Aperture Antenna Effects After Propagation through Strongly Disturbed Random Media

Second-order statistics of radio wave propagation through the structured ionosphere

“…The core of the pulse propagation and scattering problems in random media is that of ÿnding the two-position and two-frequency MCF, therefore so many works have been devoted to solutions, respectively for plane wave, spherical wave, beam wave and their applications. There are several excellent books (Ishimaru, 1997;Tatarskii, 1971;Tatarskii et al, 1993;Uscinski, 1977), some earlier investigations (e.g., Fante, 1974Fante, , 1981Brown, 1972;Hong and Ishimaru, 1976;Hong et al, 1977;Ishimaru and Hong, 1975;Lee, 1974;Fremouw et al, 1980;Knepp, 1983Knepp, , 1985Liu et al, 1974;Yeh, 1977,1981;Prokhorov et al, 1975;Sreenivasiah and Ishimaru, 1979;Sreenivasiah et al, 1976;Yeh and Liu, 1982;Booker et al, 1985;Flattà e, 1983;Rino et al, 1981), and some more recent works (e.g., Kravtsov, 1992;Oz and Heyman, 1996;Wu, 1999;Liu, 1986, 1989;Young et al, 1996;Gherm et al, 2000;Samelsohn and Freilikher, 2002;Xu et al, 2003b,c,d). Besides the above literature on transionospheric propagation, Gherm et al (1997a, b) has presented a detailed numerical investigation of the two-frequency MCF for HF wave propagation in the uctuating ionosphere.…”

“…A channel is said to be frequency-selective if the transmission bandwidth is greater than the coherence bandwidth and it is time-selective if the coded symbol duration exceeds the channel coherence time. Another parameter is coherence angle, for example in x direction, Â cohx ≈ lx=z, where lx is the coherence distance in the x direction, which is different from the angle-of-arrival variance (Nickisch, 1992;Knepp, 1985).…”

A multiple phase screen technique for electromagnetic wave propagation through random ionospheric irregularities

“…The coherent integration process of the energy collected by the receiver antenna is degraded when its diameter, in the case of parabolic type antennas, is near or less than the coherence distance. Therefore antenna effects must be included in the computation and this is done by filtering the spatial wave front realization at the receiver location by the antenna aperture weighting function [Knepp, 1985]. It has been shown that in the case of severe fading conditions, the delivered signal power can be reduced (coherent integration loss) and the coherence time and bandwidth can be increased [Knepp, 1985 Henceforth we wish to restrict the use of MPS to cases where the distance from the transmitter to the irregularities slab is superior to the distance from the slab to the receiver.…”

“…Therefore antenna effects must be included in the computation and this is done by filtering the spatial wave front realization at the receiver location by the antenna aperture weighting function [Knepp, 1985]. It has been shown that in the case of severe fading conditions, the delivered signal power can be reduced (coherent integration loss) and the coherence time and bandwidth can be increased [Knepp, 1985 Henceforth we wish to restrict the use of MPS to cases where the distance from the transmitter to the irregularities slab is superior to the distance from the slab to the receiver. This is generally verified on downlinks where the source is far away from the medium and the wave incident on the plasma slab is a plane wave.…”

“…Hence the fading can show statistical decorrelation at different frequencies in the signal bandwidth, and it is therefore useful to evaluate a coherence bandwidth Be. Coherent integration loss and scattering loss are also observed in highly disturbed cases; both effects are closely related to the size and directivity of antennas [Knepp, 1985].…”