Mohd Nazri A. Karim

Log Periodic Fractal Koch Antenna for UHF Band Applications

In this paper, the design of Log Periodic Fractal Koch Antennas (LPFKA) is proposed for Ultra High Frequency (UHF) band applications. The procedure to design the LPFKA with three different numbers of iterations in order to reduce the antenna size is discussed. The Computer Simulation Technology (CST) software has been used to analyze the performances of the designed antennas such as return loss, radiation patterns, current distribution and gain. The antennas have been fabricated using FR4 laminate board with wet etching technique. Using fractal Koch technique, the size of the antenna can be reduced up to 27% when the series iteration is applied to the antennas without degrading the overall performances. Both simulated and measured results are compared, analyzed and presented in this paper.

Left Handed Metamaterial Design for Microstrip Antenna Application

This paper describes the design and simulation of the left-handed metamaterial structure incorporated with a single microstrip patch antenna. The combination of the modified square rectangular split ring (SRR) and the capacitance loaded strip (CLS) was used to obtain the negative value of permeability, mur and the negative permittivity, epsivr. From the simulation done, the gain of the antenna has been increased up to 4 dB. This had proven that the LH MTM can enhance the gain of the antenna.

Analysis of Fractal Koch Dipole Antenna for UHF band application

The fractal Koch curve is certainly one of the most popular and well known fractals. This paper discussed the analysis of the fractal Koch dipole array antenna (FKDA). The primary goals of this project is to proof of the concept of fractal Koch dipole array using log periodic technique to reduce the antenna size. This antenna is operating at ultra high frequency (UHF) band frequency from 300 MHz to 3 GHz. The analysis is based on the number of elements, degree of flare angle, current distribution, radiation pattern and gain of the antennas. The antenna has been simulated using Computer Simulation Technology CST 2008. The performance of the antennas has been observe and discussed in this paper.

Antenna array at 2.4 GHz for wireless LAN system using point to point communication

This paper described the design of microstrip patch antenna array operating at 2.4 GHz for Wireless Video using point to point communication system. The array of four by four microstrip square patch antennas with inset feed technique were designed, simulated, fabricated and measured with the aid of microwave office software. The simulation and measurement results are able to operate in ISM band for point to point communication system. The four by four arrays had a return loss of -8 dB with 16% bandwidth. The gain obtained from measurement is 14 dBi with 30deg half power beamwidth (HPBW) for H plane and 28deg for E Plane.

Electromagnetic Band Gap Structure for Planar Ultra Wide Band Antenna

An innovative technique involving the usage of a mushroom Electromagnetic Band Gap (mEBG) structure with an ultra wideband (UWB) antenna is reported in this work. A single unit of mEBG lattice is incorporated within a novel UWB antenna to perform the band rejection operation. The antenna can be fixed to reject or reduce the transmit power for any band within the UWB spectrums of frequencies through a careful design of this mEBG structure, thus solving the problems concerning interference and reducing the requirements for complex filtering electronics within the UWB devices.

A novel 2D Sierpinski gasket electromagnetic band gap structure for multiband microstrip antenna

A novel Sierpinski gasket high impedance EBG structures, based on two dimensional fractalized high impedance frequency selective structure (FSS) technique incorporated with vias for fractal/multiband microstrip antennas that radiate multiband frequencies is proposed in this paper. These structures which possess multi band-gapspsila characteristics, act as a means to suppress the surface waves effectively, thus improves the radiation pattern of the antenna. Models of these EBG structures have been developed and constructed on an inexpensive fire retardant-4 (FR4) board, using wet etching techniques. The parameters involved such as their shapes, width, length, the dielectric constant, the via position and measurement technique was studied and analyzed numerically and experimentally in order to merge out with the optimum designs. The results gained were very encouraging.

Microstrip antenna array's gain enhancement via Electromagnetic Band Gap structures

For a point-to-point communication system, an antenna array with high gain is essential and in this work, by incorporating electromagnetic band gap (EBG) structures at a specific location within the antennas peripherals, the gain of the antenna could be enhanced further. The EBG structures reduced mutual couplings between the adjacent patches thus make them radiates effectively. On the other hand, the EBG structures located at the edge of the antenna suppressed surface waves and prevent it from propagating to the edges, thus reduced the side and back lobes. This further enhances the front radiation characteristics of the antenna and also increased the gain. The techniques and guidelines on how to achieve the objectives is presented and the simulated and measured results complement each other.

Fractal Koch curve for UHF band application

This paper discussed the implementation of the planar dipole antenna using Koch curve structure at UHF band application. The 2nd iteration of Koch curve is arrange in series to reduced the height of the antenna and the ground plane is optimized during simulation. The simulation and measurement of return loss and radiation pattern have been discussed in this paper. The operating frequencies of the antenna is between 680 MHz to 730 MHz which can be used for received channel 57 until 62 in the UHF band frequency.

Modified Slotted Patch Electromagnetic Band Gap for Antenna Array Application

A modified slotted patch EBG structure has been investigated by measuring the forward transmission coefficient, S21. The thickness and dielectric constant of the substrate, the size and the gap of the elements in EBG structure has been modified and simulated to see the S21 value and followed by a discussion of the design and the evaluation of the structure itself. The simulation process was carried out using Microwave Office 2006 software. The 3 by 3 modified slotted patch EBG structures which has 11 mm x 11 mm elements size was fabricated using inexpensive fire retardant-4 (FR4) board, using wet etching techniques. The stimulated and measured S21 result shows the band gap of the structure, which are found to be between 2.24 GHz and 2.6 GHz at -20 dB. This structure is then incorporated into a 2 by 2 rectangular microstrip antenna array, operating at 2.4. The result shows that the radiation pattern improved with reducing side and back lobe with an extra gain of 1 dB compared with the antenna without the EBG structure.

Fractal Koch Dipole antenna for digital TV application

This paper describes the design of Fractal Koch Dipole array (FKDA) using log periodic technique for a sample 3 elements and design to operate at UHF band frequencies. The planar fractal Koch has been investigated in a planar log periodic dipole array in order to miniaturize its size using fractal technique. The simulation process was carried out using 3D simulator software CST 2008. The antenna structure was fabricated using Fire Retardant-4 (FR4) board, using wet etching techniques. The antenna is designed to operate at UHF Band (470 MHz- 806 MHz). The design procedures are elaborated in this paper. Both simulated and measured return loss S11 result exhibit similar characteristic which have same frequency range with a return loss magnitude less than -10 dB. The comparisons in term of gain and radiation pattern at a single frequency for simulated and measured result are discussed in this paper.