Mohd Khairul Hisham Ismail

Circular Collaborative Beamforming for Improved Radiation Beampattern in WSN

This paper presents a novel collaborative beamforming (CB) method of wireless sensor network (WSN) by organizing sensor node location in a circular arrangement. Appropriate selection of active CB nodes and cluster is needed each time to perform CB. The nodes are modeled in circular array location in order to consider it as a circular antenna array (CAA). This newly proposed circular collaborative beamforming (CCB) is further presented to solve two different objectives, that is, sidelobe level (SLL) suppression and first null beamwidth (FNBW). Analyses obtained are compared to those from previous work. The findings demonstrate a better CB performance of intelligent capability, and the difference is shown in normalized power characteristic.

Reconfigurable harmonic suppressed fractal dipole antenna

A small active frequency reconfigurable Koch dipole antenna is presented with harmonic suppression capability. Open circuit stub is coupled to the antennas terminal and the tapered balun. Three pairs of diodes are used for tuning purposes. The first prototype can be tuned at 722.7 MHz, 809 MHz, 1050.5 MHz, and 2361.5 MHz, respectively. At the same time the antenna can suppress undesired harmful harmonic frequencies of 2.4 GHz, 2.75 GHz, and 2.85 GHz. Simulation and measurement results obtained are in good agreement, which have confirmed the design concept.

Reduced Size Harmonic Suppressed Fractal Dipole Antenna with Integrated Reconfigurable Feature

The presence of harmonics are undesirable in many applications. Embedding fractal technology into an antenna makes it possible to reduce the physical size, increase its operating bandwidth and directivity. However, the technique can cause significant undesired harmonics problems associated with higher order modes of the antenna. This paper presents simulation and measurement work of a reduced size Koch fractal meander dipole antenna that has tunable capability of a reconfigurable operation within the observed range of 400Mhz to 3.5GHz. Each undesired harmonic is removed using one or two stubs. A microwave switch-able dipole antenna concept using Koch curve integrated with open circuit stubs is presented. The structure employed fractal technology that can eliminate higher order modes. With the utilization of Koch curves, the antenna size is reduced, but the number of higher order modes has proportionally increased. The size of the proposed antenna is small with regards to the operating frequency. The stub has improved the antenna performance.

Low profile printed antenna with a pair of step-loading for dual-frequency operation

Several techniques have been reported to reduce the size of a microstrip antenna having dual operating frequencies. A single low profile printed antenna which provides dual-band operation by having two-step slots loading embedded close to the radiating edge is presented. The ratio of the two frequencies can be well controlled by the aspect ratio of the step-loading dimension. Simulations performed on the designed antennas showed good dual band operation of f/sub 1/=1.575 GHz (GPS) and f/sub 2/= 1.8 GHz (GSM) with better than -10 dB achieved return losses. Satisfactory performance of dual matching are achieved when coaxial and EMC feeds are employed. The accuracy of the design is validated by using two different electromagnetic simulation softwares.

Broadband microstrip-to-parallel strip transition balun with reduced size

A tapered balun of broadband microstrip-to-parallel strip transition using triangular structure with linear transition for a dipole antenna is proposed. The original balun consists of linear profile with the size of one quarter wavelength for both the height and width. By studying the current distributions at balun surface, it can be reduced to 25%, 50%, and 75% from the original size. Measured results based on return loss and insertion loss for all baluns were found to be better than -10 dB and -3 dB, respectively, from 400 MHz to 3.5 GHz.

Intelligent circular collaborative beamforming array in wireless sensor network for efficient radiation

This article presents a novel method of optimizing sensor node location of wireless sensor network (WSN) in a circular arrangement. Appropriate selection of active collaborative beamforming (CB) nodes and cluster are needed each time to perform CB in WSNs. The nodes are modeled in circular array location in order to consider it as a circular antenna array (CAA). This newly proposed intelligent circular sensor node array (ICSA) is further presented to solve the problem. In particular, the selected collaborative nodes and the desired objective can vary significantly. Analyses obtained are compared to those from previous work. The findings demonstrate a better beamforming performance, and the difference is shown in normalized power gain.

Preliminary design of rectangular nano-antenna at PHz

This paper presents preliminary investigation and design of a rectangular nano-antenna that exhibits pentahertz (PHz) radiation. A plasmonic material is proposed as the substrate to be used for the antenna. The configuration chosen for the antenna radiating element is the rectangular structure. Numerical simulation based on FDTD has been performed on the designed antenna with varying substrate thickness. It was found that the antenna can operate well at the desired PHz frequency.

Experimental investigation of dual operation EMC-fed antenna having dual-perturbed structures

This paper presents the experimental investigation of a dual-operation antenna operating in the L-band region. The basis of the design is the basic rectangular patch. The patch is perturbed with embedded two L-section structures. The chosen frequencies are 1.575 GHz for Global Positioning System (GPS) satellite receiver and 1.8 GHz for Global System for Mobile (GSM). The antenna has been measured for its one and two-port performance. Optimum feed location was determined to be at the 14.5 mm location from the antenna edge. It was found that the antenna operates well near the designed frequency of operations.

Narrowband-to-Narrowband Frequency Reconfiguration with Harmonic Suppression Using Fractal Dipole Antenna

Harmonic suppressed fractal antenna with switches named TMFDB25 is developed to select desired frequency band from 400 MHz to 3.5 GHz. The radiating element length is changed to tune the operating frequency while the stub is used to eliminate the undesired harmonic frequency. The balun circuit is reduced by 75% from the original size. The antenna is built on a low loss material. It has the ability to select a single frequency out of fifteen different bands and maintain the omnidirectional radiation pattern properties. Furthermore, the antenna is designed, built, and tested. Simulation and measurement results show that the antenna operates well at the specific frequency range. Therefore, the antenna is suitable to be used for switching frequencies in the band of TV, GSM900/1800, 3G, ISM 2.4 GHz, and above.

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.