Khairun Nidzam Ramli

Design and analysis of UC-EBG on mutual coupling reduction

A new Uniplanar Compact Electromagnetic Bandgap (UC-EBG) structure is proposed in order to achieve a smaller unit cell operating at lower frequency stop band. Its design is detailed and an experimental result is presented. The property of the proposed UC-EBG is compared with the distorted uniplanar compact EBG (DUC-EBG). The application of the proposed UC-EBG is examined. A parametric study on various thicknesses of dielectric substrate is also discussed.

HYBRID COMPUTATIONAL SCHEME FOR ANTENNA- HUMAN BODY INTERACTION

A new hybrid method of moments (MoM)/finite-difference timsdomain (FDTD), with a sub-gridded finite-difference timedomain (SGFDTD) approach is presented. The method overcomes the drawbacks of homogeneous MOM and FDTD simulations, and so permits accurate analysis of realistic applications. As a demonstration, it is applied to the short-range interaction between an inhomogeneous human body and a small UHF WID antenna tag, operating at, 900MHz. Near-field and far-field performance for the antenna are assessed for different placements over the body. The cumulativt. distribution function of the radiation efficiency and the absorbed power are presented and analyzed. The algorithm has a fivefold speed advantage over fine-gridded FDTD.

Design Sierpinski Gasket Antenna for WLAN Application

This project mainly discussed on designing and fabricating the antenna using fractal concept to obtain the dual band resonant frequency at 2.4 GHz and 5.8 GHz for wireless local area network (WLAN) application. The application of fractal geometry can be used to miniaturize the antenna due to their self-similarity and this project focusing on designing the Sierpinski gasket antenna for first iteration. The antenna had been simulated using CST microwave studio, while the fabricated antenna had been tested using network analyzer. The results of both antenna simulation and measurement are in good agreement with the design expectation. The antenna was fabricated on printed circuit board (PCB) using epoxy/ glass (FR- 4) substrate with 30cm by 30cm metallic copper ground plane.

The Complete Surface-Current Distribution in a Normal-Mode Helical Antenna

An investigation of the surface-current distribution in a normal-mode helical antenna (NMHA) is reported. This enables precise prediction of the performance of normal-mode helical antennas, since traditional wire-antenna simulations ignore important details. A Moment-Method formulation was developed, using two geometrically orthogonal basis functions to represent the total nonuniform surface-current distribution over the wire of the helix. Extended basis functions were used to reliably treat the discontinuity of the current at the free ends. A surface kernel was used all over the antennas structure. The surface-current distribution was computed for different antenna geometries, such as dipoles, loops, and helices. For helices, the currents were investigated for different pitch distances and numbers of turns. It was found that the axially-directed component of the current distribution around the surface of the wire was highly nonuniform, and that there was also a significant circumferential current flow due to inter-turn capacitance, both effects that are overlooked by standard filamentary current representations using an extended kernel. The impedance characteristic showed good agreement with the predictions of a standard filamentary-current code, in the case of applied uniform excitation along the local axis of the wire. However, the power-loss computations of the present technique produce significantly different results compared to those well-established methods when the wires are closely spaced.

Compact UWB wearable antenna with improved bandwidth and low SAR

SAR calculation for UWB textile antenna is reported in this paper. This paper presents simulation results of the antenna performance at the conditions of free space and placement at a distance from a portion of a human body. A summary of measurement results of the return loss of the antenna is also included. The simulated S11 parameter shows that the antenna operates within the range 2.25 GHz and 12.19 GHz. The measured return loss has shown that the antenna can operate within 3.04 GHz-10.3 GHz giving a bandwidth of 108%. The performance antenna near to a human body has been simulated and examined. The SAR (10g) has been evaluated using a four-layer body model.

Probability of symbol error of Multi Slot Amplitude Coding (MSAC) technique in optical communication system

This paper reports a novel method on the probability of symbol error estimation for high speed Multi Slot Amplitude Coding (MSAC) technique in optically amplified communication system. The system setup is based on simple intensity modulation and direct detection scheme which is cost effective. In this proposed method, possibility of symbol error is estimated based on individual probability density function of particular signal level and slot of MSAC symbol. This proposed method is validated by the symbol-to-symbol error technique.

