Muhammad Ramlee Kamarudin

Antennas and propagation for on-body communication systems

On-body communication channels are of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper describes investigations into channel characterization and antenna performance at 2.45 GHz. It is shown that significant channel fading occurs during normal activity, due primarily to the dynamic nature of the human body, but also due to multipath around the body and from scattering by the environment. This fading can be mitigated by the use of antenna diversity, and gains of up to 10 dB are obtained. Separation of the antennas performance from the channel characteristics is difficult, but results show that for many channels, an antenna polarized normal to the bodys surface gives the best path gain. Simulation and modeling present many challenges, particularly in terms of the problems scale, and the need for accurate modeling of the body and its movement.

A Beam Steering Radial Line Slot Array (RLSA) Antenna with Reconfigurable Operating Frequency

A beam steering radial line slot array (RLSA) antenna with reconfigurable operating frequency is proposed in this paper. The RLSA antenna is fed by an aperture coupled structure, which incorporates PIN diode switches that are integrated with the feed line. It is found that the beam steering ability and reconfigurable operating frequency are greatly influenced by the spiral and radius of feed line respectively. The activation of certain PIN diode switches configuration would then determine the beam steered angle and the frequency of operation. This novel antenna design is capable of steering its radiated beam to four different angles; 0°/360°, 90°, 180°, and 270°. Furthermore, the proposed antenna can be configured to operate from a single centre frequency, up to four operating centre frequencies concurrently, at each steered beam direction. The four frequencies are 2.3 GHz, 2.6 GHz, 2.9 GHz and 3.3 GHz. This antenna is a promising candidate to be installed for a smart antenna system, cognitive radio, radar or direction finding applications in the future.

A reconfigurable radial line slot array (RLSA) antenna for beam shape and broadside application

A reconfigurable beam shape and broadside radiation pattern microstrip antenna is introduced in this paper. The antennas radiating surface is designed using a radial line slot array (RLSA) arrangement, which is fed from an aperture coupled structure. This novel feeding structure for an RLSA antenna incorporates PIN diode switches which are integrated with the feed line structure to enable the various outcomes of the radiation patterns. The circular arrangement of slots at the radiating surface contributes to the reduction in size of the proposed antenna compared to conventional microstrip antenna that can yield the same antenna gain. The proposed antenna design operates at 2.3 GHz frequency band and has a maximum gain of 14.64 dB. It also produces a broadside radiation pattern with a wider beamwidth covering from −85° to 85° compared to the conventional microstrip antenna which could only cover from −50° to 50°. The proposed antenna has an enormous potential for point-to-point and point-to-multipoint communication, WiMAX, and radar application.

Performance of antennas in the on-body environment

This paper presents the performance of antenna combinations for on body communications. Several different antennas have been designed and built such as monopole antennas, patch antenna, loop antenna, patch and patch array antennas. These antennas were designed for the operation in the unlicensed ISM band, 2.45 GHz. The antennas then were tested in the on body environment. The performance of the antenna combinations is determined by measuring the path gain between two on-body paths for a range of body postures. Measurement results show that the combination of monopole antennas performs best in most of the measurement cases compared to other combinations. The comparison between calculation and measurement results, which consider the free space loss and antenna gain give results that are within 10dB of measurements for most body postures.

A MIMO ANTENNA DESIGN CHALLENGES FOR UWB APPLICATION

This paper proposes a compact printed ultra-wideband (UWB) multiple-input-multiple-output (MIMO) antenna with a dimension of 38 £ 91mm 2 . The presented UWB-MIMO antenna comprises two identical patch elements with D separation distance on the same substrate. The basic single antenna structure has a novel design comprising seven circles surrounding a center circle with partial ground plane implementation. Furthermore, the experimental antenna has peak gain of 5.3dBi between an operating frequency of 2.8GHz and 8.0GHz under a minimum re∞ection coe-cient of less than i10dB (S11 < i10dB). Moreover, the antenna successfully achieved mutual coupling minimization of < i17dB, eventually resulting in enhancement of radiation e-ciency. Besides, the UWB- MIMOs correlation coe-cient was efiectively reduced to less than i22dB, which re∞ected an improvement in the antennas diversity. In this paper, the proposed antenna is examined both numerically and experimentally.

