M. K. Suaidi

Impedance modeling for a unit cell of the square loop frequency selective surface at 2.4 GHz

This paper presented an impedance modeling of the Equivalent Circuit (EC) for a unit cell of the square loop Frequency Selective Surface (FSS) structure. The unit cell of the square loop FSS is designed and simulated using the CST Microwave Studio software at 2.4 GHz based on industrial, scientific and medical bands (ISM) standard. The square loop FSS is simulated without FSS, with square FSS and FSS with slot. The investigation has been done on the length of substrate (s), width of substrate (w), length of square FSS (a) and length of slot (b). Imaginary (Im) component of EC has been modeled based on physical parameters of the square loop FSS in wavelength. EC gives a simple alternative method in FSS analyses which are useful for quickly predicting the performance of FSS.

The performance comparison of printed dipole antenna with two different structures of AMC ground plane

The performances of the triple-band meandered dipole antenna backed by two different Artificial Magnetic Conductor (AMC) structures are discussed in this paper. Two kinds of AMC structures are presented namely rectangular-patch with rectangular slot and rectangular-patch with slotted rectangular and I-shaped slot. The AMCs are designed to operate at 0.92GHz and 2.45GHz. The performances of the antenna with and without the dual-band AMC ground plane are investigated in terms of return loss, realized gain and power received. It clearly shows that the printed dipole antenna has a lower gain compared to the printed dipole antenna with high-impedance structure ground plane (GP). Furthermore, the received power of the dipole antenna backed by the 2×2 rectangular-patch with slotted rectangular and I-slot AMC receives a slightly higher power compared to the dipole antenna backed by the 2×2 rectangular-patch with rectangular slot AMC.

Concurrent MAC with Short Signaling for multi-hop Wireless Mesh Networks

The IEEE 802.11 Distributed Coordination Function (DCF) Medium Access Control (MAC) protocol continues to suffer from throughput degradation when directly applied in multi-hop Wireless Mesh Network (WMN). The Request-to-Send/Clear-to-Send (RTS/CTS) signaling partially solved hidden node problems however the exposed node problems remain unaddressed. The IEEE 802.11 MAC does not allow the exposed nodes to initiates its transmission for the entire duration of ongoing transmission over multi-hop network leads to throughput degradation. Moreover, the amount of needed signaling packets takes place at every hop reduces the overall multi-hop throughput significantly. This project proposes a set of enhancement to the existing IEEE 802.11 DCF MAC by enabling concurrent transmission by the exposed nodes and reduces the amount of signaling packets (CMAC-SS) required at every hop until the data packet reaches its destination. Analytical models are developed and simulated over quasi-static Rayleigh fading channel. The multi-hop network performances are evaluated in terms of throughput and delay. The CMAC-SS protocol outperforms the existing IEEE DCF MAC with more than 14% increase in overall throughput of multi-hop WMN.

The mitered and circular bend method of Butler Matrix design for WLAN application

A beamforming network using Butler Matrix technique at WLAN application is presented. This paper describes the design, simulation and fabrication of a 4 times 4 Butler Matrix for the 2.4 GHz (WLAN). A Butler Matrix is a multiport component which when loaded with radiating elements enables production of a beam of microwave energy in a specified direction in transmission line, dependent upon which input port is activated. The circular and mitered bends was applied in designing the beamforming network based on Butler Matrix technique. Results from simulation and fabrication is then being compared in term of return loss (Sii), transmission coefficient (Sji), isolation (Sij) and the phase difference (beta) between each port (4times4). The measurement patterns result achieved by this project is then compared with the simulation result. The design has been measured by using Advantest R3767 Network Analyzer.

The study of X-circular polarized by using double circle slot at 2.4 GHz

This paper discussed the study on the circular polarized patch antenna by using double circle slot technique in single patch and X-polarized patch antenna. The operating frequency for the proposed antenna is 2.4GHz with 29.86MHz of bandwidth and return loss is -34.85dB. The antenna had been designed and simulated using CST Microwave Studio simulation software. The circular polarization (CP) operation was obtained by implemented double circle slot at center of circular patch antenna. Based on simulation, it obtained a gain of 6.79dB with minimum axial ratio (AR) is 1.75dB and a 3db AR bandwidth of 214.7MHz.

