Sener Uysal

Synthesis, design, and construction of ultra-wide-band nonuniform quadrature directional couplers in inhomogeneous media

A computer-aided synthesis design procedure is given for nonuniform quadrature directional couplers in inhomogeneous media. A wiggly geometry is used which effectively slows the odd-mode phase velocity to match the even-mode phase velocity. The wiggly geometry results in improved isolation and increased effective dielectric constant. This technique provides a shorter coupler length due to increased effective dielectric constant. Cubic splines of strip width, strip spacing, and wiggle depth as functions of coupling coefficient are computed using static capacitances of uniform coupled lines. These functions are then used as synthesis functions to evaluate the continuous physical parameters of nonuniform coupled lines by using the continuously varying coupling coefficient. A nonuniform interdigitated coupler is introduced to realize the tight coupling values. >

Novel microstrip multifunction directional couplers and filters for microwave and millimeter-wave applications

The design of a particular class of microstrip couplers and filters is presented. The synthesis functions obtained from the solution of first-order nonlinear differential equation of nonuniform lines with a loose coupling assumption are modified and validated for higher coupling values. The design employs a nonuniform coupled line configuration along which a realizable continuous coupling coefficient is obtained by modifying the reflection coefficient distribution function. This modification results in a frequency-selective coupling which minimizes the out-of-band coupling in the specified frequency range. As a result, it is possible to realize -3 dB directional couplers using double-coupled lines without the need for tandem connections or extreme photolithographic techniques. Experimental results for microwave band-pass and periodic couplers are presented together with the computed results. Potential applications of these components are discussed, and the work is extended to include millimeter-wave realization. >

Synthesis and design of wideband symmetrical nonuniform directional couplers for MIC applications

A computer-aided-design (CAD) synthesis procedure using cubic splines for wideband symmetrical nonuniform directional couplers in inhomogeneous media is presented. Solutions for the potential problems inherent to these couplers are given. Results are presented for a 2-18-GHz, five-section, -3-dB nonuniform tandem directional coupler designed and built on an alumina substrate.<<ETX>>

A comparative study on different photovoltaic array topologies under partial shading conditions

This paper mainly analyzes the performance of different photovoltaic array configurations under various shading patterns. A Matlab/Simulink based simulation model of a PV module is utilized as the smallest building block of the mentioned topologies. The model is validated using the datasheet parameters of the ‘SOLAREX MSX-60’ PV module. The performance and output characteristics of ‘Series-Parallel’, ‘Total-Cross-Tied’ and ‘Bridge-Link’ array topologies are analyzed and compared using a 6×6 PV array under 6 different shading scenarios. The effects of bypass diodes during partial shading conditions are considered and the analysis results are presented and compared with and without bypass diodes. The mentioned shading scenarios are defined in such a way to simulate the passage of a cloud in different patterns. The results show that all the mentioned topologies have similar performances under identical illuminations while the ‘Total-Cross-Tied’ (TCT) configuration, despite the high complexity of the system, outperforms both ‘Series-Parallel’ (SP) and ‘Bridge-Link’ (BL) structures under partial shading conditions. ‘Bridge-Link’ and ‘Series-Parallel’ configurations stand on the 2nd and 3rd performance stages respectively while a Series-Parallel connection presents the least system complexity. The analyses and results provide detailed information on the characteristics of different array topologies which can be utilized by system designers to estimate the power yield and choose the most appropriate system configuration with respect to the existing environmental conditions to improve the overall efficiency.

Bowtie patch antennas and simple arrays for wireless indoor communications

Several bowtie patch-antenna configurations are studied for their suitability for use in broad-band indoor wireless communications. A microstrip bowtie antenna (MBA), based on the design of equilateral triangular patches, is first designed and tested. The same design is used to realize a coplanar-waveguide bowtie antenna (CPWBA) with finite ground plane. The CPWBA is coax-fed from its apex and matched in C-band. The resonant slot length of this antenna is around three times that of the guided wavelength. The measured gain for the CPWBA antenna is 8.1 dB. The same MBA is also used in the realization of (1/spl times/2)-, (2/spl times/1)-, and (2/spl times/2)-element MBA arrays. The MBA and resultant arrays use microstrip feed networks matched to the input impedance at around 10 GHz. The gain of the MBA is 6.2 dB; the gains for the arrays vary within 13.7 and 17.3 dB. The 2:1 voltage standing-wave ratio bandwidths lie in the 9.7%-10.8% range for the realized antennas. The radiation patterns can be optimized to fit the required diversity for the specific indoor wireless communication environment; the beamwidths are demonstrated to vary between 15/spl deg/ and 85/spl deg/, which allow for multipath minimization and radiation diversity within the premises, thereby providing interference-free illumination.

