DISPERSIVE DISTORTIONS OF TRANSIONOSPHERIC BROAD-BAND VHF SIGNALS

The dispersive distortions of broadband signals propagating through the Earth's ionosphere are examined in relation to their influence on the range resolution of radars with frequencies from 100 MHz to 30 GHz. Polarization dispersion is taken into account in addition to phase dispersion, but scattering effects are neglected. Analytical expressions are deduced for the envelope and the frequency modulation of the convolution of the received and transmitted signals. The envelope and the frequency modulation of the convolution depend on the polarization, the Earth's magnetic field, and the total electron content of the ionosphere. The magnetic field does not affect the convolution if the carrier frequency of the broadband signal is more than 600-800 MHz. The distortion of the convolution envelope limits the range resolution of radars. The minimum resolution varies from 270 m to 3 cm when the carrier frequency increases from 100 MHz to 30 GHz.