Yan P.,UTRC - United Technologies Research Center |
Yan P.,Shandong University |
Ozbay H.,Bilkent University |
Sansal M.,Meteksan Defence Industry Inc.
Proceedings of the IEEE Conference on Decision and Control | Year: 2011
It has been shown that parameter varying systems with time delays can be robustly stabilized by switching control, provided that the plant's parameter varies slowly enough such that the dwell time conditions of the switched controllers can be satisfied. In this paper, the minimization of dwell time is considered, where an iterative search algorithm is developed from the singular value perspectives. The local minimal dwell time obtained in this paper can be used to estimate the upper bound on how fast the plant's parameters can vary. Meanwhile, the switching controller synthesis with optimal dwell time is also discussed, where robust stabilizer design algorithm is presented to achieve robust stability at certain operating range, as well as the local minimal dwell time for controller switching. A numerical example is given to illustrate the proposed algorithm. © 2011 IEEE.
Bulus U.,Meteksan Defence Industry Inc.
IEEE Antennas and Propagation Magazine | Year: 2014
This study describes a design frequency for designing resonant antennas and microwave structures. Antenna design at the center frequency is a common method for designing resonant antennas. When the designers begin an antenna design, they start to fi nd the center frequency by just taking the average of the target frequency-range boundaries. In fact, the dimensions are inversely proportional to the frequency, and directly proportional to the wavelength. This paper explains that the frequency of the center wavelength must be used as the design frequency. © 1990-2011 IEEE.
Unal A.,Hacettepe University |
Unal A.,Meteksan Defence Industry Inc. |
Koksal A.,Hacettepe University
2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), USNC-URSI 2015 - Proceedings | Year: 2015
Radiation and scattering problems involving dielectric objects can be formulated by using surface integral equation (SIE) methods or volume integral (VIE) equation methods. SIE methods employ unknown currents that reside on the surface of the geometry and are employed to formulate problems involving homogeneous bodies. VIE methods, on the other hand, employ unknown current densities that are distributed inside the geometry and allow problems involving inhomogeneous bodies to be solved. Numerical solution to these problems start with the discretization of the integral equations by a method of moments (MoM) scheme. Discretized integral equations are then converted into matrix equations which are solved to obtain unknown current coefficients. Number of elements in these matrix equations are closely related to the electrical size of the problem. Since VIE methods use voluminous currents, matrix sizes can quickly become very large. Usually these computationally intensive operations are required in multiple frequencies covering a bandwidth. In this case, lengthy solution process needs to be repeated for each frequency of interest. © 2015 IEEE.
Kars S.,Meteksan Defence Industry Inc. |
Oguztuzun H.,Middle East Technical University
Communications in Computer and Information Science | Year: 2011
Naval wargames play an important role for both training of naval cadets and trying out tactics for naval warfare. Constructing an ontology can be regarded as a way to formalize the mission space component of a simulation conceptual model. An ontology has been developed to capture the entities involved in a naval wargame and the relationships among them. The ontology is defined in OWL (Web Ontology Language), using the Protégé ontology editor and knowledge-base framework. This paper presents the ontology development process, discusses the decisions made throughout the creation of the ontology, and identifies the lessons learned. © 2011 Springer-Verlag.
Kurudere S.,Meteksan Defence Industry Inc. |
Erturk V.B.,Bilkent University
European Microwave Week 2014: Connecting the Future, EuMW 2014 - Conference Proceedings; EuMC 2014: 44th European Microwave Conference | Year: 2014
A novel configuration for substrate integrated waveguide (SIW) based bandpass filter with interdigital type resonators is presented. In the proposed structure, interdigital type resonators consisting of vias and circular caps at top of them are combined into a bowtie SIW structure. SIW is fed by a tapered microstrip line transition providing low loss and good matching. In order to improve harmonic suppression performance of the filter, the dumbbell shaped defected ground structure (DGS) is etched to the ground side of the microstrip line feeding section. The proposed filter structure is put in a conducting box in order to improve attenuation levels at the band edges and prevent radiation to the outside. The prototype is designed at 9 GHz center frequency with 500 MHz bandwidth, analyzed and fabricated for verification. The measurement results are in good agreement with the simulations, and the filter exhibits more than 30 dB harmonic suppression. © 2014 European Microwave Association.