Hussain M. Al-Rizzo

Flexible and Compact AMC Based Antenna for Telemedicine Applications

We present a flexible, compact antenna system intended for telemedicine applications. The design is based on an M-shaped printed monopole antenna operating in the Industrial, Scientific, and Medical (ISM) 2.45 GHz band integrated with a miniaturized slotted Jerusalem Cross (JC) Artificial Magnetic Conductor (AMC) ground plane. The AMC ground plane is utilized to isolate the users body from undesired electromagnetic radiation in addition to minimizing the antennas impedance mismatch caused by the proximity to human tissues. Specific Absorption Rate (SAR) is analyzed using a numerical human body model (HUGO) to assess the feasibility of the proposed design. The antenna expresses 18% impedance bandwidth; moreover, the inclusion of the AMC ground plane increases the front to back ratio by 8 dB, provides 3.7 dB increase in gain, in addition to 64% reduction in SAR. Experimental and numerical results show that the radiation characteristics, impedance matching, and SAR values of the proposed design are significantly improved compared to conventional monopole and dipole antennas. Furthermore, it offers a compact and flexible solution which makes it a good candidate for the wearable telemedicine application.

A Compact Polyimide-Based UWB Antenna for Flexible Electronics

In this letter, we present a compact ultrawideband (UWB) antenna printed on a 50.8-μm Kapton polyimide substrate. The antenna is fed by a linearly tapered coplanar waveguide (CPW) that provides smooth transitional impedance for improved matching. The proposed design is tuned to cover the 2.2-14.3-GHz frequency range that encompasses both the 2.45-GHz Industrial, Scientific, Medical (ISM) band and the standard 3.1-10.6-GHz UWB band. Furthermore, the antenna is compared to a conventional CPW-fed antenna to demonstrate the significance of the proposed design. A parametric study is first performed on the feed of the proposed design to achieve the desired impedance matching. Next, a prototype is fabricated; measurement results show good agreement with the simulated model. Moreover, the antenna demonstrates a very low susceptibility to performance degradation due to bending effects in terms of impedance matching and far-field radiation patterns, which makes it suitable for integration within modern flexible electronic devices.

Compact Polyimide-Based Antennas for Flexible Displays

In this paper, we present two compact ultra thin and flexible printed monopole antennas intended for integration with flexible displays, such as flexible organic light-emission displays (FOLEDs) and active matrix electro-phoretic displays (AM-EPDs). The proposed antennas are designed to provide Wireless local area network (WLAN) and Bluetooth connectivity for flexible displays. The first design is a dual band antenna operating at 2.45 GHz and 5.2 GHz while the second is a single band antenna operating at 2.4 GHz. Both antennas were printed on a Kapton polyimide-based substrate with dimensions (35 mm×25 mm) and (26.5 mm×25 mm) for the dual and single band respectively. Antenna properties, such as gain, far-field radiation patterns, scattering parameter S11 are provided. Moreover, the effect of folding/bending was performed experimentally on both designs to study its influence on the antennas performance. The proposed compact, thin and flexible designs along with antennas characteristics are perfectly suitable for integration into flexible displays for WLAN and Bluetooth connectivity.

A Survey on Multipath Routing Protocols for QoS Assurances in Real-Time Wireless Multimedia Sensor Networks

The vision of wireless multimedia sensor networks (WMSNs) is to provide real-time multimedia applications using wireless sensors deployed for long-term usage. Quality of service assurances for both best effort data and real-time multimedia applications introduced new challenges in prioritizing multipath routing protocols in WMSNs. Multipath routing approaches with multiple constraints have received considerable research interest. In this paper, a comprehensive survey of both best effort data and real-time multipath routing protocols for WMSNs is presented. Results of a preliminary investigation into design issues affecting the development of strategic multipath routing protocols that support multimedia data in WMSNs are also presented and discussed from the network application perspective.

