Interest in Wireless Body Area Networks (WBANs) has increased significantly in recent years thanks to the advances in microelectronics and wireless communications. Owing to the very stringent application requirements in terms of reliability, energy efficiency, and low device complexity, the design of these networks requires the definition of new protocols with respect to those used in general purpose wireless sensor networks. This motivates the effort in research activities and in standardisation process of the last years. This survey paper aims at reporting an overview of WBAN main applications, technologies and standards, issues in WBANs design, and evolutions. Some case studies are reported, based on both real implementation and experimentation on the field, and on simulations. These results have the aim of providing useful insights for WBAN designers and of highlighting the main issues affecting the performance of these kind of networks.

A Survey on Wireless Body Area Networks: Technologies and Design Challenges

In this paper, we present the design, simulation, and measurement of a dual-band metamaterial absorber in the microwave region. Simulated and experimental results show that the absorber has two perfect absorption points near 11.15GHz and 16.01GHz. Absorptions under difierent polarizations of incident EM waves are measured with magnitude of over 97% at low-frequency peak and 99% at high-frequency peak respectively. Current distribution at the dual absorptive peaks is also given to study the physical mechanism of power loss. Moreover, it is verifled by experiment that the absorptions of this kind of metamaterial absorber remain over 90% at the low-frequency peak and 92% at the high-frequency peak with wide incident angles ranging from 0 - to 60 - for both transverse electric wave and transverse magnetic wave.

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Perfect Metamaterial Absorber with Dual Bands

A new compact planar ultrawideband (UWB) antenna designed for on-body communications is presented. The antenna is characterized in free space, on a homogeneous phantom modeling a human arm, and on a realistic high-resolution whole-body voxel model. In all configurations it demonstrates very satisfactory features for on-body propagation. The results are presented in terms of return loss, radiation pattern, efficiency, and E-field distribution. The antenna shows very good performance within the 3-11.2 GHz range, and therefore it might be used successfully for the 3.1-10.6 GHz IR-UWB systems. The simulation results for the return loss and radiation patterns are in good agreement with measurements. Finally, a time-domain analysis over the whole-body voxel model is performed for impulse radio applications, and transmission scenarios with several antennas placed on the body are analyzed and compared.

A Compact UWB Antenna for On-Body Applications

A comparison between difierent modern population based optimization methods applied to the design of scannable circular antenna arrays is presented in this paper. This design of scannable circular arrays considers the optimization of the amplitude and phase excitations across the antenna elements to operate with optimal performance in the whole azimuth plane (360 - ). Simulation results for scannable circular arrays with the amplitude and phase excitation optimized by genetic algorithms, particle swarm optimization and the difierential evolution method are provided. Furthermore, in order to set which design case could provide a better performance in terms of the side lobe level and the directivity, a comparative analysis of the performance of the optimized designs with the case of conventional progressive phase excitation is achieved. Simulation results show that

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A Comparison of Genetic Algorithms, Particle Swarm Optimization and the Differential Evolution Method for the Design of Scannable Circular Antenna Arrays

The design, realization, and experimental characterization of a 400-element electronically reconfigurable transmitarray operating in the Ka-band is presented. It is based on linearly polarized unit-cells with 180° phase-shifting capability. Several sequential rotation schemes have been compared numerically to generate a circularly polarized beam over a broad frequency band, and a random distribution has been selected to mitigate spurious cross-polarized side-lobes when scanning the main beam. The 2-D electronic beam-steering capabilities of ±60° have been verified experimentally. The prototype, illuminated by a horn antenna as a focal source, exhibits a broadside gain of 20.8 dBi at 29.0 GHz and a 3-dB bandwidth of 14.6% with radiation efficiency of 58%. The axial ratio remains below 2 dB within this bandwidth. Next, a planar substrate integrated waveguide focal source array was designed in order to reduce the focal distance by about 50% and thereby significantly improve the antenna compactness, and similar radiation performance is demonstrated numerically and experimentally. © 1963-2012 IEEE.

