Mazlina Esa

Hilbert Curve Fractal Antenna for RFID Application

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

Microstrip U-shaped dual-band antenna

This paper presents the design of a dual-operation antenna having microstrip configuration. The chosen dual-operation frequencies are that of indoor mobile system; 0.9 GHz and 2.4 GHz. The design starts with a microstrip square patch antenna being fed by a coaxial probe from underneath the substrate. An FR4 material was used for the design. The antenna was first cut into U-shaped configuration to operate at lower frequency of 0.9 GHz. A smaller square patch was then separately designed to operate at the lower frequency of 2.4 GHz. The feeding is similar, i.e coaxial probe feed. Successive simulations were performed on both antennas. Upon achieving a good impedance match at the input of the U-shaped antenna, the antenna was then integrated with the separately designed smaller square patch element. The smaller patch was coupled to internal region of the U-shaped configuration. The integrated U-shaped antenna was then optimized through successive cycles of simulations in order to operate well at the two frequencies of operations.

Equivalent J - Inverter Network Parameters Analysis and Cancellation of Spurious Response of Parallel Coupled Microstrip Line

In this paper, the frequency-dispersive characteristic of a two-port parallel coupled microstrip line (PCML) is presented using equivalent J-inverter network parameters which were obtain from its admittance parameters. The extracted J-inverter parameters, J-susceptance and electrical line length, were used to obtain the transmission zero frequency, fundamental response frequency and harmonic response frequency of the PCML. The transmission zero frequency can be realigned by varying a centrally located single groove size to suppress the first spurious harmonic passband of the filter. A technique was identified by using J-inverter parameters to cancel the spurious response. It was found that the transmission zero of J-susceptance null of the PCML can be realigned to cancel the first harmonic resonance. This was done by using a single groove with specific dimension. The proposed technique was justified by two single-stage bandpass filter of PCML with tight coupling characteristic

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

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.

Antenna with DGS for improved performance

A recently introduce technique for improving cross-polarisation in microstrip antenna is to employ defected ground structure (DGS). In this paper, the experimental investigations have been carried out on a microstrip antenna that has been embedded with a DGS element having V-slot shape. It was found that the undesired cross-polarisation has been reduced while the impedance bandwidth has broadened.

Intelligent optimization of node coordination in Wireless Sensor Network

This paper presents a method which intelligently determines the optimum node coordination of sensor nodes topology. The topology is in linear array, aimed for beamforming in Wireless Sensor Networks (WSNs). The array is constructed in random sensor node deployment. The selected nodes should align similar to a uniform linear array (ULA) to minimize the position errors which will improve the beamforming performance (gain, transmission range and characteristics). Instead of utilizing random beamforming which needs a large number of sensor nodes to interact with each other and form a narrow radiation beam, the proposed approach is emphasized to only a number of sensor nodes which can construct a linear array. Beamforming technologies can increase the system performance, increase the transmission range and control the directionality of the reception or transmission of a signal. The proposed work utilizes beamforming technique by using ULA to establish a communication link in a WSN.

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.

Modified bifin fractal antenna with size reduction

This paper discusses the resonance of a modified bifin fractal antenna in comparison to the corresponding printed modified bifin having a centre-feed microstrip line. The antennas are designed based on a finite biconical antenna operating at 1.575 GHz. The Global Positioning Satellite system receiver operates at this frequency. Modifications have been made to the bifin structure which is half-wavelength long. The modification done on the bifin is intended to maintain the operating frequency. Hence, a compact structure can be obtained. By employing a configuration that resembles the fractal, the modified antenna is further reduced in size. The modified bifin antennas have 60/spl deg/ arm flare angle. The antennas have been successfully investigated using numerical simulations. The one-port performance of each modified fractal bifin is investigated and analysed. The structures operate at the corresponding frequency of operations.

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.