Diffraction effects in microwave propagation at the origin of superluminal behaviors

Ranfagni, A.; Ricci, A. M.; Ruggeri, R.; Agresti, A.

doi:10.1016/j.physleta.2008.09.012

Cited by 5 publications

(4 citation statements)

References 13 publications

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“…There, the intensity relative to the one‐way path ( R = 16 m) was found to be about one half of the intensity relative to the double‐way path ( R = 32 m) while just the opposite seemed reasonable, as in the previous case (Interference effects between contributions of ±β r directions (not con‐ sidered here) could partially explain this incongruity.). Therefore, a possible agreement with the experimental data could be achieved by interchanging the attribution of the forerunners, namely the more intense (55 × 10 −2 ) to the one‐way path, and the other (25 × 10 −2 ) to the double‐way path, in accordance with a different wave‐path interpretation (This anomaly in the observed values of the intensity gave rise to a different interpretation of forerunners as proposed in Ref 22…”

Section: Analysis Of the Experimental Resultssupporting

confidence: 62%

“…In the other case [22], an analogous system was used in a “compact range” (i.e., inside an anechoic chamber) over a feed‐target distance of 16 m. In this case, a converging device was interposed between feed and target, thus producing a sort of amplification of the effects (The multiplet structure of the forerunners, observed in this case, is presumably due to the converging device, consisting of two cylindrical reflectors, but assimilated to a spherical system constituted by the combination of a real and a virtual lens [20]).…”

Section: Analysis Of the Experimental Resultsmentioning

confidence: 99%

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Anomalous forerunners in wave propagation interpreted by a typical diffraction integral

Ranfagni

Cacciari

Ruggeri

et al. 2011

Micro & Optical Tech Letters

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which has the merit of particularly narrow band selectivity. Only the fundamental resonance is highly selected to the feeding I/O ports, which can be demonstrated by the typical stopband simulated electric current density (i.e., 13.3 GHz) of the structure shown in Figure 5. It can be seen that the closed electronic and magnetic coupling paths in the tight coupled DGS TSCFs and microstrip T-stubs lead to low radiation and free spurious. Besides, from the transmission and reflection characteristics of the structure depicted in Figure 4, it demonstrates a low radiation stopband with good spurious suppression in the wide frequency range from the first spurious P p2 up to 20 GHz. Thus, the wide stopband responses are from the intrinsic characteristics of the proposed structure. Based on the investigation above, it can be concluded that the proposed scheme has the following two functions: (1) high selectivity on the fundamental frequency;(2) high rejection on high-order modes or spurious. In addition, it is found that an optimized stopband frequency responses can be obtained, when the ratios of the DGS dimensions (i.e., S 1 : W A : S 2 ) and the T-stub (i.e., W 2 to L 2 /2) are chosen at 3:1:1 and 3:4, respectively.ABSTRACT: By using radar techniques over distances of 16 and 80 m, microwave propagation experiments revealed the presence of anomalous forerunners situated in advanced positions with respect to the main (luminal) peak. These results can be interpreted by a typical diffraction integral, which accounts for the existence of (fast) complex waves, which are usually considered only in the near-field region, but are still surviving beyond this limit.ABSTRACT: An algorithm based on wavelet transform is utilized in detecting and examining the heartbeat signal obtained from a Doppler radar. Time-frequency localization properties of wavelet transform were used to examine the signal and provided detail of swift and slow changes in heart rate over very small periods resulting in better determination of the accuracy of the Doppler radar. Till 1 m, a very accurate and robust performance was observed for the Doppler radar. Even at 2-m heart rate was detectable but not with reasonable accuracy.

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Section: Analysis Of the Experimental Resultssupporting

confidence: 62%

Section: Analysis Of the Experimental Resultsmentioning

confidence: 99%

Anomalous forerunners in wave propagation interpreted by a typical diffraction integral

Ranfagni

Cacciari

Ruggeri

et al. 2011

Micro & Optical Tech Letters

Self Cite

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show abstract

“…Effects of small retardation have been observed in the propagation of evanescent waves working, for instance, with side-by-side prisms [11], undersized waveguides [12][13][14][15], in misaligned horn antennas [16,17], in experiments on frustrated total internal reflections [18] (see also the review paper [19] and references therein) etc. Superluminar behaviors have been observed also in microwave propagation experiments implementing radar technique [20] and was evidenced by the presence of forerunners in advanced positions with the main luminal peak.…”

mentioning

confidence: 74%

Anomalously small retardation of bound (force) electromagnetic fields in antenna near zone

Missevitch¹,

Kholmetskii²,

Smirnov‐Rueda³

2011

EPL

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At fundamental level this work uncovers the actually incomplete knowledge of the energy transmission and propagation related to bound (force) electromagnetic (EM) fields. To deal with this problem, we present an experimental approach to a separate study of propagation characteristics of bound and radiation EM fields produced by antennas in a vacuum. A series of our recent experiments continues (J. Appl. Phys., 101 (2007) 023532; 102 (2007) 013529) with improved technical realizations extended for different ultra-high-frequency (UHF) radiation wavelengths. The experimental results show anomalously small retardation of bound EM fields within about the half of the near zone size.

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“…This latter value is surely overestimated, due to the absence of the exponential attenuation of Equation (11). If this effect is taken into account [32], as a result, we obtain…”

Section: Interpretation Of the Experimental Resultsmentioning

confidence: 91%

Modulation Transfer between Microwave Beams: Asymptotic Evaluation of Integrals with Pole Singularities near a First-Order Saddle Point

Cacciari,

Ranfagni

2024

Axioms

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Experimental results of delay-time measurements in the transfer of modulation between microwave beams, as reported in previous articles, were interpreted on a competition (interference) between two waves, one of which is modulated and the other is a continuous wave (c.w.). The creation of one of these waves was attributed to a saddle-point contribution, while the other was attributed to pole singularities. In this paper, such an assumption is justified by a quantitative field-amplitude analysis in order to make the modeling plausible. In particular, two ways of calculating field amplitudes are considered. These lead to results that are quantitatively markedly different, although qualitatively similar.

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Diffraction effects in microwave propagation at the origin of superluminal behaviors

Cited by 5 publications

References 13 publications

Anomalous forerunners in wave propagation interpreted by a typical diffraction integral

Anomalous forerunners in wave propagation interpreted by a typical diffraction integral

Anomalously small retardation of bound (force) electromagnetic fields in antenna near zone

Modulation Transfer between Microwave Beams: Asymptotic Evaluation of Integrals with Pole Singularities near a First-Order Saddle Point

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