Zvonimir Sipus

Bio: Zvonimir Sipus is an academic researcher from University of Zagreb. The author has contributed to research in topics: Microstrip antenna & Antenna (radio). The author has an hindex of 25, co-authored 277 publications receiving 3017 citations. Previous affiliations of Zvonimir Sipus include Chalmers University of Technology & Carlos III Health Institute.

Waveguide miniaturization using uniaxial negative permeability metamaterial

Abstract: A rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability is investigated both theoretically and experimentally. It is shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus, it can be considered as a dual of the ordinary waveguide. The transversal dimension of this waveguide can be arbitrarily smaller than half of a wavelength in the filling material, provided that the transversal permeability is negative. This peculiar behavior may be used for fabrication of miniaturized rectangular waveguides. Several experimental miniaturized waveguides loaded with double ring resonators in 7 GHz frequency band have been designed, fabricated and tested. The measured results revealed backward-wave passband located below the cutoff frequency. Furthermore, it was experimentally shown that the increase of the physical length of the waveguide caused the decrease of the electrical length. This is a direct proof of the backward-wave propagation since the phase of the backward wave increases along the waveguide.

Non-Uniform Metasurface Luneburg Lens Antenna Design

Abstract: A metasurfing concept is demonstrated and applied in the design of Luneburg lens antennas. Using an array of size-varying circular patches on a dielectric substrate inside a parallel-plate waveguide (PPW) structure variable surface impedance is obtained, which realizes an equivalent refraction index as that of a Luneburg lens. The obtained lens has good bandwidth characteristics and significant fabrication advantages with respect to conventional dielectric lenses. Based on this PPW lens, an H-plane antenna has been designed and simulated.

Roadmap on metasurfaces

Abstract: Metasurfaces are thin two-dimensional metamaterial layers that allow or inhibit the propagation of electromagnetic waves in desired directions. For example, metasurfaces have been demonstrated to p ...

Cost-Effective Gap Waveguide Technology Based on Glide-Symmetric Holey EBG Structures

Abstract: We present a novel electromagnetic bandgap (EBG) structure, which can be used to manufacture low-cost waveguiding structures at high frequencies. The unit cell of the proposed EBG consists of glide-symmetric holes in parallel plate waveguide. Using this unit cell in groove gap waveguide technology has a number of advantages over pin-type EBG at high frequencies, such as acquiring higher accuracy because of larger periodicity as well as an easier and cheaper manufacturing process. The performance of the proposed waveguiding structure is demonstrated using both a straight and a double 90° bent lines through simulation and measurement.

A Survey on Internet of Things: Architecture, Enabling Technologies, Security and Privacy, and Applications

Abstract: Fog/edge computing has been proposed to be integrated with Internet of Things (IoT) to enable computing services devices deployed at network edge, aiming to improve the user’s experience and resilience of the services in case of failures. With the advantage of distributed architecture and close to end-users, fog/edge computing can provide faster response and greater quality of service for IoT applications. Thus, fog/edge computing-based IoT becomes future infrastructure on IoT development. To develop fog/edge computing-based IoT infrastructure, the architecture, enabling techniques, and issues related to IoT should be investigated first, and then the integration of fog/edge computing and IoT should be explored. To this end, this paper conducts a comprehensive overview of IoT with respect to system architecture, enabling technologies, security and privacy issues, and present the integration of fog/edge computing and IoT, and applications. Particularly, this paper first explores the relationship between cyber-physical systems and IoT, both of which play important roles in realizing an intelligent cyber-physical world. Then, existing architectures, enabling technologies, and security and privacy issues in IoT are presented to enhance the understanding of the state of the art IoT development. To investigate the fog/edge computing-based IoT, this paper also investigate the relationship between IoT and fog/edge computing, and discuss issues in fog/edge computing-based IoT. Finally, several applications, including the smart grid, smart transportation, and smart cities, are presented to demonstrate how fog/edge computing-based IoT to be implemented in real-world applications.

Statistical optics

Abstract: Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

Local Metamaterial-Based Waveguides in Gaps Between Parallel Metal Plates

Abstract: This letter presents a new metamaterial-based waveguide technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and sub- millimeter waves. The latter is due to the fact that there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture or multilayer structure on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited (in cutoff) by realizing a high surface impedance (ideally a perfect magnetic conductor) in the textured surface at both sides of all ridges. Thereby, cavity resonances do not appear either within the band of operation. The present letter introduces the gap waveguide and presents some initial simulated results.