Multi-walled carbon nanotube-based RF antennas

A novel application that utilizes conductive patches composed of purified multi-walled carbon nanotubes (MWCNTs) embedded in a sodium cholate composite thin film to create microstrip antennas operating in the microwave frequency regime is proposed. The MWCNTs are suspended in an adhesive solvent to form a conductive ink that is printed on flexible polymer substrates. The DC conductivity of the printed patches was measured by the four probe technique and the complex relative permittivity was measured by an Agilent E5071B probe. The commercial software package, CST Microwave Studio (MWS), was used to simulate the proposed antennas based on the measured constitutive parameters. An excellent agreement of less than 0.2% difference in resonant frequency is shown. Simulated and measured results were also compared against identical microstrip antennas that utilize copper conducting patches. The proposed MWCNT-based antennas demonstrate a 5.6% to 2.2% increase in bandwidth, with respect to their corresponding copper-based prototypes, without significant degradation in gain and/or far-field radiation patterns.

Channel assignment in an IEEE 802.11 WLAN based on Signal-To-Interference Ratio

In this paper, we propose a channel-assignment algorithm at the Access Points (APs) of a wireless local area network (WLAN) in order to maximize signal-to-interference ratio (SIR) at the user level. We start with the channel assignment at the APs, which is based on minimizing the total interference between APs. Based on this initial assignment, we calculate the SIR for each user. The algorithm can be applied to any WLAN, irrespective of the user distribution and user load. Results show that the proposed algorithm is capable of significantly increasing the SIR over the WLAN, which in turn improves throughput.

Channel Assignment and Load Distribution in a Power-Managed Wlan

For a wireless local area network (WLAN), we propose an algorithm based on power management of access points (APs) to improve load distribution and provide an improved channel assignment. We formulate an algorithm that adjusts the transmitted power of the beacon packets of the most congested access point (MCAP). The transmitted power of the data packets is not altered thus avoiding auto-rating. The algorithm then determines a user assignment that distributes the load efficiently. Finally, we apply a channel assignment algorithm to each AP with the objective of minimizing the total interference over the WLAN. Results show that the proposed algorithm is capable of significantly reducing the congestion at the MCAPs, providing better load distribution, and enhancing channel assignment.

Optimized Multi-Constrained Quality-of-Service Multipath Routing Approach for Multimedia Sensor Networks

Modern multimedia sensor networks impose strict constraints on both the delay and energy consumption when time-critical data must be reported to the sink within a limited bandwidth without any loss. Failure to transmit an event to the sink occurs for many reasons, including inherence limitations of sensors, power consumption, and reliability. We propose a mathematical model for a novel quality-of-service (QoS) routing-determination method. The proposed scheme enables determining the optimal path to provide appropriate shared radio satisfying the QoS for a wide range of real-time intensive media. The mathematical model is based on the Lagrangian relaxation method, to control adaptive switching of hop-by-hop QoS routing protocols. The embedded criteria for each objective function are used to decide which path from source to sink will be selected. Simulation results show that, compared with existing routing protocols, the approach proposed in this paper significantly improves the packet received ratio, energy consumption, and average end-to-end delay of the sensor node.

Design, Fabrication, and Testing of Flexible Antennas

Their light weight, low-cost manufacturing, ease of fabrication, and the availability of inex‐ pensive flexible substrates (i.e.: papers, textiles, and plastics) make flexible electronics an ap‐ pealing candidate for the next generation of consumer electronics [2]. Moreover, recent developments in miniaturized and flexible energy storage and self-powered wireless com‐ ponents paved the road for the commercialization of such systems [3].

Wearable Yagi microstrip antenna for telemedicine applications

This paper presents a button shaped antenna based on a microstrip Yagi array. The proposed antenna is suitable for Wireless Body Area Network (WBAN) and telemedicine applications operating at 2.45 GHz. Antenna properties, such as far-field radiation patterns, coupling coefficient, measured by the scattering parameter S11, and gain are provided. Moreover, the simulated performance of the proposed antenna is compared to circular and rectangular patch button shaped antennas having similar sizes. Design and simulations are performed using CST Microwave Studio software which is based on the Finite Integration Technique (FIT). The proposed antenna achieved a gain of 6.7 dB, (F/B) ratio of 11.7 dB and a semi-directional radiation pattern required for on body and off body applications.