Circularly-Polarized Reconfigurable Transmitarray in Ka-Band With Beam Scanning and Polarization Switching Capabilities

The design of an antipodal Vivaldi antenna for ultra wideband (UWB) applications is presented. The main purpose of this design is the reduction of three parameters of transient distortion, reflection coefficient and cross polarization level. Multi-objective particle swarm optimization (MOPSO) is applied to handle these objectives simultaneously. All antenna simulations are performed using the CST MWS software. Several design cases of the resultant Pareto fronts are compared, and finally, a sample of the Pareto front is fabricated. To assess the time domain performance of the antenna, two identical antennas are placed in an end-to-end orientation. The simulated correlation factor in this scenario is more than 93%. Measurement results show that the |S11| of the developed antenna is less than -10 dB, the cross polarization level is below -11.5 dB and the gain is between 4.5 dBi and 9 dBi over the whole UWB frequency band.

Improvement of Time and Frequency Domain Performance of Antipodal Vivaldi Antenna Using Multi-Objective Particle Swarm Optimization

A method to obtain optimum tradeoffs (Pareto front) between sidelobe level (SLL) and beamwidth (BW) in time domain for ultrawideband (UWB) antenna arrays is presented. Multiobjective particle swarm optimization (MOPSO) is used to deal with these two conflicting objectives. In the optimization process, mutual coupling effects between elements are not considered. However, the multiple solutions obtained from MOPSO enable the designer to consider the mutual coupling effect as an additional constraint. Each element of the array is an antipodal Vivaldi antenna. The optimization template is applied for three different time-domain pattern descriptors. In comparison to arrays with the same number of elements reported in literature, the Pareto fronts obtained in this study provide lower BW and SLL. A four-element sample from resultant Pareto fronts was simulated by using CST Microwave Studio software. This array shows a 13.7-17.2 dBi gain over the whole frequency band from 3-11 GHz, 7.2° BW, and -12 dB SLL for energy pattern.

Time-Domain Design of UWB Vivaldi Antenna Array Using Multiobjective Particle Swarm Optimization

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Modified Multi-Objective Particle Swarm Optimization for Electromagnetic Absorber Design

This letter proposes a simple design approach to gain stable omnidirectional radiation pattern in printed ultrawideband (UWB) antennas. Monitoring of the current distributions in different frequencies shows that a combination of standing and traveling modes exists on the antenna. By determining the dominant mode at higher and lower frequencies, the corresponding optimum size of antenna that guarantees a stable omnidirectional radiation pattern and a good return loss is obtained. Using the proposed method, two compact antennas with circular ground and miniaturized fractal ground are designed. Simulation and measurement results show a good impedance matching and an excellent omnidirectional radiation pattern for proposed antennas.

Systematic Design of UWB Monopole Antennas With Stable Omnidirectional Radiation Pattern

In this letter, an ultrawideband (UWB) microstrip-fed planar monopole antenna with stable radiation pattern is presented. Although compact and simple structure of the planar antennas made them a good candidate in UWB applications, due to unwanted current distribution on the ground section, they suffer from transient distortion and radiation pattern rotation in different frequencies. To alleviate this effect, a metallic staircase plane is placed in the bottom of the substrate. In addition, a mushroom-like electromagnetic band-gap (EBG) structure is embedded on the top layer of the substrate to increase the gain in higher frequencies. Measurement results show 2.2-6 dB gain in broadside direction in 3-10-GHz frequency. A new definition of pattern stability factor (PSFII) is proposed, which is proper for both directional and omnidirectional radiation patterns. Calculated PSFII for the proposed antenna is higher than 95%, which shows a stable radiation pattern. Furthermore, it shows a low distortion manner where the fidelity factor in the main beam direction is more than 95%. In comparison to similar antennas presented in literature, PSFII and gain have been improved noticeably.

Somayyeh Chamaani

Papers

Improvement of Time and Frequency Domain Performance of Antipodal Vivaldi Antenna Using Multi-Objective Particle Swarm Optimization

Time-Domain Design of UWB Vivaldi Antenna Array Using Multiobjective Particle Swarm Optimization

Modified Multi-Objective Particle Swarm Optimization for Electromagnetic Absorber Design

Systematic Design of UWB Monopole Antennas With Stable Omnidirectional Radiation Pattern

UWB Monopole Antenna With Stable Radiation Pattern and Low Transient Distortion