Spectral and correlation characteristics of fluctuations of a point radiation source bearing under strong effect of a sea surface in W-band range

Abstract

Results of experimental investigation of amplibde interference-fading and angular fluctuation of a point source near a sea surface are discussed. The analysis enables one to make conclusion that on sliding propagation along the line-of-sight sea path, even in case of a strongly rough surface, there is a rather high probability of existence of the limited number of quasi-mirror reflections. In this paper the main results of experitrental investigation of statistic characteristics of amplitude and arrival angle fluctuation of detecting and direct 3"-band signals are reported, related to the case of over sea propagation with sliding angles from 1 to lOmrad (distances from 300m to 5000m).The investigations llfilled of the mutual correlation function of signals in the amplitude and angular direction finder channels have shown that the distance dependence of correlation coefficient (&do)) have a sufficiently well pronounced extreme (such dependence type will be subsequently referred to as "resonance w e " ) . Such a "resonance type" dependence was observed during the investigation of radio wave propagation in the surface troposphere layer [I].As an argument of the functional dependence &E$ (Z*) in these papers the parameter G=l /S(w)) as used which represents the ratio of troposphere inhomogeneity dimensions (0 to the Fresnel first zone dimensions (w)). The correlation maxima were observed at G=1. As stated above, in the case under consideration, the increasing of correlation may be produced by the existence of the limited number of reflectors on the interface, their dimensions being considerabie with the first Fresnel zone dimensions.We have established that the "resonance"-dependence extreme position on the distance axis is connected with the sea-way period value (the dispersion relation for gravitational waves is A~s P , the A(meters) and T(sec) being the dimensional and time period of the sea-way respectively).The smaller was the period the smaller were the distances at which the maximum values of the mutual correlation coefficient module( 1 &do) I) were registered. In case of the emission source being at the bore sight, basically the negative correlation was observed.. In some experiments it was discovered that angle and amplitude spectra-width (dF) distance dependence have the "resonance" form. We have established that when the sea-way period decreasing the effect of fadings, which show up in reducing of quasi-mirror reflection intensity manifests itself at lesser distances. In such a manner one would explain a faster drop in the correlation level with an increasing distance when the sea-way period decreases and therefore the shifting of the extremum toward the lesser distances. The similar results that enter into the treatment of fading effects were obtained in [2].For systematizing of results we have used a wave parameter L)eA(hl+h2)/(2DJDA) having the meaning of unevenness correlation radius (in our case it is /Ih, one-half of the sea wave length) to the first Fresnel zone longitudinal dimension ratio [3]. ...