Dual Linearly Polarized Microstrip Array Antenna

Recently, Multiple Input Multiple Output (MIMO) has become popular research topic among researchers for development of a new wireless communications technology. The system capacity can be increase with deployment of MIMO technique in the communications system. Thus, the used of high frequency bandwidth can be avoid since this method required high cost implementation. High transmitted power also is not required because all transmitted branch will transmit same power in MIMO system. There are three major studies in MIMO which are research on array antenna and adaptive signal processing, research on information theory and coding algorithm and research on MIMO channel propagation (Nirmal et al., 2004). MIMO channel capacity can be increase with the increase of number of transmitter and receiver. When the number of the antennas used is fixed, the channel capacity is related to the spatial correlation and the diversity gain from antenna spacing configuration at 17

Investigation of broadband inverted suspended rectangular patch linear polarized antenna

In this paper, broadband inverted suspended linear polarized antennas with operating frequency at 2.4GHz for Wireless Local Area Network (WLAN) application are designed. Various shapes of slot are added on the inverted suspended rectangular patch to investigate the effect of the antenna performance. The antennas are designed by using L-probe amendment with inverted suspended rectangular patch, where this approach is used to enhance the bandwidth and gain of the antennas. The simulation is done by using Computer Simulation Technology (CST) software. The bandwidths for the inverted suspended linear polarized antennas with different shape of slot are more than 200MHz, which meet broadband application. Besides, the axial ratio for each antenna is above 3dB.

Application of Genetic Algorithm to the Design Optimization of Complex Energy Saving Glass Coating Structure

Attenuation of GSM, GPS and personal communication signal leads to poor communication inside the building using regular shapes of energy saving glass coating. Thus, the transmission is very low. A brand new type of band pass frequency selective surface (FSS) for energy saving glass application is presented in this paper for one unit cell. Numerical Periodic Method of Moment approach according to a previous study has been applied to determine the new optimum design of one unit cell energy saving glass coating structure. Optimization technique based on the Genetic Algorithm (GA) is used to obtain an improved in return loss and transmission signal. The unit cell of FSS is designed and simulated using the CST Microwave Studio software at based on industrial, scientific and medical bands (ISM). A unique and irregular shape of an energy saving glass coating structure is obtained with lower return loss and improved transmission coefficient.

Transmission of Microwave Signal through Metal-Oxide Thin Film of Energy Saving Glass Using Different Shape of Frequency Selective Structure

Metal oxide thin films are widely used for energy saving glass coating. This coating has the ability of blocking the infrared signal while being transparent to other visible part of the spectrum. However, there is one critical disadvantage of this metal oxide coating which it attenuates useful radio frequency and microwave signal such as GSM mobile signal, personal communication, GPS signal through them. These important microwave signals are fall within the range of 800 MHz to 2200 MHz. Frequency selective structure has been applied to solve the attenuation of microwave signal. With the adding of frequency selective structure, it can bring huge improvement of the transmission loss through it. Computer simulation using CST software is used to investigate the transmission loss through the metal oxide coated glass. The frequency selective structure will be etched out from the metallic oxide coated on the glass. Results showed that different shape of the structure will have different peak transmission loss through the glass. When cross dipole and circle shape been simulated using CST software, it can clearly see that the transmission lost and peak frequency had changed drastically. Then, triangle and pentagon shape also have different transmission through it. In addition, conductivity and electrical properties of coated metal oxide thin film is also very important. The transmission through the different ohmic sheet resistance of metal oxide thin film was also investigated. The sheet resistance value was obtained from the reported experimental results. Simulated results showed that full width half maximum, maximum transmission loss and peak frequency loss was very much dependent on the metal oxide sheet resistance. Therefore, the control of the thickness and oxygen content in metal oxide thin film are very much important to optimize the transmission loss through it for energy saving glass applications.

Investigation of single and two notch on circular polarized patch antenna

This paper presents the investigation on the effect of two main parameters of a circular polarized patch antenna by using notch technique. The results show that this technique can improve the performance of return loss and gain of the patch antenna. The operating frequency of the proposed antenna is 2.4GHz with 32.66MHz of bandwidth and return loss is -49.63dB. The antenna had been designed and simulated using CST Microwave Studio simulation software. The circular polarization (CP) operation was obtained by implementing double circle slot at 45° orientation on the circular patch antenna. Based on simulation, the antenna gain of 6.36dB with minimum axial ratio (AR) of 1.43dB and 3dB AR bandwidth of 180.54MHz was achieved.