Sadiq Ullah

Design of Dual Band Wearable Antenna Using Metamaterials

Abstract This paper presents two types of dual band (2.4 and 5.8 GHz) wearable planar dipole antennas, one printed on a conventional substrate and the other on a two-dimensional metamaterial surface (Electromagnetic Bandgap (EBG) structure). The operation of both antennas is investigated and compared under different bending conditions (in E and H-planes) around human arm and leg of different radii. A dual band, Electromagnetic Band Gap (EBG) structure on a wearable substrate is used as a high impedance surface to control the Specific Absorption Rate (SAR) as well as to improve the antenna gain up to 4.45 dBi. The EBG inspired antenna has reduced the SAR effects on human body to a safe level (<2W/Kg). I.e. the SAR is reduced by 83.3% for lower band and 92.8% for higher band as compared to the conventional antenna. The proposed antenna can be used for wearable applications with least health hazard to human body in Industrial, Scientific and Medical (ISM) band (2.4 GHz, 5.2 GHz) applications. The antennas on human body are simulated and analyzed in CST Microwave Studio (CST MWS).

Polarisation dependent EBG surface with an inclined sheet via

This paper presents a novel polarisation dependent EBG (PDEBG) surface which makes use of sheet vias. The performance of the surface is analysed whilst varying the length, thickness and inclination of the vias. It is observed that the phase difference between the x-polarised and y-polarised component of the reflected wave can be controlled by varying these parameters. Furthermore, the surface exhibits a polarisation conversion property with potential use in a variety of antennas.

Design and SAR Analysis of Wearable Antenna on Various Parts of Human Body, Using Conventional and Artificial Ground Planes

This paper presents design and specific absorption rate analysis of a 2.4 GHz wearable patch antenna on a conventional and electromagnetic bandgap (EBG) ground planes, under normal and bent conditions. Wearable materials are used in the design of the antenna and EBG surfaces. A woven fabric (Zelt) is used as a conductive material and a 3 mm thicker Wash Cotton is used as a substrate. The dielectric constant and tangent loss of the substrate are 1.51 and 0.02 respectively. The volume of the proposed antenna is 113×96.4×3 mm3. The metamaterial surface is used as a high impedance surface which shields the body from the hazards of electromagnetic radiations to reduce the Specific Absorption Rate (SAR). For on-body analysis a three layer model (containing skin, fats and muscles) of human arm is used. Antenna employing the EBG ground plane gives safe value of SAR (i.e. 1.77W/kg 2W/kg). The efficiency of the EBG based antenna is improved from 52 to 74%, relative to the conventional counterpart. The proposed antenna can be used in wearable electronics and smart clothing.

Reliability of network simulators and simulation based research

Network simulators have gained an increased importance in the research community to an extent that approximately 11% of the research papers that appeared in the proceedings of leading international conferences used network simulators to test their claims. It is anticipated that due to the several advantages network simulators will become more prevalent in the research community in future. However, with the growing popularity of the network simulators, challenges in the form of consistent revelations about their inaccuracies have started to seriously question the use of such simulators and simulation based research. This paper attempts to answer the questions (1) How can assumptions/simplifications in modeling affect realism of simulations? (2) How credibility of simulation based research be improved?, and (3) What necessary steps must be taken to make network simulators credible? The paper provides deliberated recommendations for improving the authenticity of simulation based experiments. The authors believe that the discussion in this paper will greatly facilitate the repeatability of simulation based research and will help researchers to select the most suitable (credible) simulator.

Design and analysis of a novel tri-band flower-shaped planar antenna for GPS and WiMAX applications

Abstract This paper presents the design of a tri-band flower-shaped planar monopole antenna operating at three frequencies i.e. 1.576 (GPS), 2.668, and 3.636 GHz (Mobile WiMAX). The radiating element of the antenna is backed by a 1.6 mm thicker FR-4 substrate having a dielectric constant of 4.3. The substrate is backed by a truncated ground plane. The antenna is fed through a 50 Ω microstrip line. The flower shape of the radiating element is derived from the basic circular shape by introducing in it rounded slots of various radii. The upper part of the antenna is flower shaped while the lower part comprises a microstrip feed line and two branches, each having two “leaves” at the end. The leaves and branches contribute in the impedance matching of the lower (1.576 GHz) and middle (2.668 GHz) frequency bands. The antenna gives an acceptable simulated efficiency >70% in the three frequency bands. Suitable gains of 1.63, 2.59, and 3.23 dB are obtained at 1.576, 2.668, and 3.636 GHz, respectively. The antenna matched with a VSWR < 1.2 in the three frequency bands. The prototype of the antenna is fabricated and tested in the laboratory, and good agreement in simulated and measured results is achieved. The proposed design is a visually appealing and may find uses as an external antenna in GPS and WiMAX applications.

