Mazlina Esa

Bio: Mazlina Esa is an academic researcher from Universiti Teknologi Malaysia. The author has contributed to research in topics: Band-pass filter & Antenna (radio). The author has an hindex of 8, co-authored 81 publications receiving 311 citations.

Hilbert Curve Fractal Antenna for RFID Application

Abstract: The implementation of Radio Frequency Identification (RFID) involved two main components; the transponder and the reader. The transponder or simply known as a tag comprises of a programmable chip and an antenna. The antenna of the tag has to be of compact size. This paper presents a compact antenna based on the Hilbert curve fractal. The basic antenna is designed at 2.4 GHz, one of the frequencies used in RFID applications. The antenna geometry went through three iterations of fractal process. The designed antennas were then simulated using electromagnetic simulation software. It was observed that a compact Hilbert curve fractal antenna performs well at the desired frequency of operation.

Circular Collaborative Beamforming for Improved Radiation Beampattern in WSN

Abstract: 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.

Wideband and harmonic suppression method of Parallel Coupled Microstrip Bandpass Filter using centered single groove

Abstract: In this paper, a single grooved wideband Parallel Coupled Microstrip Bandpass Filter (PCMBF) with improved passband response and first harmonic suppression is described. The suppression of first harmonic spurious response was done by using a transmission zero frequency realignment method. The realignment was done by using a single groove with specific dimensions. The transmission zero and first harmonic frequencies can be realigned by varying a single groove size which is located at the center of the Parallel Coupled Microstrip Line (PCML). The wideband with harmonic suppression is achieved in three- stage PCMBF by using two single-stage bandpass filter of identical tight coupler with optimized grooved.

Compact UWB PCML bandpass filter with L- and C-shaped resonator

Abstract: A novel ultra-wideband (UWB) bandpass filter with four resonant modes is proposed based on a parallel coupled microstrip line (PCML) with L- and C-shaped resonators. The coupling factor of the PCML structure depends on the impedance of the feeding network. The PCML coupling factor can be enhanced by using a feeding network with smaller characteristic impedance. With an L-shaped feeding network and C-shaped middle microstrip line a non-uniform resonator is constructed with the first two resonant modes falling within the UWB. The other two resonant modes within the UWB can be obtained by adjusting the width of both the L- and C-shaped resonators. Overall the designed filter exhibits good UWB passband behaviour with insertion loss<−0.2 dB and group delay<0.15 ns.

Reconfigurable harmonic suppressed fractal dipole antenna

Abstract: A small active frequency reconfigurable Koch dipole antenna is presented with harmonic suppression capability. Open circuit stub is coupled to the antenna's 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.

Distributed and Collaborative Beamforming in Wireless Sensor Networks: Classifications, Trends, and Research Directions

Abstract: Distributed and collaborative beamforming (DCBF) scheme in wireless sensor networks (WSNs) is receiving new-found interest in recent times due to the rapid advancements in wireless technology and embedded systems. Although studies on distributed and collaborative beamforming have been carried out for more than ten years, the DCBF was initially considered impractical due to high complexity and hardly achievable requirements. It gained prominence only in the past few years as small wireless communication electronic sensors with high processing capability became easily available. Recent works showcasing distributed and collaborative beamforming as a suitable solution for 5G communication systems such as mm-wave communication and machine to machine communications has further ignited the interest in this research field. Motivated by these factors, this paper presents a survey on the research trends of distributed and collaborative beamforming in WSNs. We provide classifications of the DCBF research areas and conduct an extensive review of the various proposals which have appeared in the literature for each classification. This survey uncovered that majority of existing research can be broadly divided into four major research trends: beampattern analysis, power and lifetime optimization, synchronization, and finally, prototype design. The inherent features, constraints and challenges of each research category in the distributed and collaborative beamforming are presented and the lessons learned from the shortcomings of previous research are summarized. Finally, this paper has unveiled open research directions in the field of distributed and collaborative beamforming in WSNs.

