A compact ultra wideband circularly-polarized slot antenna is proposed with a methodology for automated re-optimization for packaging with proprietary devices. The slot structure employs a dual-feed with an integrated compact ultra wideband phase shifter. The design process involves an advanced optimization algorithm and demonstrates the use of spline curves for generation of circularly polarized signals. These allow easy optimization, while preserving phase coherency across a wide band. The prototyped antenna has a circularly-polarized bandwidth of 54% (from 3.2 GHz -6.1 GHz).

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It has been 20 years since the word ultrawideband has first been used in open literature. In these 20 years, ideas have been transformed into real products. Yet some might object that ultrawidebandhas not yet lived up to the promises of gigabit wireless. This review shows that despite some drawbacks, ultrawideband is not only needed because of the spectrum gridlock but it still can deliver its promises including gigabit wireless. To do so the gap between the potential, which is achievable, and the current performance must be closed. Thus, this review identifies some main issues of UWB (range, BER performance, data-rate, chip complexity and issues associated by strong narrowband interference). It shows that their reasons are well understood and addressed by erudite research which includes low complexity chip design, alternative modulation schemes, multiple antenna systems, UWB radio-over-fibre, higher band UWB and interferer detection and suppression techniques. A specific feature of this review is the cross-layer approach. The latest findings from different system layers, e.g., wave propagation, are linked to the system performance or complexity. Aims and structureThe ultrawideband wireless communication technology for civilian use has been subject to intensive scientific investigation for the last two decades. At the time of writing this article, the search for "ultrawideband" and "UWB" in IEEExplore TM gives 860 journal papers and 1560 conference papers between 1991 and 2011. This amount of scientific work has resulted in serious progress from theoretical considerations to real products in the market place. However, the intensity of research activities is not being reduced as there is still a gap between the theoretical potential and the actual performance of practical systems. The main objective of this paper is to show that this gap is well understood and how on-going research activities aim to close it.As the gap must be identified first, the paper begins with explanation of the need for ultrawideband wireless communication (Section 2.1) followed by brief summary of the history of the technology (Section 2.2) and its current situation, achievements and issues which are thought to be the reason for the existence of the gap (Section 2.3). Section 3 then introduces the current UWB regulations in the leading markets to provide more understanding for the framework of UWB systems and also to introduce some recent changes which for instance increased the need for development of efficient detect and avoid algorithms. Section 4 then identifies range, BER performance, data-rate, chip complexity and issues associated by strong narrowband interference as the most burning issues of current UWB. Section 5 then groups current research activities in six subsets, describes them and shows how these activities aim to address one or more issues listed in section 4.

As a result of the recent ruling by the European Commission, ultrawideband wireless communications can now pervade small confined environments such as cars or trains. This paper studies frequency selective fading experienced by ultrawideband wireless channels in these confined environments. It focuses on the relationship between the severity of fading and the environment * + * +

Abstract-An innovative method to measure angular velocity using circularly-polarized antennas is proposed. Due to the properties of circular polarization, the angular velocity is frequency modulated (FM) on a wireless carrier. This enables a low-cost precise continuous measurement of angular velocity using a standard FM demodulator. The hardware can be easily adapted for both high and low angular velocity values. The precise alignment angle between the antennas can be determined if the initial antenna orientation is known. The angular error is shown to be less than 1.5° for antennas with a 1 dB axial-ratio. The basic method is applicable for a fixed distance between the antennas. Therefore, an advanced method which provides data for variable distances is also presented.

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This paper presents wideband measurements in a laboratory environment. These measurements provide further evidence in support of the previously published hypothesis that the clusters within the Saleh-Valenzuela propagation model are manifestations of antenna impulse responses. The issue caused by frequency variations of the antenna radiation pattern of wideband antennas and by the selection of antenna type are discussed. It is shown that due to limited movement in target applications of extremely wideband systems, the variation of antenna impulse responses due to the change of mutual antenna position does not significantly change. Thus, the deterministic nature of the antenna impulse responses can be exploited in the design of more efficient receivers.

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