A novel dual-wideband printed monopole antenna is proposed for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed antenna consists of a T-shaped monopole on top and dual combined G-shaped slots etched symmetrically on the ground plane to achieve a dual-wideband performance. Prototype of the proposed antenna has been constructed and tested. The measured 10 dB bandwidths for return loss are 1.76 GHz from 2.13 to 3.89 GHz and 0.92 GHz from 5.03 to 5.95 GHz, covering all the 2.4/5.2/5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX bands. And this antenna also has omni-directional patterns over the lower operating range.

Ferromagnetic Si1−xMnx was prepared by implanting B+ and Mn+ ions in sequence into p-type Si(100) at room temperature and post-annealing at 700–900 °C. Superparamagnetic nano-sized silicide precipitates, 10–27 at.% Mn, were found near the surface of all Si1−xMnx samples. Annealing at 800 °C or below leads to the formation of a thin Si(Mn) layer, with 1.1 at.% Mn, ∼180 nm beneath the surface, giving rise to ferromagnetism with a Curie temperature above 250 K. The high-temperature ferromagnetism is attributed to the indirect exchange mediated by localized carriers in the impurity states. The Mn content of 1–1.5 at.%, having been separately reported to show room-temperature ferromagnetism several times by different groups, seems meaningful for Si-based diluted magnetic semiconductors (DMS). Possible extensions of our work presented here are elucidated.

Abstract-In this paper, a method to broaden the beamwidths of a crossed dipole antenna is proposed. By introducing four parasitic strips around the crossed dipole antenna, the beamwidths of the crossed dipole antenna in the vertical plane are broadened effectively, making the patterns uniform over a wide frequency band. An Lband prototype, operating in the frequency range 1.1 GHz to 1.6 GHz, is fabricated and tested. The simulated and measured results show that the beamwidths at lower frequencies are broadened and uniform radiation patterns over the whole operating frequency band are obtained, making the crossed dipole suitable for wideband marine GPS (Global Positioning System) applications.

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