Osman Ayop

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.

Design and Analysis of Microstrip Reflectarray Antenna with Minkowski Shape Radiating Element

This paper describes the design and analysis of a Microstrip Re∞ectarray Antenna (MRA) with Minkowski shape radiating element at frequency of 11GHz. This structure has been analyzed and compared with the traditional re∞ectarray element (square element patch). It is found that this antenna array has lower sidelobe level (SLL) characteristic which is down to i25dB. This MRA has maximum realized gain of 29.6dB with half-power beamwidth (HPBW) of 3.7 - . The validation for the proposed MRA is done by comparing the simulated and measured E-plane radiation pattern. A very good agreement is found from the comparison between simulation and measurement.

Triple-band printed dipole antenna with single-band AMC-HIS

In this paper, the designed of triple-band printed dipole antennas are incorporated with single-band artiflcial magnetic conductor (AMC). The single-band AMCs are designed to resonate at 0.92GHz, 2.45GHz and 5.8GHz using TLC-32 dielectric substrate. The four important parameters in AMC high impedance surface (HIS) design are also described in this paper. By simulating a unit cell of the AMC structure using a transient solver in Computer Simulation Technology (CST) software, the characteristic of the AMC can be characterized. The AMC condition is characterized by the frequency or frequencies where the magnitude of the re∞ection coe-cient is +1 and its phase is 0 - . It has high surface impedance (Zs) and it re∞ects the external electromagnetic waves without the phase reversal. This characteristic of AMC enables the printed dipole to work properly when the antenna with AMC ground plane (GP) is directly attached to the metal object. The performances of the antenna with and without AMC structure as a ground plane to the antenna such as return loss, realized gain, radiation e-ciency, radiation pattern and directivity are studied. Reported results show that the performances of the antenna are improved. Hence, the designed dipole tag antenna can be used for metal object identiflcations when the AMC structure is introduced as a ground to the antenna. The properties of the antenna are also remained well when the size of metal plate attached to them is increased.

Triple band circular ring-shaped metamaterial absorber for x-band applications

This paper presents the design, fabrication, and measurement of triple band metamaterial absorber at 8GHz, 10GHz and 12GHz which are in the X-band frequency range. The unit cell of the metamaterial consists of three concentric copper rings at difierent radii, printed on 0.8mm thick FR4 substrate in order to obtain triple resonant frequencies. The highly symmetrical ring structure in nature makes this absorber insensitive to any polarization state of incident electromagnetic (EM) waves for normal incident waves. The proposed structure is capable to operate at wide variations angle of incident wave. The simulated result shows that the triple-band metamaterial absorber achieves high absorbance for normal incident electromagnetic waves of 97.33%, 91.84% and 90.08% at 8GHz, 10GHz and 12GHz, respectively, when subjected to normal incident electromagnetic. With metamaterial absorber maintaining 50% of absorbance value, the corresponding full width half maximum (FWHM) are 5.61%, 2.90% and 2.33%. The operating angles in which the metamaterial structure can maintain 50% absorbance at TE mode and TM mode are 67 - and 64 - , respectively. The experimental result verifles that the absorber is well performed at three difierent resonant frequencies with absorbance greater than 80%.

Analysis of mushroom-like electromagnetic band gap structure using suspended transmission line technique

In this report, an analysis of a mushroom EBG (mEBG) structure using method of suspended transmission line has been discussed. This structure consists of nine elements of metallic patch grounded with metal. The parametric studies are patch width, substrate thickness, relative permittivity, gap width between adjacent patch and the size of via radius. These studies involve the bandstop and bandpass characteristic of the electromagnetic bad gap structure. The result shows that the bandstop frequency of mEBG structure is affected when varying each of the parameters. This is due to the changes of the equivalent LC network of the mushroom-like EBG structures. By increasing the value of the patch width and relative permittivity, the operating frequency and bandwidth will decay due to the increment of the total capacitance value. Varying the gap between adjacent patches does not give significant effect to the band gap frequency because it only changes the value of fringe capacitor, which is very small compared to the overall capacitances. Increasing the size of via radius will increase the frequency band gap and bandwidth due to the reduction of total capacitance. Lastly, increasing the substrate thickness will reduce the operating frequency however increase the bandwidth. This is because the value of inductor increases more than the increment of the total capacitance.

A dual band gap slotted patch electromagnetic band gap for dual band microstrip antenna

This paper described the design of the dual band gap slotted patch EBG structure. By introducing double L slot into each EBG patch, a smaller rectangular patch has been introduced in each EBG patch resulting to the achievement of the second stop band frequency. The comparison between mushroom EBG structures has been investigated. The parametric study has been done involve the analysis of patch width effect of EBG and gap effects between elements in the EBG. The operating frequencies are 2.4 GHz ISM and 5.8 GHz UNI band. The slotted patch EBG structure and mushroom EBG structure have been simulated by using 3D simulation CST software. The design is based on FR4 board with has relative permittivity 4.7 and tangent loss 0.019.

Planar Dipole Antenna with and without Circular Parasitic Element

This paper describe the design of planar dipole antenna with circular parasitic element. The comparison between the planar dipole antenna with and without parasitic element has been presented followed by a discussion of the design. The simulation process was carried out using microwave office and CST software. These antennas were fabricated using inexpensive Fire Retardant-4 (FR4) board, using wet etching techniques. The S11 result shows the operating frequency is between 2.08 GHz and 3.48 GHz for planar dipole antenna with parasitic element. For planar dipole antenna without parasitic element, two ranges of operating frequency is between and 2.1 GHz and 3.08 GHz and another one operational frequency was found at 4.04 GHz and 4.98 GHz.

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.

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.

Circular Polarization Array Antenna

A 4 by 4 circular polarization microstrip square patch array antennas based on quarter-wave impedance matching and T-junction power divider were designed, simulated, fabricated and measured. The patch type used to generate circular polarization is corner-truncated square microstrip antenna. All the designs met the WLAN circular polarization point to point application set by IEEE802.11b standard and operates in ISM band at 2.4 GHz. Analysis shows that larger arrays provide better return loss, more bandwidth, smaller beam width and higher gain comparing with single element antenna as a reference. A 4 by 4 circular polarization square patch arrays have a side lobe IEEE802.11b standardes. This is due to mutual coupling effects occurred in arrays. All the measurement results show a good return loss more than -15dB. These indicate a good impedance matching is achieved in designing the patches and feeds.