Piers Online 

About: Piers Online is an academic journal. The journal publishes majorly in the area(s): Antenna (radio) & Microstrip antenna. It has an ISSN identifier of 1931-7360. Over the lifetime, 983 publications have been published receiving 5150 citations.

Calculating SAR in two Models of the Human Head Exposed to Mobile Phones Radiations at 900 and 1800 MHz

Abstract: Since the 1990's, use of mobile phones has augmented worldwide generating a public concern as to whether frequent utilization of such devices is unsafe. This provoked EMF researchers to find suitable techniques of assessing radiation blueprint and exposure hazards if any. Most research groups focused on two techniques: experimental measurements and finite-difference time-domain (FDTD) computations. Computation of the specific absorption rate (SAR) generated by cellular phones inside two models of the human head is presented in this paper. Two models of mobile phones were considered working at 900 and 1800MHz bands according to the Global System for Mobile Communication. Radiated energy distributions and averaged SAR values in 1g and 10g of tissue were computed inside the models of head using FDTD. Computations were compared with a realistic head model constructed with the MRI scans. The distribution of the local SAR in the head was similar to that of the simplified head models. The maximum local SAR calculated was 53.43W/kg and the maximum SAR(10g) was 2.96W/kg, both for 1W output power from the antenna. The results indicated the area of the maximum local SAR was situated in outer layer of skull, where muscle and skin were. The important parameters in absorbed energy in the head were the type of antenna, current distribution and the distance between head and antenna. The head models used for simulation proved as insignificant parameter in the calculations.

Space-filling Patch Antennas with CPW Feed

Abstract: In this paper, the performances of some space-filling monopole antennas with coplanar waveguide have been investigated. It may be contended that the bends and corners of these geometries would add to the radiation efficiency of the antenna, thereby improving its gain. Advantage of these configurations is that they lead to mutiband conformal antennas. A new version of Gosper curve patch antenna is introduced and its performance has been compared to conventional Gosper curve patch antenna.

Temperature and Mineralogy Dependable Model for Microwave Dielectric Spectra of Moist Soils

Abstract: In this paper, a physically based dielectric model in microwave band for moist soils is developed to account for both the temperature and granulometric mineralogy of the soil. The generalized refractive mixing dielectric model (GRMDM) previously developed by V. L. Mironov etal. was used as a mean to determine the spectroscopic parameters for 5 soils which complex dielectric constant spectra were measured and presented in Technical Report EL-95-34, December 1995 by J. O. Curtis etal. The measurement results used covered the temperatures of 10, 20, 30, and 40 - C, gravimetric clay contents from 0 to 0.76g/g, and frequencies from 0.3 to 26.5GHz. Relating to each individual soil, such GRMDM spectroscopic parameters as dielectric constants in low frequency limit, relaxation times, and ohmic conductivities, pertaining to both bound and unbound soil water, were fltted as functions of temperature with the Clausiuss- Mossotii, Debye and linear equations, respectively. As a result, a set of physical parameters for a temperature dependable generalized refractive mixing dielectric model (TD GRMDM), consisting of the volumetric expansion coe-cients, activation energies, enthropies of activation and others, were obtained. Finally, the parameters of the TD GRMDM as functions of gravimetric clay content were fltted to yield the closing set of polinomial formulas, which, in conjunction with the TD GRMDM, represent a temperature and mineralogy dependable soil dielectric model (TMD SDM). Thus developed, the TMD SDM provides for predictions of the complex dielectric constant of moist soils as a function of moisture, wave frequency, temperature and gravimetric clay content. Further the TMD SDM prediction error was estimated with the use of the ndependent dielectric data.

Antenna Design for Ultra Wideband Application Using a New Multilayer Structure

Abstract: As wireless communication applications require more and more bandwidth, the demand for wideband antennas increases as well. For instance, the ultra wideband radio (UWB) utilizes the frequency band of 3.1–10.6GHz.This paper presents a work carried out within ULTRAWAVES in the area of antenna design and analysis. A new multilayer microstrip antenna is introduced using Stacked Multiresonator patches. In order to achieve suitable bandwidth, the antenna size is fine for mobile applications. The antenna is designed, optimized and simulated using Ansoft designer. In addition results and conclusions are presented. DOI: 10.2529/PIERS060531145356

The Estimation of Buried Pipe Diameters by Generalized Hough Transform of Radar Data

Abstract: The generalized Hough transform method is applied to the measurement of the diameters of buried cylindrical pipes by Ground Penetration Radar (GPR). 600 MHz radar scans across long pipes, buried in one metre or so of soil, show complex reflection patterns consisting of a series of inverted hyperbolic arcs. The time of flight t(y) as the radar probe is scanned along an axis, y, perpendicular to the pipe, shows an arc whose shape and position depends on 4 unknown variables: y0, the position of the center of the pipe along the scan, z0, the depth of the pipe center, R0, its radius and V0 the velocity in the medium. Analytic expressions for the solution of these variables have been obtained. They use sets of times ti at corresponding positions yi, along the arc, depending on the number of variables to be determined. In the generalized Hough method many such sets of times are chosen randomly from points on the arcs. The results are presented for example as peaks in an accumulator space for each variable. The method is demonstrated for a 0.18 m radius concrete pipe buried at a nominal 1 m depth in a road. Using data acquired at 600MHz frequency (around 0.16m wavelength in soil) the estimated radius was 0.174 ± 0.059 m.