Time filter

Source Type

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.

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.

Kurudere S.,Meteksan Defence Industry Inc. | Erturk V.B.,Bilkent University
Microwave and Optical Technology Letters | Year: 2015

A novel configuration of interdigital bandpass filter based on the substrate integrated waveguide (SIW) technology is proposed. In addition to the interdigital resonators in SIW that determine the main response/characteristics of the filter, narrowing the width of the SIW at the center of the filter and additional vias at its input and output parts act as two additional control mechanisms to achieve the desired filter response. Moreover, dumbbells are etched to the ground side of the microstrip feeding sections at both ends of the filter to improve its harmonic suppression. A prototype filter is designed and fabricated for verification. The measured results are in good agreement with the simulations, and the filter exhibits very good harmonic suppression. © 2015 Wiley Periodicals, Inc.

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.

Aban V.V.,Meteksan Defence Industry Inc. | Hava A.M.,Middle East Technical University
16th International Power Electronics and Motion Control Conference and Exposition, PEMC 2014 | Year: 2014

In this study, the input filter design and dc-bus voltage control of ac motor drives utilizing low capacitance film capacitor are investigated. The dc-bus voltage instability problem arising due to the resonance between the dc-bus capacitor and circuit inductances is explained. A dimensioning algorithm of dc-bus filter components for stable operation is given. The simulation results of the low capacitance motor drives with and without dc-link inductor are provided to observe the stability of the dc-bus at different resonant frequencies. Voltage and current mode active stabilization methods found in literature aiming to actively damp the resonances in the dc-bus are analyzed and evaluated in the simulations for 2.2 kW and 37 kW rated induction motors driving constant torque load (CTL) and variable torque loads (VTL). Results are analyzed both in terms of input (line current) power quality and output (motor motion) quality. © 2014 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.

Yayan M.,Meteksan Defence Industry Inc. | Duman O.,Meteksan Defence Industry Inc.
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2015

In this paper, design of a directional blade antenna with tilted beam operating at C band is presented. Blade antennas are preferred for both airborne and ground based communication systems because of their compact size, light weight and low air friction capabilities. Especially for ground based defense systems, tilted beam directional blade antenna may be a useful solution due to the slope of the platform where antenna is placed. The antenna configuration is modeled and optimized using CST Microwave Studio Suite, EM simulation software. Antenna beam is tilted by 15 degrees utilizing placement of a parasitic element ahead of the antenna. © 2015 IEEE.

Yayan M.,Meteksan Defence Industry Inc. | Duman O.,Meteksan Defence Industry Inc.
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2015

In this paper, method for increasing the sectoral gain of a 3-notched directional blade antenna operating in C-band is introduced. By inserting an additional 4th notch and using a cylindrical parasitic element all around the radiator, sectoral gain covering 70 degrees along the broadside radiation of the blade antenna is increased by approximately % 30. Antenna configuration is modeled and optimized using CST Microwave Studio Suite, EM simulation Software. © 2015 IEEE.

Unal A.,Meteksan Defence Industry Inc. | Dincer O.,Meteksan Defence Industry Inc.
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2015

An efficient Ka band substrate integrated waveguide (SIW) slot array antenna is presented. Proposed antenna consists of an arrangement of linear SIW arrays that are fed with a parallel feeding circuit implemented by using both metallic waveguide and SIW power dividers. By using this hybrid feeding scheme, feed line losses are minimized. Measured antenna parameters such as gain, beam width and side lobe levels are compared with electromagnetic simulations and results are reported. © 2015 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.

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