Mohd Fairus Mohd Yusoff

Hilbert Curve Fractal Antenna for RFID Application

The implementation of radio frequency identification (RFID) involved two main components; the transponder and the reader. The transponder or simply known as a tag comprises of a programmable chip and an antenna. The antenna of the tag has to be of compact size. This paper presents a compact antenna based on the Hilbert curve fractal. The basic antenna is designed at 2.4 GHz, one of the frequencies used in RFID applications. The antenna geometry went through three iterations of fractal process. The designed antennas were then simulated using electromagnetic simulation software. It was observed that a compact Hilbert curve fractal antenna performs well at the desired frequency of operation

Compact Dual-Port Polarization-Reconfigurable Antenna With High Isolations for MIMO Application

This letter proposes the design of a dual-port microstrip patch antenna with polarization reconfigurability features. The reconfigurability is realized through the modification of the feed network. The antenna consists of a circular-shaped patch on the upper substrate as a radiating element, and a coplanar-waveguide (CPW) slotline transmission located in the ground plane. To obtain a good impedance matching, the CPW slotline is terminated with a tapered impedance transformer. Dual ports are constructed by utilizing the CPW feeding structure and the odd and even feedline modes of the CPW. Four p-i-n diodes are used as switches to alter the flow of the current. The p-i-n diodes are placed on the CPW transmission slotline interjunction. Consequently, the excited polarization can be altered and determined, depending on the switch configurations. This antenna demonstrates good port-to-port isolation and a compact structure and is suitable to be used in systems that operate in a wireless local area network (WLAN) frequency band.

Wideband Antenna with Reconfigurable Band Notched Using EBG Structure

A wideband antenna with band notch function using electromagnetic bandgap (EBG) structure is proposed. The antenna is capable of reconfiguring up to three band notch operation. Three EBGs are aligned underneath the feed line of the wideband antenna. The transmission lines over EBGs unit cells perform as a band stop filter. A switch is placed on each of the EBG structure, which enables the reconfigurable band stop operation. The simulated and measured reflection coefficients, together with the radiation patterns, are shown to demonstrate the performance of the antenna.

Ultra-wideband antenna with tunable Artificial Magnetic Conductor

This paper presents a tunable Artificial Magnetic Conductor (AMC) unit cell design by means of four copper strips. With the inclusion of copper strips, the initial reflection phase of dual band AMC changes from 2.45 GHz and 5.8 GHz to single frequency of 3 GHz. To facilitate the tunable function on antenna performance, an Ultra-Wideband (UWB) antenna has been designed and analyzed. Performance comparison is carried out with and without incorporation of AMC. The AMC is tuned to change frequency using copper strips. Result in terms of reflection phase, return loss and radiation pattern are discussed.

Design of Microwave Direct-Coupled Cavity Waveguide Filter for VSAT Communication at C-Band Using MathCAD Software

Waveguides are robust structure and handle high power well, compared to transmission line filter such as coplanar lines, microstrips and striplines. As such, it is used in a very small aperture terminal (VSAT) communication system operating at C-band. In this paper, the mathematical computations for the design dimensions of a direct-coupled cavity waveguide bandpass filter are implemented using MathCAD mathematical software, based on the insertion loss method. Firstly, the design specifications are set. These include operating frequency, operating bandwidth, minimum attenuation, ultimate attenuation, and type of filter response. An optimum number of filter orders will be determined. The cavity waveguide filter consists of vertical inductive diaphragm of circular holes, which represent the cavity. Computation of the filter performances in terms of the insertion and return losses were successfully achieved. Comparisons with electromagnetic simulations were also made. Good correlation can be observed between the computed performances using MathCAD and simulated performances using simulation software

Analysis of Wideband Antenna Performance over Dual Band Artificial Magnetic Conductor (AMC) Ground Plane

