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Journal ArticleDOI

A comparative study of scintillation analysis over two line-of-sight paths at 6.7 GHz and 7.6 GHz

01 Jul 1983-IEEE Transactions on Antennas and Propagation (IEEE)-Vol. 31, Iss: 4, pp 620-624
TL;DR: In this article, a comparison of the signal intensity fluctuations or scintillation of signal level, observed over two line-of-sight links is presented, which are situated over Calcutta, DumDum-Andul (6.7 GHz) and Delhi, Delhi-Sonepat (7.6 GHz).
Abstract: A comparison of the signal intensity fluctuations or scintillation of signal level, observed over two line-of-sight links is presented. These links are situated over Calcutta, DumDum-Andul (6.7 GHz) and Delhi, Delhi-Sonepat (7.6 GHz). The study reveals departures, in the occurrence and variation of the scintillation over the Calcutta path as compared with the path over Delhi. This deviation has been attributed to the large variation in humidity which exists in the coastal region, and also which plays a major role in microwave propagation in the troposphere.
Citations
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Proceedings ArticleDOI
11 Oct 1989
TL;DR: In this paper, the effects of refractive and absorptive fluctuation in air have been studied for millimeter-wave propagation through clear-air turbulence, rain, fog, and snow.
Abstract: Observations and theory for millimeter-wave propagation through clear-air turbulence, rain, fog, and snow are reviewed. Measurements have shown the effects of refractive and absorptive fluctuation in air. Measured quantities include the intensity, the phase difference between spaced antennas for a single electromagnetic frequency as well as phase difference at a single antenna for waves having differing frequencies. Typical statistics of these quantities are their variances, structure functions, temporal spectra, and probability distributions.

4 citations

Journal ArticleDOI
TL;DR: Scintillation and multipath fadings are observed in microwave LOS links established at different locations in India and both types of fading occur for significant percentage of time in a year over northern plains.
Abstract: Scintillation and multipath fadings are observed in microwave LOS links established at different locations in India. Scintillation fading dominates over the southern plains while the multipath fading prevails for more time in east coast. Both types of fading occur for significant percentage of time in a year over northern plains. The association of meteorological parameters with fading phenomenon is also investigated.
References
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Journal ArticleDOI
01 Dec 1975
TL;DR: In this article, the most recent developments on the propagation of optical beams in a turbulent medium, such as the clear atmosphere, are reviewed, including beam spreading, beam wander, loss of coherence, scintillations, angle-of-arrival variations, and short-pulse effects.
Abstract: The most recent developments on the propagation of optical beams in a turbulent medium, such as the clear atmosphere, are reviewed. Among the phenomena considered are beam spreading, beam wander, loss of coherence, scintillations, angle-of-arrival variations, and short-pulse effects.

566 citations

Journal ArticleDOI
TL;DR: In this paper, a simplified method of scaling scintillation index is described, and the accuracy of the simplified method is determined by a comparison with measurements of SCI by machine computation.

117 citations

Journal ArticleDOI
TL;DR: In this paper, a general formulation for temporal frequency spectra of the fluctuations of plane, spherical, and beam waves operating at two frequencies is given based on weak turbulence and frozen-in assumptions.
Abstract: General formulations for temporal frequency spectra of the fluctuations of plane, spherical, and beam waves operating at two frequencies are given based on weak turbulence and frozen-in assumptions. The cross spectra and the coherence are obtained for the amplitude at two frequencies, the phase at two frequencies, and the amplitude at one frequency and the phase at another frequency. The results are examined in detail for plane and spherical waves. For the spectrum of the index of refraction \kappa^{-n} in the inertial subrange, the amplitude spectrum behaves as k^{(5-n)/2} for \omega \rightarrow 0 and k^{2}\omega^{1-n} for \omega \rightarrow \infty . The phase spectrum for \omega\rightarrow 0 and for \omega\rightarrow\infty behaves as k^{2}\omega^{1-n} with different constants. These results agree well with the experimental work of Janes et al. [11] at 9.6 and 34.5 GHz, and explains the ratio of the spectra at two frequencies. Also noted is the experimental slope of -2.6 as and for \omega \rightarrow \infty which may be compared with 1-n = -2.66 using the Kolmogorov spectrum of n = 11/3 . The amplitude and phase coherence are calculated, and the results agree well with the experimental data. This agreement is indicative of the general validity of the theory for frequencies as low as 10\sim30 GHz and the path length as long as 60 km. It is also shown that using the preceding theory, the wind velocity and the structure constant C_{n} can be deduced from the experimental data. Theoretical wind velocity of 15.6 knots obtained from the propagation data compares favorably with the meteorologically measured value of 14 knots, and two values of C_{n} obtained independently from the amplitude and phase measurements closely agree with each other.

102 citations

Journal ArticleDOI
TL;DR: In this article, the relative potentials of various experimental radio techniques from the point of view of determining the atmospheric fine-scale structure were discussed, and a unified set of simple approximate expressions for the measured quantity in terms of parameters describing the refractive-index time-space structure was derived.
Abstract: This review is concerned with the relative potentials of various experimental radio techniques from the point of view of determining the atmospheric fine-scale structure. After having derived a unified set of simple approximate expressions for the ‘measured quantity’ in terms of parameters describing the refractive-index time-space structure, some of the more important sources of error are discussed. Finally, on the basis of numerous experimental results, the form of the refractive-index spectrum is deduced by using the previously derived theoretical expressions.

25 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented line-of-sight propagation characteristics observed at 6 GHz over Indian East Coast are presented in a dual-frequency experiment, where the observed wavelength dependence under varied turbulent conditions has been found to be λ −1·3 to λ-0·8 while under layered conditions, the dependence varies from λ 0·4 to κ 2·3 depending upon layer dimensions, the dual frequency experiment has a special significance due to the paucity of results regarding the wavelength dependence in turbulent conditions in India.
Abstract: Line-of-sight propagation characteristics observed at 6 GHz over Indian East Coast are presented in this paper. Scintillation frequency observed at 6700 MHz and 6580 MHz over Dum Dum/Andul path is 1 to 4 while refractive index fluctuations evaluated for incoherent scattered signal varies from 0.32 to 0.90 × 10-8. Wind component (V cos θ) along the line joining the two terminals shows that scintillation frequency increases as wind increases. The observed wavelength dependence under varied turbulent conditions has been found to be λ-1·3 to λ-0·8 while under layered conditions, the dependence varies from λ0·4 to λ2·3 depending upon layer dimensions, The dual frequency experiment has a special significance due to the paucity of results regarding the wavelength dependence under turbulent conditions in India.

1 citations