Ercan Yaldiz

Analysis of the Effects of GSM Bands to the Electromagnetic Pollution in the RF Spectrum

In this study, electromagnetic (EM) pollution measure- ments in crowded residential areas were performed, and statistical analysis of values recorded for the EM sources causing pollution was carried out. The actual measurement values and estimated values by the analysis model obtained through the statistical analysis were com- pared. Also, amplitude ∞uctuations of the electromagnetic radiations from EM pollution sources were detected for a long time, and statisti- cal analyses were made. EM fleld levels were measured in the districts of Turkish capital, Ankara where cellular base stations and TV/Radio stations are densely populated. EM radiation levels were measured for the GSM900, GSM1800, FM, UHF4, VHF4 and VHF5 stations for certain spectrum ranges under far-fleld conditions by utilizing isotropic fleld probe and selective spectrum analyzer. The measurements were fulfllled by using NARDA SRM3000 radiation meter with isotropic an- tenna that can be utilized in 75MHz{3GHz frequency range. The ob- tained measurement levels were compared with the limit values given by International Commission for Non-Ionizing Radiation Protection (ICNIRP). The measurement results for each pollution sources were compared, and their contributions to the combined radiation were an- alyzed. The values for the EM pollution in the measurement regions were embedded over the digital maps created for the related places. During this process, comparisons of the pollution maps were made by utilizing Natural Neighbour (NN) interpolation technique.

A novel software for an energy efficient GPR

In this paper, a simulator software based on MATLAB environment has been developed so that an energy efficient ground penetrating radar (GPR) can be modelled. Thus, applications of the radar in practice will easily be performed. In the software, the output power of GPR has been assumed as variable in order to reduce energy consumption. Power values have been computed in simulations with the proposed software for two different models which have comprised mediums with horizontal sublayer and inclined sublayer. Compared with common algorithm, power savings (PS) of 43% for the horizontal situation and 22% for the inclined one have been obtained.

Model Problems of Pulse Sensing

The radio-locating means for determination of layered media parameters and visualization of objects or voids hidden in them have gained wide-spread acceptance in various fields, namely, civil engineering, geodesy, use of hydraulic-engineering structures and of oil-pipe-lines, etc. The solution of the engineering problems arising therewith requires the development of essentially new approaches. Traditional theoretical and experimental methods have made possible only the first generation of radars with both small signal penetration depth and incomplete retrieval of useful information from remote sensing data. Quite reasonable hopes for improvement of the situation are widely associated with the construction of radars based on nonsinusoidal waves. A central theoretical problem here consists in correct interpretation of the results of measurements, demanding for its solution adequate mathematical models (and algorithms) describing the transient processes in the part of space under research. Model problems of pulse sensing are initial boundary value ones in unbounded regions with inhomogeneous compact objects. The key to the effective solution of them lies with a proper truncation of the computational domain in finite-difference methods, i.e. in a limitation of such kind that, on the one hand, reduces the essentially open problem to the closed one, and, on the other hand, does not effect on accuracy and reliability of the data obtained. Our paper is just devoted to the analysis of this problem. In the first section, the problem of scattering of nonsinusoidal waves by a perfectly conducting compact object imbedded in an inhomogeneous half-space with an irregular boundary is considered. The second section is devoted to the extension of the results to other situations peculiar for pulse sensing: an inhomogeneous compact object and a stratified dielectric structure in a field of nonsinusoidal waves and a pattern-forming structure. All model problems are two-

SAR Values in a Homogenous Human Head Model

The purpose of this chapter is to present how to determine and reduce specific absorption rate (SAR) on mobile phone user. Both experimental measurement technique and a numerical computing method are expressed here. Furthermore, an application on reduction of SAR value induced in human head is carried out with numerical computing. Mobile phone working at 900 MHz frequency shielded with copper is considered in order to furnish reduction of SAR in simulations which are conducted to calculate the maximum SAR values in Matlab programming language using two dimensional (2D) Finite Difference Time Domain (FDTD) method. Calculations are separately made for both 1 g and 10 g. Head model structure is assumed uniform.

Implementation of FMCW radar for training applications

In this study, a frequency modulated continuous wave (FMCW) radar has been implemented. The FMCW is obtained by modulating CW signal. The triangular wave signal has been selected as modulation signal and a modulator circuit has been performed. The FMCW radar system provides the target velocity and range information in sufficient resolution within a 100-meter range at a central operating frequency of 2.4 GHz. The range and velocity information of target object is obtained by Matlab program on the computer. In future work, radar RF components will be improved to increase output power and range.

Direction of Arrival Estimation by Using Artificial Neural Networks

In the literature there are many algorithms for direction of arrival estimation like MUSIC, ESPRIT, First order forward prediction, Capon etc. These algorithms have heavy calculation operations. This situation could cause lags in response time of the algorithm, and may pose an important disadvantage in real time applications. To overcome this problem, artificial neural network (ANN) could be used. The training stage of an ANN needs significant time and sources but after training, the estimation by using ANN is very fast. In this study, an ANN approach has been proposed for direction of arrival estimation in uniform linear array antenna. In training, the whole pseudo spectrum is scanned by 10 degree steps. In the simulation process, it is accepted that a uniform linear array consists of 5 isotropic antenna elements and there are 1 to 4 arrival signals. Tests of the trained ANN have been done for various directions of arrival angles, and satisfactory results have been obtained.

Direct Digital Frequency Synthesizer Designs in MATLAB

This study presents the structure of the Direct Digital Frequency Synthesizers (DDFSs) which have several advantages compared to conventional synthesizers such as high frequency, fast switching speed and low power dissipations. In order to lessen the physical area and power dissipation, ROM compression techniques are applied in designs. Bipartite Table Method (BTM) and Multipartite Table Method (MTM) are utilized in this study because of the fact that they provide high compression rates. By using MTM, the compression rates of 157.54:1, 726.71:1 and 3463.29:1 are obtained at 58.40 dB, 75.30 dB and 84.66 dB SFDR levels, respectively.