Ahmet Ozek

Design and analysis of a compact dual-mode dual-band microstrip bandpass filter

Design and fabrication of compact dual-mode dual-band microstrip bandpass filters with a novel feed scheme is presented. The proposed filters have two square loop resonators for two passbands, and each resonator is fed by the feedlines located at the upper corners of the resonators. By using the perturbation elements such as patches or corner-cuts, two degenerate modes of each passband can be easily excited, so mode frequencies and transmission zeros of the passbands can be controlled independently. Also, the proposed feed scheme provides the harmonic suppression for the first passband. In addition, theoretical results have been obtained by using an equivalent circuit model, and a coupling scheme is also presented. The designed filters have an electrical length of for the quarter wavelength resonator, where is the guided wavelength at 1.8 GHz. Two bandpass filters having elliptical and linear phase filtering characteristics in each passband have been designed, fabricated, and tested. Measured results are in an excellent agreement with simulated and calculated ones. In all frequency responses, return losses are better than 15 dB and insertion losses are at acceptable values for both passbands.

Feature matching based positioning algorithm for swarm robotics

Abstract In this study, a positioning algorithm which is inspired by model matching type positioning systems is presented for swarm robotics. Unlike the conventional model matching systems, the system is designed to be operated as distributed. The algorithm consists of online and offline stages. While specific data collection and positioning are computed in the offline stage, specific data exchange is performed in the online stage. In the positioning algorithm to be used, a swarm robot system where each robot receives an image from a camera located under itself and where the robots share these images with each other and perform positioning is taken as a basis. The positions computed are the positions of the robots with respect to each other. Position estimation is based on feature detection and description from images. To determine the optimal positioning algorithm, performance comparison is performed among different combinations of feature detection and description algorithms.

A novel compact quad-band microstrip bandstop filter design using open-circuited stubs

A novel compact quad-band microstrip bandstop filter design is presented. Input and output ports of the filter are connected with a high impedance transmission line. Proposed filter is designed by using open-circuited stubs attached to the input and output ports. Thus, based on the fr - 3fr harmonic property of the stub-loaded resonators, four stopbands at 1.15-2.22, 2.94-4.56, 4.95-6.98 and 8.26-8.96 GHz are obtained. Insertion losses of all stopbands are better than 15 dB inside the stopbands. Under the even and odd mode excitations, resonance conditions of the structure are also investigated. For the experimental verification of the simulated results, proposed filter has been fabricated. Simulated and measured results are in a good agreement.

Design of dual-mode substrate integrated waveguide filter using inductive slots

This paper presents a single-cavity dual-mode bandpass filter design based on a substrate integrated waveguide (SIW) resonator. The proposed resonator has various types of inductive loading, such as symmetrical/asymmetrical, thin and narrow slots which are used to achieve a compact circuit size. The presented structure has also a new perturbation arrangement for dual-mode SIW resonators depending on the movement of narrow slots. The designed structure is fabricated for the experimental verification of the proposed model. According to measured results, center frequency is obtained at 5.1GHz with a fractional bandwidth of %4.5. The measured insertion and in-band return losses are about −1.24 dB and about −15.4 dB, respectively. Measured results show a good agreement with the simulated results.