R.B. Ahmad

Microwave wedge absorber design using rice husk - an evaluation on placement variation

Placement variation is one example of parameters that critically affects the performance of RF absorbers. In this work, four designed variation patterns - W, X, Y, and Z were discussed to compare the reflectivity (S11) of designed wedge microwave absorbers. Two sub-shapes were investigated in this work - straight wedge and oblique wedge, each type having three variation of top width dimension. The other investigation includes performance comparison between four and nine elements array of straight wedges and oblique wedges. These wedge absorbers were simulated using CST Microwave Studio software, with rice husk as its material (dielectric constant, εr = 2.89). The wedge absorbers have been designed to operate effectively between the frequencies of 1 GHz to 20 GHz.

A development of Fractal PIFA (planar inverted F antenna) with bandwidth enhancement for mobile phone applications

A novel Fractal planar inverted F antenna (F-PIFA) based on the self affinity design is presented in this paper. The procedure for designing a Fractal Planar Inverted F Antenna is explained and the 2nd iteration of Sierpinski Carpet is chosen to use in mobile phones. The F-PIFA has a total dimension 27mm × 27mm are designed and optimized in order to receive GSM (Global System for Mobile Communication) and UMTS (Universal Mobile Telecommunication System) and HiperLAN (HigH Performance Radio LAN with the frequency range from 1710 MHz to 2170 MHz, 1885 to 2200 MHz for 3G and 4800MHz to 5800MHz for HiperLAN respectively. The antenna achieved the GSM, UMTS and HiperLan frequency with −6dB return loss and has almost omnidirectional radiation pattern. This antenna has been tested using mobile phone model and all the performance met the criteria for a mobile phone application.

A parametric study of broadband Planar Inverted F antenna (PIFA) for WLAN application

A novel of comprehensive study and useful information for the design of broadband planar inverted F antenna (PIFA) is proposed. The antenna including the ground plane has a total dimension 6 mm times 70 mm times 30 mm has been optimized to be operating within WLAN application standards. The size of this antenna makes it ideally suitable for handheld wireless communicators. The physical parameters of the antenna, including shorting plate width, antenna height and ground plane dimensions, are studied. The influence of various parameters on antenna characteristics has been investigated using simulation software tool. By understanding the effect of each parameter, a novel comprehensive study for a better design of broadband PIFA is proposed. These results are very useful in the design of PIFA.

A dual band planar monopole antenna with inverted-M parasitic plane

Introduction of parasitic plane as additional radiator helps to produce desired resonant frequencies, while helping to minimize the size of the antenna. A dual-band monopole antenna with parasitic plane is designed to satisfy dual-band applications, namely UMTS and WLAN 802.11. This work is an effort to investigate the effect of employing an inverted M-shaped parasitic plane, which introduces double slits in the monopole structure. The antenna parametric analysis of the antenna configuration was performed using experimental method. Results simulated and measured shows good correlation and the antenna is verified to be working in a dual band mode.

Review of angle of arrival (AOA) estimations through received signal strength indication (RSSI) for wireless sensors network (WSN)

Awareness of the physical location of each node is required by the many wireless sensor network (WSN) applications. There are various tracking schemes available such as time-of-flight, time difference of arrival and angle of arrival. This review paper focuses and describes previous related work regarding of the angle of arrival (AOA) estimations in particular through received signal strength indication (RSSI). AOA estimation is useful in tracking the desired signal and also improving the signal reception for movable users. With the AOA detection, the beam pattern of the antenna system can be reconfigured either mechanically or electrically to improve the signal reception. The AOA estimation with RSSI offers less complexity since the phase information of the signal will not be used to calculate the angle as usually practiced in the traditional phased array antenna systems. Hence this review focuses on identifying the advantages and disadvantages in AOA estimation through RSSI. The potential future direction of this research will be proposed at the end of this review.

The effect of shorting pin locations on the performance of a pattern reconfigurable Yagi-Uda patch antenna

This paper presents a linearly polarized Yagi-Uda patch antenna deployed with rectangular parasitic elements. In this work, the effect of shorting location or switching location towards the performance of beam tilt angle and reflection coefficient is investigated. By varying the shorting location, the direction of a main beam can be tilted to various angles. However, since the beam patterns overlap with each and other, only four shorting locations are proposed to achieve three sets of directive beam patterns which have maximum separation between them. The antenna is capable to steer the main beam to three different directions at theta of +30°, 0° and -30° at H-plane while sustaining a constant reflection coefficient bandwidth of 274 MHz around center frequency of 5.8 GHz. Operating around 5.8 GHz frequency, this antenna is capable to be used for WIFI and WIMAX applications.

A reconfigurable microstrip rectangular parasitic array antenna

This paper presents a linearly polarized beam reconfigurable microstrip parasitic antenna deployed with rectangular parasitic elements. In this design, three variation of beam steering is controlled adopting two RF switches (currently copper pins for proof of concept). The effects of some parameter changes such as the spacing between parasitic element and center element and size of the parasitic element are analyzed in order to investigate the beam steering characteristic of this antenna. The proposed antenna able to steer the main beam to three different directions +30°, 0° and - 30° while maintaining constant return loss bandwidth around center frequency of 5.8 GHz. Operating around 5.8 GHz frequency, this antenna is capable to be used for WIFI and WIMAX applications.

The effect of isolation loss towards the beam steering of a parasitic patch array antenna

This paper investigates the effect of isolation loss (ISO) towards the beam steering capability of a parasitic patch array antenna. Parasitic patch antenna is mainly used to steer the main beam towards a desired direction and suppress the signal in unwanted directions. In such a scenario, the ability to steer the beam with reduced side lobe level is considered important to enhance the signal reception while minimizing the unwanted signals such as interference and noise. The investigations carried out in this work explore the insight of the RF switch in order to achieve the beam steering with minimized side lobe level. A three element parasitic patch antenna is designed to achieve beam steering at -30°, 0° and 30°, with minimized side lobe level deployed with the suitable choice of RF switch. Through the investigations conducted in this work, it has been identified that increased ISO at OFF state of the RF switch improves the performance of beam steering.

Radiation pattern reconfigurable antenna: The design challenges at GHz frequencies

This paper presents the design challenges that could be faced by radiation pattern reconfigurable antenna in the Gigahertz (GHz) frequencies. This is due to the close relationship between the antenna radiation mechanism to the insertion loss and isolation loss contributed by RF switch at ON and OFF state respectively. Apart from that, the size of the antenna at higher frequencies especially above 10 GHz will be intrinsically small, thus requiring the methods for the installation of the RF switches on the antenna to be critical. In this paper, the theory and existing works on radiation pattern reconfigurable antenna are reviewed. Useful insights will be proposed in this review for future consideration in designing and implementing radiation pattern reconfigurable antennas above 20 GHz with satisfactory performance.