and low cost bandpass filter which has a controllable pass- and rejection band nature.

Field of a large circular loop antenna around a conducting sphere

The electromagnetic field of a circular loop antenna of radius a, carrying a nonuniform current I(ϕ), in the presence of a conducting sphere of radius b<a located symmetrically is considered. The current distribution on the thin-wire circular loop driven by a delta-function generator is determined by a Fourier series expansion in terms of tesseral harmonics. Eigenfunction series solutions for the field are assumed in different regions. The unknown coefficients are computed by enforcing boundary conditions at the interfaces of these different regions. Field components are obtained analytically in closed form and field patterns are plotted for various cases.

Field of a circular loop near a symmetrical spherical cap

The field of a thin circular loop antenna symmetrically placed near a conducting spherical cap is computed. The total field is expressed in terms of three modal expansions in three different regions. Most of the unknown coefficients are obtained analytically. Some are solved numerically by using point matching. The same problem is also solved numerically by the Method of Moments, where the surface of the cap is approximated by planar triangular patches. Computed results obtained by both methods are in excellent agreement.

The exact computational solution approach by integral representation with an application to radiation characteristics of aperture antennas

A treatise of a new computational approach was constructed in this paper. The extraction mechanism is focused on the exact evaluations of radiated field by integral representations. The approach of integral representations gives an incomplete set of equations, however; this difficulty was passed by extending boundary conditions with a matching algorithm through integral representations. The equations are solved with a scenario managing algorithm by iterative reconfigurations of radiated field. The method is explained with the radiation problem of circular aperture by illustrations. The approach is suitable for optimization purposes of antenna design.