A Coplanar Waveguide (CPW) wideband antenna operates from 2.69 GH to 6.27 GHz which act as reference antenna (RA) has been designed. A Dual Band AMC (DBAMC) unit cells have been proposed to operate at 2.45 GHz and 5.8 GHz. AMC is a metamaterial which mimics the behavior of zero reflection phase of Perfect Magnetic Conductor (PMC) at resonance frequency which not naturally existed in nature. Subsequently the antenna is incorporated with AMC unit cell, herein referred as Antenna with Dual Band AMC (ADBAMC). The DBAMC succesfully excites additional resonance at 2.45 GHz outside the initial operating range of standalone CPW wideband antenna. Incorporation of DBAMC to antenna achieves back lobe suppression at 2.45 GHz and 5.8 GHz. The overall average gain of AMC incorporated antenna is improved from 2.69 to 6.29 GHz as opposed to the standalone reference CPW wideband antenna. Study of surface current is also presented and discussed.

C-band direct-coupled cavity waveguide filter design using MathCAD software

This paper presents the design of a direct coupled cavity waveguide bandpass filter operating at C-band, with the aid of a mathematical software. The application chosen is for the receiving circuitry of a high power communication system. The basis of the design is the insertion loss method. The direct-coupled cavity bandpass filter can handle high power compared to transmission line filter such as microstrip and striplines. The design procedure starts by computing the relevant prototype parameters based on the required specifications. The design specification includes the operating frequency, cut-off frequency, ultimate attenuation, minimum attenuation, and response type. The computation involves varying the number of orders and determining the optimum number of order. The design focuses on the equi-ripple response. The dimensions of a rectangular waveguide having inductive diaphragm with circular holes were then designed. The inductive diaphragm represents the cavity. Computation of the filter performances in terms of the insertion and return losses were successfully achieved. Good agreements between the theoretical computations and electromagnetic simulations have been achieved.

Indoor Channel Capacity Measurement of 2 x 2 MIMO Polarization Diversity Antenna

With the rapid growth of communications via the Internet, the need for an effective firewall system which has not badly affect the overall network performances has been increased. In this paper, a Field Programmable Gate Array (FPGA) -based firewall system with high performance has been implemented using Network FPGA (NetFPGA) with Xilinx Kintex-7 XC7K325T FPGA. Based on NetFPGA reference router project, a NetFPGA-based firewall system was implemented. The hardware module performs rule matching operation using content addressable memory (CAM) for higher speed data processing. To evaluate system performance, throughput, latency, and memory utilization were measured for different cases using different tools, also the number of rules that an incoming packet is subjected to was varied to get more readings using both software and hardware features. The results showed that the designed firewall system provides better performance than traditional firewalls. System throughput was doubled times of the one with Linux-Iptables firewalls.

Reflectarray antenna performances using combination of rectangular and Jerusalem unit cells at 5.2 GHz

The need for high gain antennas becomes essential, especially for radar and long distance communication. The aim of this study was to design a reflectarray antenna using combination of rectangular and Jerusalem unit cell at 5.2 GHz. Through simulation, it is found that for a 20 × 20 unit cell elements, the performances of combination unit cell exhibits marked improvement compared to reflectarray antenna using Jerusalem unit cell. Additionally, the performances of reflection coefficient, S11 and gain of the combine unit cell with conventional rectangular reflectarray antenna exhibit very few changes except for side lobe level that show appreciable decrement from −16.2dB to −21.8dB. The result indicates that there is a possibility of improving antenna performances by using combination of various unit cells.

Novel nano structure for green energy harvesting at 10 μm thermal radiation

n recent years, the potential of renewable green energy sources has been extensively studied. The proven technology which is photovoltaic solar cells strictly depends on daylight and produces low-efficiently. To overcome the restrictions, one technology studied is through harvesting the thermal radiation energy which can provide a 24-hour energy source. The continuity of energy sources promises very good energy conversion especially for military applications. This article presents a new structure that can harvest the abundant thermal radiation energy into usable energy at the wavelength of 10 μm. A rectangular structure with a perturbation slit was designed to integrate with a rectifier circuit for green energy conversion. The slit tunnel junction guided the electromagnetic field in to a junction where the energy could be collected and converted. An enhancement factor of approximately 110.6 can be achieved by a perturbation slit length of 1.0 μm. The results extracted from the proposed design promise a better candidate to overcome the disadvantages of photovoltaic solar cells for energy harvesting devices.