S. A. Hamzah

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.

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.

Evaluation on optimum geometrical of linear node array for self-organization in a wireless sensor network

A novel approach which combines an adaptive linear antenna array and a non-linear function of particle swarm methodology has been developed to estimate the performance of antenna gain in the presence of sensor node geometry location uncertainties. The randomness of sensor nodes geometry location can produce higher energy consumption as it permits the generation of high peaks in radiation beampattern performance. It is shown in simulations that the method is powerful in term of required main beam angle and side lobe level reduction. Results indicate an improve performance in term of radiation beampattern and motivate exploiting this newly-developed optimum method in node geometrical location strategies of WSNs.

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.

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.

Reduced size harmonic suppressed fractal dipole antenna with integrated reconfigurability

Reduced size frequency reconfigurable fractal dipole antenna with harmonic suppression capability is presented in this paper. The proposed antenna consists of a narrow band radiating element, stub-filters and taper balun, producing harmonic suppression characteristics. In order to investigate the antenna performance, an extensive simulation (by CST and HFSS) and measurement works have been carried out. This technique is suitable for creating reconfigurable antenna with harmonic suppression or for single band antennas.

Enhancement factor for electrical near-field on perturbation slit nano structure with peak resonance at 30 THz

This paper presents the investigation carried out on electrical near-field enhancement of a perturbation slit of a rectangular radiating nanostructure. The operating frequency is defined at thermal radiation spectrum from 20 THz to 40 THz. Single and two identical perturbation slits are introduced at the center of the nano structure. It was found that the former is able to enhance the near-field distribution to 120 times while the latter is approximately 80 times. In addition, the splitting of the near-field amplitude resembles that of an energy divider.