Bora Doken

Design for the structural surface material enabling shielding for interference mitigation within the buildings in the unlicensed 2.4ghz ISM band

This work is proposed to design shielding for interference mitigation and network security within the buildings in the unlicensed 2.4GHz ISM band and to provide maximum transparency at broadcast frequencies. Thus, mobile phones, radio and television signals in buildings will not be affected. Frequency Selective Surface (FSS) is attached onto existing common construction material to transform the standard material into a band stop frequency selective wall. To obtain the band response of FSS having a desired frequency interval, a new FSS periodic element geometry is introduced. The obtained results show that desired frequency response is achieved. HFSS software is used for simulation purposes.

A new reflector antenna design providing two different patterns

Antennas with cosecant squared pattern are designed for air-surveillance radar systems. These permit an adapted distribution of the radiation in the beam and causing a more ideal space scanning. In the practice a cosecant squared pattern can be achieved by a deformation of a parabolic reflector. Moreover, it can be achieved by using multiple feed antennas with normal parabolic reflector surfaces. A fan beam antenna which is a directional antenna producing a main beam having a narrow beamwidth in one dimension and a wider beamwidth in the other dimension can also be used for similar purposes. This pattern can be achieved by a truncated parabolic reflector or a circular parabolic reflector. Frequency selective surfaces (FSSs) have been used in the reflector antenna designs in recent years. A FSS is an array of periodically arranged patches or apertures, showing a particular filtering behavior. Its selectivity in frequency is obtained by the design and allows the transmission of signals in a certain frequency range only. This work is proposed to design a reflector antenna that provides both fan beam and cosecant squared pattern by using a FSS. For the simulation and optimization of the antenna, high frequency simulation software (HFSS) and SUPERNEC antenna simulation programs are used.

A novel multi-band frequency selective surface for ka-band applications

In this paper, single layer multi-band reflective frequency selective surface (FSS) design is presented. Proposed design have stable frequency response up to 60 degrees of incidence angles. In the proposed hybrid design, three-armed geometry is placed in the center and two armed geometries are placed in each quadrant of the unit cell in order to reflect the incoming waves in 26.5 GHz frequency band. Two-legged geometries are placed in corners and square loop geometries are placed in each quadrant of the unit cell in order to reflect the incoming waves in 40 GHz frequency band. Analysis of the proposed surfaces are executed with Ansoft HFSS v.19 software. Simulation results show that proposed dual-band FSS reflects incoming electromagnetic waves between 25.5-27.3 GHz and 41.8-45.1 GHz frequencies. Achieved return losses are less than 0.55 dB in the desired frequency bands for the incident angles between 0° and 60° at both TE and TM polarizations. Proposed FSS can be used as a subreflector in multiband reflector antenna designs for satellite communication applications. Obtained results are also compared with similar works and discussed.

Bandwidth improvement in microstrip patch antenna

The microstrip antenna (MSA) is one of the most widely used microwave antennas possessing several advantages. However, it presents a low impedance bandwidth, low gain, and tolerance problems. Due to the increasing usage of wireless communication applications, the performance improvement studies of such systems has found a growing investigation area in recent years. One new area of applying wireless networking is intra-satellite communication in satellites. The aim of this study is to design a simple Ultra-Wide Band (UWB) microstrip antenna for the wireless intra-satellite communication systems. One of the important tasks of designing a microstrip patch antenna is to choose proper feeding position. The designed antenna showed comparatively better bandwidth after adjusting feeding position at 20 mm from the left edge of the substrate. Proposed microstrip patch antenna provides frequency agility, feedline flexibility, beam scanning bi-directional pattern.

Switchable frequency selective surface design for 2.45GHz ISM band

Mutual interference between adjacent wireless networks in indoor environment is becoming an important issue due to reducing the communication speed significantly. Isolating the wireless networks by using frequency selective surfaces (FSSs) can be an efficient solution for such interference problems. Isolating and non-isolating features are needed from FSSs due intensive usage of wireless communication systems. As a solution proposal, a novel switchable band stop FSS design is presented in this work. Switching feature is achieved by inclusion PIN diodes on the conducting path of circular loop element geometry. Eight number of PIN diodes are placed 45 degrees intervals in order to achieve polarization stability and desired switching performance. Analyzes of the proposed surfaces are executed with Ansoft HFSS v.15 software. According to the simulation results, desired frequency response is achieved.

Frequency selective surface with wide range of tunability

Recent communication systems demand multifunctional frequency selective surfaces (FSSs) which have more than one frequency response. As a solution proposal, a novel band stop periodic element geometry which can be tuned between 1.8 GHz-5.8 GHz frequency bands is presented in this work. Trapezoid loop geometry is used as an FSS geometry in order to achieve wide tuning range. Tuning feature is achieved by inclusion of varactor diodes between trapezoid loop geometries. Proposed structure allows independent tuning for vertical and horizontal polarizations. Analyzes of the proposed surfaces are executed with Ansoft HFSS v.15 software.

A New Hybrid Frequency Selective Surface Design in the 2.4GHz and 5.8GHz ISM Bands

With the advancement in telecommunication in indoor environment, the use of wireless technology for information systems has drastically increased. The intensive use of indoor wireless devices in 2.4GHz and 5.8GHz ISM bands causes mutual interference in neighboring networks which degrades the system performance. Secure personal communication within such wireless networks is also another important problem. A band-stop frequency selective surface (operating in the WLAN frequency band) which is attached to the walls of buildings can provide a solution for these interference and security problems. In this work, a new band-stop hybrid frequency selective surface element consisting of two circular looped type geometries is introduced which is capable of attenuating the incoming 2.4GHz and 5.8GHz ISM signals minimum 13dB for all polarizations and incident angles varies from 00 to 450. Besides, a periodic cell size (p=26,5mmm) which is almost one fifth of the first resonance wavelength is obtained.