Miniature dual-frequency half planar inverted F-L-antenna for WLAN/cellular applications

A reduced size miniature dual-bands planar inverted F-L antenna for WLAN and cellular applications is achieved by applying the magnetic wall concept. The proposed antenna provides a 12% and 9.3% bandwidth at S11 ≪ −10 dB for 2.5 GHz and 5.2 GHz WLAN bands that completely encompasses the desired ISM2400 and IEEE802.11a standards. The proposed antenna is minimised to a volume of 30 × 15 × 8 mm, which is about 0.25 wavelengths at the centre frequency 2450MHz, while the antenna height achieved was about λ/15 at the centre frequency. The experimental and simulated return losses of the proposed antenna on a small finite ground plane (30 × 15mm) show good agreement. The simulated gains and far field radiation patterns are presented to fully characterize the performance of this antenna.

Rectangular patch with partial ground wearable antenna for 2.4 GHz applications

This paper presents an investigations of antenna performances and under bent condition on denim substrate material. The antenna consists of a rectangular patch with triangular slot cut at the center and a partial ground plane. The proposed antenna design working on 2.4 GHz wearable applications and achieves an impedance bandwidth from 1.948 - 4 GHz. The measured result are compared with simulated results and good agreement is achieved. The proposed antenna is a suitable candidate for wearable applications.

Ultra–Wideband Antenna Enhancement with Reconfiguration and Notching Techniques Evaluation

Many researchers have proposed notches and strips for band ‎enhancement or ‎interference reduction of ultra‎–‎wideband (UWB) antenna. Previous studies ‎illustrated the ‎advantage of using slot technologies and strips to change the ‎antenna impedance matching. ‎This study presents a comprehensive overview of ‎the performances of reconfiguration techniques on UWB ‎antennas based on filtering ‎and matching band. Several studies are considered, and ‎the performance of ‎antennas designs that applied slot, strips, parasitic ‎stubs, and spiral loop ‎resonators are compared. Unwanted bands, ‎such as WLAN and WiMAX ‎systems, are interfered with UWB communications. ‎The notches are used for ‎either band rejection or bandwidth enhancement. ‎Moreover, a hexagonal UWB ‎patch antenna with the coplanar waveguide is demonstrated in this paper. The ‎improvement of the UWB antenna bandwidth is realised by incising the patch ‎size. Loading two L-shape strips on the radiation patch achieved band rejection at 5.15 GHz. The simulated parametric study represents different results achieved with ‎different side–‎patch lengths. The best achievements of the proposed design are the ‎UWB bandwidth from 2.8 GHz to 11.5 GHz, and the radiation gain of 4 dB at ‎‎5.8 GHz. Good omnidirectional radiation patterns observe on E-plane by ‎bidirectional patterns provide on H-plane. Finally, the performance and ‎implementing the studied UWB antennas are discussed in details.‎

A COMPACT CPW FED UWB ANTENNA WITH QUAD BAND NOTCH CHARACTERISTICS FOR ISM BAND APPLICATIONS

A quad band-notched compact ultra-wideband (UWB) patch antenna to operate on the industry, scientific, and medical (ISM) bands are presented in this study. A modified hexagonal patch vertex-fed with a coplanar waveguide (CPW) is fabricated on an FR-4 substrate with size of 43× 28× 1.6 mm3 and fractional bandwidth of 133%. The compact antenna operates at a frequency of 2.45 GHz, which is often required for the efficient performance of ISM utilisation. The existing bands share the same bandwidth as that of UWB systems. Therefore, a notched band at 3GHz for worldwide interoperability for microwave access (WiMAX), and a further resonance band at 2.45 GHz for ISM are generated by implementing a meander-line strip on the antenna. Furthermore, the design demonstrates a couple of F-shaped slots and an inverted diamond-shaped slot on the patch. Moreover, a pair of Jshaped slots is loaded on the ground plane. The downlink C-band, wireless local area network (WLAN), and downlink X-band are rejected by the proposed slots, respectively. The current distribution, gain, radiation efficiency, and quad notched parameters of the proposed antenna are studied by using CST software. The demonstrated prototype covers an ISM band at (2.2 GHz–2.6 GHz) with a return loss of −23.45 dB and omnidirectional radiation patterns. A good agreement is observed between measured and the simulated results. This paper has presented a solution for both interference and miniaturised issues.