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Presidential Executive Order 13407 has mandated the creation of an integrated public alert and warning system (IPAWS) to inform the public during periods of national emergency. This will ensure that under all conditions the President can rapidly and effectively address and warn the public over a broad range of communications devices and under any emergency condition (FEMA/DHS has set a goal to alert 85% of the population within a 10 minute time frame). This paper demonstrates Alerting Penetration Models, which allow estimation of the impacts from deployment of various alerting systems: Radio, TV, Internet, and Cell Phone.
There has been much research devoted to determining lower bounds on the quality factor of antennas. This paper explains simple general expressions for the lower bounds on the quality factor (Q) of electric- and magnetic-dipole antennas, in arbitrarily shaped electrically small volumes, excited by general sources and by global electric-current sources alone.
Wireless geolocation - or position determination - may be accomplished via many different techniques, including Received Signal Strength (RSS). RSS techniques are interesting for their simplicity and generality, and can be accomplished from a set of reference stations radiating any set of waveforms. This motivates the idea of performing RSS-type positioning from a set of Signals-of-Opportunity (SoO) that happen to be in a local area (e.g. commercial radio, TV sources, etc.).
When designing an antenna to occupy a volume with dimensions small relative to the wavelength, one of the primary challenges is optimizing the bandwidth. Analyzing the behavior of two-, four-, and six-arm small multielement spherical antennas provides physical insight into the multiresonant impedance behavior of these antennas, clearly illustrating their ultimate performance limits and yielding ideas for improved designs. The analysis can be applied towards understanding the behavior of other multielement antenna structures as well.
The behavior of a two element segmented capped monopole antenna is described in terms of three natural resonances of the antenna structure. A numerical eigenmode solver is used to derive the resonant frequency and quality factor of the natural resonances, as well as the impedance properties of these modes when excited individually. Analyzing the antenna in terms of its natural resonant modes provides physical insights into both its behavior and the fundamental limitations of its performance.
As wireless technology progresses, there is higher demand for both increased bandwidth and low-cost, highly-integrated systems. The W-band allows a move to a higher wave regime, while planar antennas containing materials with low permitivity and low loss tangent (such as fused silica quartz) allow for high efficiency, narrow bandwidths, low radiating efficiencies, and standardized manufacturing processes.
When exploring alternatives to the patch antenna, it is important to compare not only the performance of the full antenna designs, but also the physical properties of the resonant modes of the alternative structures directly with those of the patch. This paper studies a periodically structured surface resonator that is used to provide a wider bandwidth alternative to a simple patch antenna with a thickness of less than 1/30 of a wavelength. The bandwidth improvement results, in part, because the resonator has a fundamental radiation mode with a lower radiation Q-factor than the simple patch of the same electrical volume.
Transmitting sources may be located by estimating the angles-of-arrival at a receiving array if the “direct path” is present, (i.e, the straight line path between source and destination). Angle-of-arrival estimation may be efficiently performed by well-known approaches such as MUSIC and ESPRIT, which are one-dimensional angle estimation methods. Yet many real-world applications require a two-dimensional angle-of-arrival estimation because the sources and receive array may not lie in a single plane.
The study of electrically small radiofrequency (RF) antenna elements is of both practical and fundamental importance. From a practical standpoint, emerging applications such multi-input multi-output (MIMO) mobile communications systems and RF-tagging benefit from the ability to make antenna size smaller. In this paper, we consider the use of materials with negative electric permittivity as a building block for constructing effective small antenna elements. Although such materials do not occur naturally at microwave frequencies, negative permittivity can be realized at microwave frequencies using plasmas of the appropriate charge density.
A penetration test is a method of evaluating the security of a target by simulating an attack. Because multi-step attacks are often the most effective way for an attacker to compromise a system or network, we consider the problem of automatically designing a penetration test to remotely evaluate the security of a target computer or network device.
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