Full-wave computation of clutter for VHF ground RADAR over irregular terrain

The present paper proposes a method to compute the complex impulse response of wireless channels based on a parabolic equation (PE) propagation algorithm. The choice of a full-wave method, instead of an asymptotic algorithm (knife-edge, UTD/GTD), has been made considering that the last is inappropriate for terrestrial VHF/UHF paths. It is indeed well known that, in these bands, scatterers and diffracting obstacles are often close to each other and to the ground (in comparison with the wavelength). The propagation algorithm gives the complex signal (amplitude and phase) at the receiver in CW operation for several values of the frequency (ie, sampled values of the transfer function). The impulse response of the deterministic channel is then obtained after FFT computing. The main limitation of this method is the fact that horizontal scattering and diffraction as well as depolarization cannot be fully taken into account because of its 2D nature. This method seems well suited to transmission and RADAR applications (prediction and simulation). We show sample computations of ground clutter for a monostatic VHF RADAR in pulse mode over an irregular terrain. Moreover, it can be extended to stochastic channels. We also exhibit comparisons between computed results and experimental data obtained with a vector-type Cox sounder for terrestrial VHF links located in rural areas.