Daniel G. Rucker

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.

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.

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.

Flexible printed monopole antennas for WLAN applications

In this paper, we present two thin/flexible printed monopole antennas for Wireless Local Area Network (WLAN) applications. The first design is a single band antenna which operates at 2.4 GHz while the second one is a dual band antenna operates at 2.5 GHz and 5.2 GHz. The dimensions of the proposed antennas are: (26.5 mm × 25) and (35 mm × 25) mm for the single band and dual band respectively. Antenna properties, such as gain, far-field radiation patterns, coupling coefficient, expressed in terms of the scattering parameter S11 are provided. Design and simulations are performed using CST Microwave Studio software which is based on the Finite Integration Technique (FIT). Moreover, the effect of folding the antenna was performed experimentally on both designs to study its influence on the antenna performance. The achieved gain for the single band antenna is 1.8 dB with a measured bandwidth of 270 MHz. The dual band antenna achieved a gain of 1.8 dB and 4 dB at 2.5 GHz and 5.2 GHz respectively, and measured bandwidths of 305 MHz and 480 MHz at the first and second band respectively. The proposed thin and flexible designs along with antennas characteristics are suitable for integration into flexible technologies for WLAN applications.

Mutual coupling reduction of dual-band printed monopoles using MNG metamaterial

In this paper, a μ-Negative metamaterial (MNG) is utilized for mutual coupling reduction between dual-band printed monopole antennas used in Multiple Input Multiple Output (MIMO). A dual-band MNG metamaterial is designed to specifically possess negative effective permeability at the two resonant frequencies where the antennas are operating. MNG is inserted between the two printed monopoles (back to back) to decrease the correlation between them. The printed monopole antennas were designed to operate in the Wireless Local Area Network (WLAN) bands 2.45 GHz and 5.2 GHz. Antenna characteristics such as, scattering parameters far-field radiation patterns with and without the presence of MNG are provided. The design of the MNG unit cell and its effective constitutive parameters are also provided. Design and simulations are conducted using Ansofts HFSS software which is based on the Finite Element Method (FEM). The proposed technique achieved a 14 dB reduction in mutual coupling at 2.45 GHz and 13 dB at 5.2 GHz. A gain of 2 dB higher than the normal case at the second band is observed while it is maintained the same on the first band. Furthermore, the MNG based antenna system maintains a relatively low profile (16 mm) which is convenient for compact systems and hand-held devices.

An investigation on the effect of bending of Split Ring Resonators

This paper investigates the effect of bending on Split Ring Resonators (SRR) by means of numerical simulations. This study is important since SRR is a basic bulk component of Left Handed Metamaterials (LHMs) which plays a vital role in the recent advancement of microwave applications. Modeling and analysis of SRR has been carried out using the commercially available software Ansofts High Frequency Structure Simulator (HFSS) which is based on the Finite Element Method (FEM). To the best knowledge of the authors, this kind of study is being conducted for the first time in the field of metamaterial science. We show that bending of SRR affects the retrieved values of the constitutive parameters which must be taken into account when designing flexible metamaterial. Edge Coupled SRR (EC-SRR) is considered in this research. Several degrees of bending have been investigated for comparison purposes.

Microstrip Antenna Arrays for Implantable and Wearable Wireless Applications

Flexible microstrip antenna arrays have become a necessity in today’s miniaturized biomedical wireless devices. Implantable and wearable biomedical devices such as pacemakers, drug delivery systems, heart rate monitors, and respiratory monitors need to communicate with exterior base station devices and relayed to healthcare professionals. In this paper, multiple flexible microstrip antenna arrays are designed and simulated for these applications. The frequency bands of 5.2 GHz and 5.8 GHz are utilized to provide a high bandwidth communication link. CST Microwave Studio was used for the modeling and simulation of the antennas. The reflection coefficient, gain, and correlation coefficient for each antenna are presented and discussed. The presented antennas can be utilized together as an array for enhanced gain or independently in a Multiple Input Multiple Output (MIMO) system.

Enhanced Low-Angle GPS Coverage Using Solid and Annular Microstrip Antennas on Folded and Drooped Ground Planes

Folded and drooped microstrip antennas are investigated in this communication for their potential applications in GPS marine navigation. Numerical and experimental results are reported to identify the effects of the percentage of the patch extending around to the folded side, position, and angle of the bend on the performance of the proposed antennas in comparison to the conventional flat counterparts. The folded antennas provide marginally improved 3-dB beam width and excellent phase center stability without degrading the bore-sight gain. A novel drooped square annular element operating in the TM 30 mode is proposed and validated both numerically and experimentally. The drooped annular antenna is shown to have substantially improved above-horizon coverage to suit applications requiring acquisition of satellites from horizon to horizon with a pattern ripple less than 2 dB over the upper hemisphere and with an impedance bandwidth of 2%. The polarization rejection is marginally degraded at bore-sight. At the horizon, the cross component becomes dominant by 1.5 dB.