Propagation of wide bandwidth signals in a tropospheric ducting system

The propagation properties of wide bandwidth signals transmitted through a tropospheric ducting medium are examined analytically. A flat earth model with a perfect surface conductivity (sea surface) is taken. The refractive index profile n(h) is assumed a stepwise function of the height h. Horizontal and vertical polarized waves are treated in parallel by employing similar procedures. The corresponding boundary value problems are solved by using spectral representations for the primary antenna and induced fields. Guided and radiated mode contributions are then computed by applying approximate asymptotic integration techniques under a continuous wave (CW) excitation. The behavior of wide bandwidth signals propagating in a tropospheric duct is examined in terms of the inverse Fourier transformation of the CW field expressions. Several geometries are considered such as both transmitting and receiving antennas being inside the tropospheric waveguide or the opposite. Particular attention is given to the case when the communication path crosses the waveguide ceiling. In order to determine the influence of the multipath propagation, occurring inside the ducting medium, into a real communication link a phase shift keying modulation is considered. Numerical results are given for several tropospheric ducting media in terms of the bit error rate.