ELECTRONICALLY SWITCHED BEAM DISK-LOADED MONOPOLE ARRAY ANTENNA

A disk-loaded monopole array antenna with coplanar waveguide (CPW) feeding systems that has the capability of beam switching has been successfully demonstrated. The antenna utilises the advantages of CPW and the transmission line of input impedance equation and is integrated with RF/Microwave devices to enable beam switching in the elevated and azimuthal planes. The measured gain of the antenna in the direction of the open-circuited parasite element is in the range of 5.10 to 5.60dBi. It has good input return loss at 2.45GHz and produces useful gain in the direction of the open circuited element. The E- and H-plane patterns show that the beam can be steered by pin diodes switching.

An MIMO Rectangular Dielectric Resonator Antenna for 4G Applications

A multiple-input-multiple-output (MIMO) rectangular dielectric resonator antenna (RDRA) for 2.6-GHz Long Term Evolution (LTE) applications is investigated and presented. Two orthogonal modes of the RDRA are excited by using two different feed mechanisms: coplanar waveguide (CPW) and coaxial probe. The measured impedance bandwidth for port 1 and port 2 is 47% (2.09-3.38 GHz) and 25% (2.40-3.09 GHz), respectively. The measured correlation coefficient is 0.03 with nearly 10 dB diversity gain at frequency 2.6 GHz. The MIMO RDRA gives isolation of above 20 dB over the operating frequency. The gain of 4.97 dBi is obtained for port 1 and 4.51 dBi for port 2 at 2.6 GHz. The S-parameters, isolation, gain, correlation coefficient, and diversity gain of the MIMO RDRA are studied, and reasonable agreement between the measured and simulated results is observed .

Antennas for on-body communication systems

The optimum choice of antenna for on-body communications is discussed in this paper. Several different antennas, including the monopole, the loop and patch and patch arrays have been fabricated and tested in the on-body environment. In particular, path gain measurements of two on-body paths has been performed for a range of body postures. It is clear that the monopole antenna performs best in most of the measurement cases. A first order analysis of the path loss, consisting of antenna gain deduced from link geometry and a free space loss appropriate to the path distance, give results that are within 10 dB of measurements for most body postures.

Reconfigurable Four-Parasitic-Elements Patch Antenna for High-Gain Beam Switching Application

A reconfigurable beamforming of a four-parasitic-elements patch antenna (FPPA) for WiMAX application is presented. The proposed FPPA is successfully capable to steer the radiation pattern in azimuth planes (0 ^°, 45 ^°, 135 ^°, 225 ^°, and 315 ^° angles) and in elevation plane (0 ^°, 13 ^°, 15 ^°, 10 ^°, and 12 ^°). This is realized in the unique form of four parasitic elements encircling the center main radiator. The activation of the parasitic required a shorting pin to the ground that indicates on state condition, and vice versa. It is discovered in CST simulation software that the specified location of the pins are really significant to ensure the parasitic performs either as a reflector or director. Moreover, each of the shorting pins is linked to the RF p-i-n diode BAR5002v switch. Also, the FPPA is fabricated on a 130-mm square Taconic substrate. The proposed antenna design has a maximum gain of 8.2 dBi at all desired angles with a half-power beamwidth of 58 ^°.

Pattern-Reconfigurable Microstrip Patch Antenna With Multidirectional Beam for WiMAX Application

A parasitic planar patch antenna capable of multi directional pattern reconfiguration is presented. The antenna structure consists of a driven element surrounded by four parasitic elements that act either as reflector(s) or director(s) depending on the switching arrangement. Beam reconfiguration is achieved by using four p-i-n diode switches where the effect of switching technique on the overall element performance is investigated numerically and experimentally. The proposed antenna achieves nine distinguished main beam angular positions. Moreover, the proposed antenna has achieved excellent realized gain levels at all configuration scenarios with a minimum value of 7 dBi. Simulation and measurement results show good agreement and promising applications of such antenna structure in enhanced WiMAX systems.