Patch antenna using EBG structure for ISM band wearable applications

This paper is about designing Microstrip Patch Antenna with wearable Substrate with additional EBG structure for better gain to be operated in ISM band (2.4 GHz). A Wearable substrate is used in textile garments so this antenna structure is designed specifically for wearing garments, thats why SAR (Specific Absorption Rate) has been measured in this paper. For designing EBG structure help in improving gain and better results for SAR. CST studio software has been used for simulation of this antenna.

Design of a dual band frequency reconfigurable patch antenna for GSM and Wi-Fi applications

Reconfigurable antennas due to their versatile qualities are highly demanded nowadays. A novel frequency reconfigurable patch antenna with two metallic rings around a rectangular patch is presented in this paper. Frequency reconfigurability can be achieved by changing the radiating surface of antenna. Surrounding metallic rings are connected to center patch with switches. The antenna operate in 1.8 GHz and 2.4 GHz frequency bands, when the switches are turned ON and OFF respectively. When the switches are turned ON they add external rings to radiating surface, hence increasing the surface size which in return changes the operating frequency of antenna. Different types of switching elements like MEMS, varactor diodes PIN diodes or optical switches can be used depending upon the nature of application. In this paper optical switches are chosen due to their advantage of not interfering with antenna radiation characteristics due to no need of biased lines. Antenna presented in this paper can be reconfigured to operate on Wi-Fi (2.4 GHz) and GSM (1.8 GHz) frequencies at a time. The antenna gives directivity and efficiency of (7.89 dBi, 48 %) and (8.2 dBi, 93 %) at 1.8 GHz and 2.4 GHz respectively. CST (Computer Simulation Tool) is used for design and simulation of proposed antenna.

Design of tetra-band frequency reconfigurable antenna for portable wireless applications

This paper presents the design of multi and wide band frequency reconfigurable monopole antenna, using FR4 as a substrate with thickness of 1.6mm. The radiating element is printed on a truncated metallic ground plane. The antenna works in a single-band and two dual-band modes using two switches. The single-band (WiMAX at 3.45GHz) mode is obtained when both switches (SW1 and SW2) are in OFF state. The first Dual-band (Wi-Fi at 2.45 GHz and WLAN at 5.45 GHz) mode is achieved when one particular switch of the two switches is turned ON. When both switches are turned ON, the antenna functions in the second dual band mode(GSM at 1.8GHz and WLAN at 5.45GHz). This monopole antenna is designed using computer simulation technology 2011(CST Microwave studio). The designed antennas performance is examined on the basis of return loss, radiation pattern, Gain,Efficiency and VSWR.

Specific Absorption Rate Analysis of a WLAN antenna using Slotted I-type electromagnetic bandgap (EBG) structure

In this paper on body investigation has been done on microstrip patch antenna using Velcro as a substrate at 2.4 GHz and different parameters (gain, directivity, efficiency) were watched. Alongside this the estimation of SAR (Specific Absorption Rate) has been measured averaged over the 10 g of tissue. Gain and directivity were extraordinarily influenced in view of ingestion of radiation by the human body with efficiency of 40.81% while the estimation of SAR is 4.63 W/kg which is beyond the safe level of 2 W/kg as indicated by European IEC Standard. Slotted I Metamaterial surface is utilized as a ground plane for Microstrip patch antennadue to which the SAR is decreased from 4.63 W/kg to 1.23 W/kg i.e. 73.43% diminishment in SAR as indicated by the standard which is in the protected zone. In addition ithas enhanced the efficiency from 40.81% to 41.35%.This is because of its two important properties of suppressing the surface waves and in phase reflection. Simulations are accomplished in CST MWS.

Antenna design for advance wireless systems using metamaterial surfaces

This paper presents a comparative study of the performance of a 2.4GHz microstrip patch antenna, using various metamaterial surfaces, each working as a ground plane for the proposed antenna. A 1.6 mm thicker Rogers RT/ Duroid 5880 is used as a substrate material in the design of the antenna. The relative permittivity of the substrate is 2.2. The conventional patch antenna is properly matched to 50 ohms, using an inset-feed mechanism. The gain of the 2.4 GHz patch antenna backed by a conventional ground plane is 7.21dBi. The antenna is then backed by three different types of metamaterial surfaces, Frequency Selective Surface (FSS), Electromagnetic Band Gap (EBG) surface and Artificial Magnetic Conductor Surface (AMC) and their performances are compared and quantified in terms of gain. It is found that the AMC based patch antenna gives the highest gain (9.01dBi) among the used surfaces. It is also found that the surface waves are suppressed relatively more by the FSS ground plane. The artificial surfaces improve the efficiency of the conventional patch antenna due to their high-impedance characteristics, which helps in reducing the losses with in the substrate material. Simulations are performed in High Frequency Structure Simulator (HFSS).