The authors have used the finite-difference time-domain method and a new millimeter-resolution anatomically based model of the human to study electromagnetic energy coupled to the head due to mobile telephones at 835 and 1900 MHz. Assuming reduced dimensions characteristic of today's mobile telephones, the authors have obtained SAR distributions for two different lengths of monopole antennas of lengths /spl lambda//4 and 3/spl lambda//8 for a model of the adult male and reduced-scale models of 10- and 5-year-old children and find that peak one-voxel and 1-g SARs are larger for the smaller models of children, particularly at 835 MHz. Also, a larger in-depth penetration of absorbed energy for these smaller models is obtained. The authors have also studied the effect of using the widely disparate tissue properties reported in the literature and of using homogeneous instead of the anatomically realistic heterogeneous models on the SAR distributions. Homogeneous models are shown to grossly overestimate both the peak 1-voxel and 1-g SARs. Last, the authors show that it is possible to use truncated one-half or one-third models of the human head with negligible errors in the calculated SAR distributions. This simplification will allow considerable savings in computer memory and computation times.

The objective of this paper is to design a microstrip patch antenna for communication with medical implants in the 402-405-MHz Medical Implant Communications Services band. Microstrip antenna design parameters are evaluated using the finite-difference time-domain method, and are compared to measured results. The effects of shape, length, size, location of feed point and ground point, substrate and superstrate materials, and their thicknesses are evaluated. An extensive study of the performance of the antennas to changes in these parameters was undertaken. The results of this paper provide guidance in the design of implantable microstrip antennas.

Spread spectrum time domain reflectometry (SSTDR) and sequence time domain reflectometry have been demonstrated to be effective technologies for locating intermittent faults on aircraft wires carrying typical signals in flight. This paper examines the parameters that control the accuracy, latency, and signal to noise ratio for these methods. Both test methods are shown to be effective for wires carrying ACpower signals, and SSTDR is shown to be particularly effective at testing wires carrying digital signals such as Mil-Std 1553 data. Results are demonstrated for both controlled and uncontrolled impedance cables. The low test signal levels and high noise immunity of these test methods make them well suited to test for intermittent wiring failures such as open circuits, short circuits, and arcs on cables in aircraft in flight.

In this paper, we review the state of the art in the detection, location, and diagnosis of faults in electrical wiring interconnection systems (EWIS) including in the electric power grid and vehicles and machines. Most electrical test methods rely on measurements of either currents and voltages or on high frequency reflections from impedance discontinuities. Of these high frequency test methods, we review phasor, travelling wave and reflectometry methods. The reflectometry methods summarized include time domain reflectometry (TDR), sequence time domain reflectometry (STDR), spread spectrum time domain reflectometry (SSTDR), orthogonal multi-tone reflectometry (OMTDR), noise domain reflectometry (NDR), chaos time domain reflectometry (CTDR), binary time domain reflectometry (BTDR), frequency domain reflectometry (FDR), multicarrier reflectometry (MCR), and time-frequency domain reflectometry (TFDR). All of these reflectometry methods result in complex data sets (reflectometry signatures) that are the result of reflections in the time/frequency/spatial domains. Automated analysis techniques are needed to detect, locate, and diagnose the fault including genetic algorithm (GA), neural networks (NN), particle swarm optimization, teaching–learning-based optimization, backtracking search optimization, inverse scattering, and iterative approaches. We summarize several of these methods including electromagnetic time-reversal (TR) and the matched-pulse (MP) approach. We also discuss the issue of soft faults (small impedance changes) and methods to augment their signatures, and the challenges of branched networks. We also suggest directions for future research and development.

Aging aircraft wiring poses a significant safety threat and has been implicated in losses of both military and commercial aircraft. This paper describes the conceptual design and function of a "smart wiring system" based on a low-cost frequency-domain reflectometer (FDR) that can be used to test the integrity of aircraft cables nondestructively on board. This system will enable the pilot or maintainer to test all critical wiring systems prior to flight at the push of a button. The details and test results from the FDR system on realistic aircraft wires are described. The system has a bandwidth of 0.8-1.2 GHz, a range of 4.5 m, and a resolution of 3 cm and can determine the length and terminating impedance of a cable harnesses from measurements at a single end. The system is now being miniaturized to be imbedded in a "connector saver" format for aftermarket installation on common existing platforms.