Frequency and Pattern Reconfigurable Slot Antenna

Abstract: A novel frequency and pattern reconfigurable slot antenna is proposed. Slot antenna produces a bidirectional radiation pattern, thus a reflector is positioned behind of the antenna to generate a directional radiation pattern. Two switches are placed in the slot to produce three reconfigurable frequency bands: at 1.82 GHz, 1.93 GHz and 2.10 GHz. The introduction of four slits at the edge of the ground plane offers pattern reconfigurability. To tune the beam angles, three switches are inserted into each slit. By manipulating the phase of upper and lower slits in the ground plane, the proposed antenna is capable of reconfiguring its beam to three different angles at 0°, -15° and +15°. The simulated and measured results of reflection coefficient and radiation patterns are presented and compared.

A wide-frequency range AC magnetometer to measure the specific absorption rate in nanoparticles for magnetic hyperthermia

Abstract: Measurement of specific absorption rate ( SAR ) of magnetic nanoparticles is crucial to assert their potential for magnetic hyperthermia. To perform this task, calorimetric methods are widely used. However, those methods are not very accurate and are difficult to standardize. In this paper, we present AC magnetometry results performed with a lab-made magnetometer that is able to obtain dynamic hysteresis-loops in the AC magnetic field frequency range from 50 kHz to 1 MHz and intensities up to 24 kA m −1 . In this work, SAR values of maghemite nanoparticles dispersed in water are measured by AC magnetometry. The so-obtained values are compared with the SAR measured by calorimetric methods. Both measurements, by calorimetry and magnetometry, are in good agreement. Therefore, the presented AC magnetometer is a suitable way to obtain SAR values of magnetic nanoparticles.

Self-similar design for stretchable wireless LC strain sensors

Abstract: Stretchable sensors provide a foundation for applications that exceed the scope of conventional device technologies due to their unique capacity to integrate with soft materials and curvilinear surfaces. This article presents the implementation and characterization of a large-area stretchable wireless RF strain sensor, operating at around 760 MHz, based on the concept of self-similar design. It has an electrical LC resonant circuit formed by a self-similar inductor coil and a capacitor to facilitate passive wireless sensor. The inductance of the wireless sensor varies with the elongation of the PDMS substrate, so is the resonance frequency of the sensor that is detected using an external coil linked to a vector network analyzer. Finite element modeling was used in combination with experimental verification to demonstrate that the wireless strain sensor with 300 pm width can be stretched up to 40%. Self-similar structured coil incorporating variable inductance has been implemented to monitor the strain of artificial skin. Strain response of the stretchable wireless sensor has been characterized by experiments, and demonstrates high strain responsivity about 33.7 MHz/10%, which confirms the feasibility of strain sensing for biomedical and wearable applications. (C) 2015 Elsevier B.V. All rights reserved.

Multiobjective Beampattern Optimization in Collaborative Beamforming via NSGA-II With Selective Distance

Abstract: Collaborative beamforming is usually characterized by high, asymmetrical sidelobe levels due to the randomness of node locations. Previous works have shown that the optimization methods aiming to reduce the peak sidelobe level (PSL) alone do not guarantee the overall sidelobe reduction of the beampattern, especially when the nodes are random and cannot be manipulated. Hence, this paper proposes a multiobjective amplitude and phase optimization technique with two objective functions: PSL minimization and directivity maximization, in order to improve the beampattern. A novel selective Euclidean distance approach in the nondominated sorting genetic algorithm II (NSGA-II) is proposed to steer the candidate solutions toward a better solution. Results obtained by the proposed NSGA with selective distance (NSGA-SD) are compared with the single-objective PSL optimization performed using both GA and particle swarm optimization. The proposed multiobjective NSGA provides up to 40% improvement in PSL reduction and 50% improvement in directivity maximization and up to 10% increased performance compared to the legacy NSGA-II. The analysis of the optimization method when considering mutual coupling between the nodes shows that this improvement is valid when the inter-node Euclidean separations are large.