A novel dual-band conical-helix/monopole antenna is proposed to operate as an on-body central antenna for Wireless Body Area Network (WBAN). The proposed antenna communicates in three ways: (i) off-body communication through its end-fire radiation with the ceil-mounted WiMax antenna at 5.8 GHz, (ii) on-body communication through its broadside radiation with the on-skin biosensor antennas at 3.0 GHz, and (iii) in-body communication with the in-body (implanted) biosensor antennas at 3.0 GHz. The characteristics of the proposed antenna are investigated through electromagnetic simulation and experimental measurements where a prototype of this antenna is fabricated for this purpose. The antenna is matched with 50 Ω coaxial feeder over the dual frequency bands, mounted on a copper circular disc, and covered with a very thin dielectric radom for mechanical protection. Such an antenna covered by the radom is shaped like a hemispherical button that can be attached to patient clothes and, hence, it can be considered as a wearable antenna. The radiation patterns obtained by experimental measurements show good agreement with those obtained by the CST R simulator and are shown to be appropriate for communication with the ceil-mounted WiMAX antenna and the biosensor antennas at 5.8 GHz and 3.0 GHz, respectively. The distribution of the microwave power density near the body surface is evaluated by simulation and experimental measurements to ensure the realization of the electromagnetic exposure safety limits. The Specific Absorption Rate (SAR) distribution inside the human tissues of concern is evaluated showing a safe level of electromagnetic exposure. Quantitative assessment of the WBAN communication system performance is achieved when the proposed antenna is employed as an on-body central antenna for the WBAN. Thanks to the optimized design of the proposed antenna the Bit-Error-Rate (BER) is shown to be very low even when the input power fed to the antenna is only 1 mW.

Abstract-In this work, a new method is introduced to model the excitation and loading for antennas composed of arbitrarily shaped conducting surfaces treated by the elctric field integral equation method described by Raw-Wilton-Glisson (RWG). Instead of using a single non-boundary edge to represent a zero-width exciting gap according to the conventional method, the proposed method uses either single or multiple pairs of facing boundary edges to form a real gap of arbitrary shape and width. The new method has many advantages over the conventional (zero-width) source/load representation considering the flexibility in shaping the gap to fit the antenna surface and the accuracy of the obtained results especially for the antenna input impedance and the input current distribution. The new method is described mathematically in detail. Modified basis functions are described for the gap source/load. Numerical results are obtained to investigate the dependence of the antenna input impedance and the current distribution along the gap length on the gap width, the geometrical shape of the gap and the surface segmentation resolution along the gap length.

Abstract-Circularly-polarized arrays of cavity backed slot (CBS) antennas are proposed for X-band satellite-earth communications. Two configurations of such circularly polarized arrays are investigated: cross-shaped and square-shaped arrays. Both configurations can produce right-hand circular polarization (RHCP) as well as lefthand circular polarization (LHCP) by proper setting of excitation phase for each element in the array. The finite-difference timedomain (FDTD) method is used to analyze the characteristics of the proposed arrays including the input impedance, S-parameters, radiation pattern, gain and axial ratio. The results show that the proposed array configurations seem very promising and useful for geostationary satellite applications.

The present p a per prop oses a new g round p enetratin g radar (GPR) system for obtainin g hi g h resolution ima g es for objects buried under the surface of a g round soil.

Abstract-Conical log spiral antennas are famous for being appropriate for tracking, telemetry and command (TT&C) applications in low earth orbit (LEO) satellites. In this work, a conical linear (Archimedean) spiral antenna is introduced and investigated for the same purpose. The electric field integral equation (EFIE) technique is applied to a triangular-patch surface model of the conical equiangular linear spiral antenna. This antenna is optimized to produce the radiation characteristics required for TT&C applications for LEO satellites. The input impedance, polarization and radiation patterns of this antenna are investigated over the operating band of frequencies. Some of the obtained results especially those concerning the input impedance, radiation pattern, polarization and bandwidth are verified experimentally. It is shown that the proposed antenna is quite appropriate for TT&C in LEO satellite applications.