Stavros V. Georgakopoulos

Higher-order finite-difference schemes for electromagnetic radiation, scattering, and penetration .2. Applications

For pt.1 see ibid., vol.44, no.1, p.134-42 (2002). Higher-order schemes for the finite-difference time-domain (FDTD) method - in particular, a second-order-in-time, fourth-order-in-space method, FDTD(2,4) - are applied to a number of problems. The problems include array analysis, cavity resonances, antenna coupling, and shielding effectiveness case studies. The latter includes a simplified model of a commercial airliner, with a personal electronic device operating in the vicinity of the aircraft. The FDTD computations are also compared to measured data for this case. Incorporating PEC and other types of material boundaries into higher-order FDTD is problematic; a hybrid approach using the standard FDTD method in the proximity of the boundary is proposed, and shown to perform well.

HIRF penetration through apertures: FDTD versus measurements

The penetration of high-intensity radiated fields (HIRF) into conducting enclosures via apertures is an EMI issue that is relevant to all aviation. The stories are numerous, of disrupted communications, disabled navigation equipment, etc., due to the effects of EM sources external to the aircraft. Here, the FDTD method is used to predict the shielding effectiveness of conducting enclosures with apertures, and the numerical results are compared with measurements. Several issues related to the FDTD analysis of highly resonant and high-quality factor (high-Q) structures, such as windowing and acceleration techniques, are examined and discussed.

Wireless Power Transfer in Concrete via Strongly Coupled Magnetic Resonance

The wireless efficiency of the strongly coupled magnetic resonance (SCMR) method is studied here for non-homogenous interfaces. Specifically, SCMRs wireless power transfer from a source in air to a sensor embedded in concrete is analyzed. The concrete material properties are modeled for various humidity levels using the extended Debye model. The performance of SCMR is examined for both plain and reinforced concrete. Finally, rectification of the RF power is performed and the DC power delivered to the embedded sensors battery is calculated.

HIRF penetration and PED coupling analysis for scaled fuselage models using a hybrid subgrid FDTD(2,2)/FDTD(2,4) method

A hybrid method of subgrid FDTD(2,2) with FDTD(2,4) is presented. Both the standard FDTD(2,2) as well as the hybrid technique are applied to shielding effectiveness analysis of a scaled model of a Boeing 757. Also, analysis of EMI generated by personal electronic devices is performed on the same scaled fuselage model.

Orientation insensitive power transfer by magnetic resonance for mobile devices

The efficiency of wireless power transfer (WPT) from an orientation insensitive system to a mobile device by strongly coupled magnetic resonance (SCMR) is reported here. This paper compares an optimal loop-based design in standard SCMR systems with misalignment insensitive system (3D and 3loop structure), which exhibits higher efficiency than typical SCMR devices in several directions in a sphere.

Optimal Design Parameters for Wireless Power Transfer by Resonance Magnetic

The wireless power transfer (WPT) efficiency of systems based on strongly coupled magnetic resonance (SCMR) depends on the Q-factor of the system elements, which is a function of the geometrical parameters. This letter analytically derives the equations that can be used to design optimal loop and helical elements for SCMR systems. Also, for loops and helices, a global maximum condition is derived in order to design SCMR systems with maximal efficiency.

Coupling modeling and reduction techniques of cavity-backed slot antennas: FDTD versus measurements

Cavity-backed slot (CBS) antennas are commonly used in Earth-based and space-borne applications. In this manuscript, the finite-difference time-domain (FDTD) method is used to analyze different antenna characteristics of such elements including input impedance, coupling, and radiation patterns. Emphasis is given to coupling calculations, especially to different methods to reduce coupling. Specifically, coupling reduction is attempted using lossy material superstrates or ground plane discontinuities, such as slits. Numerical issues concerning the analysis of CBS antennas in the context of FDTD are also discussed.

A hybrid fourth-order FDTD utilizing a second-order FDTD subgrid

A hybrid method utilizing the second-order accurate in time and fourth-order accurate in space FDTD (2, 4) coupled with the standard second-order accurate both in time and space FDTD (2, 2) on a subgrid is presented. The accuracy of the method is tested by computing the S-parameters of two monopoles mounted on a ground plane and it is found to be very satisfactory. Significant computational savings both in memory and time are accomplished by using this hybrid method.

Wireless power transmission to sensors embedded in concrete via Magnetic Resonance

The feasibility of efficient wireless power transfer through Strongly Coupled Magnetic Resonance (SCMR) in non-homogenous interface such as air-concrete is studied here. Specifically, the efficiency of wireless power transmission from a source in air to a sensor embedded in concrete via strongly coupled magnetic resonance is analyzed. The concrete material is modeled for various humidity levels using the extended Debyes model. The efficiency of the SCMR is also analyzed for various depths inside the concrete.

An Origami Reconfigurable Axial-Mode Bifilar Helical Antenna

This communication presents a new reconfigurable origami bifilar helical antenna. This antenna can change its operating frequencies by changing its height. Also, analytical equations for the design of such antennas are derived based on an equivalent model of a standard helical antenna. An origami bifilar helical antenna is designed and its performance is verified using simulations and measurements.