A compact coplanar stripline lowpass filter

The design methodology of a lowpass filter using transverse slit and parallel-coupled gap coplanar stripline (CPS) discontinuities is presented. A 5th order Chebyshev lowpass filter with a passband ripple of 0.5 dB is designed with a cut-off frequency of 5 GHz. Very good agreement has been observed between the experimental results and simulated data. The realized filter occupies less than 50 mm/sup 2/ on an alumina substrate which is smaller than other planar filters with the same cutoff and attenuation characteristics.

Forest Fire Detection in Wireless Sensor Network Using Fuzzy Logic

The multi-purpose integrated homeland surveillance security systems are usually located in remote areas. Intelligent decision making (IDM) capability emerges as the primary feature in the realization of the T/R architecture. The aim of employing IDM is two-fold. First is to save energy, as the system operation is desired to be autonomous based on the available solar power and the corresponding battery-bank. Second is to activate the necessary action(s) required based on the pre-defined sensitivity levels. The current work is focused on the second aim using the pre-defined sensitivity levels. We propose to use a wireless sensor network (WSN) for data harvesting to be used as raw input data into our control system. Fire detection has been chosen to illustrate the IDM capability of the system. A Fuzzy Logic algorithm is developed using five membership functions as temperature, smoke, light, humidity and distance. Simulation results for the probability of fire based on the fuzzy rules using the status of the membership functions are presented in the paper.

Nonuniform transmission line codirectional couplers for hybrid MIMIC and superconductive applications

A new design approach for thin-film codirectional quadrature couplers and their applications is described. An in-depth analysis and semi-empirical design curves are presented for these couplers. Forward-wave coupling is achieved by making use of the difference between even- and odd-mode phase velocities. Modified nonuniform codirectional couplers with a dummy channel for continuously decreasing or increasing taper and employing wiggly, serpentined and smooth coupled edges have been designed and tested. It is found that a wiggly coupler can achieve a 50% length reduction compared to a smooth-edge coupler. A further 60% length reduction compared to a wiggly coupler is achieved by a serpentine coupler. Coupler performance for wiggly and serpentined configurations is computed by choosing a realizable phase velocity function for a given coupler length. Either constant 90/spl deg/ or /spl minus/90/spl deg/ phase shift is possible with these couplers giving significant design flexibility in some applications. The results for a K/sub u/-band /spl Sigma//spl minus//spl Delta/ magic-T circuit employing a 0 dB wiggly coupler and a /spl minus/3 dB smooth-edge coupler are also presented in the paper. >

Integration of RFID and WSN for supply chain intelligence system

Radio Frequency Identification (RFID) system is used for detecting and identifying the tagged objects by electromagnetic signals. Wireless Sensor Networks (WSN), which consists of a huge numbers of nodes, can monitor the condition of the environment including pressure, humidity, and temperature. Data is transferred via nodes to a certain location. Integration of RFID and WSN provides a new feature and improves their functionalities. In the RFID system, each tag can only communicate with a reader. By integrating RFID tags with nodes, communication of the RFID tags with each other is possible and also integration of readers with nodes facilitates negotiation of readers together. The RFID and WSN integration in supply chain provides system intelligence. In such a case, tag is embedded in objects and reader is integrated with nodes. Therefore, identification and detection of tagged items is provided by using RFID and monitoring of environment can be obtained by using WSN. The present case study is simulated in the Petri Net Toolbox in MATLAB environment. It represented the negotiation of smart devices spontaneously in managing variety of instructions in order to enhance system performance.

A simple MATLAB/Simulink simulation for PV modules based on one-diode model

This paper proposes a simple and practical simulation model for solar modules using MATLAB/Simulink. The model is based on a single-diode mathematical model of a solar cell and is capable of accurate modeling of I-V and P-V characteristics of a solar module. Model parameters are obtained from manufacturers datasheets and series and shunt resistances are calculated using a simple method based on open-circuit voltage, short-circuit current and irradiance values. The model is interfaced with SimPowerSystems toolbox. This feature makes the model capable of being used with power electronic devices and elements for advance analyses. The model is validated using measured I-V characteristics of a commercially available crystalline silicon solar module and the effects of environmental conditions (temperature and irradiance) as well as the effects of cell parameters like series and shunt resistances on module characteristics are investigated. The proposed model is capable of being used by solar energy researchers, system analysts and designers as a simple and helpful tool for advance analysis requirements.