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Two novel designs of planar elliptical slot antennas are presented. Printed on a dielectric substrate and fed by either microstrip line or coplanar waveguide with U-shaped tuning stub, the elliptical/circular slots have been demonstrated to exhibit an ultrawideband characteristic. The performances and characteristics of the proposed antennas are investigated both numerically and experimentally. Based on these analyses, an empirical formula is introduced to approximately determine the lower edge of the 10 dB operating bandwidth. It is also shown that these antennas are nearly omnidirectional over a majority fraction of the bandwidth.Index Terms-Coplanar waveguide (CPW), microstrip line, printed antenna, slot antenna, ultrawideband (UWB).

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A finite element model has been established and used to predict the temperature history of direct laser fabricated (DLFed) Ti-6Al-4V thin wall samples. The effects of laser power and the effect of location within a sample on its temperature history have been modelled and compared with temperatures measured during DLF using thermocouples. The thermal history of the material has been correlated with the observed differences in the microstructures obtained at different locations in a given sample or for a given location in samples obtained at different laser powers.

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1 reconfigures its radiation direction in three switchable directions in the H-plane, that is, Ϫ25°, 0°, and ϩ25°. In comparison with the original RMPA, it eliminates two switches and sacrifices only a slight decrease in the tilt angle of the pattern. After replacing the switches with varactors, variation 2 is able to continuously scan its radiation pattern from Ϫ27°and 27°by controlling the value of the varactors. Variation 3 expands the H-plane pattern scan range to Ϫ(32°, 54°) ഫ (32°, 54°) by using inductors to series-resonate the varactors in variation 2. Variations 1 and 2 have a combined impedance and pattern bandwidth of more than 4.5% with respect to the center frequency, while variation 3 has a bandwidth of only 1.5%. In all the experiments, copper strips were used as switches in an on/off state and differently valued chip capacitors were used to mimic the behavior of the varactors. Implementation of electronic control of the radiation behavior of these antennas using PIN diodes and varactors is underway.

This paper presents a study of a novel monopole antenna for ultrawide-band (UWB) applications. Printed on a dielectric substrate and fed by a 50 microstrip line, a planar circular disc monopole has been demonstrated to provide an ultra wide 10 dB return loss bandwidth with satisfactory radiation properties. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated. A good agreement is achieved between the simulation and the experiment. In addition, the time domain performance of the proposed antenna is also evaluated in simulations.Index Terms-Circular disc monopole, microstripline-fed, printed antennas, ultrawideband (UWB).