Abstract: The performance of hybrid amplify and forward -
decode and forward (AF-DF) hybrid radio frequency/free space
optical (RF/FSO) communication system, that adopts M-ary pulse
position modulation (MPPM) techniques, is analyzed. Both exact
and approximate symbol-error rates (SERs) are derived. The random
variations of the received optical irradiance, produced by the
atmospheric turbulence, is modeled by the gamma-gamma (GG)
statistical distribution. A closed-form expression for the probability
density function (PDF) is derived for the whole above system
is obtained. Thanks to the use of hybrid AF-DF hybrid RF/FSO
configuration and MPPM, the effects of atmospheric turbulence is
mitigated; hence the capacity of combating atmospheric turbulence
and the transmissitted signal quality are improved.
Abstract: This paper presents a novel statistical description of
the counterpoise effective length due to lightning surges, where the
(impulse) effective length had been obtained by means of regressive
formulas applied to the transient simulation results. The effective
length is described in terms of a statistical distribution function, from
which median, mean, variance, and other parameters of interest could
be readily obtained. The influence of lightning current amplitude,
lightning front duration, and soil resistivity on the effective length has
been accounted for, assuming statistical nature of these parameters. A
method for determining the optimal counterpoise length, in terms of
the statistical impulse effective length, is also presented. It is based on
estimating the number of dangerous events associated with lightning
strikes. Proposed statistical description and the associated method
provide valuable information which could aid the design engineer in
optimising physical lengths of counterpoises in different grounding
arrangements and soil resistivity situations.
Abstract: This paper presents a low cost automatic system for
sampling the electric field in a limited area. The scanning area is a
flat surface parallel to the ground at a selected height. We discuss
in detail the hardware, software and all the arrangements involved
in the system operation. In order to show the system performance
we include a campaign of narrow band measurements with 6017
sample points in the surroundings of a cellular base station. A
commercial isotropic antenna with three orthogonal axes was used
as sampling device. The results are analyzed in terms of its space
average, standard deviation and statistical distribution.