Propagation of broadband HF signals in a medium with nonlinear dispersion

Effect of nonlinear dispersion on distortions of broadband signals due to propagation in ionospheric channel is considered with allowance for matched processing in detector. Distortions of the shape of pulse response are studied versus nonlinearity parameter, and the effect of geophysical factors on the parameter is analyzed. The pulse response is used to estimate the group delay. It is demonstrated that the problem of propagation of broadband signals is reduced to the analysis of distortions of an equivalent signal with uniform in-phase spectrum in the ionospheric channel similar to the distortions of the pulse response of the channel. For the polynomial dispersion characteristic of the channel, the effect of nonlinearity on the pulse characteristics is described using incomplete Airy functions and the shape of the envelope of such a characteristic becomes asymmetric. Owing to uncertainty, the parameter of the group delay in the channel with the nonlinear dispersion cannot be accurately determined using the data on the pulse characteristic as distinct from the dispersion-free or linear-dispersion channel.